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

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Message-Id: <20220612085330.1451496-1-asmadeus@codewreck.org>
Date:   Sun, 12 Jun 2022 17:53:23 +0900
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     Christian Schoenebeck <linux_oss@...debyte.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>
Cc:     v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        Dominique Martinet <asmadeus@...ewreck.org>
Subject: [PATCH 00/06] fid refcounting improvements and fixes

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 */);
                /* 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