/* * linux/fs/jbd/transaction.c * * Written by Stephen C. Tweedie , 1998 * * Copyright 1998 Red Hat corp --- All Rights Reserved * * This file is part of the Linux kernel and is made available under * the terms of the GNU General Public License, version 2, or at your * option, any later version, incorporated herein by reference. * * 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 #include #include #include #include #include #include #include #include #include static void __journal_temp_unlink_buffer(struct journal_head *jh); /* * get_transaction: obtain a new transaction_t object. * * Simply allocate and initialise a new transaction. Create 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. * * Called under j_state_lock */ static transaction_t * 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; spin_lock_init(&transaction->t_handle_lock); /* 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; return transaction; } /* * 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. */ /* * 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) { transaction_t *transaction; int needed; int nblocks = handle->h_buffer_credits; transaction_t *new_transaction = NULL; int ret = 0; if (nblocks > journal->j_max_transaction_buffers) { printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n", current->comm, nblocks, journal->j_max_transaction_buffers); ret = -ENOSPC; goto out; } alloc_transaction: if (!journal->j_running_transaction) { new_transaction = kzalloc(sizeof(*new_transaction), GFP_NOFS); if (!new_transaction) { congestion_wait(BLK_RW_ASYNC, HZ/50); goto alloc_transaction; } } jbd_debug(3, "New handle %p going live.\n", handle); repeat: /* * We need to hold j_state_lock until t_updates has been incremented, * for proper journal barrier handling */ spin_lock(&journal->j_state_lock); repeat_locked: if (is_journal_aborted(journal) || (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) { spin_unlock(&journal->j_state_lock); ret = -EROFS; goto out; } /* Wait on the journal's transaction barrier if necessary */ if (journal->j_barrier_count) { spin_unlock(&journal->j_state_lock); wait_event(journal->j_wait_transaction_locked, journal->j_barrier_count == 0); goto repeat; } if (!journal->j_running_transaction) { if (!new_transaction) { spin_unlock(&journal->j_state_lock); goto alloc_transaction; } get_transaction(journal, new_transaction); new_transaction = NULL; } transaction = journal->j_running_transaction; /* * If the current transaction is locked down for commit, wait for the * lock to be released. */ if (transaction->t_state == T_LOCKED) { DEFINE_WAIT(wait); prepare_to_wait(&journal->j_wait_transaction_locked, &wait, TASK_UNINTERRUPTIBLE); spin_unlock(&journal->j_state_lock); schedule(); finish_wait(&journal->j_wait_transaction_locked, &wait); goto repeat; } /* * 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. */ spin_lock(&transaction->t_handle_lock); needed = transaction->t_outstanding_credits + nblocks; 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. */ DEFINE_WAIT(wait); jbd_debug(2, "Handle %p starting new commit...\n", handle); spin_unlock(&transaction->t_handle_lock); prepare_to_wait(&journal->j_wait_transaction_locked, &wait, TASK_UNINTERRUPTIBLE); __log_start_commit(journal, transaction->t_tid); spin_unlock(&journal->j_state_lock); schedule(); finish_wait(&journal->j_wait_transaction_locked, &wait); goto repeat; } /* * 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. * * The worst part is, any transaction currently committing can * reduce the free space arbitrarily. Be careful to account for * those buffers when checkpointing. */ /* * @@@ AKPM: This seems rather over-defensive. We're giving commit * a _lot_ of headroom: 1/4 of the journal plus the size of * the committing transaction. Really, we only need to give it * committing_transaction->t_outstanding_credits plus "enough" for * the log control blocks. * Also, this test is inconsistent with the matching one in * journal_extend(). */ if (__log_space_left(journal) < jbd_space_needed(journal)) { jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle); spin_unlock(&transaction->t_handle_lock); __log_wait_for_space(journal); goto repeat_locked; } /* OK, account for the buffers that this operation expects to * use and add the handle to the running transaction. */ handle->h_transaction = transaction; transaction->t_outstanding_credits += nblocks; transaction->t_updates++; transaction->t_handle_count++; jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n", handle, nblocks, transaction->t_outstanding_credits, __log_space_left(journal)); spin_unlock(&transaction->t_handle_lock); spin_unlock(&journal->j_state_lock); lock_map_acquire(&handle->h_lockdep_map); out: