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authorTheodore Ts'o <tytso@mit.edu>2013-04-03 22:02:52 -0400
committerBen Hutchings <ben@decadent.org.uk>2013-05-13 15:02:14 +0100
commit164ed4383ca615f9a4f19673ac82372ccf96a33f (patch)
tree359d6a139073c97ef0d779421767e87b597aab6f /fs
parent7e6c247f30c65913688850620e40b418223a5ff3 (diff)
ext4/jbd2: don't wait (forever) for stale tid caused by wraparound
commit d76a3a77113db020d9bb1e894822869410450bd9 upstream. In the case where an inode has a very stale transaction id (tid) in i_datasync_tid or i_sync_tid, it's possible that after a very large (2**31) number of transactions, that the tid number space might wrap, causing tid_geq()'s calculations to fail. Commit deeeaf13 "jbd2: fix fsync() tid wraparound bug", later modified by commit e7b04ac0 "jbd2: don't wake kjournald unnecessarily", attempted to fix this problem, but it only avoided kjournald spinning forever by fixing the logic in jbd2_log_start_commit(). Unfortunately, in the codepaths in fs/ext4/fsync.c and fs/ext4/inode.c that might call jbd2_log_start_commit() with a stale tid, those functions will subsequently call jbd2_log_wait_commit() with the same stale tid, and then wait for a very long time. To fix this, we replace the calls to jbd2_log_start_commit() and jbd2_log_wait_commit() with a call to a new function, jbd2_complete_transaction(), which will correctly handle stale tid's. As a bonus, jbd2_complete_transaction() will avoid locking j_state_lock for writing unless a commit needs to be started. This should have a small (but probably not measurable) improvement for ext4's scalability. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reported-by: Ben Hutchings <ben@decadent.org.uk> Reported-by: George Barnett <gbarnett@atlassian.com> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/fsync.c3
-rw-r--r--fs/ext4/inode.c3
-rw-r--r--fs/jbd2/journal.c31
3 files changed, 33 insertions, 4 deletions
diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index bb6c7d811313..a8d03a4d3f8b 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -260,8 +260,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
if (journal->j_flags & JBD2_BARRIER &&
!jbd2_trans_will_send_data_barrier(journal, commit_tid))
needs_barrier = true;
- jbd2_log_start_commit(journal, commit_tid);
- ret = jbd2_log_wait_commit(journal, commit_tid);
+ ret = jbd2_complete_transaction(journal, commit_tid);
if (needs_barrier)
blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
out:
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3270ffd791fb..025b4b6573d7 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -147,8 +147,7 @@ void ext4_evict_inode(struct inode *inode)
journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
tid_t commit_tid = EXT4_I(inode)->i_datasync_tid;
- jbd2_log_start_commit(journal, commit_tid);
- jbd2_log_wait_commit(journal, commit_tid);
+ jbd2_complete_transaction(journal, commit_tid);
filemap_write_and_wait(&inode->i_data);
}
truncate_inode_pages(&inode->i_data, 0);
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 0fa0123151d3..17b04fcf5fa6 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -663,6 +663,37 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
}
/*
+ * When this function returns the transaction corresponding to tid
+ * will be completed. If the transaction has currently running, start
+ * committing that transaction before waiting for it to complete. If
+ * the transaction id is stale, it is by definition already completed,
+ * so just return SUCCESS.
+ */
+int jbd2_complete_transaction(journal_t *journal, tid_t tid)
+{
+ int need_to_wait = 1;
+
+ read_lock(&journal->j_state_lock);
+ if (journal->j_running_transaction &&
+ journal->j_running_transaction->t_tid == tid) {
+ if (journal->j_commit_request != tid) {
+ /* transaction not yet started, so request it */
+ read_unlock(&journal->j_state_lock);
+ jbd2_log_start_commit(journal, tid);
+ goto wait_commit;
+ }
+ } else if (!(journal->j_committing_transaction &&
+ journal->j_committing_transaction->t_tid == tid))
+ need_to_wait = 0;
+ read_unlock(&journal->j_state_lock);
+ if (!need_to_wait)
+ return 0;
+wait_commit:
+ return jbd2_log_wait_commit(journal, tid);
+}
+EXPORT_SYMBOL(jbd2_complete_transaction);
+
+/*
* Log buffer allocation routines:
*/