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authorDmitry Monakhov <dmonakhov@openvz.org>2012-10-05 11:31:55 -0400
committerTheodore Ts'o <tytso@mit.edu>2012-10-05 11:31:55 -0400
commitc278531d39f3158bfee93dc67da0b77e09776de2 (patch)
treeb83341e04d54b3f1cd8171f43ec77bbfba06e571 /fs/ext4/page-io.c
parent041bbb6d369811e948ae01f3d00414264076be35 (diff)
ext4: fix ext4_flush_completed_IO wait semantics
BUG #1) All places where we call ext4_flush_completed_IO are broken because buffered io and DIO/AIO goes through three stages 1) submitted io, 2) completed io (in i_completed_io_list) conversion pended 3) finished io (conversion done) And by calling ext4_flush_completed_IO we will flush only requests which were in (2) stage, which is wrong because: 1) punch_hole and truncate _must_ wait for all outstanding unwritten io regardless to it's state. 2) fsync and nolock_dio_read should also wait because there is a time window between end_page_writeback() and ext4_add_complete_io() As result integrity fsync is broken in case of buffered write to fallocated region: fsync blkdev_completion ->filemap_write_and_wait_range ->ext4_end_bio ->end_page_writeback <-- filemap_write_and_wait_range return ->ext4_flush_completed_IO sees empty i_completed_io_list but pended conversion still exist ->ext4_add_complete_io BUG #2) Race window becomes wider due to the 'ext4: completed_io locking cleanup V4' patch series This patch make following changes: 1) ext4_flush_completed_io() now first try to flush completed io and when wait for any outstanding unwritten io via ext4_unwritten_wait() 2) Rename function to more appropriate name. 3) Assert that all callers of ext4_flush_unwritten_io should hold i_mutex to prevent endless wait Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/ext4/page-io.c')
-rw-r--r--fs/ext4/page-io.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 5b24c407701..68e896e12a6 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -189,8 +189,6 @@ static int ext4_do_flush_completed_IO(struct inode *inode,
list_add_tail(&io->list, &complete);
}
- /* It is important to update all flags for all end_io in one shot w/o
- * dropping the lock.*/
spin_lock_irqsave(&ei->i_completed_io_lock, flags);
while (!list_empty(&complete)) {
io = list_entry(complete.next, ext4_io_end_t, list);
@@ -228,9 +226,14 @@ static void ext4_end_io_work(struct work_struct *work)
ext4_do_flush_completed_IO(io->inode, io);
}
-int ext4_flush_completed_IO(struct inode *inode)
+int ext4_flush_unwritten_io(struct inode *inode)
{
- return ext4_do_flush_completed_IO(inode, NULL);
+ int ret;
+ WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex) &&
+ !(inode->i_state & I_FREEING));
+ ret = ext4_do_flush_completed_IO(inode, NULL);
+ ext4_unwritten_wait(inode);
+ return ret;
}
ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)