diff options
Diffstat (limited to 'fs/jbd/transaction.c')
| -rw-r--r-- | fs/jbd/transaction.c | 2062 |
1 files changed, 2062 insertions, 0 deletions
diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c new file mode 100644 index 0000000..932e7c1 --- /dev/null +++ b/fs/jbd/transaction.c @@ -0,0 +1,2062 @@ +/* + * linux/fs/transaction.c + * + * Written by Stephen C. Tweedie <sct@redhat.com>, 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 <linux/time.h> +#include <linux/fs.h> +#include <linux/jbd.h> +#include <linux/errno.h> +#include <linux/slab.h> +#include <linux/timer.h> +#include <linux/smp_lock.h> +#include <linux/mm.h> +#include <linux/highmem.h> + +/* + * 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_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 = 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 = jbd_kmalloc(sizeof(*new_transaction), + GFP_NOFS); + if (!new_transaction) { + ret = -ENOMEM; + goto out; + } + memset(new_transaction, 0, sizeof(*new_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 inconsitent 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); +out: + if (new_transaction) + kfree(new_transaction); + return ret; +} + +/* 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; + + 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 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 = 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); + + 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. + */ + down(&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); + + up(&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); +} + +/* + * Report any unexpected dirty buffers which turn up. Normally those + * indicate an error, but they can occur if the user is running (say) + * tune2fs to modify the live filesystem, so we need the option of + * continuing as gracefully as possible. # + * + * The caller should already hold the journal lock and + * j_list_lock spinlock: most callers will need those anyway + * in order to probe the buffer's journaling state safely. + */ +static void jbd_unexpected_dirty_buffer(struct journal_head *jh) +{ + struct buffer_head *bh = jh2bh(jh); + int jlist; + + if (buffer_dirty(bh)) { + /* If this buffer is one which might reasonably be dirty + * --- ie. data, or not part of this journal --- then + * we're OK to leave it alone, but otherwise we need to + * move the dirty bit to the journal's own internal + * JBDDirty bit. */ + jlist = jh->b_jlist; + + if (jlist == BJ_Metadata || jlist == BJ_Reserved || + jlist == BJ_Shadow || jlist == BJ_Forget) { + if (test_clear_buffer_dirty(jh2bh(jh))) { + set_bit(BH_JBDDirty, &jh2bh(jh)->b_state); + } + } + } +} + +/* + * 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, "buffer_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); + JBUFFER_TRACE(jh, "Unexpected dirty buffer"); + jbd_unexpected_dirty_buffer(jh); + } + } + + 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; + + /* + * 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_kmalloc(jh2bh(jh)->b_size, + GFP_NOFS); + if (!frozen_buffer) { + printk(KERN_EMERG + "%s: OOM for frozen_buffer\n", + __FUNCTION__); + 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); + jh->b_transaction = 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 = ((unsigned long) jh2bh(jh)->b_data) & ~PAGE_MASK; + 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 (frozen_buffer) + kfree(frozen_buffer); + + 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 + * @credits: variable that will receive credits for the buffer + * + * 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) { + jh->b_transaction = transaction; + JBUFFER_TRACE(jh, "file as BJ_Reserved"); + __journal_file_buffer(jh, transaction, BJ_Reserved); + } else if (jh->b_transaction == journal->j_committing_transaction) { + 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); + journal_put_journal_head(jh); +out: + return err; +} + +/** + * int journal_get_undo_access() - Notify intent to modify metadata with + * non-rewindable consequences + * @handle: transaction + * @bh: buffer to undo + * @credits: store the number of taken credits here (if not NULL) + * + * 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_kmalloc(jh2bh(jh)->b_size, GFP_NOFS); + if (!committed_data) { + printk(KERN_EMERG "%s: No memory for committed data\n", + __FUNCTION__); + 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 (committed_data) + kfree(committed_data); + return err; +} + +/** + * int journal_dirty_data() - mark a buffer as containing dirty data which + * needs to be flushed before we can commit the + * current transaction. + * @handle: transaction + * @bh: bufferhead to mark + * + * 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; + + 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. + */ + jbd_lock_bh_state(bh); + spin_lock(&journal->j_list_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_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); + /* 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_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); + __journal_temp_unlink_buffer(jh); + jh->b_transaction = handle->h_transaction; + 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 0; +} + +/** + * 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 == 0); + + 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; + + 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; + } + + /* + * 