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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/indirect.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/indirect.c')
-rw-r--r--fs/ext4/indirect.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 8d849dae8428..792e388e7b44 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -807,9 +807,11 @@ ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
retry:
if (rw == READ && ext4_should_dioread_nolock(inode)) {
- if (unlikely(!list_empty(&ei->i_completed_io_list)))
- ext4_flush_completed_IO(inode);
-
+ if (unlikely(atomic_read(&EXT4_I(inode)->i_unwritten))) {
+ mutex_lock(&inode->i_mutex);
+ ext4_flush_unwritten_io(inode);
+ mutex_unlock(&inode->i_mutex);
+ }
/*
* Nolock dioread optimization may be dynamically disabled
* via ext4_inode_block_unlocked_dio(). Check inode's state