[Concept] [PATCH 04/15] jbd2: Add transaction.c from Linux

From: Simon Glass <simon.glass@canonical.com> Add the JBD2 journaling layer transaction management from the Linux 6.18 kernel ext4 filesystem driver. transaction.c handles: - Transaction lifecycle (start, stop, restart) - Handle management for filesystem operations - Buffer attachment to transactions - Transaction state machine - Credit reservation and accounting - Metadata and data buffer journaling This is the core transaction API that ext4 uses to ensure atomic updates to filesystem metadata. Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com> Signed-off-by: Simon Glass <simon.glass@canonical.com> --- fs/jbd2/transaction.c | 2751 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 2751 insertions(+) create mode 100644 fs/jbd2/transaction.c diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c new file mode 100644 index 00000000000..3e510564de6 --- /dev/null +++ b/fs/jbd2/transaction.c @@ -0,0 +1,2751 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * linux/fs/jbd2/transaction.c + * + * Written by Stephen C. Tweedie <sct@redhat.com>, 1998 + * + * Copyright 1998 Red Hat corp --- All Rights Reserved + * + * Generic filesystem transaction handling code; part of the ext2fs + * journaling system. + * + * This file manages transactions (compound commits managed by the + * journaling code) and handles (individual atomic operations by the + * filesystem). + */ + +#include <linux/time.h> +#include <linux/fs.h> +#include <linux/jbd2.h> +#include <linux/errno.h> +#include <linux/slab.h> +#include <linux/timer.h> +#include <linux/mm.h> +#include <linux/highmem.h> +#include <linux/hrtimer.h> +#include <linux/backing-dev.h> +#include <linux/bug.h> +#include <linux/module.h> +#include <linux/sched/mm.h> + +#include <trace/events/jbd2.h> + +static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh); +static void __jbd2_journal_unfile_buffer(struct journal_head *jh); + +static struct kmem_cache *transaction_cache; +int __init jbd2_journal_init_transaction_cache(void) +{ + J_ASSERT(!transaction_cache); + transaction_cache = kmem_cache_create("jbd2_transaction_s", + sizeof(transaction_t), + 0, + SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY, + NULL); + if (!transaction_cache) { + pr_emerg("JBD2: failed to create transaction cache\n"); + return -ENOMEM; + } + return 0; +} + +void jbd2_journal_destroy_transaction_cache(void) +{ + kmem_cache_destroy(transaction_cache); + transaction_cache = NULL; +} + +void jbd2_journal_free_transaction(transaction_t *transaction) +{ + if (unlikely(ZERO_OR_NULL_PTR(transaction))) + return; + kmem_cache_free(transaction_cache, transaction); +} + +/* + * jbd2_get_transaction: obtain a new transaction_t object. + * + * Simply initialise a new transaction. Initialize it in + * RUNNING state and add it to the current journal (which should not + * have an existing running transaction: we only make a new transaction + * once we have started to commit the old one). + * + * Preconditions: + * The journal MUST be locked. We don't perform atomic mallocs on the + * new transaction and we can't block without protecting against other + * processes trying to touch the journal while it is in transition. + * + */ + +static void jbd2_get_transaction(journal_t *journal, + transaction_t *transaction) +{ + transaction->t_journal = journal; + transaction->t_state = T_RUNNING; + transaction->t_start_time = ktime_get(); + transaction->t_tid = journal->j_transaction_sequence++; + transaction->t_expires = jiffies + journal->j_commit_interval; + atomic_set(&transaction->t_updates, 0); + atomic_set(&transaction->t_outstanding_credits, + journal->j_transaction_overhead_buffers + + atomic_read(&journal->j_reserved_credits)); + atomic_set(&transaction->t_outstanding_revokes, 0); + atomic_set(&transaction->t_handle_count, 0); + INIT_LIST_HEAD(&transaction->t_inode_list); + + /* Set up the commit timer for the new transaction. */ + journal->j_commit_timer.expires = round_jiffies_up(transaction->t_expires); + add_timer(&journal->j_commit_timer); + + J_ASSERT(journal->j_running_transaction == NULL); + journal->j_running_transaction = transaction; + transaction->t_max_wait = 0; + transaction->t_start = jiffies; + transaction->t_requested = 0; +} + +/* + * Handle management. + * + * A handle_t is an object which represents a single atomic update to a + * filesystem, and which tracks all of the modifications which form part + * of that one update. + */ + +/* + * t_max_wait is carefully updated here with use of atomic compare exchange. + * Note that there could be multiplre threads trying to do this simultaneously + * hence using cmpxchg to avoid any use of locks in this case. + */ +static inline void update_t_max_wait(transaction_t *transaction, + unsigned long ts) +{ + unsigned long oldts, newts; + + if (time_after(transaction->t_start, ts)) { + newts = jbd2_time_diff(ts, transaction->t_start); + oldts = READ_ONCE(transaction->t_max_wait); + while (oldts < newts) + oldts = cmpxchg(&transaction->t_max_wait, oldts, newts); + } +} + +/* + * Wait until running transaction passes to T_FLUSH state and new transaction + * can thus be started. Also starts the commit if needed. The function expects + * running transaction to exist and releases j_state_lock. + */ +static void wait_transaction_locked(journal_t *journal) + __releases(journal->j_state_lock) +{ + DEFINE_WAIT(wait); + int need_to_start; + tid_t tid = journal->j_running_transaction->t_tid; + + prepare_to_wait_exclusive(&journal->j_wait_transaction_locked, &wait, + TASK_UNINTERRUPTIBLE); + need_to_start = !tid_geq(journal->j_commit_request, tid); + read_unlock(&journal->j_state_lock); + if (need_to_start) + jbd2_log_start_commit(journal, tid); + jbd2_might_wait_for_commit(journal); + schedule(); + finish_wait(&journal->j_wait_transaction_locked, &wait); +} + +/* + * Wait until running transaction transitions from T_SWITCH to T_FLUSH + * state and new transaction can thus be started. The function releases + * j_state_lock. + */ +static void wait_transaction_switching(journal_t *journal) + __releases(journal->j_state_lock) +{ + DEFINE_WAIT(wait); + + if (WARN_ON(!journal->j_running_transaction || + journal->j_running_transaction->t_state != T_SWITCH)) { + read_unlock(&journal->j_state_lock); + return; + } + prepare_to_wait_exclusive(&journal->j_wait_transaction_locked, &wait, + TASK_UNINTERRUPTIBLE); + read_unlock(&journal->j_state_lock); + /* + * We don't call jbd2_might_wait_for_commit() here as there's no + * waiting for outstanding handles happening anymore in T_SWITCH state + * and handling of reserved handles actually relies on that for + * correctness. + */ + schedule(); + finish_wait(&journal->j_wait_transaction_locked, &wait); +} + +static void sub_reserved_credits(journal_t *journal, int blocks) +{ + atomic_sub(blocks, &journal->j_reserved_credits); + wake_up(&journal->j_wait_reserved); +} + +/* Maximum number of blocks for user transaction payload */ +static int jbd2_max_user_trans_buffers(journal_t *journal) +{ + return journal->j_max_transaction_buffers - + journal->j_transaction_overhead_buffers; +} + +/* + * Wait until we can add credits for handle to the running transaction. Called + * with j_state_lock held for reading. Returns 0 if handle joined the running + * transaction. Returns 1 if we had to wait, j_state_lock is dropped, and + * caller must retry. + * + * Note: because j_state_lock may be dropped depending on the return + * value, we need to fake out sparse so ti doesn't complain about a + * locking imbalance. Callers of add_transaction_credits will need to + * make a similar accomodation. + */ +static int add_transaction_credits(journal_t *journal, int blocks, + int rsv_blocks) +__must_hold(&journal->j_state_lock) +{ + transaction_t *t = journal->j_running_transaction; + int needed; + int total = blocks + rsv_blocks; + + /* + * If the current transaction is locked down for commit, wait + * for the lock to be released. + */ + if (t->t_state != T_RUNNING) { + WARN_ON_ONCE(t->t_state >= T_FLUSH); + wait_transaction_locked(journal); + __acquire(&journal->j_state_lock); /* fake out sparse */ + return 1; + } + + /* + * If there is not enough space left in the log to write all + * potential buffers requested by this operation, we need to + * stall pending a log checkpoint to free some more log space. + */ + needed = atomic_add_return(total, &t->t_outstanding_credits); + if (needed > journal->j_max_transaction_buffers) { + /* + * If the current transaction is already too large, + * then start to commit it: we can then go back and + * attach this handle to a new transaction. + */ + atomic_sub(total, &t->t_outstanding_credits); + + /* + * Is the number of reserved credits in the current transaction too + * big to fit this handle? Wait until reserved credits are freed. + */ + if (atomic_read(&journal->j_reserved_credits) + total > + jbd2_max_user_trans_buffers(journal)) { + read_unlock(&journal->j_state_lock); + jbd2_might_wait_for_commit(journal); + wait_event(journal->j_wait_reserved, + atomic_read(&journal->j_reserved_credits) + total <= + jbd2_max_user_trans_buffers(journal)); + __acquire(&journal->j_state_lock); /* fake out sparse */ + return 1; + } + + wait_transaction_locked(journal); + __acquire(&journal->j_state_lock); /* fake out sparse */ + return 1; + } + + /* + * The commit code assumes that it can get enough log space + * without forcing a checkpoint. This is *critical* for + * correctness: a checkpoint of a buffer which is also + * associated with a committing transaction creates a deadlock, + * so commit simply cannot force through checkpoints. + * + * We must therefore ensure the necessary space in the journal + * *before* starting to dirty potentially checkpointed buffers + * in the new transaction. + */ + if (jbd2_log_space_left(journal) < journal->j_max_transaction_buffers) { + atomic_sub(total, &t->t_outstanding_credits); + read_unlock(&journal->j_state_lock); + jbd2_might_wait_for_commit(journal); + write_lock(&journal->j_state_lock); + if (jbd2_log_space_left(journal) < + journal->j_max_transaction_buffers) + __jbd2_log_wait_for_space(journal); + write_unlock(&journal->j_state_lock); + __acquire(&journal->j_state_lock); /* fake out sparse */ + return 1; + } + + /* No reservation? We are done... */ + if (!rsv_blocks) + return 0; + + needed = atomic_add_return(rsv_blocks, &journal->j_reserved_credits); + /* We allow at most half of a transaction to be reserved */ + if (needed > jbd2_max_user_trans_buffers(journal) / 2) { + sub_reserved_credits(journal, rsv_blocks); + atomic_sub(total, &t->t_outstanding_credits); + read_unlock(&journal->j_state_lock); + jbd2_might_wait_for_commit(journal); + wait_event(journal->j_wait_reserved, + atomic_read(&journal->j_reserved_credits) + rsv_blocks + <= jbd2_max_user_trans_buffers(journal) / 2); + __acquire(&journal->j_state_lock); /* fake out sparse */ + return 1; + } + return 0; +} + +/* + * start_this_handle: Given a handle, deal with any locking or stalling + * needed to make sure that there is enough journal space for the handle + * to begin. Attach the handle to a transaction and set up the + * transaction's buffer credits. + */ + +static int start_this_handle(journal_t *journal, handle_t *handle, + gfp_t gfp_mask) +{ + transaction_t *transaction, *new_transaction = NULL; + int blocks = handle->h_total_credits; + int rsv_blocks = 0; + unsigned long ts = jiffies; + + if (handle->h_rsv_handle) + rsv_blocks = handle->h_rsv_handle->h_total_credits; + + /* + * Limit the number of reserved credits to 1/2 of maximum transaction + * size and limit the number of total credits to not exceed maximum + * transaction size per operation. + */ + if (rsv_blocks > jbd2_max_user_trans_buffers(journal) / 2 || + rsv_blocks + blocks > jbd2_max_user_trans_buffers(journal)) { + printk(KERN_ERR "JBD2: %s wants too many credits " + "credits:%d rsv_credits:%d max:%d\n", + current->comm, blocks, rsv_blocks, + jbd2_max_user_trans_buffers(journal)); + WARN_ON(1); + return -ENOSPC; + } + +alloc_transaction: + /* + * This check is racy but it is just an optimization of allocating new + * transaction early if there are high chances we'll need it. If we + * guess wrong, we'll retry or free unused transaction. + */ + if (!data_race(journal->j_running_transaction)) { + /* + * If __GFP_FS is not present, then we may be being called from + * inside the fs writeback layer, so we MUST NOT fail. + */ + if ((gfp_mask & __GFP_FS) == 0) + gfp_mask |= __GFP_NOFAIL; + new_transaction = kmem_cache_zalloc(transaction_cache, + gfp_mask); + if (!new_transaction) + return -ENOMEM; + } + + jbd2_debug(3, "New handle %p going live.