[PATCH 4/5] btrfs: allow dedupe of same inode

Mark Fasheh
2015-06-22T22:47:58Z

clone() supports cloning within an inode so extent-same can do
the same now. This patch fixes up the locking in extent-same to
know about the single-inode case. In addition to that, we add a
check for overlapping ranges, which clone does not allow.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
---
fs/btrfs/ioctl.c | 76 ++++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 60 insertions(+), 16 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8d6887d..83f4679 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2979,27 +2979,61 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
int ret;
u64 len = olen;
struct cmp_pages cmp;
+ int same_inode = 0;
+ u64 same_lock_start = 0;
+ u64 same_lock_len = 0;

- /*
- * btrfs_clone() can't handle extents in the same file
- * yet. Once that works, we can drop this check and replace it
- * with a check for the same inode, but overlapping extents.
- */
if (src == dst)
- return -EINVAL;
+ same_inode = 1;

if (len == 0)
return 0;

- btrfs_double_inode_lock(src, dst);
+ if (same_inode) {
+ mutex_lock(&src->i_mutex);

- ret = extent_same_check_offsets(src, loff, &len, olen);
- if (ret)
- goto out_unlock;
+ ret = extent_same_check_offsets(src, loff, &len, olen);
+ if (ret)
+ goto out_unlock;

- ret = extent_same_check_offsets(dst, dst_loff, &len, olen);
- if (ret)
- goto out_unlock;
+ /*
+ * Single inode case wants the same checks, except we
+ * don't want our length pushed out past i_size as
+ * comparing that data range makes no sense.
+ *
+ * extent_same_check_offsets() will do this for an
+ * unaligned length at i_size, so catch it here and
+ * reject the request.
+ *
+ * This effectively means we require aligned extents
+ * for the single-inode case, whereas the other cases
+ * allow an unaligned length so long as it ends at
+ * i_size.
+ */
+ if (len != olen) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ /* Check for overlapping ranges */
+ if (dst_loff + len > loff && dst_loff < loff + len) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+
+ same_lock_start = min_t(u64, loff, dst_loff);
+ same_lock_len = max_t(u64, loff, dst_loff) + len - same_lock_start;
+ } else {
+ btrfs_double_inode_lock(src, dst);
+
+ ret = extent_same_check_offsets(src, loff, &len, olen);
+ if (ret)
+ goto out_unlock;
+
+ ret = extent_same_check_offsets(dst, dst_loff, &len, olen);
+ if (ret)
+ goto out_unlock;
+ }

/* don't make the dst file partly checksummed */
if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
@@ -3012,18 +3046,28 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
if (ret)
goto out_unlock;

- btrfs_double_extent_lock(src, loff, dst, dst_loff, len);
+ if (same_inode)
+ lock_extent_range(src, same_lock_start, same_lock_len);
+ else
+ btrfs_double_extent_lock(src, loff, dst, dst_loff, len);

/* pass original length for comparison so we stay within i_size */
ret = btrfs_cmp_data(src, loff, dst, dst_loff, olen, &cmp);
if (ret == 0)
ret = btrfs_clone(src, dst, loff, olen, len, dst_loff);

- btrfs_double_extent_unlock(src, loff, dst, dst_loff, len);
+ if (same_inode)
+ unlock_extent(&BTRFS_I(src)->io_tree, same_lock_start,
+ same_lock_start + same_lock_len - 1);
+ else
+ btrfs_double_extent_unlock(src, loff, dst, dst_loff, len);

btrfs_cmp_data_free(&cmp);
out_unlock:
- btrfs_double_inode_unlock(src, dst);
+ if (same_inode)
+ mutex_unlock(&src->i_mutex);
+ else
+ btrfs_double_inode_unlock(src, dst);

return ret;
}
--
2.1.2

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