From: Qu Wenruo Date: Fri, 8 Aug 2014 05:06:20 +0000 (+0800) Subject: btrfs: Use right extent length when inserting overlap extent map. X-Git-Tag: omap-fixes-against-v3.17-rc3~41^2~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51f395ad4058883e4273b02fdebe98072dbdc0d2;p=pandora-kernel.git btrfs: Use right extent length when inserting overlap extent map. When current btrfs finds that a new extent map is going to be insereted but failed with -EEXIST, it will try again to insert the extent map but with the length of sectorsize. This is OK if we don't enable 'no-holes' feature since all extent space is continuous, we will not go into the not found->insert routine. But if we enable 'no-holes' feature, it will make things out of control. e.g. in 4K sectorsize, we pass the following args to btrfs_get_extent(): btrfs_get_extent() args: start: 27874 len 4100 28672 27874 28672 27874+4100 32768 |-----------------------| |---------hole--------------------|---------data----------| 1) not found and insert Since no extent map containing the range, btrfs_get_extent() will go into the not_found and insert routine, which will try to insert the extent map (27874, 27847 + 4100). 2) first overlap But it overlaps with (28672, 32768) extent, so -EEXIST will be returned by add_extent_mapping(). 3) retry but still overlap After catching the -EEXIST, then btrfs_get_extent() will try insert it again but with 4K length, which still overlaps, so -EEXIST will be returned. This makes the following patch fail to punch hole. d77815461f047e561f77a07754ae923ade597d4e btrfs: Avoid trucating page or punching hole in a already existed hole. This patch will use the right length, which is the (exsisting->start - em->start) to insert, making the above patch works in 'no-holes' mode. Also, some small code style problems in above patch is fixed too. Reported-by: Filipe David Manana Signed-off-by: Qu Wenruo Reviewed-by: Filipe David Manana Tested-by: Filipe David Manana Signed-off-by: Chris Mason --- Reading git-diff-tree failed