btrfs: allow dedupe of same inode

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>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9ebe2dd..af06494 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2991,27 +2991,61 @@ 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) !=
@@ -3024,18 +3058,28 @@ 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;
 }