[PATCH v1 4/8] btrfs: Add mountpoint checking during btrfs_copy_file_range

We need to verify that both the source and the destination files are
part of the same filesystem, otherwise we can't create a reflink.

Signed-off-by: Anna Schumaker <redacted>
---
 fs/btrfs/ioctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 62ae286..9c0c955 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c

@@ -3856,6 +3856,10 @@ ssize_t btrfs_copy_file_range(struct file *file_in, loff_t pos_in,
 {
 	ssize_t ret;
 
+	if (inode_in->i_sb != inode_out->i_sb ||
+	    file_in->f_path.mnt != file_out->f_path.mnt)
+		return -EXDEV;
+
 	ret = btrfs_clone_files(file_out, file_in, pos_in, len, pos_out);
 	if (ret == 0)
 		ret = len;

-- 
2.5.1

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On Fri, Sep 04, 2015 at 04:16:58PM -0400, Anna Schumaker wrote:

The same check exists in btrfs_clone_files (added in the previous
patch), what's the reason to add it here again?

+
 	ret = btrfs_clone_files(file_out, file_in, pos_in, len, pos_out);

On 09/09/2015 05:18 AM, David Sterba wrote:

On Fri, Sep 04, 2015 at 04:16:58PM -0400, Anna Schumaker wrote:

quoted

We need to verify that both the source and the destination files are
part of the same filesystem, otherwise we can't create a reflink.

Signed-off-by: Anna Schumaker <redacted>
---
 fs/btrfs/ioctl.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 62ae286..9c0c955 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c

@@ -3856,6 +3856,10 @@ ssize_t btrfs_copy_file_range(struct file *file_in, loff_t pos_in,
 {
 	ssize_t ret;
 
+	if (inode_in->i_sb != inode_out->i_sb ||
+	    file_in->f_path.mnt != file_out->f_path.mnt)
+		return -EXDEV;

The same check exists in btrfs_clone_files (added in the previous
patch), what's the reason to add it here again?

To be really, really sure that it's not a cross-device copy?  :)

In reality, it was an oversight and I'll drop the patch.  Thanks for letting me know!

Anna

quoted

+
 	ret = btrfs_clone_files(file_out, file_in, pos_in, len, pos_out);