From: Surbhi Palande Subject: [PATCH v2] Adding support to freeze and unfreeze a journal Date: Sat, 7 May 2011 23:04:22 +0300 Message-ID: <1304798662-3884-1-git-send-email-surbhi.palande@canonical.com> References: Cc: jack@suse.cz, toshi.okajima@jp.fujitsu.com, tytso@mit.edu, m.mizuma@jp.fujitsu.com, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, sandeen@redhat.com To: adilger.kernel@dilger.ca Return-path: Received: from adelie.canonical.com ([91.189.90.139]:35680 "EHLO adelie.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756050Ab1EGUEc (ORCPT ); Sat, 7 May 2011 16:04:32 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On freezing the F.S, the journal should be frozen as well. This implies not being able to start any new transactions on a frozen journal. Similarly, thawing a F.S should thaw a journal and this should conversely start accepting new transactions. While the F.S is frozen any request to start a new handle should end up on a wait queue till the F.S is thawed back again. Adding support to freeze and thaw a journal and leveraging this support in freezing and thawing ext4. Signed-off-by: Surbhi Palande --- Changes since v1: * Check for the j_flag and if frozen release the j_state_lock before sleeping on wait queue * Export the freeze, thaw routines * Added a barrier after setting the j_flags = JBD2_FROZEN fs/ext4/super.c | 20 ++++++-------------- fs/jbd2/journal.c | 1 + fs/jbd2/transaction.c | 43 +++++++++++++++++++++++++++++++++++++++++++ include/linux/jbd2.h | 9 +++++++++ 4 files changed, 59 insertions(+), 14 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 8553dfb..796aa4c 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4179,23 +4179,15 @@ static int ext4_freeze(struct super_block *sb) journal = EXT4_SB(sb)->s_journal; - /* Now we set up the journal barrier. */ - jbd2_journal_lock_updates(journal); - + error = jbd2_journal_freeze(journal); /* - * Don't clear the needs_recovery flag if we failed to flush + * Don't clear the needs_recovery flag if we failed to freeze * the journal. */ - error = jbd2_journal_flush(journal); - if (error < 0) - goto out; - - /* Journal blocked and flushed, clear needs_recovery flag. */ - EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); - error = ext4_commit_super(sb, 1); -out: - /* we rely on s_frozen to stop further updates */ - jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal); + if (error >= 0) { + EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER); + error = ext4_commit_super(sb, 1); + } return error; } diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index e0ec3db..5e46333 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -842,6 +842,7 @@ static journal_t * journal_init_common (void) init_waitqueue_head(&journal->j_wait_checkpoint); init_waitqueue_head(&journal->j_wait_commit); init_waitqueue_head(&journal->j_wait_updates); + init_waitqueue_head(&journal->j_wait_frozen); mutex_init(&journal->j_barrier); mutex_init(&journal->j_checkpoint_mutex); spin_lock_init(&journal->j_revoke_lock); diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index 05fa77a..3283c77 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -171,6 +171,17 @@ repeat: journal->j_barrier_count == 0); goto repeat; } + /* dont let a new handle start when a journal is frozen. + * jbd2_journal_freeze calls jbd2_journal_unlock_updates() only after + * the jflags indicate that the journal is frozen. So if the + * j_barrier_count is 0, then check if this was made 0 by the freezing + * process + */ + if (journal->j_flags & JBD2_FROZEN) { + read_unlock(&journal->j_state_lock); + jbd2_check_frozen(journal); + goto repeat; + } if (!journal->j_running_transaction) { read_unlock(&journal->j_state_lock); @@ -489,6 +500,38 @@ int jbd2_journal_restart(handle_t *handle, int nblocks) } EXPORT_SYMBOL(jbd2_journal_restart); +int jbd2_journal_freeze(journal_t *journal) +{ + int error = 0; + /* Now we set up the journal barrier. */ + jbd2_journal_lock_updates(journal); + + /* + * Don't clear the needs_recovery flag if we failed to flush + * the journal. + */ + error = jbd2_journal_flush(journal); + if (error >= 0) { + write_lock(&journal->j_state_lock); + journal->j_flags = journal->j_flags | JBD2_FROZEN; + write_unlock(&journal->j_state_lock); + } + jbd2_journal_unlock_updates(journal); + return error; +} +EXPORT_SYMBOL(jbd2_journal_freeze); + +void jbd2_journal_thaw(journal_t * journal) +{ + write_lock(&journal->j_state_lock); + journal->j_flags = journal->j_flags &= ~JBD2_FROZEN; + write_unlock(&journal->j_state_lock); + smp_wmb(); + wake_up(&journal->j_wait_frozen); +} +EXPORT_SYMBOL(jbd2_journal_thaw); + + /** * void jbd2_journal_lock_updates () - establish a transaction barrier. * @journal: Journal to establish a barrier on. diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index a32dcae..31d6c23 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -835,6 +835,9 @@ struct journal_s /* Wait queue to wait for updates to complete */ wait_queue_head_t j_wait_updates; + /* Wait queue to wait for journal to thaw*/ + wait_queue_head_t j_wait_frozen; + /* Semaphore for locking against concurrent checkpoints */ struct mutex j_checkpoint_mutex; @@ -1013,7 +1016,11 @@ struct journal_s #define JBD2_ABORT_ON_SYNCDATA_ERR 0x040 /* Abort the journal on file * data write error in ordered * mode */ +#define JBD2_FROZEN 0x080 /* Journal thread is frozen as the filesystem is frozen */ + +#define jbd2_check_frozen(journal) \ + wait_event(journal->j_wait_frozen, ((journal->j_flags & JBD2_FROZEN) != JBD2_FROZEN)) /* * Function declarations for the journaling transaction and buffer * management @@ -1121,6 +1128,8 @@ extern void jbd2_journal_invalidatepage(journal_t *, struct page *, unsigned long); extern int jbd2_journal_try_to_free_buffers(journal_t *, struct page *, gfp_t); extern int jbd2_journal_stop(handle_t *); +extern int jbd2_journal_freeze(journal_t *); +extern void jbd2_journal_thaw(journal_t *); extern int jbd2_journal_flush (journal_t *); extern void jbd2_journal_lock_updates (journal_t *); extern void jbd2_journal_unlock_updates (journal_t *); -- 1.7.1