if (unlikely(new_transaction)) /* It's usually NULL */ kfree(new_transaction); return ret; } static struct lock_class_key jbd_handle_key; /* Allocate a new handle. This should probably be in a slab... */ static handle_t *new_handle(int nblocks) { handle_t *handle = jbd_alloc_handle(GFP_NOFS); if (!handle) return NULL; memset(handle, 0, sizeof(*handle)); handle->h_buffer_credits = nblocks; handle->h_ref = 1; lockdep_init_map(&handle->h_lockdep_map, "jbd_handle", &jbd_handle_key, 0); return handle; } /** * handle_t *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. * * This function is visible to journal users (like ext3fs), so is not * called with the journal already locked. * * Return a pointer to a newly allocated handle, or an ERR_PTR() value * on failure. */ handle_t *journal_start(journal_t *journal, int nblocks) { 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; } handle = new_handle(nblocks); if (!handle) return ERR_PTR(-ENOMEM); current->journal_info = handle; err = start_this_handle(journal, handle); if (err < 0) { jbd_free_handle(handle); current->journal_info = NULL; handle = ERR_PTR(err); } return handle; } /** * int journal_extend() - extend buffer credits. * @handle: handle to 'extend' * @nblocks: nr blocks 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 modications in advance, but can * extend its credit if it needs more. * * 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 journal_extend(handle_t *handle, int nblocks) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; int result; int wanted; result = -EIO; if (is_handle_aborted(handle)) goto out; result = 1; spin_lock(&journal->j_state_lock); /* Don't extend a locked-down transaction! */ if (handle->h_transaction->t_state != T_RUNNING) { jbd_debug(3, "denied handle %p %d blocks: " "transaction not running\n", handle, nblocks); goto error_out; } spin_lock(&transaction->t_handle_lock); wanted = transaction->t_outstanding_credits + nblocks; if (wanted > journal->j_max_transaction_buffers) { jbd_debug(3, "denied handle %p %d blocks: " "transaction too large\n", handle, nblocks); goto unlock; } if (wanted > __log_space_left(journal)) { jbd_debug(3, "denied handle %p %d blocks: " "insufficient log space\n", handle, nblocks); goto unlock; } handle->h_buffer_credits += nblocks; transaction->t_outstanding_credits += nblocks; result = 0; jbd_debug(3, "extended handle %p by %d\n", handle, nblocks); unlock: spin_unlock(&transaction->t_handle_lock); error_out: spin_unlock(&journal->j_state_lock); out: return result; } /** * int journal_restart() - restart a handle. * @handle: handle to restart * @nblocks: nr credits requested * * Restart a handle for a multi-transaction filesystem * operation. * * If the journal_extend() call above fails to grant new buffer credits * to a running handle, a call to journal_restart will commit the * handle's transaction so far and reattach the handle to a new * transaction capabable of guaranteeing the requested number of * credits. */ int journal_restart(handle_t *handle, int nblocks) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; 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; /* * First unlink the handle from its current transaction, and start the * commit on that. */ J_ASSERT(transaction->t_updates > 0); J_ASSERT(journal_current_handle() == handle); spin_lock(&journal->j_state_lock); spin_lock(&transaction->t_handle_lock); transaction->t_outstanding_credits -= handle->h_buffer_credits; transaction->t_updates--; if (!transaction->t_updates) wake_up(&journal->j_wait_updates); spin_unlock(&transaction->t_handle_lock); jbd_debug(2, "restarting handle %p\n", handle); __log_start_commit(journal, transaction->t_tid); spin_unlock(&journal->j_state_lock); lock_map_release(&handle->h_lockdep_map); handle->h_buffer_credits = nblocks; ret = start_this_handle(journal, handle); return ret; } /** * void 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 journal_lock_updates(journal_t *journal) { DEFINE_WAIT(wait); spin_lock(&journal->j_state_lock); ++journal->j_barrier_count; /* Wait until there are no running updates */ while (1) { transaction_t *transaction = journal->j_running_transaction; if (!transaction) break; spin_lock(&transaction->t_handle_lock); if (!transaction->t_updates) { spin_unlock(&transaction->t_handle_lock); break; } prepare_to_wait(&journal->j_wait_updates, &wait, TASK_UNINTERRUPTIBLE); spin_unlock(&transaction->t_handle_lock); spin_unlock(&journal->j_state_lock); schedule(); finish_wait(&journal->j_wait_updates, &wait); spin_lock(&journal->j_state_lock); } spin_unlock(&journal->j_state_lock); /* * We have now established a barrier against other normal updates, but * we also