\n", handle); + + /* + * We need to hold j_state_lock until t_updates has been incremented, + * for proper journal barrier handling + */ +repeat: + read_lock(&journal->j_state_lock); + BUG_ON(journal->j_flags & JBD2_UNMOUNT); + if (is_journal_aborted(journal) || + (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) { + read_unlock(&journal->j_state_lock); + jbd2_journal_free_transaction(new_transaction); + return -EROFS; + } + + /* + * Wait on the journal's transaction barrier if necessary. Specifically + * we allow reserved handles to proceed because otherwise commit could + * deadlock on page writeback not being able to complete. + */ + if (!handle->h_reserved && journal->j_barrier_count) { + read_unlock(&journal->j_state_lock); + wait_event(journal->j_wait_transaction_locked, + journal->j_barrier_count == 0); + goto repeat; + } + + if (!journal->j_running_transaction) { + read_unlock(&journal->j_state_lock); + if (!new_transaction) + goto alloc_transaction; + write_lock(&journal->j_state_lock); + if (!journal->j_running_transaction && + (handle->h_reserved || !journal->j_barrier_count)) { + jbd2_get_transaction(journal, new_transaction); + new_transaction = NULL; + } + write_unlock(&journal->j_state_lock); + goto repeat; + } + + transaction = journal->j_running_transaction; + + if (!handle->h_reserved) { + /* We may have dropped j_state_lock - restart in that case */ + if (add_transaction_credits(journal, blocks, rsv_blocks)) { + /* + * add_transaction_credits releases + * j_state_lock on a non-zero return + */ + __release(&journal->j_state_lock); + goto repeat; + } + } else { + /* + * We have handle reserved so we are allowed to join T_LOCKED + * transaction and we don't have to check for transaction size + * and journal space. But we still have to wait while running + * transaction is being switched to a committing one as it + * won't wait for any handles anymore. + */ + if (transaction->t_state == T_SWITCH) { + wait_transaction_switching(journal); + goto repeat; + } + sub_reserved_credits(journal, blocks); + handle->h_reserved = 0; + } + + /* OK, account for the buffers that this operation expects to + * use and add the handle to the running transaction. + */ + update_t_max_wait(transaction, ts); + handle->h_transaction = transaction; + handle->h_requested_credits = blocks; + handle->h_revoke_credits_requested = handle->h_revoke_credits; + handle->h_start_jiffies = jiffies; + atomic_inc(&transaction->t_updates); + atomic_inc(&transaction->t_handle_count); + jbd2_debug(4, "Handle %p given %d credits (total %d, free %lu)\n", + handle, blocks, + atomic_read(&transaction->t_outstanding_credits), + jbd2_log_space_left(journal)); + read_unlock(&journal->j_state_lock); + current->journal_info = handle; + + rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_); + jbd2_journal_free_transaction(new_transaction); + /* + * Ensure that no allocations done while the transaction is open are + * going to recurse back to the fs layer. + */ + handle->saved_alloc_context = memalloc_nofs_save(); + return 0; +} + +/* Allocate a new handle. This should probably be in a slab... */ +static handle_t *new_handle(int nblocks) +{ + handle_t *handle = jbd2_alloc_handle(GFP_NOFS); + if (!handle) + return NULL; + handle->h_total_credits = nblocks; + handle->h_ref = 1; + + return handle; +} + +handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks, + int revoke_records, gfp_t gfp_mask, + unsigned int type, unsigned int line_no) +{ + handle_t *handle = journal_current_handle(); + int err; + + if (!journal) + return ERR_PTR(-EROFS); + + if (handle) { + J_ASSERT(handle->h_transaction->t_journal == journal); + handle->h_ref++; + return handle; + } + + nblocks += DIV_ROUND_UP(revoke_records, + journal->j_revoke_records_per_block); + handle = new_handle(nblocks); + if (!handle) + return ERR_PTR(-ENOMEM); + if (rsv_blocks) { + handle_t *rsv_handle; + + rsv_handle = new_handle(rsv_blocks); + if (!rsv_handle) { + jbd2_free_handle(handle); + return ERR_PTR(-ENOMEM); + } + rsv_handle->h_reserved = 1; + rsv_handle->h_journal = journal; + handle->h_rsv_handle = rsv_handle; + } + handle->h_revoke_credits = revoke_records; + + err = start_this_handle(journal, handle, gfp_mask); + if (err < 0) { + if (handle->h_rsv_handle) + jbd2_free_handle(handle->h_rsv_handle); + jbd2_free_handle(handle); + return ERR_PTR(err); + } + handle->h_type = type; + handle->h_line_no = line_no; + trace_jbd2_handle_start(journal->j_fs_dev->bd_dev, + handle->h_transaction->t_tid, type, + line_no, nblocks); + + return handle; +} +EXPORT_SYMBOL(jbd2__journal_start); + + +/** + * jbd2_journal_start() - Obtain a new handle. + * @journal: Journal to start transaction on. + * @nblocks: number of block buffer we might modify + * + * We make sure that the transaction can guarantee at least nblocks of + * modified buffers in the log. We block until the log can guarantee + * that much space. Additionally, if rsv_blocks > 0, we also create another + * handle with rsv_blocks reserved blocks in the journal. This handle is + * stored in h_rsv_handle. It is not attached to any particular transaction + * and thus doesn't block transaction commit. If the caller uses this reserved + * handle, it has to set h_rsv_handle to NULL as otherwise jbd2_journal_stop() + * on the parent handle will dispose the reserved one. Reserved handle has to + * be converted to a normal handle using jbd2_journal_start_reserved() before + * it can be used. + * + * Return a pointer to a newly allocated handle, or an ERR_PTR() value + * on failure. + */ +handle_t *jbd2_journal_start(journal_t *journal, int nblocks) +{ + return jbd2__journal_start(journal, nblocks, 0, 0, GFP_NOFS, 0, 0); +} +EXPORT_SYMBOL(jbd2_journal_start); + +static void __jbd2_journal_unreserve_handle(handle_t *handle, transaction_t *t) +{ + journal_t *journal = handle->h_journal; + + WARN_ON(!handle->h_reserved); + sub_reserved_credits(journal, handle->h_total_credits); + if (t) + atomic_sub(handle->h_total_credits, &t->t_outstanding_credits); +} + +void jbd2_journal_free_reserved(handle_t *handle) +{ + journal_t *journal = handle->h_journal; + + /* Get j_state_lock to pin running transaction if it exists */ + read_lock(&journal->j_state_lock); + __jbd2_journal_unreserve_handle(handle, journal->j_running_transaction); + read_unlock(&journal->j_state_lock); + jbd2_free_handle(handle); +} +EXPORT_SYMBOL(jbd2_journal_free_reserved); + +/** + * jbd2_journal_start_reserved() - start reserved handle + * @handle: handle to start + * @type: for handle statistics + * @line_no: for handle statistics + * + * Start handle that has been previously reserved with jbd2_journal_reserve(). + * This attaches @handle to the running transaction (or creates one if there's + * not transaction running). Unlike jbd2_journal_start() this function cannot + * block on journal commit, checkpointing, or similar stuff. It can block on + * memory allocation or frozen journal though. + * + * Return 0 on success, non-zero on error - handle is freed in that case. + */ +int jbd2_journal_start_reserved(handle_t *handle, unsigned int type, + unsigned int line_no) +{ + journal_t *journal = handle->h_journal; + int ret = -EIO; + + if (WARN_ON(!handle->h_reserved)) { + /* Someone passed in normal handle? Just stop it. */ + jbd2_journal_stop(handle); + return ret; + } + /* + * Usefulness of mixing of reserved and unreserved handles is + * questionable. So far nobody seems to need it so just error out. + */ + if (WARN_ON(current->journal_info)) { + jbd2_journal_free_reserved(handle); + return ret; + } + + handle->h_journal = NULL; + /* + * GFP_NOFS is here because callers are likely from writeback or + * similarly constrained call sites + */ + ret = start_this_handle(journal, handle, GFP_NOFS); + if (ret < 0) { + handle->h_journal = journal; + jbd2_journal_free_reserved(handle); + return ret; + } + handle->h_type = type; + handle->h_line_no = line_no; + trace_jbd2_handle_start(journal->j_fs_dev->bd_dev, + handle->h_transaction->t_tid, type, + line_no, handle->h_total_credits); + return 0; +} +EXPORT_SYMBOL(jbd2_journal_start_reserved); + +/** + * jbd2_journal_extend() - extend buffer credits. + * @handle: handle to 'extend' + * @nblocks: nr blocks to try to extend by. + * @revoke_records: number of revoke records to try to extend by. + * + * Some transactions, such as large extends and truncates, can be done + * atomically all at once or in several stages. The operation requests + * a credit for a number of buffer modifications in advance, but can + * extend its credit if it needs more. + * + * jbd2_journal_extend tries to give the running handle more buffer credits. + * It does not guarantee that allocation - this is a best-effort only. + * The calling process MUST be able to deal cleanly with a failure to + * extend here. + * + * Return 0 on success, non-zero on failure. + * + * return code < 0 implies an error + * return code > 0 implies normal transaction-full status. + */ +int jbd2_journal_extend(handle_t *handle, int nblocks, int revoke_records) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + int result; + int wanted; + + if (is_handle_aborted(handle)) + return -EROFS; + journal = transaction->t_journal; + + result = 1; + + read_lock(&journal->j_state_lock); + + /* Don't extend a locked-down transaction! */ + if (transaction->t_state != T_RUNNING) { + jbd2_debug(3, "denied handle %p %d blocks: " + "transaction