linux-kernel - Re: [PATCH 00/06] fid refcounting improvements and fixes

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Date:   Mon, 13 Jun 2022 15:20:53 -0500
From:   Tyler Hicks <tyhicks@...ux.microsoft.com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
Cc:     Christian Schoenebeck <linux_oss@...debyte.com>,
        v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/06] fid refcounting improvements and fixes

On 2022-06-12 17:53:23, Dominique Martinet wrote:
> So:
>  - I could reproduce Tyler's generic 531 leak, fixed it by the first
>    commit in v9fs_vfs_atomic_open_dotl
>  - Found another less likely leak while reworking code
>  - Christian's comment that it's not obvious that clunk is just a
>    refcount decrease was very true: I think it's worth the churn,
>    so I've rename this all through a new helper...
>  - ... with the not-so-hidden intent to improve debugging by adding
>    a tracepoint for them, which I have also done.
> 
> I've also taken my comment in the other thread further and went ahead
> and made it in its own commit. Tyler, if you're ok with this I'll just
> squash it up. You can see rebased patches here:
> https://github.com/martinetd/linux/
> 
> Note that I also took the permission to add back '/* clone */' as a
> comment to your changing p9_client_walk's arguments: while I can agree
> variables are hard to track, figuring out what the heck that boolean
> argument means is much harder to me and I honestly preferred the
> variable.
> Having both through a comment is good enough for me if you'll accept
> this:
> ----
> @@ -222,7 +221,8 @@ static struct p9_fid *v9fs_fid_lookup_with_uid(struct dentry *dentry,
>                  * We need to hold rename lock when doing a multipath
>                  * walk to ensure none of the patch component change
>                  */
> -               fid = p9_client_walk(old_fid, l, &wnames[i], clone);
> +               fid = p9_client_walk(old_fid, l, &wnames[i],
> +                                    old_fid == root_fid /* clone */);

This is no problem at all. The rebased patches look good to me. Squash
your fix to my fix and it should be ready to go.

Thanks again!

Tyler

>                 /* non-cloning walk will return the same fid */
>                 if (fid != old_fid) {
>                         p9_client_clunk(old_fid);
> ----
> 
> 
> The last commit is just cleanups and should be no real change.
> 
> Dominique Martinet (6):
>   9p: fix fid refcount leak in v9fs_vfs_atomic_open_dotl
>   9p: fix fid refcount leak in v9fs_vfs_get_link
>   9p: v9fs_fid_lookup_with_uid fix's fix suggestion
>   9p fid refcount: add p9_fid_get/put wrappers
>   9p fid refcount: add a 9p_fid_ref tracepoint
>   9p fid refcount: cleanup p9_fid_put calls
> 
> 
> (diff stats include Tyler's commits)
> 
>  fs/9p/fid.c               | 71 +++++++++++++++-------------
>  fs/9p/fid.h               |  6 +--
>  fs/9p/vfs_addr.c          |  4 +-
>  fs/9p/vfs_dentry.c        |  4 +-
>  fs/9p/vfs_dir.c           |  2 +-
>  fs/9p/vfs_file.c          |  9 ++--
>  fs/9p/vfs_inode.c         | 97 +++++++++++++++++----------------------
>  fs/9p/vfs_inode_dotl.c    | 79 ++++++++++++-------------------
>  fs/9p/vfs_super.c         |  8 ++--
>  fs/9p/xattr.c             |  8 ++--
>  include/net/9p/client.h   |  3 ++
>  include/trace/events/9p.h | 48 +++++++++++++++++++
>  net/9p/client.c           | 42 +++++++++++------
>  13 files changed, 211 insertions(+), 170 deletions(-)
> 
> -- 
> 2.35.1
>