need to barrier against other journal_lock_updates() calls * to make sure that we serialise special journal-locked operations * too. */ mutex_lock(&journal->j_barrier); } /** * void journal_unlock_updates (journal_t* journal) - release barrier * @journal: Journal to release the barrier on. * * Release a transaction barrier obtained with journal_lock_updates(). * * Should be called without the journal lock held. */ void journal_unlock_updates (journal_t *journal) { J_ASSERT(journal->j_barrier_count != 0); mutex_unlock(&journal->j_barrier); spin_lock(&journal->j_state_lock); --journal->j_barrier_count; spin_unlock(&journal->j_state_lock); wake_up(&journal->j_wait_transaction_locked); } static void warn_dirty_buffer(struct buffer_head *bh) { char b[BDEVNAME_SIZE]; printk(KERN_WARNING "JBD: Spotted dirty metadata buffer (dev = %s, blocknr = %llu). " "There's a risk of filesystem corruption in case of system " "crash.\n", bdevname(bh->b_bdev, b), (unsigned long long)bh->b_blocknr); } /* * 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; journal_t *journal; int error; char *frozen_buffer = NULL; int need_copy = 0; if (is_handle_aborted(handle)) return -EROFS; transaction = handle->h_transaction; journal = transaction->t_journal; jbd_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. */ lock_buffer(bh); jbd_lock_bh_state(bh); /* 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)) { /* * First question: is this buffer already part of the current * transaction or the existing committing transaction? */ if (jh->b_transaction) { J_ASSERT_JH(jh, jh->b_transaction == transaction || jh->b_transaction == journal->j_committing_transaction); if (jh->b_next_transaction) J_ASSERT_JH(jh, jh->b_next_transaction == transaction); warn_dirty_buffer(bh); } /* * In any case 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); set_buffer_jbddirty(bh); } unlock_buffer(bh); error = -EROFS; if (is_handle_aborted(handle)) { jbd_unlock_bh_state(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) goto done; /* * this is the first time this transaction is touching this buffer, * reset the modified flag */ jh->b_modified = 0; /* * 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); jh->b_next_transaction = transaction; goto done; } /* Is there data here we need to preserve? */ if (jh->b_transaction && jh->b_transaction != transaction) { 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 (jh->b_jlist == BJ_Shadow) { DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow); wait_queue_head_t *wqh; wqh = bit_waitqueue(&bh->b_state, BH_Unshadow); JBUFFER_TRACE(jh, "on shadow: sleep"); jbd_unlock_bh_state(bh); /* commit wakes up all shadow buffers after IO */ for ( ; ; ) { prepare_to_wait(wqh, &wait.wait, TASK_UNINTERRUPTIBLE); if (jh->b_jlist != BJ_Shadow) break; schedule(); } finish_wait(wqh, &wait.wait); goto repeat; } /* Only do the copy if the currently-owning transaction * still needs it. If it is on the Forget list, the * committing transaction is past that stage. The * buffer had better remain locked during the kmalloc, * but that should be true --- we hold the journal lock * still and the buffer is already on the BUF_JOURNAL * list so won't be flushed. * * 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_Forget || force_copy) { JBUFFER_TRACE(jh, "generate frozen data"); if (!frozen_buffer) { JBUFFER_TRACE(jh, "allocate memory for buffer"); jbd_unlock_bh_state(bh); frozen_buffer = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS); if (!frozen_buffer) { printk(KERN_EMERG "%s: OOM for frozen_buffer\n", __func__); JBUFFER_TRACE(jh, "oom!"); error = -ENOMEM; jbd_lock_bh_state(bh); goto done; } goto repeat; } jh->b_frozen_data = frozen_buffer; frozen_buffer = NULL; need_copy = 1; } jh->b_next_transaction = transaction; } /* * Finally, 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"); spin_lock(&journal->j_list_lock); __journal_file_buffer(jh, transaction, BJ_Reserved); spin_unlock(&journal->j_list_lock); } done: if (need_copy) { struct page *page; int offset; char *source; J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)), "Possible IO failure.