[RFC][PATCH v2 03/34] follow_automount(): get rid of dead^Wstillborn code

Al Viro
2020-02-23T01:16:58Z

1) no instances of ->d_automount() have ever made use of the "return
ERR_PTR(-EISDIR) if you don't feel like mounting anything" - that's
a rudiment of plans that got superseded before the thing went into
the tree. Despite the comment in follow_automount(), autofs has
never done that.

2) if there's no ->d_automount() in dentry_operations, filesystems
should not set DCACHE_NEED_AUTOMOUNT in the first place. None have
ever done so...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/namei.c | 28 +++-------------------------
fs/namespace.c | 9 ++++++++-
2 files changed, 11 insertions(+), 26 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 626eddb33508..39dd56f5171f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1210,10 +1210,7 @@ EXPORT_SYMBOL(follow_up);
*/
static int follow_automount(struct path *path, struct nameidata *nd)
{
- struct vfsmount *mnt;
-
- if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
- return -EREMOTE;
+ struct dentry *dentry = path->dentry;

/* We don't want to mount if someone's just doing a stat -
* unless they're stat'ing a directory and appended a '/' to
@@ -1228,33 +1225,14 @@ static int follow_automount(struct path *path, struct nameidata *nd)
*/
if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
- path->dentry->d_inode)
+ dentry->d_inode)
return -EISDIR;

nd->total_link_count++;
if (nd->total_link_count >= 40)
return -ELOOP;

- mnt = path->dentry->d_op->d_automount(path);
- if (IS_ERR(mnt)) {
- /*
- * The filesystem is allowed to return -EISDIR here to indicate
- * it doesn't want to automount. For instance, autofs would do
- * this so that its userspace daemon can mount on this dentry.
- *
- * However, we can only permit this if it's a terminal point in
- * the path being looked up; if it wasn't then the remainder of
- * the path is inaccessible and we should say so.
- */
- if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
- return -EREMOTE;
- return PTR_ERR(mnt);
- }
-
- if (!mnt)
- return 0;
-
- return finish_automount(mnt, path);
+ return finish_automount(dentry->d_op->d_automount(path), path);
}

/*
diff --git a/fs/namespace.c b/fs/namespace.c
index 6228fd1ef94f..a9e556224945 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2824,9 +2824,16 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
int finish_automount(struct vfsmount *m, struct path *path)
{
struct dentry *dentry = path->dentry;
- struct mount *mnt = real_mount(m);
struct mountpoint *mp;
+ struct mount *mnt;
int err;
+
+ if (!m)
+ return 0;
+ if (IS_ERR(m))
+ return PTR_ERR(m);
+
+ mnt = real_mount(m);
/* The new mount record should have at least 2 refs to prevent it being
* expired before we get a chance to add it
*/
--
2.11.0