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Commit e1d227a4 authored by Mark Fasheh's avatar Mark Fasheh Committed by Chris Mason
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btrfs: Handle unaligned length in extent_same 



The extent-same code rejects requests with an unaligned length. This
poses a problem when we want to dedupe the tail extent of files as we
skip cloning the portion between i_size and the extent boundary.

If we don't clone the entire extent, it won't be deleted. So the
combination of these behaviors winds up giving us worst-case dedupe on
many files.

We can fix this by allowing a length that extents to i_size and
internally aligining those to the end of the block. This is what
btrfs_ioctl_clone() so we can just copy that check over.

Signed-off-by: default avatarMark Fasheh <mfasheh@suse.de>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 070034bd

fs/btrfs/ioctl.c

+14 −6
Original line number Diff line number Diff line
@@ -2889,12 +2889,19 @@ static int btrfs_cmp_data(struct inode *src, u64 loff, struct inode *dst, 
	return ret;

}



static int extent_same_check_offsets(struct inode *inode, u64 off, u64 len)

static int extent_same_check_offsets(struct inode *inode, u64 off, u64 *plen,

				     u64 olen)

{

	u64 len = *plen;

	u64 bs = BTRFS_I(inode)->root->fs_info->sb->s_blocksize;



	if (off + len > inode->i_size || off + len < off)

	if (off + olen > inode->i_size || off + olen < off)

		return -EINVAL;



	/* if we extend to eof, continue to block boundary */

	if (off + len == inode->i_size)

		*plen = len = ALIGN(inode->i_size, bs) - off;



	/* Check that we are block aligned - btrfs_clone() requires this */

	if (!IS_ALIGNED(off, bs) || !IS_ALIGNED(off + len, bs))

		return -EINVAL;
@@ -2902,10 +2909,11 @@ static int extent_same_check_offsets(struct inode *inode, u64 off, u64 len) 
	return 0;

}



static int btrfs_extent_same(struct inode *src, u64 loff, u64 len,

static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,

			     struct inode *dst, u64 dst_loff)

{

	int ret;

	u64 len = olen;



	/*

	 * btrfs_clone() can't handle extents in the same file
@@ -2920,11 +2928,11 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 len, 


	btrfs_double_lock(src, loff, dst, dst_loff, len);



	ret = extent_same_check_offsets(src, loff, len);

	ret = extent_same_check_offsets(src, loff, &len, olen);

	if (ret)

		goto out_unlock;



	ret = extent_same_check_offsets(dst, dst_loff, len);

	ret = extent_same_check_offsets(dst, dst_loff, &len, olen);

	if (ret)

		goto out_unlock;
@@ -2937,7 +2945,7 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 len, 


	ret = btrfs_cmp_data(src, loff, dst, dst_loff, len);

	if (ret == 0)

		ret = btrfs_clone(src, dst, loff, len, len, dst_loff);

		ret = btrfs_clone(src, dst, loff, olen, len, dst_loff);



out_unlock:

	btrfs_double_unlock(src, loff, dst, dst_loff, len);