\n"); page = jh2bh(jh)->b_page; offset = offset_in_page(jh2bh(jh)->b_data); source = kmap_atomic(page, KM_USER0); memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size); kunmap_atomic(source, KM_USER0); } jbd_unlock_bh_state(bh); /* * If we are about to journal a buffer, then any revoke pending on it is * no longer valid */ journal_cancel_revoke(handle, jh); out: if (unlikely(frozen_buffer)) /* It's usually NULL */ jbd_free(frozen_buffer, bh->b_size); JBUFFER_TRACE(jh, "exit"); return error; } /** * int 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 an 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 journal_get_write_access(handle_t *handle, struct buffer_head *bh) { struct journal_head *jh = journal_add_journal_head(bh); int rc; /* 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); 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. */ /** * int 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 journal_get_create_access(handle_t *handle, struct buffer_head *bh) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; struct journal_head *jh = journal_add_journal_head(bh); int err; jbd_debug(5, "journal_head %p\n", jh); err = -EROFS; if (is_handle_aborted(handle)) goto out; 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. */ jbd_lock_bh_state(bh); spin_lock(&journal->j_list_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 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"); __journal_file_buffer(jh, transaction, BJ_Reserved); } else if (jh->b_transaction == journal->j_committing_transaction) { /* first access by this transaction */ jh->b_modified = 0; JBUFFER_TRACE(jh, "set next transaction"); jh->b_next_transaction = transaction; } spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); /* * 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"); journal_cancel_revoke(handle, jh); out: journal_put_journal_head(jh); return err; } /** * int 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, 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 journal_get_undo_access(handle_t *handle, struct buffer_head *bh) { int err; struct journal_head *jh = journal_add_journal_head(bh); char *committed_data = NULL; 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 = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS); if (!committed_data) { printk(KERN_EMERG "%s: No memory for committed data\n", __func__); err = -ENOMEM; goto out; } } jbd_lock_bh_state(bh); 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) { jbd_unlock_bh_state(bh); goto repeat; } jh->b_committed_data = committed_data; committed_data = NULL; memcpy(jh->b_committed_data, bh->b_data, bh->b_size); } jbd_unlock_bh_state(bh); out: journal_put_journal_head(jh); if (unlikely(committed_data)) jbd_free(committed_data, bh->b_size); return err; } /** * int journal_dirty_data() - mark a buffer as containing dirty data to be flushed * @handle: transaction * @bh: bufferhead to mark * * Description: * Mark a buffer as containing dirty data which needs to be flushed before * we can commit the current transaction. * * The buffer is placed on the transaction's data list and is marked as * belonging to the transaction. * * Returns error number or 0 on success. * * journal_dirty_data() can be called via page_launder->ext3_writepage * by kswapd. */ int journal_dirty_data(handle_t *handle, struct buffer_head *bh) { journal_t *journal = handle->h_transaction->t_journal; int need_brelse = 0; struct journal_head *jh; int ret = 0; if (is_handle_aborted(handle)) return ret; jh = journal_add_journal_head(bh); JBUFFER_TRACE(jh, "entry"); /* * The buffer could *already* be dirty. Writeout can start * at any time. */ jbd_debug(4, "jh: %p, tid:%d\n", jh, handle->h_transaction->t_tid); /* * What if the buffer is already part of a running transaction? * * There are two cases: * 1) It is part of the current running transaction. Refile it, * just in case we have allocated it as metadata, deallocated * it, then reallocated it as data. * 2) It is part of the previous, still-committing transaction. * If all we want to do is to guarantee that the buffer will be * written to disk before this new transaction commits, then * being sure that the *previous* transaction has this same * property is sufficient for us! Just leave it on its old * transaction. * * In case (2), the buffer must not already exist as metadata * --- that would violate write ordering (a transaction is free * to write its data at any point, even before the previous * committing transaction has committed). The caller must * never, ever allow this to happen: there's nothing we can do * about it in this layer. */ jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); /* Now that we have bh_state locked, are we really still mapped? */ if (!buffer_mapped(bh)) { JBUFFER_TRACE(jh, "unmapped buffer, bailing out"); goto no_journal; } if (jh->b_transaction) { JBUFFER_TRACE(jh, "has transaction"); if (jh->b_transaction != handle->h_transaction) { JBUFFER_TRACE(jh, "belongs to older transaction"); J_ASSERT_JH(jh, jh->b_transaction == journal->j_committing_transaction); /* @@@ IS THIS TRUE ? */ /* * Not any more. Scenario: someone does a write() * in data=journal mode. The buffer's transaction has * moved into commit. Then someone does another * write() to the file. We do the