/* * linux/fs/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 extern spinlock_t journal_datalist_lock; /* * 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. */ static transaction_t * get_transaction (journal_t * journal, int is_try) { transaction_t * transaction; transaction = jbd_kmalloc (sizeof (transaction_t), GFP_NOFS); if (!transaction) return NULL; memset (transaction, 0, sizeof (transaction_t)); transaction->t_journal = journal; transaction->t_state = T_RUNNING; transaction->t_tid = journal->j_transaction_sequence++; transaction->t_expires = jiffies + journal->j_commit_interval; /* Set up the commit timer for the new transaction. */ J_ASSERT (!journal->j_commit_timer_active); journal->j_commit_timer_active = 1; journal->j_commit_timer->expires = 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; jbd_debug(3, "New handle %p going live.\n", handle); repeat: lock_journal(journal); if (is_journal_aborted(journal) || (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) { unlock_journal(journal); return -EROFS; } /* Wait on the journal's transaction barrier if necessary */ if (journal->j_barrier_count) { unlock_journal(journal); sleep_on(&journal->j_wait_transaction_locked); goto repeat; } repeat_locked: if (!journal->j_running_transaction) get_transaction(journal, 0); /* @@@ Error? */ J_ASSERT(journal->j_running_transaction); 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) { unlock_journal(journal); jbd_debug(3, "Handle %p stalling...\n", handle); sleep_on(&journal->j_wait_transaction_locked); 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. */ 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. */ jbd_debug(2, "Handle %p starting new commit...\n", handle); log_start_commit(journal, transaction); unlock_journal(journal); sleep_on(&journal->j_wait_transaction_locked); lock_journal(journal); goto repeat_locked; } /* * 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 inconsitent with the matching one in * journal_extend(). */ needed = journal->j_max_transaction_buffers; if (journal->j_committing_transaction) needed += journal->j_committing_transaction-> t_outstanding_credits; if (log_space_left(journal) < needed) { jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle); log_wait_for_space(journal, needed); 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)); unlock_journal(journal); return 0; } /* * Obtain a new handle. * * 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 ext2fs), so is not * called with the journal already locked. * * Return a pointer to a newly allocated handle, or NULL 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 = jbd_kmalloc(sizeof (handle_t), GFP_NOFS); if (!handle) return ERR_PTR(-ENOMEM); memset (handle, 0, sizeof (handle_t)); handle->h_buffer_credits = nblocks; handle->h_ref = 1; current->journal_info = handle; err = start_this_handle(journal, handle); if (err < 0) { kfree(handle); current->journal_info = NULL; return ERR_PTR(err); } return handle; } /* * Return zero on success */ static int try_start_this_handle(journal_t *journal, handle_t *handle) { transaction_t *transaction; int needed; int nblocks = handle->h_buffer_credits; int ret = 0; jbd_debug(3, "New handle %p maybe going live.\n", handle); lock_journal(journal); if (is_journal_aborted(journal) || (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) { ret = -EROFS; goto fail_unlock; } if (journal->j_barrier_count) goto fail_unlock; if (!journal->j_running_transaction && get_transaction(journal, 1) == 0) goto fail_unlock; transaction = journal->j_running_transaction; if (transaction->t_state == T_LOCKED) goto fail_unlock; needed = transaction->t_outstanding_credits + nblocks; /* We could run log_start_commit here */ if (needed > journal->j_max_transaction_buffers) goto fail_unlock; needed = journal->j_max_transaction_buffers; if (journal->j_committing_transaction) needed += journal->j_committing_transaction-> t_outstanding_credits; if (log_space_left(journal) < needed) goto fail_unlock; handle->h_transaction = transaction; transaction->t_outstanding_credits += nblocks; transaction->t_updates++; jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n", handle, nblocks, transaction->t_outstanding_credits, log_space_left(journal)); unlock_journal(journal); return 0; fail_unlock: unlock_journal(journal); if (ret >= 0) ret = -1; return ret; } /* * Try to start a handle, but non-blockingly. If we weren't able * to, return an ERR_PTR value. */ handle_t *journal_try_start(journal_t *journal, int nblocks) { handle_t *handle = journal_current_handle(); int err; if (!journal) return ERR_PTR(-EROFS); if (handle) { jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref, handle->h_ref + 1); J_ASSERT(handle->h_transaction->t_journal == journal); if (is_handle_aborted(handle)) return ERR_PTR(-EIO); handle->h_ref++; return handle; } else { jbd_debug(4, "no current transaction\n"); } if (is_journal_aborted(journal)) return ERR_PTR(-EIO); handle = jbd_kmalloc(sizeof (handle_t), GFP_NOFS); if (!handle) return ERR_PTR(-ENOMEM); memset (handle, 0, sizeof (handle_t)); handle->h_buffer_credits = nblocks; handle->h_ref = 1; current->journal_info = handle; err = try_start_this_handle(journal, handle); if (err < 0) { kfree(handle); current->journal_info = NULL; return ERR_PTR(err); } return handle; } /* * journal_extend: extend buffer credits. * * 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; lock_journal (journal); result = -EIO; if (is_handle_aborted(handle)) goto error_out; result = 1; /* 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; } 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 error_out; } if (wanted > log_space_left(journal)) { jbd_debug(3, "denied handle %p %d blocks: " "insufficient log space\n", handle, nblocks); goto error_out; } handle->h_buffer_credits += nblocks; transaction->t_outstanding_credits += nblocks; result = 0; jbd_debug(3, "extended handle %p by %d\n", handle, nblocks); error_out: unlock_journal (journal); return result; } /* * journal_restart: 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); transaction->t_outstanding_credits -= handle->h_buffer_credits; transaction->t_updates--; if (!transaction->t_updates) wake_up(&journal->j_wait_updates); jbd_debug(2, "restarting handle %p\n", handle); log_start_commit(journal, transaction); handle->h_buffer_credits = nblocks; ret = start_this_handle(journal, handle); return ret; } /* * Barrier operation: establish a transaction barrier. * * 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) { lock_journal(journal); ++journal->j_barrier_count; /* Wait until there are no running updates */ while (1) { transaction_t *transaction = journal->j_running_transaction; if (!transaction) break; if (!transaction->t_updates) break; unlock_journal(journal); sleep_on(&journal->j_wait_updates); lock_journal(journal); } unlock_journal(journal); /* 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. */ down(&journal->j_barrier); } /* * Release a transaction barrier obtained with journal_lock_updates(). * * Should be called without the journal lock held. */ void journal_unlock_updates (journal_t *journal) { lock_journal(journal); J_ASSERT (journal->j_barrier_count != 0); up(&journal->j_barrier); --journal->j_barrier_count; wake_up(&journal->j_wait_transaction_locked); unlock_journal(journal); } /* * journal_get_write_access: notify intent to modify a buffer for metadata * (not data) update. * * 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). * * 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. */ static int do_get_write_access(handle_t *handle, struct journal_head *jh, int force_copy) { transaction_t *transaction = handle->h_transaction; journal_t *journal = transaction->t_journal; int error; char *frozen_buffer = NULL; int need_copy = 0; jbd_debug(5, "buffer_head %p, force_copy %d\n", jh, force_copy); JBUFFER_TRACE(jh, "entry"); repeat: /* @@@ Need to check for errors here at some point. */ /* * AKPM: neither bdflush nor kupdate run with the BKL. There's * nothing we can do to prevent them from starting writeout of a * BUF_DIRTY buffer at any time. And checkpointing buffers are on * BUF_DIRTY. So. We no longer assert that the buffer is unlocked. * * However. It is very wrong for us to allow ext3 to start directly * altering the ->b_data of buffers which may at that very time be * undergoing writeout to the client filesystem. This can leave * the filesystem in an inconsistent, transient state if we crash. * So what we do is to steal the buffer if it is in checkpoint * mode and dirty. The journal lock will keep out checkpoint-mode * state transitions within journal_remove_checkpoint() and the buffer * is locked to keep bdflush/kupdate/whoever away from it as well. * * AKPM: we have replaced all the lock_journal_bh_wait() stuff with a * simple lock_journal(). This code here will care for locked buffers. */ /* * The buffer_locked() || buffer_dirty() tests here are simply an * optimisation tweak. If anyone else in the system decides to * lock this buffer later on, we'll blow up. There doesn't seem * to be a good reason why they should do this. */ if (jh->b_cp_transaction && (buffer_locked(jh2bh(jh)) || buffer_dirty(jh2bh(jh)))) { unlock_journal(journal); lock_buffer(jh2bh(jh)); spin_lock(&journal_datalist_lock); if (jh->b_cp_transaction && buffer_dirty(jh2bh(jh))) { /* OK, we need to steal it */ JBUFFER_TRACE(jh, "stealing from checkpoint mode"); J_ASSERT_JH(jh, jh->b_next_transaction == NULL); J_ASSERT_JH(jh, jh->b_frozen_data == NULL); J_ASSERT(handle->h_buffer_credits > 0); handle->h_buffer_credits--; /* This will clear BH_Dirty and set BH_JBDDirty. */ JBUFFER_TRACE(jh, "file as BJ_Reserved"); __journal_file_buffer(jh, transaction, BJ_Reserved); /* And pull it off BUF_DIRTY, onto BUF_CLEAN */ refile_buffer(jh2bh(jh)); /* * The buffer is now hidden from bdflush. It is * metadata against the current transaction. */ JBUFFER_TRACE(jh, "steal from cp mode is complete"); } spin_unlock(&journal_datalist_lock); unlock_buffer(jh2bh(jh)); lock_journal(journal); } J_ASSERT_JH(jh, !buffer_locked(jh2bh(jh))); error = -EROFS; if (is_handle_aborted(handle)) goto out_unlocked; error = 0; spin_lock(&journal_datalist_lock); /* 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_locked; /* 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; J_ASSERT_JH(jh, handle->h_buffer_credits > 0); handle->h_buffer_credits--; goto done_locked; } /* 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) { JBUFFER_TRACE(jh, "on shadow: sleep"); spin_unlock(&journal_datalist_lock); unlock_journal(journal); /* commit wakes up all shadow buffers after IO */ sleep_on(&jh2bh(jh)->b_wait); lock_journal(journal); 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"); spin_unlock(&journal_datalist_lock); unlock_journal(journal); frozen_buffer = jbd_kmalloc(jh2bh(jh)->b_size, GFP_NOFS); lock_journal(journal); if (!frozen_buffer) { printk(KERN_EMERG __FUNCTION__ "OOM for frozen_buffer\n"); JBUFFER_TRACE(jh, "oom!"); error = -ENOMEM; spin_lock(&journal_datalist_lock); goto done_locked; } goto repeat; } jh->b_frozen_data = frozen_buffer; frozen_buffer = NULL; need_copy = 1; } jh->b_next_transaction = transaction; } J_ASSERT(handle->h_buffer_credits > 0); handle->h_buffer_credits--; /* 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); jh->b_transaction = transaction; JBUFFER_TRACE(jh, "file as BJ_Reserved"); __journal_file_buffer(jh, transaction, BJ_Reserved); } done_locked: spin_unlock(&journal_datalist_lock); if (need_copy) { struct page *page; int offset; char *source; J_ASSERT_JH(jh, buffer_uptodate(jh2bh(jh))); page = jh2bh(jh)->b_page; offset = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK; source = kmap(page); memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size); kunmap(page); } /* If we are about to journal a buffer, then any revoke