not running\n", handle, nblocks); + goto error_out; + } + + nblocks += DIV_ROUND_UP( + handle->h_revoke_credits_requested + revoke_records, + journal->j_revoke_records_per_block) - + DIV_ROUND_UP( + handle->h_revoke_credits_requested, + journal->j_revoke_records_per_block); + wanted = atomic_add_return(nblocks, + &transaction->t_outstanding_credits); + + if (wanted > journal->j_max_transaction_buffers) { + jbd2_debug(3, "denied handle %p %d blocks: " + "transaction too large\n", handle, nblocks); + atomic_sub(nblocks, &transaction->t_outstanding_credits); + goto error_out; + } + + trace_jbd2_handle_extend(journal->j_fs_dev->bd_dev, + transaction->t_tid, + handle->h_type, handle->h_line_no, + handle->h_total_credits, + nblocks); + + handle->h_total_credits += nblocks; + handle->h_requested_credits += nblocks; + handle->h_revoke_credits += revoke_records; + handle->h_revoke_credits_requested += revoke_records; + result = 0; + + jbd2_debug(3, "extended handle %p by %d\n", handle, nblocks); +error_out: + read_unlock(&journal->j_state_lock); + return result; +} + +static void stop_this_handle(handle_t *handle) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal = transaction->t_journal; + int revokes; + + J_ASSERT(journal_current_handle() == handle); + J_ASSERT(atomic_read(&transaction->t_updates) > 0); + current->journal_info = NULL; + /* + * Subtract necessary revoke descriptor blocks from handle credits. We + * take care to account only for revoke descriptor blocks the + * transaction will really need as large sequences of transactions with + * small numbers of revokes are relatively common. + */ + revokes = handle->h_revoke_credits_requested - handle->h_revoke_credits; + if (revokes) { + int t_revokes, revoke_descriptors; + int rr_per_blk = journal->j_revoke_records_per_block; + + WARN_ON_ONCE(DIV_ROUND_UP(revokes, rr_per_blk) + > handle->h_total_credits); + t_revokes = atomic_add_return(revokes, + &transaction->t_outstanding_revokes); + revoke_descriptors = + DIV_ROUND_UP(t_revokes, rr_per_blk) - + DIV_ROUND_UP(t_revokes - revokes, rr_per_blk); + handle->h_total_credits -= revoke_descriptors; + } + atomic_sub(handle->h_total_credits, + &transaction->t_outstanding_credits); + if (handle->h_rsv_handle) + __jbd2_journal_unreserve_handle(handle->h_rsv_handle, + transaction); + if (atomic_dec_and_test(&transaction->t_updates)) + wake_up(&journal->j_wait_updates); + + rwsem_release(&journal->j_trans_commit_map, _THIS_IP_); + /* + * Scope of the GFP_NOFS context is over here and so we can restore the + * original alloc context. + */ + memalloc_nofs_restore(handle->saved_alloc_context); +} + +/** + * jbd2__journal_restart() - restart a handle . + * @handle: handle to restart + * @nblocks: nr credits requested + * @revoke_records: number of revoke record credits requested + * @gfp_mask: memory allocation flags (for start_this_handle) + * + * Restart a handle for a multi-transaction filesystem + * operation. + * + * If the jbd2_journal_extend() call above fails to grant new buffer credits + * to a running handle, a call to jbd2_journal_restart will commit the + * handle's transaction so far and reattach the handle to a new + * transaction capable of guaranteeing the requested number of + * credits. We preserve reserved handle if there's any attached to the + * passed in handle. + */ +int jbd2__journal_restart(handle_t *handle, int nblocks, int revoke_records, + gfp_t gfp_mask) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + tid_t tid; + int need_to_start; + int ret; + + /* If we've had an abort of any type, don't even think about + * actually doing the restart! */ + if (is_handle_aborted(handle)) + return 0; + journal = transaction->t_journal; + tid = transaction->t_tid; + + /* + * First unlink the handle from its current transaction, and start the + * commit on that. + */ + jbd2_debug(2, "restarting handle %p\n", handle); + stop_this_handle(handle); + handle->h_transaction = NULL; + + /* + * TODO: If we use READ_ONCE / WRITE_ONCE for j_commit_request we can + * get rid of pointless j_state_lock traffic like this. + */ + read_lock(&journal->j_state_lock); + need_to_start = !tid_geq(journal->j_commit_request, tid); + read_unlock(&journal->j_state_lock); + if (need_to_start) + jbd2_log_start_commit(journal, tid); + handle->h_total_credits = nblocks + + DIV_ROUND_UP(revoke_records, + journal->j_revoke_records_per_block); + handle->h_revoke_credits = revoke_records; + ret = start_this_handle(journal, handle, gfp_mask); + trace_jbd2_handle_restart(journal->j_fs_dev->bd_dev, + ret ? 0 : handle->h_transaction->t_tid, + handle->h_type, handle->h_line_no, + handle->h_total_credits); + return ret; +} +EXPORT_SYMBOL(jbd2__journal_restart); + + +int jbd2_journal_restart(handle_t *handle, int nblocks) +{ + return jbd2__journal_restart(handle, nblocks, 0, GFP_NOFS); +} +EXPORT_SYMBOL(jbd2_journal_restart); + +/* + * Waits for any outstanding t_updates to finish. + * This is called with write j_state_lock held. + */ +void jbd2_journal_wait_updates(journal_t *journal) +{ + DEFINE_WAIT(wait); + + while (1) { + /* + * Note that the running transaction can get freed under us if + * this transaction is getting committed in + * jbd2_journal_commit_transaction() -> + * jbd2_journal_free_transaction(). This can only happen when we + * release j_state_lock -> schedule() -> acquire j_state_lock. + * Hence we should everytime retrieve new j_running_transaction + * value (after j_state_lock release acquire cycle), else it may + * lead to use-after-free of old freed transaction. + */ + transaction_t *transaction = journal->j_running_transaction; + + if (!transaction) + break; + + prepare_to_wait(&journal->j_wait_updates, &wait, + TASK_UNINTERRUPTIBLE); + if (!atomic_read(&transaction->t_updates)) { + finish_wait(&journal->j_wait_updates, &wait); + break; + } + write_unlock(&journal->j_state_lock); + schedule(); + finish_wait(&journal->j_wait_updates, &wait); + write_lock(&journal->j_state_lock); + } +} + +/** + * jbd2_journal_lock_updates () - establish a transaction barrier. + * @journal: Journal to establish a barrier on. + * + * This locks out any further updates from being started, and blocks + * until all existing updates have completed, returning only once the + * journal is in a quiescent state with no updates running. + * + * The journal lock should not be held on entry. + */ +void jbd2_journal_lock_updates(journal_t *journal) +{ + jbd2_might_wait_for_commit(journal); + + write_lock(&journal->j_state_lock); + ++journal->j_barrier_count; + + /* Wait until there are no reserved handles */ + if (atomic_read(&journal->j_reserved_credits)) { + write_unlock(&journal->j_state_lock); + wait_event(journal->j_wait_reserved, + atomic_read(&journal->j_reserved_credits) == 0); + write_lock(&journal->j_state_lock); + } + + /* Wait until there are no running t_updates */ + jbd2_journal_wait_updates(journal); + + write_unlock(&journal->j_state_lock); + + /* + * We have now established a barrier against other normal updates, but + * we also need to barrier against other jbd2_journal_lock_updates() calls + * to make sure that we serialise special journal-locked operations + * too. + */ + mutex_lock(&journal->j_barrier); +} + +/** + * jbd2_journal_unlock_updates () - release barrier + * @journal: Journal to release the barrier on. + * + * Release a transaction barrier obtained with jbd2_journal_lock_updates(). + * + * Should be called without the journal lock held. + */ +void jbd2_journal_unlock_updates (journal_t *journal) +{ + J_ASSERT(journal->j_barrier_count != 0); + + mutex_unlock(&journal->j_barrier); + write_lock(&journal->j_state_lock); + --journal->j_barrier_count; + write_unlock(&journal->j_state_lock); + wake_up_all(&journal->j_wait_transaction_locked); +} + +static void warn_dirty_buffer(struct buffer_head *bh) +{ + printk(KERN_WARNING + "JBD2: Spotted dirty metadata buffer (dev = %pg, blocknr = %llu). " + "There's a risk of filesystem corruption in case of system " + "crash.\n", + bh->b_bdev, (unsigned long long)bh->b_blocknr); +} + +/* Call t_frozen trigger and copy buffer data into jh->b_frozen_data. */ +static void jbd2_freeze_jh_data(struct journal_head *jh) +{ + char *source; + struct buffer_head *bh = jh2bh(jh); + + J_EXPECT_JH(jh, buffer_uptodate(bh), "Possible IO failure.\n"); + source = kmap_local_folio(bh->b_folio, bh_offset(bh)); + /* Fire data frozen trigger just before we copy the data */ + jbd2_buffer_frozen_trigger(jh, source, jh->b_triggers); + memcpy(jh->b_frozen_data, source, bh->b_size); + kunmap_local(source); + + /* + * Now that the frozen data is saved off, we need to store any matching + * triggers. + */ + jh->b_frozen_triggers = jh->b_triggers; +} + +/* + * If the buffer is already part of the current transaction, then there + * is nothing we need to do. If it is already part of a prior + * transaction which we are still committing to disk, then we need to + * make sure that we do not overwrite the old copy: we do copy-out to + * preserve the copy going to disk. We also account the buffer against + * the handle's metadata buffer credits (unless the buffer is already + * part of the transaction, that is). + * + */ +static int +do_get_write_access(handle_t *handle, struct journal_head *jh, + int force_copy) +{ + struct buffer_head *bh; + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + int error; + char *frozen_buffer = NULL; + unsigned long start_lock, time_lock; + + journal = transaction->t_journal; + + jbd2_debug(5, "journal_head %p, force_copy %d\n", jh, force_copy); + + JBUFFER_TRACE(jh, "entry"); +repeat: + bh = jh2bh(jh); + + /* @@@ Need to check for errors here at some point. */ + + start_lock = jiffies; + lock_buffer(bh); + spin_lock(&jh->b_state_lock); + + /* If it takes too long to lock the buffer, trace it */ + time_lock = jbd2_time_diff(start_lock, jiffies); + if (time_lock > HZ/10) + trace_jbd2_lock_buffer_stall(bh->b_bdev->bd_dev, + jiffies_to_msecs(time_lock)); + + /* We now hold the buffer lock so it is safe to query the buffer + * state. Is the buffer dirty? + * + * If so, there are two possibilities. The buffer may be + * non-journaled, and undergoing a quite legitimate writeback. + * Otherwise, it is journaled, and we don't expect dirty buffers + * in that state (the buffers should be marked JBD_Dirty + * instead.) So either the IO is being done under our own + * control and this is a bug, or it's a third party IO such as + * dump(8) (which may leave the buffer scheduled for read --- + * ie. locked but not dirty) or tune2fs (which may actually have + * the buffer dirtied, ugh.) */ + + if (buffer_dirty(bh) && jh->b_transaction) { + warn_dirty_buffer(bh); + /* + * We need to clean the dirty flag and we must do it under the + * buffer lock to be sure we don't race with running write-out. + */ + JBUFFER_TRACE(jh, "Journalling dirty buffer"); + clear_buffer_dirty(bh); + /* + * The buffer is going to be added to BJ_Reserved list now and + * nothing guarantees jbd2_journal_dirty_metadata() will be + * ever called for it. So we need to set