frozen data copyout * and set b_next_transaction to point to j_running_t. * And while we're in that state, someone does a * writepage() in an attempt to pageout the same area * of the file via a shared mapping. At present that * calls journal_dirty_data(), and we get right here. * It may be too late to journal the data. Simply * falling through to the next test will suffice: the * data will be dirty and wil be checkpointed. The * ordering comments in the next comment block still * apply. */ //J_ASSERT_JH(jh, jh->b_next_transaction == NULL); /* * If we're journalling data, and this buffer was * subject to a write(), it could be metadata, forget * or shadow against the committing transaction. Now, * someone has dirtied the same darn page via a mapping * and it is being writepage()'d. * We *could* just steal the page from commit, with some * fancy locking there. Instead, we just skip it - * don't tie the page's buffers to the new transaction * at all. * Implication: if we crash before the writepage() data * is written into the filesystem, recovery will replay * the write() data. */ if (jh->b_jlist != BJ_None && jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) { JBUFFER_TRACE(jh, "Not stealing"); goto no_journal; } /* * This buffer may be undergoing writeout in commit. We * can't return from here and let the caller dirty it * again because that can cause the write-out loop in * commit to never terminate. */ if (buffer_dirty(bh)) { get_bh(bh); spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); need_brelse = 1; sync_dirty_buffer(bh); jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); /* Since we dropped the lock... */ if (!buffer_mapped(bh)) { JBUFFER_TRACE(jh, "buffer got unmapped"); goto no_journal; } /* The buffer may become locked again at any time if it is redirtied */ } /* * We cannot remove the buffer with io error from the * committing transaction, because otherwise it would * miss the error and the commit would not abort. */ if (unlikely(!buffer_uptodate(bh))) { ret = -EIO; goto no_journal; } /* We might have slept so buffer could be refiled now */ if (jh->b_transaction != NULL && jh->b_transaction != handle->h_transaction) { JBUFFER_TRACE(jh, "unfile from commit"); __journal_temp_unlink_buffer(jh); /* It still points to the committing * transaction; move it to this one so * that the refile assert checks are * happy. */ jh->b_transaction = handle->h_transaction; } /* The buffer will be refiled below */ } /* * Special case --- the buffer might actually have been * allocated and then immediately deallocated in the previous, * committing transaction, so might still be left on that * transaction's metadata lists. */ if (jh->b_jlist != BJ_SyncData && jh->b_jlist != BJ_Locked) { JBUFFER_TRACE(jh, "not on correct data list: unfile"); J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow); JBUFFER_TRACE(jh, "file as data"); __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData); } } else { JBUFFER_TRACE(jh, "not on a transaction"); __journal_file_buffer(jh, handle->h_transaction, BJ_SyncData); } no_journal: spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); if (need_brelse) { BUFFER_TRACE(bh, "brelse"); __brelse(bh); } JBUFFER_TRACE(jh, "exit"); journal_put_journal_head(jh); return ret; } /** * int 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 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 journal_dirty_metadata(handle_t *handle, struct buffer_head *bh) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; struct journal_head *jh = bh2jh(bh); jbd_debug(5, "journal_head %p\n", jh); JBUFFER_TRACE(jh, "entry"); if (is_handle_aborted(handle)) goto out; jbd_lock_bh_state(bh); 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 */ jh->b_modified = 1; J_ASSERT_JH(jh, handle->h_buffer_credits > 0); handle->h_buffer_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"); J_ASSERT_JH(jh, jh->b_transaction == journal->j_running_transaction); 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"); J_ASSERT_JH(jh, jh->b_transaction == journal->j_committing_transaction); J_ASSERT_JH(jh, jh->b_next_transaction == transaction); /* 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); __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata); spin_unlock(&journal->j_list_lock); out_unlock_bh: jbd_unlock_bh_state(bh); out: JBUFFER_TRACE(jh, "exit"); return 0; } /* * journal_release_buffer: undo a get_write_access without any buffer * updates, if the update decided in the end that it didn't need access. * */ void journal_release_buffer(handle_t *handle, struct buffer_head *bh) { BUFFER_TRACE(bh, "entry"); } /** * void 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 journal_forget (handle_t *handle, struct buffer_head *bh) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; struct journal_head *jh; int drop_reserve = 0; int err = 0; int was_modified = 0; BUFFER_TRACE(bh, "entry"); jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); if (!buffer_jbd(bh)) goto not_jbd; jh = bh2jh(bh); /* 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 not_jbd; } /* keep track of wether 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 == handle->h_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. */ if (jh->b_cp_transaction) { __journal_temp_unlink_buffer(jh); __journal_file_buffer(jh, transaction, BJ_Forget); } else { __journal_unfile_buffer(jh); if (!buffer_jbd(bh)) { spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); __bforget(bh); goto drop; } } } 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 if we * have also modified it since the original commit. */ if (jh->b_next_transaction) { J_ASSERT(jh->b_next_transaction == transaction); jh->b_next_transaction = NULL; /* * only drop a reference if this transaction modified * the buffer */ if (was_modified) drop_reserve = 1; } } not_jbd: spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); __brelse(bh); drop: if (drop_reserve) { /* no need to reserve log space for this block -bzzz */ handle->h_buffer_credits++; } return err; } /** * int journal_stop() - complete a transaction * @handle: tranaction 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. * * 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 journal_abort has been executed since the * transaction began. */ int journal_stop(handle_t *handle) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; int err; pid_t pid; J_ASSERT(journal_current_handle() == handle); if (is_handle_aborted(handle)) err = -EIO; else { J_ASSERT(transaction->t_updates > 0); err = 0; } if (--handle->h_ref > 0) { jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1, handle->h_ref); return err; } jbd_debug(4, "Handle %p going down\n", handle); /* * 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. */ pid = current->pid; if (handle->h_sync && journal->j_last_sync_writer != pid) { u64 commit_time, trans_time; journal->j_last_sync_writer = pid; spin_lock(&journal->j_state_lock); commit_time = journal->j_average_commit_time; spin_unlock(&journal->j_state_lock); trans_time = ktime_to_ns(ktime_sub(ktime_get(), transaction->t_start_time)); commit_time = min_t(u64, commit_time, 1000*jiffies_to_usecs(1)); 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; current->journal_info = NULL; spin_lock(&journal->j_state_lock); spin_lock(&transaction->t_handle_lock); transaction->t_outstanding_credits -= handle->h_buffer_credits; transaction->t_updates--; if (!transaction->t_updates) { wake_up(&journal->j_wait_updates); if (journal->j_barrier_count) wake_up(&journal->j_wait_transaction_locked); } /* * If the handle is marked SYNC, we need to set another commit * going! We also want to force a commit if the current * transaction is occupying too much of the log, or if the * transaction is too old now. */ if (handle->h_sync || transaction->t_outstanding_credits > journal->j_max_transaction_buffers || 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. */ tid_t tid = transaction->t_tid; spin_unlock(&transaction->t_handle_lock); jbd_debug(2, "transaction too old, requesting commit for " "handle %p\n", handle); /* This is non-blocking */ __log_start_commit(journal, transaction->t_tid); spin_unlock(&journal->j_state_lock); /* * Special case: JFS_SYNC synchronous updates require us * to wait for the commit to complete. */ if (handle->h_sync && !(current->flags & PF_MEMALLOC)) err = log_wait_commit(journal, tid); } else { spin_unlock(&transaction->t_handle_lock); spin_unlock(&journal->j_state_lock); } lock_map_release(&handle->h_lockdep_map); jbd_free_handle(handle); return err; } /** * int journal_force_commit() - force any uncommitted transactions * @journal: journal to force * * For synchronous operations: force any uncommitted transactions * to disk. May seem kludgy, but it reuses all the handle batching * code in a very simple manner. */ int journal_force_commit(journal_t *journal) { handle_t *handle; int ret; handle = journal_start(journal, 1); if (IS_ERR(handle)) { ret = PTR_ERR(handle); } else { handle->h_sync = 1; ret = journal_stop(handle); } return ret; } /* * * 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. * * jbd_lock_bh_state(jh2bh(jh)) 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. * * jbd_lock_bh_state(jh2bh(jh)) 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_sync_datalist, t_buffers, t_forget, * t_iobuf_list, t_shadow_list, t_log_list or t_reserved_list. If the caller * is holding onto a