pending on it is no longer valid. */ journal_cancel_revoke(handle, jh); out_unlocked: if (frozen_buffer) kfree(frozen_buffer); JBUFFER_TRACE(jh, "exit"); return error; } int journal_get_write_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 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. */ lock_journal(journal); rc = do_get_write_access(handle, jh, 0); journal_unlock_journal_head(jh); unlock_journal(journal); 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 (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); lock_journal(journal); 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. */ 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))); J_ASSERT_JH(jh, handle->h_buffer_credits > 0); handle->h_buffer_credits--; spin_lock(&journal_datalist_lock); if (jh->b_transaction == NULL) { jh->b_transaction = transaction; JBUFFER_TRACE(jh, "file as BJ_Reserved"); __journal_file_buffer(jh, transaction, BJ_Reserved); JBUFFER_TRACE(jh, "refile"); refile_buffer(jh2bh(jh)); } else if (jh->b_transaction == journal->j_committing_transaction) { JBUFFER_TRACE(jh, "set next transaction"); jh->b_next_transaction = transaction; } spin_unlock(&journal_datalist_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"); journal_cancel_revoke(handle, jh); journal_unlock_journal_head(jh); out: unlock_journal(journal); return err; } /* * journal_get_undo_access: Notify intent to modify metadata with non- * rewindable consequences * * 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) { journal_t *journal = handle->h_transaction->t_journal; int err; struct journal_head *jh = journal_add_journal_head(bh); JBUFFER_TRACE(jh, "entry"); lock_journal(journal); /* 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; if (!jh->b_committed_data) { /* Copy out the current buffer contents into the * preserved, committed copy. */ JBUFFER_TRACE(jh, "generate b_committed data"); jh->b_committed_data = jbd_kmalloc(jh2bh(jh)->b_size, GFP_NOFS); if (!jh->b_committed_data) { printk(KERN_EMERG __FUNCTION__ ": No memory for committed data!\n"); err = -ENOMEM; goto out; } memcpy (jh->b_committed_data, jh2bh(jh)->b_data, jh2bh(jh)->b_size); } out: if (!err) J_ASSERT_JH(jh, jh->b_committed_data); journal_unlock_journal_head(jh); unlock_journal(journal); return err; } /* * journal_dirty_data: 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. * * If `async' is set then the writebask will be initiated by the caller * using submit_bh -> end_buffer_io_async. We put the buffer onto * t_async_datalist. * * Returns error number or 0 on success. * * journal_dirty_data() can be called via page_launder->ext3_writepage * by kswapd. So it cannot block. Happily, there's nothing here * which needs lock_journal if `async' is set. * * When the buffer is on the current transaction we freely move it * between BJ_AsyncData and BJ_SyncData according to who tried to * change its state last. */ int journal_dirty_data (handle_t *handle, struct buffer_head *bh, int async) { journal_t *journal = handle->h_transaction->t_journal; int need_brelse = 0; int wanted_jlist = async ? BJ_AsyncData : BJ_SyncData; struct journal_head *jh; if (is_handle_aborted(handle)) return 0; 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. */ spin_lock(&journal_datalist_lock); 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_AsyncData) { 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 (!async && buffer_dirty(bh)) { atomic_inc(&bh->b_count); spin_unlock(&journal_datalist_lock); need_brelse = 1; ll_rw_block(WRITE, 1, &bh); wait_on_buffer(bh); spin_lock(&journal_datalist_lock); /* The buffer may become locked again at any time if it is redirtied */ } /* journal_clean_data_list() may have got there first */ if (jh->b_transaction != NULL) { JBUFFER_TRACE(jh, "unfile from commit"); __journal_unfile_buffer(jh); jh->b_transaction = NULL; } /* 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 != wanted_jlist) { JBUFFER_TRACE(jh, "not on