Btrfs: fix wrong extent mapping for DirectIO
btrfs_next_leaf() will use current leaf's last key to search and then return a bigger one. So it may still return a file extent item that is smaller than expected value and we will get an overflow here for @em->len. This is easy to reproduce for Btrfs Direct writting, it did not cause any problem, because writting will re-insert right mapping later. However, by hacking code to make DIO support compression, wrong extent mapping is kept and it encounter merging failure(EEXIST) quickly. Fix this problem by looping to find next file extent item that is bigger than @start or we could not find anything more. Signed-off-by: NWang Shilong <wangsl.fnst@cn.fujitsu.com> Reviewed-by: NDavid Sterba <dsterba@suse.cz> Signed-off-by: NChris Mason <clm@fb.com>
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