diff options
Diffstat (limited to 'fs/jbd2/transaction.c')
| -rw-r--r-- | fs/jbd2/transaction.c | 270 |
1 files changed, 160 insertions, 110 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index ff2f2e6ad311..f3d06174b051 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -278,22 +278,16 @@ static int start_this_handle(journal_t *journal, handle_t *handle, alloc_transaction: if (!journal->j_running_transaction) { + /* + * If __GFP_FS is not present, then we may be being called from + * inside the fs writeback layer, so we MUST NOT fail. + */ + if ((gfp_mask & __GFP_FS) == 0) + gfp_mask |= __GFP_NOFAIL; new_transaction = kmem_cache_zalloc(transaction_cache, gfp_mask); - if (!new_transaction) { - /* - * If __GFP_FS is not present, then we may be - * being called from inside the fs writeback - * layer, so we MUST NOT fail. Since - * __GFP_NOFAIL is going away, we will arrange - * to retry the allocation ourselves. - */ - if ((gfp_mask & __GFP_FS) == 0) { - congestion_wait(BLK_RW_ASYNC, HZ/50); - goto alloc_transaction; - } + if (!new_transaction) return -ENOMEM; - } } jbd_debug(3, "New handle %p going live.\n", handle); @@ -761,6 +755,30 @@ static void warn_dirty_buffer(struct buffer_head *bh) bdevname(bh->b_bdev, b), (unsigned long long)bh->b_blocknr); } +/* Call t_frozen trigger and copy buffer data into jh->b_frozen_data. */ +static void jbd2_freeze_jh_data(struct journal_head *jh) +{ + struct page *page; + int offset; + char *source; + struct buffer_head *bh = jh2bh(jh); + + J_EXPECT_JH(jh, buffer_uptodate(bh), "Possible IO failure.\n"); + page = bh->b_page; + offset = offset_in_page(bh->b_data); + source = kmap_atomic(page); + /* Fire data frozen trigger just before we copy the data */ + jbd2_buffer_frozen_trigger(jh, source + offset, jh->b_triggers); + memcpy(jh->b_frozen_data, source + offset, bh->b_size); + kunmap_atomic(source); + + /* + * Now that the frozen data is saved off, we need to store any matching + * triggers. + */ + jh->b_frozen_triggers = jh->b_triggers; +} + /* * If the buffer is already part of the current transaction, then there * is nothing we need to do. If it is already part of a prior @@ -780,7 +798,6 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, journal_t *journal; int error; char *frozen_buffer = NULL; - int need_copy = 0; unsigned long start_lock, time_lock; if (is_handle_aborted(handle)) @@ -867,119 +884,96 @@ repeat: jh->b_modified = 0; /* + * If the buffer is not journaled right now, we need to make sure it + * doesn't get written to disk before the caller actually commits the + * new data + */ + if (!jh->b_transaction) { + JBUFFER_TRACE(jh, "no transaction"); + J_ASSERT_JH(jh, !jh->b_next_transaction); + JBUFFER_TRACE(jh, "file as BJ_Reserved"); + /* + * Make sure all stores to jh (b_modified, b_frozen_data) are + * visible before attaching it to the running transaction. + * Paired with barrier in jbd2_write_access_granted() + */ + smp_wmb(); + spin_lock(&journal->j_list_lock); + __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved); + spin_unlock(&journal->j_list_lock); + 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; + goto attach_next; } - /* Is there data here we need to preserve? */ + 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); - 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 (buffer_shadow(bh)) { + JBUFFER_TRACE(jh, "on shadow: sleep"); + jbd_unlock_bh_state(bh); + wait_on_bit_io(&bh->b_state, BH_Shadow, TASK_UNINTERRUPTIBLE); + goto repeat; + } - /* There is one case we have to be very careful about. - * If the committing transaction is currently writing - * this buffer out to disk and has NOT made a copy-out, - * then we cannot modify the buffer contents at all - * right now. The essence of copy-out is that it is the - * extra copy, not the primary copy, which gets - * journaled. If the primary copy is already going to - * disk then we cannot do copy-out here. */ - - if (buffer_shadow(bh)) { - JBUFFER_TRACE(jh, "on shadow: sleep"); + /* + * Only do the copy if the currently-owning transaction still needs it. + * If buffer isn't on BJ_Metadata list, the committing transaction is + * past that stage (here we use the fact that BH_Shadow is set under + * bh_state lock together with refiling to BJ_Shadow list and at this + * point we know the buffer doesn't have BH_Shadow set). + * + * Subtle point, though: if this is a get_undo_access, then we will be + * relying on the frozen_data to contain the new value of the + * committed_data record after the transaction, so we HAVE to force the + * frozen_data copy in that case. + */ + if (jh->b_jlist == BJ_Metadata || force_copy) { + JBUFFER_TRACE(jh, "generate frozen data"); + if (!frozen_buffer) { + JBUFFER_TRACE(jh, "allocate memory for buffer"); jbd_unlock_bh_state(bh); - wait_on_bit_io(&bh->b_state, BH_Shadow, - TASK_UNINTERRUPTIBLE); - goto repeat; - } - - /* - * Only do the copy if the currently-owning transaction still - * needs it. If buffer isn't on BJ_Metadata list, the - * committing transaction is past that stage (here we use the - * fact that BH_Shadow is set under bh_state lock together with - * refiling to BJ_Shadow list and at this point we know the - * buffer doesn't have BH_Shadow set). - * - * Subtle point, though: if this is a