correct data list: unfile"); J_ASSERT_JH(jh, jh->b_jlist != BJ_Shadow); __journal_unfile_buffer(jh); jh->b_transaction = NULL; JBUFFER_TRACE(jh, "file as data"); __journal_file_buffer(jh, handle->h_transaction, wanted_jlist); } } else { JBUFFER_TRACE(jh, "not on a transaction"); __journal_file_buffer(jh, handle->h_transaction, wanted_jlist); } no_journal: spin_unlock(&journal_datalist_lock); if (need_brelse) { BUFFER_TRACE(bh, "brelse"); __brelse(bh); } JBUFFER_TRACE(jh, "exit"); journal_unlock_journal_head(jh); return 0; } /* * journal_dirty_metadata: mark a buffer as containing 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. * * 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. * * Returns error number or 0 on success. */ 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"); lock_journal(journal); if (is_handle_aborted(handle)) goto out_unlock; spin_lock(&journal_datalist_lock); set_bit(BH_JBDDirty, &bh->b_state); set_buffer_flushtime(bh); J_ASSERT_JH(jh, jh->b_transaction != NULL); /* * 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. */ /* FIXME: writepage() should be journalled */ J_ASSERT_JH(jh, jh->b_jlist != BJ_SyncData); goto done_locked; } /* That test should have eliminated the following case: */ J_ASSERT_JH(jh, jh->b_frozen_data == 0); JBUFFER_TRACE(jh, "file as BJ_Metadata"); __journal_file_buffer(jh, handle->h_transaction, BJ_Metadata); done_locked: spin_unlock(&journal_datalist_lock); JBUFFER_TRACE(jh, "exit"); out_unlock: unlock_journal(journal); return 0; } #if 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. * * journal_get_write_access() can block, so it is quite possible for a * journaling component to decide after the write access is returned * that global state has changed and the update is no longer required. */ void journal_release_buffer (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); lock_journal(journal); JBUFFER_TRACE(jh, "entry"); /* If the buffer is reserved but not modified by this * transaction, then it is safe to release it. In all other * cases, just leave the buffer as it is. */ spin_lock(&journal_datalist_lock); if (jh->b_jlist == BJ_Reserved && jh->b_transaction == transaction && !buffer_jdirty(jh2bh(jh))) { JBUFFER_TRACE(jh, "unused: refiling it"); handle->h_buffer_credits++; __journal_refile_buffer(jh); } spin_unlock(&journal_datalist_lock); JBUFFER_TRACE(jh, "exit"); unlock_journal(journal); } #endif /* * journal_forget: bforget() for potentially-journaled buffers. 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. */ void 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; BUFFER_TRACE(bh, "entry"); lock_journal(journal); spin_lock(&journal_datalist_lock); if (!buffer_jbd(bh)) goto not_jbd; jh = bh2jh(bh); 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_bit(BH_Dirty, &bh->b_state); clear_bit(BH_JBDDirty, &bh->b_state); JBUFFER_TRACE(jh, "belongs to current transaction: unfile"); J_ASSERT_JH(jh, !jh->b_committed_data); __journal_unfile_buffer(jh); jh->b_transaction = 0; /* * 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_file_buffer(jh, transaction, BJ_Forget); } else { __journal_remove_journal_head(bh); __brelse(bh); if (!buffer_jbd(bh)) { spin_unlock(&journal_datalist_lock); unlock_journal(journal); __bforget(bh); return; } } } 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; } } not_jbd: spin_unlock(&journal_datalist_lock); unlock_journal(journal); __brelse(bh); return; } #if 0 /* Unused */ /* * journal_sync_buffer: flush a potentially-journaled buffer to disk. * * Used for O_SYNC filesystem operations. If the buffer is journaled, * we need to complete the O_SYNC by waiting for the transaction to * complete. It is an error to call journal_sync_buffer before * journal_stop! */ void journal_sync_buffer(struct buffer_head *bh) { transaction_t *transaction; journal_t *journal; long sequence; struct journal_head *jh; /* If the buffer isn't journaled, this is easy: just sync it to * disk. */ BUFFER_TRACE(bh, "entry"); spin_lock(&journal_datalist_lock); if (!buffer_jbd(bh)) { spin_unlock(&journal_datalist_lock); return; } jh = bh2jh(bh); if (jh->b_transaction == NULL) { /* If the buffer has already been journaled, then this * is a noop. */ if (jh->b_cp_transaction == NULL) { spin_unlock(&journal_datalist_lock); return; } atomic_inc(&bh->b_count); spin_unlock(&journal_datalist_lock); ll_rw_block (WRITE, 1, &bh); wait_on_buffer(bh); __brelse(bh); goto out; } /* Otherwise, just wait until the transaction is synced to disk. */ transaction = jh->b_transaction; journal = transaction->t_journal; sequence = transaction->t_tid; spin_unlock(&journal_datalist_lock); jbd_debug(2, "requesting commit for jh %p\n", jh); log_start_commit (journal, transaction); while (tid_gt(sequence, journal->j_commit_sequence)) { wake_up(&journal->j_wait_done_commit); sleep_on(&journal->j_wait_done_commit); } JBUFFER_TRACE(jh, "exit"); out: return; } #endif /* * 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 old_handle_count, err; if (!handle) return 0; J_ASSERT (transaction->t_updates > 0); J_ASSERT (journal_current_handle() == handle); if (is_handle_aborted(handle)) err = -EIO; else 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... */ if (handle->h_sync) { do { old_handle_count = transaction->t_handle_count; set_current_state(TASK_RUNNING); current->policy |= SCHED_YIELD; schedule(); } while (old_handle_count != transaction->t_handle_count); } current->journal_info = NULL; 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; jbd_debug(2, "transaction too old, requesting commit for " "handle %p\n", handle); /* This is non-blocking */ log_start_commit(journal, transaction); /* * Special case: JFS_SYNC synchronous updates require us * to wait for the commit to complete. */ if (handle->h_sync && !(current->flags & PF_MEMALLOC)) log_wait_commit(journal, tid); } kfree(handle); return err; } /* * For synchronous operations: force any uncommitted trasnactions * 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 = 0; lock_kernel(); handle = journal_start(journal, 1); if (IS_ERR(handle)) { ret = PTR_ERR(handle); goto out; } handle->h_sync = 1; journal_stop(handle); out: unlock_kernel(); 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. * journal_datalist_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 journal_datalist_lock held, and the journal may not * be locked. */ 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 = 0; } 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_async_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. * * If bh->b_jlist is BJ_SyncData or BJ_AsyncData then we may have been called * via journal_try_to_free_buffer() or journal_clean_data_list(). In that * case, journal_datalist_lock will be held, and the journal may not be locked. */ void __journal_unfile_buffer(struct journal_head *jh) { struct journal_head **list = 0; transaction_t * transaction; assert_spin_locked(&journal_datalist_lock); transaction = jh->b_transaction; #ifdef __SMP__ J_ASSERT (current->lock_depth >= 0); #endif J_ASSERT_JH(jh, jh->b_jlist < BJ_Types); if (jh->b_jlist != BJ_None) J_ASSERT_JH(jh, transaction != 0); switch (jh->b_jlist) { case BJ_None: return; case BJ_SyncData: list = &transaction->t_sync_datalist; break; case BJ_AsyncData: list = &transaction->t_async_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; } __blist_del_buffer(list, jh); jh->b_jlist = BJ_None; if (test_and_clear_bit(BH_JBDDirty, &jh2bh(jh)->b_state)) { set_bit(BH_Dirty, &jh2bh(jh)->b_state); } } void journal_unfile_buffer(struct journal_head *jh) { spin_lock(&journal_datalist_lock); __journal_unfile_buffer(jh); spin_unlock(&journal_datalist_lock); } /* * Called from journal_try_to_free_buffers(). The journal is not * locked. lru_list_lock is not held. * * Here we see why journal_datalist_lock is global and not per-journal. * We cannot get back to this buffer's journal pointer without locking * out