jbddirty bit here to + * make sure the buffer is dirtied and written out when the + * journaling machinery is done with it. + */ + set_buffer_jbddirty(bh); + } + + error = -EROFS; + if (is_handle_aborted(handle)) { + spin_unlock(&jh->b_state_lock); + unlock_buffer(bh); + goto out; + } + error = 0; + + /* + * The buffer is already part of this transaction if b_transaction or + * b_next_transaction points to it + */ + if (jh->b_transaction == transaction || + jh->b_next_transaction == transaction) { + unlock_buffer(bh); + goto done; + } + + /* + * this is the first time this transaction is touching this buffer, + * reset the modified flag + */ + jh->b_modified = 0; + + /* + * If the buffer is not journaled right now, we need to make sure it + * doesn't get written to disk before the caller actually commits the + * new data + */ + if (!jh->b_transaction) { + JBUFFER_TRACE(jh, "no transaction"); + J_ASSERT_JH(jh, !jh->b_next_transaction); + JBUFFER_TRACE(jh, "file as BJ_Reserved"); + /* + * Make sure all stores to jh (b_modified, b_frozen_data) are + * visible before attaching it to the running transaction. + * Paired with barrier in jbd2_write_access_granted() + */ + smp_wmb(); + spin_lock(&journal->j_list_lock); + if (test_clear_buffer_dirty(bh)) { + /* + * Execute buffer dirty clearing and jh->b_transaction + * assignment under journal->j_list_lock locked to + * prevent bh being removed from checkpoint list if + * the buffer is in an intermediate state (not dirty + * and jh->b_transaction is NULL). + */ + JBUFFER_TRACE(jh, "Journalling dirty buffer"); + set_buffer_jbddirty(bh); + } + __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved); + spin_unlock(&journal->j_list_lock); + unlock_buffer(bh); + goto done; + } + unlock_buffer(bh); + + /* + * If there is already a copy-out version of this buffer, then we don't + * need to make another one + */ + if (jh->b_frozen_data) { + JBUFFER_TRACE(jh, "has frozen data"); + J_ASSERT_JH(jh, jh->b_next_transaction == NULL); + goto attach_next; + } + + JBUFFER_TRACE(jh, "owned by older transaction"); + J_ASSERT_JH(jh, jh->b_next_transaction == NULL); + J_ASSERT_JH(jh, jh->b_transaction == journal->j_committing_transaction); + + /* + * There is one case we have to be very careful about. If the + * committing transaction is currently writing this buffer out to disk + * and has NOT made a copy-out, then we cannot modify the buffer + * contents at all right now. The essence of copy-out is that it is + * the extra copy, not the primary copy, which gets journaled. If the + * primary copy is already going to disk then we cannot do copy-out + * here. + */ + if (buffer_shadow(bh)) { + JBUFFER_TRACE(jh, "on shadow: sleep"); + spin_unlock(&jh->b_state_lock); + wait_on_bit_io(&bh->b_state, BH_Shadow, TASK_UNINTERRUPTIBLE); + goto repeat; + } + + /* + * Only do the copy if the currently-owning transaction still needs it. + * If buffer isn't on BJ_Metadata list, the committing transaction is + * past that stage (here we use the fact that BH_Shadow is set under + * bh_state lock together with refiling to BJ_Shadow list and at this + * point we know the buffer doesn't have BH_Shadow set). + * + * Subtle point, though: if this is a get_undo_access, then we will be + * relying on the frozen_data to contain the new value of the + * committed_data record after the transaction, so we HAVE to force the + * frozen_data copy in that case. + */ + if (jh->b_jlist == BJ_Metadata || force_copy) { + JBUFFER_TRACE(jh, "generate frozen data"); + if (!frozen_buffer) { + JBUFFER_TRACE(jh, "allocate memory for buffer"); + spin_unlock(&jh->b_state_lock); + frozen_buffer = jbd2_alloc(jh2bh(jh)->b_size, + GFP_NOFS | __GFP_NOFAIL); + goto repeat; + } + jh->b_frozen_data = frozen_buffer; + frozen_buffer = NULL; + jbd2_freeze_jh_data(jh); + } +attach_next: + /* + * Make sure all stores to jh (b_modified, b_frozen_data) are visible + * before attaching it to the running transaction. Paired with barrier + * in jbd2_write_access_granted() + */ + smp_wmb(); + jh->b_next_transaction = transaction; + +done: + spin_unlock(&jh->b_state_lock); + + /* + * If we are about to journal a buffer, then any revoke pending on it is + * no longer valid + */ + jbd2_journal_cancel_revoke(handle, jh); + +out: + if (unlikely(frozen_buffer)) /* It's usually NULL */ + jbd2_free(frozen_buffer, bh->b_size); + + JBUFFER_TRACE(jh, "exit"); + return error; +} + +/* Fast check whether buffer is already attached to the required transaction */ +static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh, + bool undo) +{ + struct journal_head *jh; + bool ret = false; + + /* Dirty buffers require special handling... */ + if (buffer_dirty(bh)) + return false; + + /* + * RCU protects us from dereferencing freed pages. So the checks we do + * are guaranteed not to oops. However the jh slab object can get freed + * & reallocated while we work with it. So we have to be careful. When + * we see jh attached to the running transaction, we know it must stay + * so until the transaction is committed. Thus jh won't be freed and + * will be attached to the same bh while we run. However it can + * happen jh gets freed, reallocated, and attached to the transaction + * just after we get pointer to it from bh. So we have to be careful + * and recheck jh still belongs to our bh before we return success. + */ + rcu_read_lock(); + if (!buffer_jbd(bh)) + goto out; + /* This should be bh2jh() but that doesn't work with inline functions */ + jh = READ_ONCE(bh->b_private); + if (!jh) + goto out; + /* For undo access buffer must have data copied */ + if (undo && !jh->b_committed_data) + goto out; + if (READ_ONCE(jh->b_transaction) != handle->h_transaction && + READ_ONCE(jh->b_next_transaction) != handle->h_transaction) + goto out; + /* + * There are two reasons for the barrier here: + * 1) Make sure to fetch b_bh after we did previous checks so that we + * detect when jh went through free, realloc, attach to transaction + * while we were checking. Paired with implicit barrier in that path. + * 2) So that access to bh done after jbd2_write_access_granted() + * doesn't get reordered and see inconsistent state of concurrent + * do_get_write_access(). + */ + smp_mb(); + if (unlikely(jh->b_bh != bh)) + goto out; + ret = true; +out: + rcu_read_unlock(); + return ret; +} + +/** + * jbd2_journal_get_write_access() - notify intent to modify a buffer + * for metadata (not data) update. + * @handle: transaction to add buffer modifications to + * @bh: bh to be used for metadata writes + * + * Returns: error code or 0 on success. + * + * In full data journalling mode the buffer may be of type BJ_AsyncData, + * because we're ``write()ing`` a buffer which is also part of a shared mapping. + */ + +int jbd2_journal_get_write_access(handle_t *handle, struct buffer_head *bh) +{ + struct journal_head *jh; + journal_t *journal; + int rc; + + if (is_handle_aborted(handle)) + return -EROFS; + + journal = handle->h_transaction->t_journal; + if (jbd2_check_fs_dev_write_error(journal)) { + /* + * If the fs dev has writeback errors, it may have failed + * to async write out metadata buffers in the background. + * In this case, we could read old data from disk and write + * it out again, which may lead to on-disk filesystem + * inconsistency. Aborting journal can avoid it happen. + */ + jbd2_journal_abort(journal, -EIO); + return -EIO; + } + + if (jbd2_write_access_granted(handle, bh, false)) + return 0; + + jh = jbd2_journal_add_journal_head(bh); + /* We do not want to get caught playing with fields which the + * log thread also manipulates. Make sure that the buffer + * completes any outstanding IO before proceeding. */ + rc = do_get_write_access(handle, jh, 0); + jbd2_journal_put_journal_head(jh); + return rc; +} + + +/* + * When the user wants to journal a newly created buffer_head + * (ie. getblk() returned a new buffer and we are going to populate it + * manually rather than reading off disk), then we need to keep the + * buffer_head locked until it has been completely filled with new + * data. In this case, we should be able to make the assertion that + * the bh is not already part of an existing transaction. + * + * The buffer should already be locked by the caller by this point. + * There is no lock ranking violation: it was a newly created, + * unlocked buffer beforehand. */ + +/** + * jbd2_journal_get_create_access () - notify intent to use newly created bh + * @handle: transaction to new buffer to + * @bh: new buffer. + * + * Call this if you create a new bh. + */ +int jbd2_journal_get_create_access(handle_t *handle, struct buffer_head *bh) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + struct journal_head *jh = jbd2_journal_add_journal_head(bh); + int err; + + jbd2_debug(5, "journal_head %p\n", jh); + err = -EROFS; + if (is_handle_aborted(handle)) + goto out; + journal = transaction->t_journal; + err = 0; + + JBUFFER_TRACE(jh, "entry"); + /* + * The buffer may already belong to this transaction due to pre-zeroing + * in the filesystem's new_block code. It may also be on the previous, + * committing transaction's lists, but it HAS to be in Forget state in + * that case: the transaction must have deleted the buffer for it to be + * reused here. + */ + spin_lock(&jh->b_state_lock); + J_ASSERT_JH(jh, (jh->b_transaction == transaction || + jh->b_transaction == NULL || + (jh->b_transaction == journal->j_committing_transaction && + jh->b_jlist == BJ_Forget))); + + J_ASSERT_JH(jh, jh->b_next_transaction == NULL); + J_ASSERT_JH(jh, buffer_locked(jh2bh(jh))); + + if (jh->b_transaction == NULL) { + /* + * Previous jbd2_journal_forget() could have left the buffer + * with jbddirty bit set because it was being committed. When + * the commit finished, we've filed the buffer for + * checkpointing and marked it dirty. Now we are reallocating + * the buffer so the transaction freeing it must have + * committed and so it's safe to clear the dirty bit. + */ + clear_buffer_dirty(jh2bh(jh)); + /* first access by this transaction */ + jh->b_modified = 0; + + JBUFFER_TRACE(jh, "file as BJ_Reserved"); + spin_lock(&journal->j_list_lock); + __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved); + spin_unlock(&journal->j_list_lock); + } else if (jh->b_transaction == journal->j_committing_transaction) { + /* first access by this transaction */ + jh->b_modified = 0; + + JBUFFER_TRACE(jh, "set next transaction"); + spin_lock(&journal->j_list_lock); + jh->b_next_transaction = transaction; + spin_unlock(&journal->j_list_lock); + } + spin_unlock(&jh->b_state_lock); + + /* + * akpm: I added this. ext3_alloc_branch can pick up new indirect + * blocks which contain freed but then revoked metadata. We need + * to cancel the revoke in case we end up freeing it yet again + * and the reallocating as data - this would cause a second revoke, + * which hits an assertion error. + */ + JBUFFER_TRACE(jh, "cancelling revoke"); + jbd2_journal_cancel_revoke(handle, jh); +out: + jbd2_journal_put_journal_head(jh); + return err; +} + +/** + * jbd2_journal_get_undo_access() - Notify