Re: [PATCH] ceph: fix copy_file_range error path in short copies

On Wed, Feb 05, 2020 at 12:16:02PM +0100, Ilya Dryomov wrote:

On Wed, Feb 5, 2020 at 11:28 AM Luis Henriques lhenriques@suse.com wrote:

...

When there's an error in the copying loop but some bytes have already been copied into the destination file, it is necessary to dirty the caps and eventually update the MDS with the file metadata (timestamps, size). This patch fixes this error path.

Cc: stable@vger.kernel.org Signed-off-by: Luis Henriques lhenriques@suse.com

---

fs/ceph/file.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c index 11929d2bb594..7be47d24edb1 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -2104,9 +2104,16 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off, CEPH_OSD_OP_FLAG_FADVISE_DONTNEED, 0); if (err) { dout("ceph_osdc_copy_from returned %d\n", err);

•                   if (!ret)
  

•                   /*
  

•                    * If we haven't done any copy yet, just exit with the
  

•                    * error code; otherwise, return the number of bytes
  

•                    * already copied, update metadata and dirty caps.
  

•                    */
  

•                   if (!ret) {
                            ret = err;
  

•                   goto out_caps;
  

•                           goto out_caps;
  

•                   }
  

•                   goto out_early;
            }
            len -= object_size;
            src_off += object_size;
  

@@ -2118,6 +2125,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off, /* We still need one final local copy */ do_final_copy = true;

+out_early:

out_early is misleading, especially given that there already is out_caps, which just puts caps. I suggest something like update_dst_inode.

...

    file_update_time(dst_file);
    inode_inc_iversion_raw(dst_inode);

I think this is still buggy. What follows is this:

    if (endoff > size) {
            int caps_flags = 0;

            /* Let the MDS know about dst file size change */
            if (ceph_quota_is_max_bytes_approaching(dst_inode, endoff))
                    caps_flags |= CHECK_CAPS_NODELAY;
            if (ceph_inode_set_size(dst_inode, endoff))
                    caps_flags |= CHECK_CAPS_AUTHONLY;
            if (caps_flags)
                    ceph_check_caps(dst_ci, caps_flags, NULL);
    }

with endoff being:

    size = i_size_read(dst_inode);
    endoff = dst_off + len;

So a short copy effectively zero-fills the destination file...

Ah! What a surprise! Yet another bug in copy_file_range. /me hides

I guess that replacing 'endoff' by 'dst_off' in the 'if' statement above (including the condition itself) should fix it. But I start to think that I'm biased and unable to see the most obvious issues with this code :-/

Cheers, -- Luís