journal_clean_data_list() in some manner. * * One could use journal_datalist_lock to get unracy access to a * per-journal lock. * * Called with journal_datalist_lock held. * * Returns non-zero iff we were able to free the journal_head. */ static int __journal_try_to_free_buffer(struct buffer_head *bh, int *locked_or_dirty) { struct journal_head *jh; assert_spin_locked(&journal_datalist_lock); jh = bh2jh(bh); if (buffer_locked(bh) || buffer_dirty(bh)) { *locked_or_dirty = 1; goto out; } if (!buffer_uptodate(bh)) goto out; if (jh->b_next_transaction != 0) goto out; if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) { if (jh->b_jlist == BJ_SyncData || jh->b_jlist==BJ_AsyncData) { /* A written-back ordered data buffer */ JBUFFER_TRACE(jh, "release data"); __journal_unfile_buffer(jh); jh->b_transaction = 0; __journal_remove_journal_head(bh); __brelse(bh); } } else if (jh->b_cp_transaction != 0 && jh->b_transaction == 0) { /* written-back checkpointed metadata buffer */ if (jh->b_jlist == BJ_None) { JBUFFER_TRACE(jh, "remove from checkpoint list"); __journal_remove_checkpoint(jh); __journal_remove_journal_head(bh); __brelse(bh); } } return !buffer_jbd(bh); out: return 0; } /* * journal_try_to_free_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. Called with lru_list_lock * not held. Does its own locking. * * 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? * * This function returns non-zero if we wish try_to_free_buffers() * to be called. We do this is 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. */ int journal_try_to_free_buffers(journal_t *journal, struct page *page, int gfp_mask) { struct buffer_head *bh; struct buffer_head *tmp; int locked_or_dirty = 0; int call_ttfb = 1; J_ASSERT(PageLocked(page)); bh = page->buffers; tmp = bh; spin_lock(&journal_datalist_lock); do { struct buffer_head *p = tmp; tmp = tmp->b_this_page; if (buffer_jbd(p)) if (!__journal_try_to_free_buffer(p, &locked_or_dirty)) call_ttfb = 0; } while (tmp != bh); spin_unlock(&journal_datalist_lock); if (!(gfp_mask & (__GFP_IO|__GFP_WAIT))) goto out; if (!locked_or_dirty) goto out; /* * The VM wants us to do writeout, or to block on IO, or both. * So we allow try_to_free_buffers to be called even if the page * still has journalled buffers. */ call_ttfb = 1; out: return call_ttfb; } /* * 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. */ static int dispose_buffer(struct journal_head *jh, transaction_t *transaction) { int may_free = 1; struct buffer_head *bh = jh2bh(jh); spin_lock(&journal_datalist_lock); __journal_unfile_buffer(jh); jh->b_transaction = 0; if (jh->b_cp_transaction) { JBUFFER_TRACE(jh, "on running+cp transaction"); __journal_file_buffer(jh, transaction, BJ_Forget); clear_bit(BH_JBDDirty, &bh->b_state); may_free = 0; } else { JBUFFER_TRACE(jh, "on running transaction"); __journal_remove_journal_head(bh); __brelse(bh); } spin_unlock(&journal_datalist_lock); return may_free; } /* * journal_flushpage * * 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 flushpage 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) { transaction_t *transaction; struct journal_head *jh; int may_free = 1; BUFFER_TRACE(bh, "entry"); if (!buffer_mapped(bh)) return 1; /* It is safe to proceed here without the * journal_datalist_spinlock 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; jh = bh2jh(bh); 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"); return dispose_buffer(jh, journal->j_running_transaction); } 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"); return dispose_buffer(jh, journal->j_committing_transaction); } else { /* The orphan record's transaction has * committed. We can cleanse this buffer */ clear_bit(BH_JBDDirty, &bh->b_state); goto zap_buffer; } } } else if (transaction == journal->j_committing_transaction) { /* If it is committing, we simply cannot touch it. We * can remove it's next_transaction pointer from the * running transaction if that is set, but