Re: [PATCH] fix: release unused ceph cap reservation on readdir error

[Viacheslav Dubeyko]

On Wed, 2026-07-15 at 23:46 +0530, deepakroag wrote:
> Return unused reserved caps to the MDS client pool when
> ceph_readdir_prepopulate() exits with an error.
> 
> Corrected standalone submission: this patch was mistakenly
> sent earlier as [PATCH 4/4] in an unrelated multi-subsystem
> series.  It is ceph-only and resubmitted here as [PATCH 1/1].

Frankly speaking, it will be better to explain the issue detection and
analysis here.

> 
> Link:
> https://lore.kernel.org/ceph-devel/20260715143646.15828-4-gaikwad.dcg@xxxxxxxxx/
> 
> Signed-off-by: deepakroag <gaikwad.dcg@xxxxxxxxx>
> ---
>  fs/ceph/inode.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
> index 61d7c0b81..2d6a80054 100644
> --- a/fs/ceph/inode.c
> +++ b/fs/ceph/inode.c
> @@ -2188,6 +2188,8 @@ int ceph_readdir_prepopulate(struct
> ceph_mds_request *req,
>  		dput(dn);
>  	}
>  out:
> +	if (err)
> +		ceph_unreserve_caps(req->r_mdsc, &req-
> >r_caps_reservation);
>  	if (err == 0 && skipped == 0) {
>  		set_bit(CEPH_MDS_R_DID_PREPOPULATE, &req-
> >r_req_flags);
>  		req->r_readdir_cache_idx = cache_ctl.index;

OK. So, we need to do this because handle_reply() [1] execute this
after ceph_readdir_prepopulate():

  if (err == 0) {
      ...
      ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
  }

However, we are missing another execution branch [2]:

  if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
      return readdir_prepopulate_inodes_only(req, session);

I believe that we need to improve the patch.

Thanks,
Slava.

[1]
https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/ceph/mds_client.c#L4186
[2]
https://elixir.bootlin.com/linux/v7.2-rc3/source/fs/ceph/inode.c#L2017