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| author | Dmitry Monakhov <dmonakhov@openvz.org> | 2013-03-04 05:36:06 (GMT) |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-03-04 05:36:06 (GMT) |
| commit | ec22ba8edb507395c95fbc617eea26a6b2d98797 (patch) | |
| tree | a04ffae5cd5f0d1724aa64f26046d5f85bb75af5 /fs/ext4/extents.c | |
| parent | 357b66fdc8ad4cea6e6336956a70742f961f0a4d (diff) | |
| download | linux-ec22ba8edb507395c95fbc617eea26a6b2d98797.tar.xz | |
ext4: disable merging of uninitialized extents
Derived from Jan's patch:http://permalink.gmane.org/gmane.comp.file-systems.ext4/36470
Merging of uninitialized extents creates all sorts of interesting race
possibilities when writeback / DIO races with fallocate. Thus
ext4_convert_unwritten_extents_endio() has to deal with a case where
extent to be converted needs to be split out first. That isn't nice
for two reasons:
1) It may need allocation of extent tree block so ENOSPC is possible.
2) It complicates end_io handling code
So we disable merging of uninitialized extents which allows us to simplify
the code. Extents will get merged after they are converted to initialized
ones.
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/extents.c')
| -rw-r--r-- | fs/ext4/extents.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index bef194a..60818ed 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -1584,10 +1584,12 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1, unsigned short ext1_ee_len, ext2_ee_len, max_len; /* - * Make sure that either both extents are uninitialized, or - * both are _not_. + * Make sure that both extents are initialized. We don't merge + * uninitialized extents so that we can be sure that end_io code has + * the extent that was written properly split out and conversion to + * initialized is trivial. */ - if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2)) + if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2)) return 0; if (ext4_ext_is_uninitialized(ex1)) |