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authorDmitry Monakhov <dmonakhov@openvz.org>2013-03-04 00:36:06 -0500
committerTheodore Ts'o <tytso@mit.edu>2013-03-04 00:36:06 -0500
commitec22ba8edb507395c95fbc617eea26a6b2d98797 (patch)
treea04ffae5cd5f0d1724aa64f26046d5f85bb75af5 /fs/ext4
parent357b66fdc8ad4cea6e6336956a70742f961f0a4d (diff)
downloadop-kernel-dev-ec22ba8edb507395c95fbc617eea26a6b2d98797.zip
op-kernel-dev-ec22ba8edb507395c95fbc617eea26a6b2d98797.tar.gz
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')
-rw-r--r--fs/ext4/extents.c8
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))
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