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| author | Al Viro <viro@zeniv.linux.org.uk> | 2025-04-24 08:45:05 +0300 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2025-05-05 20:42:49 +0300 |
| commit | 006ff7498fe89bd9dfb891101f02557d5cfcf427 (patch) | |
| tree | df927455a4886400412ba2d83fead6b597258949 /Documentation | |
| parent | 92a09c47464d040866cf2b4cd052bc60555185fb (diff) | |
| download | linux-006ff7498fe89bd9dfb891101f02557d5cfcf427.tar.xz | |
saner calling conventions for ->d_automount()
Currently the calling conventions for ->d_automount() instances have
an odd wart - returned new mount to be attached is expected to have
refcount 2.
That kludge is intended to make sure that mark_mounts_for_expiry() called
before we get around to attaching that new mount to the tree won't decide
to take it out. finish_automount() drops the extra reference after it's
done with attaching mount to the tree - or drops the reference twice in
case of error. ->d_automount() instances have rather counterintuitive
boilerplate in them.
There's a much simpler approach: have mark_mounts_for_expiry() skip the
mounts that are yet to be mounted. And to hell with grabbing/dropping
those extra references. Makes for simpler correctness analysis, at that...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Acked-by: David Howells <dhowells@redhat.com>
Tested-by: David Howells <dhowells@redhat.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/porting.rst | 7 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.rst | 4 |
2 files changed, 8 insertions, 3 deletions
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 767b2927c762..749637231773 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -1203,3 +1203,10 @@ should use d_drop();d_splice_alias() and return the result of the latter. If a positive dentry cannot be returned for some reason, in-kernel clients such as cachefiles, nfsd, smb/server may not perform ideally but will fail-safe. + +--- + +**mandatory** + +Calling conventions for ->d_automount() have changed; we should *not* grab +an extra reference to new mount - it should be returned with refcount 1. diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index ae79c30b6c0c..cc0a58e96770 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -1411,9 +1411,7 @@ defined: If a vfsmount is returned, the caller will attempt to mount it on the mountpoint and will remove the vfsmount from its - expiration list in the case of failure. The vfsmount should be - returned with 2 refs on it to prevent automatic expiration - the - caller will clean up the additional ref. + expiration list in the case of failure. This function is only used if DCACHE_NEED_AUTOMOUNT is set on the dentry. This is set by __d_instantiate() if S_AUTOMOUNT is |