nothing * else. */ JBUFFER_TRACE(jh, "on committing transaction"); if (jh->b_next_transaction) { J_ASSERT(jh->b_next_transaction == journal->j_running_transaction); jh->b_next_transaction = NULL; } 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); may_free = dispose_buffer(jh, transaction); } zap_buffer: if (buffer_dirty(bh)) mark_buffer_clean(bh); J_ASSERT_BH(bh, !buffer_jdirty(bh)); clear_bit(BH_Uptodate, &bh->b_state); clear_bit(BH_Mapped, &bh->b_state); clear_bit(BH_Req, &bh->b_state); clear_bit(BH_New, &bh->b_state); return may_free; } /* * Return non-zero if the page's buffers were successfully reaped */ int journal_flushpage(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->buffers) return 1; /* We will potentially be playing with lists other than just the * data lists (especially for journaled data mode), so be * cautious in our locking. */ lock_journal(journal); head = bh = page->buffers; do { unsigned int next_off = curr_off + bh->b_size; next = bh->b_this_page; /* AKPM: doing lock_buffer here may be overly paranoid */ if (offset <= curr_off) { /* This block is wholly outside the truncation point */ lock_buffer(bh); may_free &= journal_unmap_buffer(journal, bh); unlock_buffer(bh); } curr_off = next_off; bh = next; } while (bh != head); unlock_journal(journal); if (!offset) { if (!may_free || !try_to_free_buffers(page, 0)) return 0; J_ASSERT(page->buffers == NULL); } return 1; } /* * 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 = 0; assert_spin_locked(&journal_datalist_lock); #ifdef __SMP__ J_ASSERT (current->lock_depth >= 0); #endif J_ASSERT_JH(jh, jh->b_jlist < BJ_Types); J_ASSERT_JH(jh, jh->b_transaction == transaction || jh->b_transaction == 0); if (jh->b_transaction) { if (jh->b_jlist == jlist) return; __journal_unfile_buffer(jh); } else { 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_AsyncData: list = &transaction->t_async_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; } __blist_add_buffer(list, jh); jh->b_jlist = jlist; if (jlist == BJ_Metadata || jlist == BJ_Reserved || jlist == BJ_Shadow || jlist == BJ_Forget) { if (atomic_set_buffer_clean(jh2bh(jh))) { set_bit(BH_JBDDirty, &jh2bh(jh)->b_state); } } } void journal_file_buffer(struct journal_head *jh, transaction_t *transaction, int jlist) { spin_lock(&journal_datalist_lock); __journal_file_buffer(jh, transaction, jlist); spin_unlock(&journal_datalist_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. */ void __journal_refile_buffer(struct journal_head *jh) { assert_spin_locked(&journal_datalist_lock); #ifdef __SMP__ J_ASSERT_JH(jh, current->lock_depth >= 0); #endif __journal_unfile_buffer(jh); /* If the buffer is now unused, just drop it. If it has been modified by a later transaction, add it to the new transaction's metadata list. */ jh->b_transaction = jh->b_next_transaction; jh->b_next_transaction = NULL; if (jh->b_transaction != NULL) { __journal_file_buffer(jh, jh->b_transaction, BJ_Metadata); J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING); } else { /* Onto BUF_DIRTY for writeback */ refile_buffer(jh2bh(jh)); } } /* * For the unlocked version of this call, also make sure that any * hanging journal_head is cleaned up if necessary. * * __journal_refile_buffer is usually called as part of a single locked * operation on a buffer_head, in which the caller is probably going to * be hooking the journal_head onto other lists. In that case it is up * to the caller to remove the journal_head if necessary. For the * unlocked journal_refile_buffer call, the caller isn't going to be * doing anything else to the buffer so we need to do the cleanup * ourselves to avoid a jh leak. * * *** The journal_head may be freed by this call! *** */ void journal_refile_buffer(struct journal_head *jh) { struct buffer_head *bh; spin_lock(&journal_datalist_lock); bh = jh2bh(jh); __journal_refile_buffer(jh); __journal_remove_journal_head(bh); spin_unlock(&journal_datalist_lock); __brelse(bh); }