copy of one of thee pointers, it could go bad. * Generally the caller needs to re-read the pointer from the transaction_t. * * Called under j_list_lock. The journal may not be locked. */ static void __journal_temp_unlink_buffer(struct journal_head *jh) { struct journal_head **list = NULL; transaction_t *transaction; struct buffer_head *bh = jh2bh(jh); J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); 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_SyncData: list = &transaction->t_sync_datalist; break; 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_IO: list = &transaction->t_iobuf_list; break; case BJ_Shadow: list = &transaction->t_shadow_list; break; case BJ_LogCtl: list = &transaction->t_log_list; break; case BJ_Reserved: list = &transaction->t_reserved_list; break; case BJ_Locked: list = &transaction->t_locked_list; break; } __blist_del_buffer(list, jh); jh->b_jlist = BJ_None; if (test_clear_buffer_jbddirty(bh)) mark_buffer_dirty(bh); /* Expose it to the VM */ } /* * Remove buffer from all transactions. * * Called with bh_state lock and j_list_lock * * jh and bh may be already freed when this function returns. */ void __journal_unfile_buffer(struct journal_head *jh) { __journal_temp_unlink_buffer(jh); jh->b_transaction = NULL; journal_put_journal_head(jh); } void journal_unfile_buffer(journal_t *journal, struct journal_head *jh) { struct buffer_head *bh = jh2bh(jh); /* Get reference so that buffer cannot be freed before we unlock it */ get_bh(bh); jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); __journal_unfile_buffer(jh); spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); __brelse(bh); } /* * Called from journal_try_to_free_buffers(). * * Called under jbd_lock_bh_state(bh) */ static void __journal_try_to_free_buffer(journal_t *journal, struct buffer_head *bh) { struct journal_head *jh; jh = bh2jh(bh); if (buffer_locked(bh) || buffer_dirty(bh)) goto out; if (jh->b_next_transaction != NULL) goto out; spin_lock(&journal->j_list_lock); if (jh->b_transaction != NULL && jh->b_cp_transaction == NULL) { if (jh->b_jlist == BJ_SyncData || jh->b_jlist == BJ_Locked) { /* A written-back ordered data buffer */ JBUFFER_TRACE(jh, "release data"); __journal_unfile_buffer(jh); } } else if (jh->b_cp_transaction != NULL && jh->b_transaction == NULL) { /* written-back checkpointed metadata buffer */ if (jh->b_jlist == BJ_None) { JBUFFER_TRACE(jh, "remove from checkpoint list"); __journal_remove_checkpoint(jh); } } spin_unlock(&journal->j_list_lock); out: return; } /** * int journal_try_to_free_buffers() - try to free page buffers. * @journal: journal for operation * @page: to try and free * @gfp_mask: we use the mask to detect how hard should we try to release * buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to * release the buffers. * * * 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 __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 journal_dirty_data on this * buffer. So we need to lock against that. 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 0 on failure, 1 on success */ int journal_try_to_free_buffers(journal_t *journal, struct page *page, gfp_t gfp_mask) { struct buffer_head *head; struct buffer_head *bh; int ret = 0; J_ASSERT(PageLocked(page)); head = page_buffers(page); 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 * journal_put_journal_head(). */ jh = journal_grab_journal_head(bh); if (!jh) continue; jbd_lock_bh_state(bh); __journal_try_to_free_buffer(journal, bh); journal_put_journal_head(jh); jbd_unlock_bh_state(bh); if (buffer_jbd(bh)) goto busy; } while ((bh = bh->b_this_page) != head); ret = try_to_free_buffers(page); 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 jbd_lock_bh_state(bh). */ 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"); __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 * __journal_file_buffer */ clear_buffer_dirty(bh); __journal_file_buffer(jh, transaction, BJ_Forget); may_free = 0; } else { JBUFFER_TRACE(jh, "on running transaction"); __journal_unfile_buffer(jh); } return may_free; } /* * journal_invalidatepage * * 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 invalidatepage 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"); retry: /* * 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 */ if (!buffer_jbd(bh)) goto zap_buffer_unlocked; spin_lock(&journal->j_state_lock); jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); jh = journal_grab_journal_head(bh); if (!jh) goto zap_buffer_no_jh; /* * 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 */ 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); goto zap_buffer; } } } else if (transaction == journal->j_committing_transaction) { JBUFFER_TRACE(jh, "on