fs: allow cross-vfsmount reflink/dedupe

Bugzilla: http://bugzilla.redhat.com/2088133

commit 9f5710b
Author: Josef Bacik <josef@toxicpanda.com>
Date:   Fri Feb 18 09:38:14 2022 -0500

    fs: allow cross-vfsmount reflink/dedupe

    Currently we disallow reflink and dedupe if the two files aren't on the
    same vfsmount.  However we really only need to disallow it if they're
    not on the same super block.  It is very common for btrfs to have a main
    subvolume that is mounted and then different subvolumes mounted at
    different locations.  It's allowed to reflink between these volumes, but
    the vfsmount check disallows this.  Instead fix dedupe to check for the
    same superblock, and simply remove the vfsmount check for reflink as it
    already does the superblock check.

    Reviewed-by: Darrick J. Wong <djwong@kernel.org>
    Reviewed-by: Nikolay Borisov <nborisov@suse.com>
    Signed-off-by: Josef Bacik <josef@toxicpanda.com>
    Reviewed-by: David Sterba <dsterba@suse.com>
    Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>

Author: alberand

fs/ioctl.c

@@ -236,9 +236,6 @@ static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
 
 	if (!src_file.file)
 		return -EBADF;
-	ret = -EXDEV;
-	if (src_file.file->f_path.mnt != dst_file->f_path.mnt)
-		goto fdput;
 	cloned = vfs_clone_file_range(src_file.file, off, dst_file, destoff,
 				      olen, 0);
 	if (cloned < 0)
@@ -247,7 +244,6 @@ static long ioctl_file_clone(struct file *dst_file, unsigned long srcfd,
 		ret = -EINVAL;
 	else
 		ret = 0;
-fdput:
 	fdput(src_file);
 	return ret;
 }

fs/remap_range.c

@@ -362,11 +362,6 @@ loff_t do_clone_file_range(struct file *file_in, loff_t pos_in,
 
 	WARN_ON_ONCE(remap_flags & REMAP_FILE_DEDUP);
 
-	/*
-	 * FICLONE/FICLONERANGE ioctls enforce that src and dest files are on
-	 * the same mount. Practically, they only need to be on the same file
-	 * system.
-	 */
 	if (file_inode(file_in)->i_sb != file_inode(file_out)->i_sb)
 		return -EXDEV;
 
@@ -458,7 +453,7 @@ loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
 		goto out_drop_write;
 
 	ret = -EXDEV;
-	if (src_file->f_path.mnt != dst_file->f_path.mnt)
+	if (file_inode(src_file)->i_sb != file_inode(dst_file)->i_sb)
 		goto out_drop_write;
 
 	ret = -EISDIR;