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| author | Dmitry Monakhov <dmonakhov@openvz.org> | 2012-10-05 19:31:55 +0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2012-10-05 19:31:55 +0400 |
| commit | c278531d39f3158bfee93dc67da0b77e09776de2 (patch) | |
| tree | b83341e04d54b3f1cd8171f43ec77bbfba06e571 /fs/ext4/indirect.c | |
| parent | 041bbb6d369811e948ae01f3d00414264076be35 (diff) | |
| download | linux-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.c | 8 |
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 |