intent to modify metadata with + * non-rewindable consequences + * @handle: transaction + * @bh: buffer to undo + * + * Sometimes there is a need to distinguish between metadata which has + * been committed to disk and that which has not. The ext3fs code uses + * this for freeing and allocating space, we have to make sure that we + * do not reuse freed space until the deallocation has been committed, + * since if we overwrote that space we would make the delete + * un-rewindable in case of a crash. + * + * To deal with that, jbd2_journal_get_undo_access requests write access to a + * buffer for parts of non-rewindable operations such as delete + * operations on the bitmaps. The journaling code must keep a copy of + * the buffer's contents prior to the undo_access call until such time + * as we know that the buffer has definitely been committed to disk. + * + * We never need to know which transaction the committed data is part + * of, buffers touched here are guaranteed to be dirtied later and so + * will be committed to a new transaction in due course, at which point + * we can discard the old committed data pointer. + * + * Returns error number or 0 on success. + */ +int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh) +{ + int err; + struct journal_head *jh; + char *committed_data = NULL; + + if (is_handle_aborted(handle)) + return -EROFS; + + if (jbd2_write_access_granted(handle, bh, true)) + return 0; + + jh = jbd2_journal_add_journal_head(bh); + JBUFFER_TRACE(jh, "entry"); + + /* + * Do this first --- it can drop the journal lock, so we want to + * make sure that obtaining the committed_data is done + * atomically wrt. completion of any outstanding commits. + */ + err = do_get_write_access(handle, jh, 1); + if (err) + goto out; + +repeat: + if (!jh->b_committed_data) + committed_data = jbd2_alloc(jh2bh(jh)->b_size, + GFP_NOFS|__GFP_NOFAIL); + + spin_lock(&jh->b_state_lock); + if (!jh->b_committed_data) { + /* Copy out the current buffer contents into the + * preserved, committed copy. */ + JBUFFER_TRACE(jh, "generate b_committed data"); + if (!committed_data) { + spin_unlock(&jh->b_state_lock); + goto repeat; + } + + jh->b_committed_data = committed_data; + committed_data = NULL; + memcpy(jh->b_committed_data, bh->b_data, bh->b_size); + } + spin_unlock(&jh->b_state_lock); +out: + jbd2_journal_put_journal_head(jh); + if (unlikely(committed_data)) + jbd2_free(committed_data, bh->b_size); + return err; +} + +/** + * jbd2_journal_set_triggers() - Add triggers for commit writeout + * @bh: buffer to trigger on + * @type: struct jbd2_buffer_trigger_type containing the trigger(s). + * + * Set any triggers on this journal_head. This is always safe, because + * triggers for a committing buffer will be saved off, and triggers for + * a running transaction will match the buffer in that transaction. + * + * Call with NULL to clear the triggers. + */ +void jbd2_journal_set_triggers(struct buffer_head *bh, + struct jbd2_buffer_trigger_type *type) +{ + struct journal_head *jh = jbd2_journal_grab_journal_head(bh); + + if (WARN_ON_ONCE(!jh)) + return; + jh->b_triggers = type; + jbd2_journal_put_journal_head(jh); +} + +void jbd2_buffer_frozen_trigger(struct journal_head *jh, void *mapped_data, + struct jbd2_buffer_trigger_type *triggers) +{ + struct buffer_head *bh = jh2bh(jh); + + if (!triggers || !triggers->t_frozen) + return; + + triggers->t_frozen(triggers, bh, mapped_data, bh->b_size); +} + +void jbd2_buffer_abort_trigger(struct journal_head *jh, + struct jbd2_buffer_trigger_type *triggers) +{ + if (!triggers || !triggers->t_abort) + return; + + triggers->t_abort(triggers, jh2bh(jh)); +} + +/** + * jbd2_journal_dirty_metadata() - mark a buffer as containing dirty metadata + * @handle: transaction to add buffer to. + * @bh: buffer to mark + * + * mark dirty metadata which needs to be journaled as part of the current + * transaction. + * + * The buffer must have previously had jbd2_journal_get_write_access() + * called so that it has a valid journal_head attached to the buffer + * head. + * + * The buffer is placed on the transaction's metadata list and is marked + * as belonging to the transaction. + * + * Returns error number or 0 on success. + * + * Special care needs to be taken if the buffer already belongs to the + * current committing transaction (in which case we should have frozen + * data present for that commit). In that case, we don't relink the + * buffer: that only gets done when the old transaction finally + * completes its commit. + */ +int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + struct journal_head *jh; + int ret = 0; + + if (!buffer_jbd(bh)) + return -EUCLEAN; + + /* + * We don't grab jh reference here since the buffer must be part + * of the running transaction. + */ + jh = bh2jh(bh); + jbd2_debug(5, "journal_head %p\n", jh); + JBUFFER_TRACE(jh, "entry"); + + /* + * This and the following assertions are unreliable since we may see jh + * in inconsistent state unless we grab bh_state lock. But this is + * crucial to catch bugs so let's do a reliable check until the + * lockless handling is fully proven. + */ + if (data_race(jh->b_transaction != transaction && + jh->b_next_transaction != transaction)) { + spin_lock(&jh->b_state_lock); + J_ASSERT_JH(jh, jh->b_transaction == transaction || + jh->b_next_transaction == transaction); + spin_unlock(&jh->b_state_lock); + } + if (data_race(jh->b_modified == 1)) { + /* If it's in our transaction it must be in BJ_Metadata list. */ + if (data_race(jh->b_transaction == transaction && + jh->b_jlist != BJ_Metadata)) { + spin_lock(&jh->b_state_lock); + if (jh->b_transaction == transaction && + jh->b_jlist != BJ_Metadata) + pr_err("JBD2: assertion failure: h_type=%u " + "h_line_no=%u block_no=%llu jlist=%u\n", + handle->h_type, handle->h_line_no, + (unsigned long long) bh->b_blocknr, + jh->b_jlist); + J_ASSERT_JH(jh, jh->b_transaction != transaction || + jh->b_jlist == BJ_Metadata); + spin_unlock(&jh->b_state_lock); + } + goto out; + } + + spin_lock(&jh->b_state_lock); + + if (is_handle_aborted(handle)) { + /* + * Check journal aborting with @jh->b_state_lock locked, + * since 'jh->b_transaction' could be replaced with + * 'jh->b_next_transaction' during old transaction + * committing if journal aborted, which may fail + * assertion on 'jh->b_frozen_data == NULL'. + */ + ret = -EROFS; + goto out_unlock_bh; + } + + journal = transaction->t_journal; + + if (jh->b_modified == 0) { + /* + * This buffer's got modified and becoming part + * of the transaction. This needs to be done + * once a transaction -bzzz + */ + if (WARN_ON_ONCE(jbd2_handle_buffer_credits(handle) <= 0)) { + ret = -ENOSPC; + goto out_unlock_bh; + } + jh->b_modified = 1; + handle->h_total_credits--; + } + + /* + * fastpath, to avoid expensive locking. If this buffer is already + * on the running transaction's metadata list there is nothing to do. + * Nobody can take it off again because there is a handle open. + * I _think_ we're OK here with SMP barriers - a mistaken decision will + * result in this test being false, so we go in and take the locks. + */ + if (jh->b_transaction == transaction && jh->b_jlist == BJ_Metadata) { + JBUFFER_TRACE(jh, "fastpath"); + if (unlikely(jh->b_transaction != + journal->j_running_transaction)) { + printk(KERN_ERR "JBD2: %s: " + "jh->b_transaction (%llu, %p, %u) != " + "journal->j_running_transaction (%p, %u)\n", + journal->j_devname, + (unsigned long long) bh->b_blocknr, + jh->b_transaction, + jh->b_transaction ? jh->b_transaction->t_tid : 0, + journal->j_running_transaction, + journal->j_running_transaction ? + journal->j_running_transaction->t_tid : 0); + ret = -EINVAL; + } + goto out_unlock_bh; + } + + set_buffer_jbddirty(bh); + + /* + * Metadata already on the current transaction list doesn't + * need to be filed. Metadata on another transaction's list must + * be committing, and will be refiled once the commit completes: + * leave it alone for now. + */ + if (jh->b_transaction != transaction) { + JBUFFER_TRACE(jh, "already on other transaction"); + if (unlikely(((jh->b_transaction != + journal->j_committing_transaction)) || + (jh->b_next_transaction != transaction))) { + printk(KERN_ERR "jbd2_journal_dirty_metadata: %s: " + "bad jh for block %llu: " + "transaction (%p, %u), " + "jh->b_transaction (%p, %u), " + "jh->b_next_transaction (%p, %u), jlist %u\n", + journal->j_devname, + (unsigned long long) bh->b_blocknr, + transaction, transaction->t_tid, + jh->b_transaction, + jh->b_transaction ? + jh->b_transaction->t_tid : 0, + jh->b_next_transaction, + jh->b_next_transaction ? + jh->b_next_transaction->t_tid : 0, + jh->b_jlist); + WARN_ON(1); + ret = -EINVAL; + } + /* And this case is illegal: we can't reuse another + * transaction's data buffer, ever. */ + goto out_unlock_bh; + } + + /* That test should have eliminated the following case: */ + J_ASSERT_JH(jh, jh->b_frozen_data == NULL); + + JBUFFER_TRACE(jh, "file as BJ_Metadata"); + spin_lock(&journal->j_list_lock); + __jbd2_journal_file_buffer(jh, transaction, BJ_Metadata); + spin_unlock(&journal->j_list_lock); +out_unlock_bh: + spin_unlock(&jh->b_state_lock); +out: + JBUFFER_TRACE(jh, "exit"); + return ret; +} + +/** + * jbd2_journal_forget() - bforget() for potentially-journaled buffers. + * @handle: transaction handle + * @bh: bh to 'forget' + * + * We can only do the bforget if there are no commits pending against the + * buffer. If the buffer is dirty in the current running transaction we + * can safely unlink it. + * + * bh may not be a journalled buffer at all - it may be a non-JBD + * buffer which came off the hashtable. Check for this. + * + * Decrements bh->b_count by one. + * + * Allow this call even if the handle has aborted --- it may be part of + * the caller's cleanup after an abort. + */ +int jbd2_journal_forget(handle_t *handle, struct buffer_head *bh) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + struct journal_head *jh; + int drop_reserve = 0; + int err = 0; + int was_modified = 0; + int wait_for_writeback = 0; + + if (is_handle_aborted(handle)) + return -EROFS; + journal = transaction->t_journal; + + BUFFER_TRACE(bh, "entry"); + + jh = jbd2_journal_grab_journal_head(bh); + if (!jh) { + __bforget(bh); + return 0; + } + + spin_lock(&jh->b_state_lock); + + /* Critical error: attempting to delete a bitmap buffer, maybe? + * Don't do any jbd operations, and return an error. */ + if (!J_EXPECT_JH(jh, !jh->b_committed_data, + "inconsistent data on disk")) { + err = -EIO; + goto drop; + } + + /* keep track of whether or not this transaction modified us */ + was_modified = jh->b_modified; + + /* + * The buffer's going from the transaction, we must drop + * all references -bzzz + */ + jh->b_modified = 0; + + if (jh->b_transaction == transaction) { + J_ASSERT_JH(jh, !jh->b_frozen_data); + + /* If we are forgetting a buffer which is already part + * of this transaction, then we can just drop it from + * the transaction immediately. */ + clear_buffer_dirty(bh); + clear_buffer_jbddirty(bh); + + JBUFFER_TRACE(jh, "belongs