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05 April 2024, 19:05:47 UTC
Revision 0f6925fa2907df58496cabc33fa4677c635e2223 authored by Qu Wenruo on 14 October 2015, 07:26:13 UTC, committed by Chris Mason on 21 October 2015, 02:07:29 UTC 
btrfs: Avoid truncate tailing page if fallocate range doesn't exceed inode size
 
Current code will always truncate tailing page if its alloc_start is
smaller than inode size.

For example, the file extent layout is like:
0	4K	8K	16K	32K
|<-----Extent A---------------->|
|<--Inode size: 18K---------->|

But if calling fallocate even for range [0,4K), it will cause btrfs to
re-truncate the range [16,32K), causing COW and a new extent.

0	4K	8K	16K	32K
|///////|	<- Fallocate call range
|<-----Extent A-------->|<--B-->|

The cause is quite easy, just a careless btrfs_truncate_inode() in a
else branch without extra judgment.
Fix it by add judgment on whether the fallocate range is beyond isize.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>
1 parent dc6c5fb
History
Tip revision: 0f6925fa2907df58496cabc33fa4677c635e2223 authored by Qu Wenruo on 14 October 2015, 07:26:13 UTC
btrfs: Avoid truncate tailing page if fallocate range doesn't exceed inode size
Tip revision: 0f6925f
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