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"); + + 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); + journal_remove_journal_head(bh); + __brelse(bh); + 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; + 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 old_handle_count, err; + + 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_UNINTERRUPTIBLE); + schedule_timeout(1); + } while (old_handle_count != transaction->t_handle_count); + } + + 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); + } + + 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. + */ +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 != 0); + + 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 */ +} + +void __journal_unfile_buffer(struct journal_head *jh) +{ + __journal_temp_unlink_buffer(jh); + jh->b_transaction = NULL; +} + +void journal_unfile_buffer(journal_t *journal, struct journal_head *jh) +{ + jbd_lock_bh_state(jh2bh(jh)); + spin_lock(&journal->j_list_lock); + __journal_unfile_buffer(jh); + spin_unlock(&journal->j_list_lock); + jbd_unlock_bh_state(jh2bh(jh)); +} + +/* + * 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 != 0) + goto out; + + spin_lock(&journal->j_list_lock); + if (jh->b_transaction != 0 && jh->b_cp_transaction == 0) { + 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); + 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); + } + } + 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 + * @unused_gfp_mask: unused + * + * + * 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? + */ +int journal_try_to_free_buffers(journal_t *journal, + struct page *page, int unused_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_remove_journal_head() and 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); + + __journal_unfile_buffer(jh); + + if (jh->b_cp_transaction) { + JBUFFER_TRACE(jh, "on running+cp transaction"); + __journal_file_buffer(jh, transaction, BJ_Forget); + clear_buffer_jbddirty(bh); + may_free = 0; + } else { + JBUFFER_TRACE(jh, "on running transaction"); + journal_remove_journal_head(bh); + __brelse(bh); + } + 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) +{ + transaction_t *transaction; + struct journal_head *jh; + int may_free = 1; + int ret; + + BUFFER_TRACE(bh, "entry"); + + /* + * It is safe to proceed here without the j_list_lock because the + * buffers cannot be stolen by try_to_free_buffers as long as we are + * holding the page lock. --sct + */ + + 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; + + 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"); + ret = __dispose_buffer(jh, + 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 ret; + } 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"); + ret = __dispose_buffer(jh, + journal->j_committing_transaction); + journal_put_journal_head(jh); + spin_unlock(&journal->j_list_lock); + jbd_unlock_bh_state(bh); + spin_unlock(&journal->j_state_lock); + return ret; + } 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) { + /* 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"); + set_buffer_freed(bh); + if (jh->b_next_transaction) { + J_ASSERT(jh->b_next_transaction == + journal->j_running_transaction); + jh->b_next_transaction = NULL; + } + 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); + may_free = __dispose_buffer(jh, transaction); + } + +zap_buffer: + 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; +} + +/** + * int journal_invalidatepage() + * @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. + * + * Return non-zero if the page's buffers were successfully reaped. + */ +int 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 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. */ + + head = bh = page_buffers(page); + 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); + + if (!offset) { + if (!may_free || !try_to_free_buffers(page)) + return 0; + J_ASSERT(!page_has_buffers(page)); + } + 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 = 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 == 0); + + if (jh->b_transaction && jh->b_jlist == jlist) + return; + + /* The following list of buffer states needs to be consistent + * with __jbd_unexpected_dirty_buffer()'s handling of dirty + * state. */ + + if (jlist == BJ_Metadata || jlist == BJ_Reserved || + jlist == BJ_Shadow || jlist == BJ_Forget) { + if (test_clear_buffer_dirty(bh) || + test_clear_buffer_jbddirty(bh)) + was_dirty = 1; + } + + if (jh->b_transaction) + __journal_temp_unlink_buffer(jh); + 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 journal->j_list_lock + * + * Called under jbd_lock_bh_state(jh2bh(jh)) + */ +void __journal_refile_buffer(struct journal_head *jh) +{ + int was_dirty; + 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); + jh->b_transaction = jh->b_next_transaction; + jh->b_next_transaction = NULL; + __journal_file_buffer(jh, jh->b_transaction, BJ_Metadata); + J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING); + + if (was_dirty) + set_buffer_jbddirty(bh); +} + +/* + * 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(journal_t *journal, struct journal_head *jh) +{ + struct buffer_head *bh = jh2bh(jh); + + jbd_lock_bh_state(bh); + spin_lock(&journal->j_list_lock); + + __journal_refile_buffer(jh); + jbd_unlock_bh_state(bh); + journal_remove_journal_head(bh); + + spin_unlock(&journal->j_list_lock); + __brelse(bh); +} |
