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authorDmitry Monakhov <dmonakhov@openvz.org>2012-10-05 19:31:55 +0400
committerTheodore Ts'o <tytso@mit.edu>2012-10-05 19:31:55 +0400
commitc278531d39f3158bfee93dc67da0b77e09776de2 (patch)
treeb83341e04d54b3f1cd8171f43ec77bbfba06e571 /fs/ext4/fsync.c
parent041bbb6d369811e948ae01f3d00414264076be35 (diff)
downloadlinux-c278531d39f3158bfee93dc67da0b77e09776de2.tar.xz
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/fsync.c')
-rw-r--r--fs/ext4/fsync.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index 460000868b8e..be1d89f385b4 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -138,7 +138,7 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
if (inode->i_sb->s_flags & MS_RDONLY)
goto out;
- ret = ext4_flush_completed_IO(inode);
+ ret = ext4_flush_unwritten_io(inode);
if (ret < 0)
goto out;