to current transaction: unfile"); + + /* + * we only want to drop a reference if this transaction + * modified the buffer + */ + if (was_modified) + drop_reserve = 1; + + /* + * We are no longer going to journal this buffer. + * However, the commit of this transaction is still + * important to the buffer: the delete that we are now + * processing might obsolete an old log entry, so by + * committing, we can satisfy the buffer's checkpoint. + * + * So, if we have a checkpoint on the buffer, we should + * now refile the buffer on our BJ_Forget list so that + * we know to remove the checkpoint after we commit. + */ + + spin_lock(&journal->j_list_lock); + if (jh->b_cp_transaction) { + __jbd2_journal_temp_unlink_buffer(jh); + __jbd2_journal_file_buffer(jh, transaction, BJ_Forget); + } else { + __jbd2_journal_unfile_buffer(jh); + jbd2_journal_put_journal_head(jh); + } + spin_unlock(&journal->j_list_lock); + } else if (jh->b_transaction) { + J_ASSERT_JH(jh, (jh->b_transaction == + journal->j_committing_transaction)); + /* However, if the buffer is still owned by a prior + * (committing) transaction, we can't drop it yet... */ + JBUFFER_TRACE(jh, "belongs to older transaction"); + /* ... but we CAN drop it from the new transaction through + * marking the buffer as freed and set j_next_transaction to + * the new transaction, so that not only the commit code + * knows it should clear dirty bits when it is done with the + * buffer, but also the buffer can be checkpointed only + * after the new transaction commits. */ + + set_buffer_freed(bh); + + if (!jh->b_next_transaction) { + spin_lock(&journal->j_list_lock); + jh->b_next_transaction = transaction; + spin_unlock(&journal->j_list_lock); + } else { + J_ASSERT(jh->b_next_transaction == transaction); + + /* + * only drop a reference if this transaction modified + * the buffer + */ + if (was_modified) + drop_reserve = 1; + } + } else { + /* + * Finally, if the buffer is not belongs to any + * transaction, we can just drop it now if it has no + * checkpoint. + */ + spin_lock(&journal->j_list_lock); + if (!jh->b_cp_transaction) { + JBUFFER_TRACE(jh, "belongs to none transaction"); + spin_unlock(&journal->j_list_lock); + goto drop; + } + + /* + * Otherwise, if the buffer has been written to disk, + * it is safe to remove the checkpoint and drop it. + */ + if (jbd2_journal_try_remove_checkpoint(jh) >= 0) { + spin_unlock(&journal->j_list_lock); + goto drop; + } + + /* + * The buffer has not yet been written to disk. We should + * either clear the buffer or ensure that the ongoing I/O + * is completed, and attach this buffer to current + * transaction so that the buffer can be checkpointed only + * after the current transaction commits. + */ + clear_buffer_dirty(bh); + wait_for_writeback = 1; + __jbd2_journal_file_buffer(jh, transaction, BJ_Forget); + spin_unlock(&journal->j_list_lock); + } +drop: + __brelse(bh); + spin_unlock(&jh->b_state_lock); + if (wait_for_writeback) + wait_on_buffer(bh); + jbd2_journal_put_journal_head(jh); + if (drop_reserve) { + /* no need to reserve log space for this block -bzzz */ + handle->h_total_credits++; + } + return err; +} + +/** + * jbd2_journal_stop() - complete a transaction + * @handle: transaction to complete. + * + * All done for a particular handle. + * + * There is not much action needed here. We just return any remaining + * buffer credits to the transaction and remove the handle. The only + * complication is that we need to start a commit operation if the + * filesystem is marked for synchronous update. + * + * jbd2_journal_stop itself will not usually return an error, but it may + * do so in unusual circumstances. In particular, expect it to + * return -EIO if a jbd2_journal_abort has been executed since the + * transaction began. + */ +int jbd2_journal_stop(handle_t *handle) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + int err = 0, wait_for_commit = 0; + tid_t tid; + pid_t pid; + + if (--handle->h_ref > 0) { + jbd2_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1, + handle->h_ref); + if (is_handle_aborted(handle)) + return -EIO; + return 0; + } + if (!transaction) { + /* + * Handle is already detached from the transaction so there is + * nothing to do other than free the handle. + */ + memalloc_nofs_restore(handle->saved_alloc_context); + goto free_and_exit; + } + journal = transaction->t_journal; + tid = transaction->t_tid; + + if (is_handle_aborted(handle)) + err = -EIO; + + jbd2_debug(4, "Handle %p going down\n", handle); + trace_jbd2_handle_stats(journal->j_fs_dev->bd_dev, + tid, handle->h_type, handle->h_line_no, + jiffies - handle->h_start_jiffies, + handle->h_sync, handle->h_requested_credits, + (handle->h_requested_credits - + handle->h_total_credits)); + + /* + * Implement synchronous transaction batching. If the handle + * was synchronous, don't force a commit immediately. Let's + * yield and let another thread piggyback onto this + * transaction. Keep doing that while new threads continue to + * arrive. It doesn't cost much - we're about to run a commit + * and sleep on IO anyway. Speeds up many-threaded, many-dir + * operations by 30x or more... + * + * We try and optimize the sleep time against what the + * underlying disk can do, instead of having a static sleep + * time. This is useful for the case where our storage is so + * fast that it is more optimal to go ahead and force a flush + * and wait for the transaction to be committed than it is to + * wait for an arbitrary amount of time for new writers to + * join the transaction. We achieve this by measuring how + * long it takes to commit a transaction, and compare it with + * how long this transaction has been running, and if run time + * < commit time then we sleep for the delta and commit. This + * greatly helps super fast disks that would see slowdowns as + * more threads started doing fsyncs. + * + * But don't do this if this process was the most recent one + * to perform a synchronous write. We do this to detect the + * case where a single process is doing a stream of sync + * writes. No point in waiting for joiners in that case. + * + * Setting max_batch_time to 0 disables this completely. + */ + pid = current->pid; + if (handle->h_sync && journal->j_last_sync_writer != pid && + journal->j_max_batch_time) { + u64 commit_time, trans_time; + + journal->j_last_sync_writer = pid; + + read_lock(&journal->j_state_lock); + commit_time = journal->j_average_commit_time; + read_unlock(&journal->j_state_lock); + + trans_time = ktime_to_ns(ktime_sub(ktime_get(), + transaction->t_start_time)); + + commit_time = max_t(u64, commit_time, + 1000*journal->j_min_batch_time); + commit_time = min_t(u64, commit_time, + 1000*journal->j_max_batch_time); + + if (trans_time < commit_time) { + ktime_t expires = ktime_add_ns(ktime_get(), + commit_time); + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_hrtimeout(&expires, HRTIMER_MODE_ABS); + } + } + + if (handle->h_sync) + transaction->t_synchronous_commit = 1; + + /* + * If the handle is marked SYNC, we need to set another commit + * going! We also want to force a commit if the transaction is too + * old now. + */ + if (handle->h_sync || + time_after_eq(jiffies, transaction->t_expires)) { + /* Do this even for aborted journals: an abort still + * completes the commit thread, it just doesn't write + * anything to disk. */ + + jbd2_debug(2, "transaction too old, requesting commit for " + "handle %p\n", handle); + /* This is non-blocking */ + jbd2_log_start_commit(journal, tid); + + /* + * Special case: JBD2_SYNC synchronous updates require us + * to wait for the commit to complete. + */ + if (handle->h_sync && !(current->flags & PF_MEMALLOC)) + wait_for_commit = 1; + } + + /* + * Once stop_this_handle() drops t_updates, the transaction could start + * committing on us and eventually disappear. So we must not + * dereference transaction pointer again after calling + * stop_this_handle(). + */ + stop_this_handle(handle); + + if (wait_for_commit) + err = jbd2_log_wait_commit(journal, tid); + +free_and_exit: + if (handle->h_rsv_handle) + jbd2_free_handle(handle->h_rsv_handle); + jbd2_free_handle(handle); + return err; +} + +/* + * + * List management code snippets: various functions for manipulating the + * transaction buffer lists. + * + */ + +/* + * Append a buffer to a transaction list, given the transaction's list head + * pointer. + * + * j_list_lock is held. + * + * jh->b_state_lock is held. + */ + +static inline void +__blist_add_buffer(struct journal_head **list, struct journal_head *jh) +{ + if (!*list) { + jh->b_tnext = jh->b_tprev = jh; + *list = jh; + } else { + /* Insert at the tail of the list to preserve order */ + struct journal_head *first = *list, *last = first->b_tprev; + jh->b_tprev = last; + jh->b_tnext = first; + last->b_tnext = first->b_tprev = jh; + } +} + +/* + * Remove a buffer from a transaction list, given the transaction's list + * head pointer. + * + * Called with j_list_lock held, and the journal may not be locked. + * + * jh->b_state_lock is held. + */ + +static inline void +__blist_del_buffer(struct journal_head **list, struct journal_head *jh) +{ + if (*list == jh) { + *list = jh->b_tnext; + if (*list == jh) + *list = NULL; + } + jh->b_tprev->b_tnext = jh->b_tnext; + jh->b_tnext->b_tprev = jh->b_tprev; +} + +/* + * Remove a buffer from the appropriate transaction list. + * + * Note that this function can *change* the value of + * bh->b_transaction->t_buffers, t_forget, t_shadow_list, t_log_list or + * t_reserved_list. If the caller is holding onto a copy of one of these + * pointers, it could go bad. Generally the caller needs to re-read the + * pointer from the transaction_t. + * + * Called under j_list_lock. + */ +static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh) +{ + struct journal_head **list = NULL; + transaction_t *transaction; + struct buffer_head *bh = jh2bh(jh); + + lockdep_assert_held(&jh->b_state_lock); + transaction = jh->b_transaction; + if (transaction) + assert_spin_locked(&transaction->t_journal->j_list_lock); + + J_ASSERT_JH(jh, jh->b_jlist < BJ_Types); + if (jh->b_jlist != BJ_None) + J_ASSERT_JH(jh, transaction != NULL); + + switch (jh->b_jlist) { + case BJ_None: + return; + case BJ_Metadata: + transaction->t_nr_buffers--; + J_ASSERT_JH(jh, transaction->t_nr_buffers >= 0); + list = &transaction->t_buffers; + break; + case BJ_Forget: + list = &transaction->t_forget; + break; + case BJ_Shadow: + list = &transaction->t_shadow_list; + break; + case BJ_Reserved: + list = &transaction->t_reserved_list; + break; + } + + __blist_del_buffer(list, jh); + jh->b_jlist = BJ_None; + if (transaction && is_journal_aborted(transaction->t_journal)) + clear_buffer_jbddirty(bh); + else if (test_clear_buffer_jbddirty(bh)) + mark_buffer_dirty(bh); /* Expose it to the VM */ +} + +/* + * Remove buffer from all transactions. The caller is responsible for dropping + * the jh reference that belonged to the transaction. + * + * Called with bh_state lock and j_list_lock + */ +static void __jbd2_journal_unfile_buffer(struct journal_head *jh) +{ + J_ASSERT_JH(jh, jh->b_transaction != NULL); + J_ASSERT_JH(jh, jh->b_next_transaction == NULL); + + __jbd2_journal_temp_unlink_buffer(jh); + jh->b_transaction = NULL; +} + +/** + * jbd2_journal_try_to_free_buffers() - try to free page buffers. + * @journal: journal for operation + * @folio: Folio to detach data from. + * + * For all the buffers on this page, + * if they are fully written out ordered data, move them onto BUF_CLEAN + * so try_to_free_buffers() can reap them. + * + * This function returns non-zero if we wish try_to_free_buffers() + * to be called. We do this if the page is releasable by try_to_free_buffers(). + * We also do it if the page has locked or dirty buffers and the caller wants + * us to perform sync or async writeout. + * + * This complicates JBD locking somewhat. We aren't protected by the + * BKL here. We wish to remove the buffer from its committing or + * running transaction's ->t_datalist via __jbd2_journal_unfile_buffer. + * + * This may *change* the value of transaction_t->t_datalist, so anyone + * who looks at t_datalist needs to lock against this function. + * + * Even worse, someone may be doing a jbd2_journal_dirty_data on this + * buffer. So we need to lock against that. jbd2_journal_dirty_data() + * will come out of the lock with the buffer dirty, which makes it + * ineligible for release here. + * + * Who else is affected by this? hmm... Really the only contender + * is do_get_write_access() - it could be looking at the buffer while + * journal_try_to_free_buffer() is changing its state. But that + * cannot happen because we never reallocate freed data as metadata + * while the data is part of a transaction. Yes? + * + * Return false on failure, true on success + */ +bool jbd2_journal_try_to_free_buffers(journal_t *journal, struct folio *folio) +{ + struct buffer_head *head; + struct buffer_head *bh; + bool ret = false; + + J_ASSERT(folio_test_locked(folio)); + + head = folio_buffers(folio); + bh = head; + do { + struct journal_head *jh; + + /* + * We take our own ref against the journal_head here to avoid + * having to add tons of locking around each instance of + * jbd2_journal_put_journal_head(). + */ + jh = jbd2_journal_grab_journal_head(bh); + if (!jh) + continue; + + spin_lock(&jh->b_state_lock); + if (!jh->b_transaction && !jh->b_next_transaction) { + spin_lock(&journal->j_list_lock); + /* Remove written-back checkpointed metadata buffer */ + if (jh->b_cp_transaction != NULL) + jbd2_journal_try_remove_checkpoint(jh); + spin_unlock(&journal->j_list_lock); + } + spin_unlock(&jh->b_state_lock); + jbd2_journal_put_journal_head(jh); + if (buffer_jbd(bh)) + goto busy; + } while ((bh = bh->b_this_page) != head); + + ret = try_to_free_buffers(folio); +busy: + return ret; +} + +/* + * This buffer is no longer needed. If it is on an older transaction's + * checkpoint list we need to record it on this transaction's forget list + * to pin this buffer (and hence its checkpointing transaction) down until + * this transaction commits. If the buffer isn't on a checkpoint list, we + * release it. + * Returns non-zero if JBD no longer has an interest in the buffer. + * + * Called under j_list_lock. + * + * Called under jh->b_state_lock. + */ +static int __dispose_buffer(struct journal_head *jh, transaction_t *transaction) +{ + int may_free = 1; + struct buffer_head *bh = jh2bh(jh); + + if (jh->b_cp_transaction) { + JBUFFER_TRACE(jh, "on running+cp transaction"); + __jbd2_journal_temp_unlink_buffer(jh); + /* + * We don't want to write the buffer anymore, clear the + * bit so that we don't confuse checks in + * __jbd2_journal_file_buffer + */ + clear_buffer_dirty(bh); + __jbd2_journal_file_buffer(jh, transaction, BJ_Forget); + may_free = 0; + } else { + JBUFFER_TRACE(jh, "on running transaction"); + __jbd2_journal_unfile_buffer(jh); + jbd2_journal_put_journal_head(jh); + } + return may_free; +} + +/* + * jbd2_journal_invalidate_folio + * + * This code is tricky. It has a number of cases to deal with. + * + * There are two invariants which this code relies on: + * + * i_size must be updated on disk before we start calling invalidate_folio + * on the data. + * + * This is done in ext3 by defining an ext3_setattr method which + * updates i_size before truncate gets going. By maintaining this + * invariant, we can be sure that it is safe to throw away any buffers + * attached to the current transaction: once the transaction commits, + * we know that the data will not be needed. + * + * Note however that we can *not* throw away data belonging to the + * previous, committing transaction! + * + * Any disk blocks which *are* part of the previous, committing + * transaction (and which therefore cannot be discarded immediately) are + * not going to be reused in the new running transaction + * + * The bitmap committed_data images guarantee this: any block which is + * allocated in one transaction and removed in the next will be marked + * as in-use in the committed_data bitmap, so cannot be reused until + * the next transaction to delete the block commits. This means that + * leaving committing buffers dirty is quite safe: the disk blocks + * cannot be reallocated to a different file and so buffer aliasing is + * not possible. + * + * + * The above applies mainly to ordered data mode. In writeback mode we + * don't make guarantees about the order in which data hits disk --- in + * particular we don't guarantee that new dirty data is flushed before + * transaction commit --- so it is always safe just to discard data + * immediately in that mode. --sct + */ + +/* + * The journal_unmap_buffer helper function returns zero if the buffer + * concerned remains pinned as an anonymous buffer belonging to an older + * transaction. + * + * We're outside-transaction here. Either or both of j_running_transaction + * and j_committing_transaction may be NULL. + */ +static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, + int partial_page) +{ + transaction_t *transaction; + struct journal_head *jh; + int may_free = 1; + + BUFFER_TRACE(bh, "entry"); + + /* + * It is safe to proceed here without the j_list_lock because the + * buffers cannot be stolen by try_to_free_buffers as long as we are + * holding the page lock. --sct + */ + + jh = jbd2_journal_grab_journal_head(bh); + if (!jh) + goto zap_buffer_unlocked; + + /* OK, we have data buffer in journaled mode */ + write_lock(&journal->j_state_lock); + spin_lock(&jh->b_state_lock); + spin_lock(&journal->j_list_lock); + + /* + * We cannot remove the buffer from checkpoint lists until the + * transaction adding inode to orphan list (let's call it T) + * is committed. Otherwise if the transaction changing the + * buffer would be cleaned from the journal before T is + * committed, a crash will cause that the correct contents of + * the buffer will be lost. On the other hand we have to + * clear the buffer dirty bit at latest at the moment when the + * transaction marking the buffer as freed in the filesystem + * structures is committed because from that moment on the + * block can be reallocated and used by a different page. + * Since the block hasn't been freed yet but the inode has + * already been added to orphan list, it is safe for us to add + * the buffer to BJ_Forget list of the newest transaction. + * + * Also we have to clear buffer_mapped flag of a truncated buffer + * because the buffer_head may be attached to the page straddling + * i_size (can happen only when blocksize < pagesize) and thus the + * buffer_head can be reused when the file is extended again. So we end + * up keeping around invalidated buffers attached to transactions' + * BJ_Forget list just to stop checkpointing code from cleaning up + * the transaction this buffer was modified in. + */ + transaction = jh->b_transaction; + if (transaction == NULL) { + /* First case: not on any transaction. If it + * has no checkpoint link, then we can zap it: + * it's a writeback-mode buffer so we don't care + * if it hits disk safely. */ + if (!jh->b_cp_transaction) { + JBUFFER_TRACE(jh, "not on any transaction: zap"); + goto zap_buffer; + } + + if (!buffer_dirty(bh)) { + /* bdflush has written it. We can drop it now */ + __jbd2_journal_remove_checkpoint(jh); + goto zap_buffer; + } + + /* OK, it must be in the journal but still not + * written fully to disk: it's metadata or + * journaled data... */ + + if (journal->j_running_transaction) { + /* ... and once the current transaction has + * committed, the buffer won't be needed any + * longer. */ + JBUFFER_TRACE(jh, "checkpointed: add to BJ_Forget"); + may_free = __dispose_buffer(jh, + journal->j_running_transaction); + goto zap_buffer; + } else { + /* There is no currently-running transaction. So the + * orphan record which we wrote for this file must have + * passed into commit. We must attach this buffer to + * the committing transaction, if it exists. */ + if (journal->j_committing_transaction) { + JBUFFER_TRACE(jh, "give to committing trans"); + may_free = __dispose_buffer(jh, + journal->j_committing_transaction); + goto zap_buffer; + } else { + /* The orphan record's transaction has + * committed. We can cleanse this buffer */ + clear_buffer_jbddirty(bh); + __jbd2_journal_remove_checkpoint(jh); + goto zap_buffer; + } + } + } else if (transaction == journal->j_committing_transaction) { + JBUFFER_TRACE(jh, "on committing transaction"); + /* + * The buffer is committing, we simply cannot touch + * it. If the page is straddling i_size we have to wait + * for commit and try again. + */ + if (partial_page) { + spin_unlock(&journal->j_list_lock); + spin_unlock(&jh->b_state_lock); + write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); + /* Already zapped buffer? Nothing to do... */ + if (!bh->b_bdev) + return 0; + return -EBUSY; + } + /* + * OK, buffer won't be reachable after truncate. We just clear + * b_modified to not confuse transaction credit accounting, and + * set j_next_transaction to the running transaction (if there + * is one) and mark buffer as freed so that commit code knows + * it should clear dirty bits when it is done with the buffer. + */ + set_buffer_freed(bh); + if (journal->j_running_transaction && buffer_jbddirty(bh)) + jh->b_next_transaction = journal->j_running_transaction; + jh->b_modified = 0; + spin_unlock(&journal->j_list_lock); + spin_unlock(&jh->b_state_lock); + write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); + return 0; + } else { + /* Good, the buffer belongs to the running transaction. + * We are writing our own transaction's data, not any + * previous one's, so it is safe to throw it away + * (remember that we expect the filesystem to have set + * i_size already for this truncate so recovery will not + * expose the disk blocks we are discarding here.) */ + J_ASSERT_JH(jh, transaction == journal->j_running_transaction); + JBUFFER_TRACE(jh, "on running transaction"); + may_free = __dispose_buffer(jh, transaction); + } + +zap_buffer: + /* + * This is tricky. Although the buffer is truncated, it may be reused + * if blocksize < pagesize and