committing transaction"); if (jh->b_jlist == BJ_Locked) { /* * The buffer is on the committing transaction's locked * list. We have the buffer locked, so I/O has * completed. So we can nail the buffer now. */ may_free = __dispose_buffer(jh, transaction); goto zap_buffer; } /* * 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) { tid_t tid = journal->j_committing_transaction->t_tid; journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); spin_unlock(&journal->j_state_lock); log_wait_commit(journal, tid); goto retry; } /* * OK, buffer won't be reachable after truncate. We just 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; journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); spin_unlock(&journal->j_state_lock); 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; journal_put_journal_head(jh); zap_buffer_no_jh: spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); spin_unlock(&journal->j_state_lock); 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); bh->b_bdev = NULL; return may_free; } /** * void journal_invalidatepage() - invalidate a journal page * @journal: journal to use for flush * @page: page to flush * @offset: length of page to invalidate. * * Reap page buffers containing data after offset in page. */ void journal_invalidatepage(journal_t *journal, struct page *page, unsigned long offset) { struct buffer_head *head, *bh, *next; unsigned int curr_off = 0; int may_free = 1; if (!PageLocked(page)) BUG(); if (!page_has_buffers(page)) return; /* We will potentially be playing with lists other than just the * data lists (especially for journaled data mode), so be * cautious in our locking. */ head = bh = page_buffers(page); do { unsigned int next_off = curr_off + bh->b_size; next = bh->b_this_page; if (offset <= curr_off) { /* This block is wholly outside the truncation point */ lock_buffer(bh); may_free &= journal_unmap_buffer(journal, bh, offset > 0); unlock_buffer(bh); } curr_off = next_off; bh = next; } while (bh != head); if (!offset) { if (may_free && try_to_free_buffers(page)) J_ASSERT(!page_has_buffers(page)); } } /* * File a buffer on the given transaction list. */ void __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); J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); 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) __journal_temp_unlink_buffer(jh); else 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_SyncData: list = &transaction->t_sync_datalist; break; case BJ_Metadata: transaction->t_nr_buffers++; list = &transaction->t_buffers; break; case BJ_Forget: list = &transaction->t_forget; break; case BJ_IO: list = &transaction->t_iobuf_list; break; case BJ_Shadow: list = &transaction->t_shadow_list; break; case BJ_LogCtl: list = &transaction->t_log_list; break; case BJ_Reserved: list = &transaction->t_reserved_list; break; case BJ_Locked: list = &transaction->t_locked_list; break; } __blist_add_buffer(list, jh); jh->b_jlist = jlist; if (was_dirty) set_buffer_jbddirty(bh); } void journal_file_buffer(struct journal_head *jh, transaction_t *transaction, int jlist) { jbd_lock_bh_state(jh2bh(jh)); spin_lock(&transaction->t_journal->j_list_lock); __journal_file_buffer(jh, transaction, jlist); spin_unlock(&transaction->t_journal->j_list_lock); jbd_unlock_bh_state(jh2bh(jh)); } /* * 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 jbd_lock_bh_state(jh2bh(jh)) * * jh and bh may be already free when this function returns */ void __journal_refile_buffer(struct journal_head *jh) { int was_dirty, jlist; struct buffer_head *bh = jh2bh(jh); J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh)); 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) { __journal_unfile_buffer(jh); return; } /* * It has been modified by a later transaction: add it to the new * transaction's metadata list. */ was_dirty = test_clear_buffer_jbddirty(bh); __journal_temp_unlink_buffer(jh); /* * We set b_transaction here because b_next_transaction will inherit * our jh reference and thus __journal_file_buffer() must not take a * new one. */ jh->b_transaction = jh->b_next_transaction; jh->b_next_transaction = NULL; if (buffer_freed(bh)) jlist = BJ_Forget; else if (jh->b_modified) jlist = BJ_Metadata; else jlist = BJ_Reserved; __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); } /* * __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 journal_refile_buffer(journal_t *journal, struct journal_head *jh) { struct buffer_head *bh = jh2bh(jh); /* Get reference so that buffer cannot be freed before we unlock it */ get_bh(bh); jbd_lock_bh_state(bh); spin_lock(&journal->j_list_lock); __journal_refile_buffer(jh); jbd_unlock_bh_state(bh); spin_unlock(&journal->j_list_lock); __brelse(bh); }