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>
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1 changed files with 5 additions and 3 deletions
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@ -1584,10 +1584,12 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
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unsigned short ext1_ee_len, ext2_ee_len, max_len;
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/*
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* Make sure that either both extents are uninitialized, or
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* both are _not_.
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* Make sure that both extents are initialized. We don't merge
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* uninitialized extents so that we can be sure that end_io code has
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* the extent that was written properly split out and conversion to
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* initialized is trivial.
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*/
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if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2))
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if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2))
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return 0;
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if (ext4_ext_is_uninitialized(ex1))
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