it is attached to the page straddling + * EOF. Since the buffer might have been added to BJ_Forget list of the + * running transaction, journal_get_write_access() won't clear + * b_modified and credit accounting gets confused. So clear b_modified + * here. + */ + jh->b_modified = 0; + spin_unlock(&journal->j_list_lock); + spin_unlock(&jh->b_state_lock); + write_unlock(&journal->j_state_lock); + jbd2_journal_put_journal_head(jh); +zap_buffer_unlocked: + clear_buffer_dirty(bh); + J_ASSERT_BH(bh, !buffer_jbddirty(bh)); + clear_buffer_mapped(bh); + clear_buffer_req(bh); + clear_buffer_new(bh); + clear_buffer_delay(bh); + clear_buffer_unwritten(bh); + bh->b_bdev = NULL; + return may_free; +} + +/** + * jbd2_journal_invalidate_folio() + * @journal: journal to use for flush... + * @folio: folio to flush + * @offset: start of the range to invalidate + * @length: length of the range to invalidate + * + * Reap page buffers containing data after in the specified range in page. + * Can return -EBUSY if buffers are part of the committing transaction and + * the page is straddling i_size. Caller then has to wait for current commit + * and try again. + */ +int jbd2_journal_invalidate_folio(journal_t *journal, struct folio *folio, + size_t offset, size_t length) +{ + struct buffer_head *head, *bh, *next; + unsigned int stop = offset + length; + unsigned int curr_off = 0; + int partial_page = (offset || length < folio_size(folio)); + int may_free = 1; + int ret = 0; + + if (!folio_test_locked(folio)) + BUG(); + head = folio_buffers(folio); + if (!head) + return 0; + + BUG_ON(stop > folio_size(folio) || stop < length); + + /* We will potentially be playing with lists other than just the + * data lists (especially for journaled data mode), so be + * cautious in our locking. */ + + bh = head; + do { + unsigned int next_off = curr_off + bh->b_size; + next = bh->b_this_page; + + if (next_off > stop) + return 0; + + if (offset <= curr_off) { + /* This block is wholly outside the truncation point */ + lock_buffer(bh); + ret = journal_unmap_buffer(journal, bh, partial_page); + unlock_buffer(bh); + if (ret < 0) + return ret; + may_free &= ret; + } + curr_off = next_off; + bh = next; + + } while (bh != head); + + if (!partial_page) { + if (may_free && try_to_free_buffers(folio)) + J_ASSERT(!folio_buffers(folio)); + } + return 0; +} + +/* + * File a buffer on the given transaction list. + */ +void __jbd2_journal_file_buffer(struct journal_head *jh, + transaction_t *transaction, int jlist) +{ + struct journal_head **list = NULL; + int was_dirty = 0; + struct buffer_head *bh = jh2bh(jh); + + lockdep_assert_held(&jh->b_state_lock); + assert_spin_locked(&transaction->t_journal->j_list_lock); + + J_ASSERT_JH(jh, jh->b_jlist < BJ_Types); + J_ASSERT_JH(jh, jh->b_transaction == transaction || + jh->b_transaction == NULL); + + if (jh->b_transaction && jh->b_jlist == jlist) + return; + + if (jlist == BJ_Metadata || jlist == BJ_Reserved || + jlist == BJ_Shadow || jlist == BJ_Forget) { + /* + * For metadata buffers, we track dirty bit in buffer_jbddirty + * instead of buffer_dirty. We should not see a dirty bit set + * here because we clear it in do_get_write_access but e.g. + * tune2fs can modify the sb and set the dirty bit at any time + * so we try to gracefully handle that. + */ + if (buffer_dirty(bh)) + warn_dirty_buffer(bh); + if (test_clear_buffer_dirty(bh) || + test_clear_buffer_jbddirty(bh)) + was_dirty = 1; + } + + if (jh->b_transaction) + __jbd2_journal_temp_unlink_buffer(jh); + else + jbd2_journal_grab_journal_head(bh); + jh->b_transaction = transaction; + + switch (jlist) { + case BJ_None: + J_ASSERT_JH(jh, !jh->b_committed_data); + J_ASSERT_JH(jh, !jh->b_frozen_data); + return; + case BJ_Metadata: + transaction->t_nr_buffers++; + list = &transaction->t_buffers; + break; + case BJ_Forget: + list = &transaction->t_forget; + break; + case BJ_Shadow: + list = &transaction->t_shadow_list; + break; + case BJ_Reserved: + list = &transaction->t_reserved_list; + break; + } + + __blist_add_buffer(list, jh); + jh->b_jlist = jlist; + + if (was_dirty) + set_buffer_jbddirty(bh); +} + +void jbd2_journal_file_buffer(struct journal_head *jh, + transaction_t *transaction, int jlist) +{ + spin_lock(&jh->b_state_lock); + spin_lock(&transaction->t_journal->j_list_lock); + __jbd2_journal_file_buffer(jh, transaction, jlist); + spin_unlock(&transaction->t_journal->j_list_lock); + spin_unlock(&jh->b_state_lock); +} + +/* + * Remove a buffer from its current buffer list in preparation for + * dropping it from its current transaction entirely. If the buffer has + * already started to be used by a subsequent transaction, refile the + * buffer on that transaction's metadata list. + * + * Called under j_list_lock + * Called under jh->b_state_lock + * + * When this function returns true, there's no next transaction to refile to + * and the caller has to drop jh reference through + * jbd2_journal_put_journal_head(). + */ +bool __jbd2_journal_refile_buffer(struct journal_head *jh) +{ + int was_dirty, jlist; + struct buffer_head *bh = jh2bh(jh); + + lockdep_assert_held(&jh->b_state_lock); + if (jh->b_transaction) + assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock); + + /* If the buffer is now unused, just drop it. */ + if (jh->b_next_transaction == NULL) { + __jbd2_journal_unfile_buffer(jh); + return true; + } + + /* + * It has been modified by a later transaction: add it to the new + * transaction's metadata list. + */ + + was_dirty = test_clear_buffer_jbddirty(bh); + __jbd2_journal_temp_unlink_buffer(jh); + + /* + * b_transaction must be set, otherwise the new b_transaction won't + * be holding jh reference + */ + J_ASSERT_JH(jh, jh->b_transaction != NULL); + + /* + * We set b_transaction here because b_next_transaction will inherit + * our jh reference and thus __jbd2_journal_file_buffer() must not + * take a new one. + */ + WRITE_ONCE(jh->b_transaction, jh->b_next_transaction); + WRITE_ONCE(jh->b_next_transaction, NULL); + if (buffer_freed(bh)) + jlist = BJ_Forget; + else if (jh->b_modified) + jlist = BJ_Metadata; + else + jlist = BJ_Reserved; + __jbd2_journal_file_buffer(jh, jh->b_transaction, jlist); + J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING); + + if (was_dirty) + set_buffer_jbddirty(bh); + return false; +} + +/* + * __jbd2_journal_refile_buffer() with necessary locking added. We take our + * bh reference so that we can safely unlock bh. + * + * The jh and bh may be freed by this call. + */ +void jbd2_journal_refile_buffer(journal_t *journal, struct journal_head *jh) +{ + bool drop; + + spin_lock(&jh->b_state_lock); + spin_lock(&journal->j_list_lock); + drop = __jbd2_journal_refile_buffer(jh); + spin_unlock(&jh->b_state_lock); + spin_unlock(&journal->j_list_lock); + if (drop) + jbd2_journal_put_journal_head(jh); +} + +/* + * File inode in the inode list of the handle's transaction + */ +static int jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *jinode, + unsigned long flags, loff_t start_byte, loff_t end_byte) +{ + transaction_t *transaction = handle->h_transaction; + journal_t *journal; + + if (is_handle_aborted(handle)) + return -EROFS; + journal = transaction->t_journal; + + jbd2_debug(4, "Adding inode %lu, tid:%d\n", jinode->i_vfs_inode->i_ino, + transaction->t_tid); + + spin_lock(&journal->j_list_lock); + jinode->i_flags |= flags; + + if (jinode->i_dirty_end) { + jinode->i_dirty_start = min(jinode->i_dirty_start, start_byte); + jinode->i_dirty_end = max(jinode->i_dirty_end, end_byte); + } else { + jinode->i_dirty_start = start_byte; + jinode->i_dirty_end = end_byte; + } + + /* Is inode already attached where we need it? */ + if (jinode->i_transaction == transaction || + jinode->i_next_transaction == transaction) + goto done; + + /* + * We only ever set this variable to 1 so the test is safe. Since + * t_need_data_flush is likely to be set, we do the test to save some + * cacheline bouncing + */ + if (!transaction->t_need_data_flush) + transaction->t_need_data_flush = 1; + /* On some different transaction's list - should be + * the committing one */ + if (jinode->i_transaction) { + J_ASSERT(jinode->i_next_transaction == NULL); + J_ASSERT(jinode->i_transaction == + journal->j_committing_transaction); + jinode->i_next_transaction = transaction; + goto done; + } + /* Not on any transaction list... */ + J_ASSERT(!jinode->i_next_transaction); + jinode->i_transaction = transaction; + list_add(&jinode->i_list, &transaction->t_inode_list); +done: + spin_unlock(&journal->j_list_lock); + + return 0; +} + +int jbd2_journal_inode_ranged_write(handle_t *handle, + struct jbd2_inode *jinode, loff_t start_byte, loff_t length) +{ + return jbd2_journal_file_inode(handle, jinode, + JI_WRITE_DATA | JI_WAIT_DATA, start_byte, + start_byte + length - 1); +} + +int jbd2_journal_inode_ranged_wait(handle_t *handle, struct jbd2_inode *jinode, + loff_t start_byte, loff_t length) +{ + return jbd2_journal_file_inode(handle, jinode, JI_WAIT_DATA, + start_byte, start_byte + length - 1); +} + +/* + * File truncate and transaction commit interact with each other in a + * non-trivial way. If a transaction writing data block A is + * committing, we cannot discard the data by truncate until we have + * written them. Otherwise if we crashed after the transaction with + * write has committed but before the transaction with truncate has + * committed, we could see stale data in block A. This function is a + * helper to solve this problem. It starts writeout of the truncated + * part in case it is in the committing transaction. + * + * Filesystem code must call this function when inode is journaled in + * ordered mode before truncation happens and after the inode has been + * placed on orphan list with the new inode size. The second condition + * avoids the race that someone writes new data and we start + * committing the transaction after this function has been called but + * before a transaction for truncate is started (and furthermore it + * allows us to optimize the case where the addition to orphan list + * happens in the same transaction as write --- we don't have to write + * any data in such case). + */ +int jbd2_journal_begin_ordered_truncate(journal_t *journal, + struct jbd2_inode *jinode, + loff_t new_size) +{ + transaction_t *inode_trans, *commit_trans; + int ret = 0; + + /* This is a quick check to avoid locking if not necessary */ + if (!jinode->i_transaction) + goto out; + /* Locks are here just to force reading of recent values, it is + * enough that the transaction was not committing before we started + * a transaction adding the inode to orphan list */ + read_lock(&journal->j_state_lock); + commit_trans = journal->j_committing_transaction; + read_unlock(&journal->j_state_lock); + spin_lock(&journal->j_list_lock); + inode_trans = jinode->i_transaction; + spin_unlock(&journal->j_list_lock); + if (inode_trans == commit_trans) { + ret = filemap_fdatawrite_range(jinode->i_vfs_inode->i_mapping, + new_size, LLONG_MAX); + if (ret) + jbd2_journal_abort(journal, ret); + } +out: + return ret; +} -- 2.43.0