Btrfs: adjust len of writes if following a preallocated extent (a23eaa87) · Commits · 戴 / test

If we have |0--hole--4095||4096--preallocate--12287| instead of using preallocated space, a 8K direct write will just create a new 8K extent and it'll end up with |0--new extent--8191||8192--preallocate--12287| It's because we find a hole em and then go to create a new 8K extent directly without adjusting @len. Signed-off-by:

Liu Bo <bo.li.liu@oracle.com> Reviewed-by:

Chris Mason <clm@fb.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -7782,10 +7782,12 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
		}

		/*
		* this will cow the extent, reset the len in case we changed
		* it above
		* this will cow the extent, if em is within [start, len], then
		* probably we've found a preallocated/existing extent, let's
		* give it a chance to use preallocated space.
		*/
		len = bh_result->b_size;
		len = min_t(u64, bh_result->b_size, em->len - (start - em->start));
		len = ALIGN(len, root->sectorsize);
		free_extent_map(em);
		em = btrfs_new_extent_direct(inode, start, len);
		if (IS_ERR(em)) {

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