get_undo_access, - * then we will be relying on the frozen_data to contain - * the new value of the committed_data record after the - * transaction, so we HAVE to force the frozen_data copy - * in that case. - */ - if (jh->b_jlist == BJ_Metadata || force_copy) { - JBUFFER_TRACE(jh, "generate frozen data"); + frozen_buffer = jbd2_alloc(jh2bh(jh)->b_size, GFP_NOFS); if (!frozen_buffer) { - JBUFFER_TRACE(jh, "allocate memory for buffer"); - jbd_unlock_bh_state(bh); - frozen_buffer = - jbd2_alloc(jh2bh(jh)->b_size, - GFP_NOFS); - if (!frozen_buffer) { - printk(KERN_ERR - "%s: OOM for frozen_buffer\n", - __func__); - JBUFFER_TRACE(jh, "oom!"); - error = -ENOMEM; - jbd_lock_bh_state(bh); - goto done; - } - goto repeat; + printk(KERN_ERR "%s: OOM for frozen_buffer\n", + __func__); + JBUFFER_TRACE(jh, "oom!"); + error = -ENOMEM; + goto out; } - jh->b_frozen_data = frozen_buffer; - frozen_buffer = NULL; - need_copy = 1; + goto repeat; } - jh->b_next_transaction = transaction; + jh->b_frozen_data = frozen_buffer; + frozen_buffer = NULL; + jbd2_freeze_jh_data(jh); } - - +attach_next: /* - * 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 + * Make sure all stores to jh (b_modified, b_frozen_data) are visible + * before attaching it to the running transaction. Paired with barrier + * in jbd2_write_access_granted() */ - if (!jh->b_transaction) { - JBUFFER_TRACE(jh, "no transaction"); - J_ASSERT_JH(jh, !jh->b_next_transaction); - JBUFFER_TRACE(jh, "file as BJ_Reserved"); - spin_lock(&journal->j_list_lock); - __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved); - spin_unlock(&journal->j_list_lock); - } + smp_wmb(); + jh->b_next_transaction = transaction; done: - if (need_copy) { - struct page *page; - int offset; - char *source; - - J_EXPECT_JH(jh, buffer_uptodate(jh2bh(jh)), - "Possible IO failure.\n"); - page = jh2bh(jh)->b_page; - offset = offset_in_page(jh2bh(jh)->b_data); - source = kmap_atomic(page); - /* Fire data frozen trigger just before we copy the data */ - jbd2_buffer_frozen_trigger(jh, source + offset, - jh->b_triggers); - memcpy(jh->b_frozen_data, source+offset, jh2bh(jh)->b_size); - kunmap_atomic(source); - - /* - * Now that the frozen data is saved off, we need to store - * any matching triggers. - */ - jh->b_frozen_triggers = jh->b_triggers; - } jbd_unlock_bh_state(bh); /* @@ -996,6 +990,55 @@ out: return error; } +/* Fast check whether buffer is already attached to the required transaction */ +static bool jbd2_write_access_granted(handle_t *handle, struct buffer_head *bh) +{ + struct journal_head *jh; + bool ret = false; + + /* Dirty buffers require special handling... */ + if (buffer_dirty(bh)) + return false; + + /* + * RCU protects us from dereferencing freed pages. So the checks we do + * are guaranteed not to oops. However the jh slab object can get freed + * & reallocated while we work with it. So we have to be careful. When + * we see jh attached to the running transaction, we know it must stay + * so until the transaction is committed. Thus jh won't be freed and + * will be attached to the same bh while we run. However it can + * happen jh gets freed, reallocated, and attached to the transaction + * just after we get pointer to it from bh. So we have to be careful + * and recheck jh still belongs to our bh before we return success. + */ + rcu_read_lock(); + if (!buffer_jbd(bh)) + goto out; + /* This should be bh2jh() but that doesn't work with inline functions */ + jh = READ_ONCE(bh->b_private); + if (!jh) + goto out; + if (jh->b_transaction != handle->h_transaction && + jh->b_next_transaction != handle->h_transaction) + goto out; + /* + * There are two reasons for the barrier here: + * 1) Make sure to fetch b_bh after we did previous checks so that we + * detect when jh went through free, realloc, attach to transaction + * while we were checking. Paired with implicit barrier in that path. + * 2) So that access to bh done after jbd2_write_access_granted() + * doesn't get reordered and see inconsistent state of concurrent + * do_get_write_access(). + */ + smp_mb(); + if (unlikely(jh->b_bh != bh)) + goto out; + ret = true; +out: + rcu_read_unlock(); + return ret; +} + /** * int jbd2_journal_get_write_access() - notify intent to modify a buffer for metadata (not data) update. * @handle: transaction to add buffer modifications to @@ -1009,9 +1052,13 @@ out: int jbd2_journal_get_write_access(handle_t *handle, struct buffer_head *bh) { - struct journal_head *jh = jbd2_journal_add_journal_head(bh); + struct journal_head *jh; int rc; + if (jbd2_write_access_granted(handle, bh)) + return 0; + + jh = jbd2_journal_add_journal_head(bh); /* We do not want to get caught playing with fields which the * log thread also manipulates. Make sure that the buffer * completes any outstanding IO before proceeding. */ @@ -1141,11 +1188,14 @@ out: int jbd2_journal_get_undo_access(handle_t *handle, struct buffer_head *bh) { int err; - struct journal_head *jh = jbd2_journal_add_journal_head(bh); + struct journal_head *jh; char *committed_data = NULL; JBUFFER_TRACE(jh, "entry"); + if (jbd2_write_access_granted(handle, bh)) + return 0; + jh = jbd2_journal_add_journal_head(bh); /* * Do this first --- it can drop the journal lock, so we want to * make sure that obtaining the committed_data is done |