diff options
| author | Al Viro <viro@www.linux.org.uk> | 2005-06-06 13:36:05 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-06 14:42:25 -0700 |
| commit | 463ffb2e9d39c2a3fd8c3c1d4a34e01f2078f972 (patch) | |
| tree | e5d9b39aca2a546bf2b832c5a2a7066e34f9c1b5 | |
| parent | d671d5e51400aab03c713a16ce3545aa81ad7b1c (diff) | |
[PATCH] namei fixes (9/19)
New helper: __follow_mount(struct path *path). Same as follow_mount(), except
that we do *not* do mntput() after the first lookup_mnt().
IOW, original path->mnt stays pinned down. We also take care to do dput()
before mntput() in the loop body (follow_mount() also needs that reordering,
but that will be done later in the series).
The following are equivalent, assuming that path.mnt == x:
(1)
follow_mount(&path.mnt, &path.dentry)
(2)
__follow_mount(&path);
if (path->mnt != x)
mntput(x);
(3)
if (__follow_mount(&path))
mntput(x);
Callers of follow_mount() in __link_path_walk() converted to (2).
Equivalent transformation + fix for too-late-mntput() race in __follow_mount()
loop.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | fs/namei.c | 25 |
1 files changed, 23 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c index 3d08478d313..23a1ad46797 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -576,6 +576,23 @@ int follow_up(struct vfsmount **mnt, struct dentry **dentry) /* no need for dcache_lock, as serialization is taken care in * namespace.c */ +static int __follow_mount(struct path *path) +{ + int res = 0; + while (d_mountpoint(path->dentry)) { + struct vfsmount *mounted = lookup_mnt(path->mnt, path->dentry); + if (!mounted) + break; + dput(path->dentry); + if (res) + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + res = 1; + } + return res; +} + static int follow_mount(struct vfsmount **mnt, struct dentry **dentry) { int res = 0; @@ -778,7 +795,9 @@ static fastcall int __link_path_walk(const char * name, struct nameidata *nd) if (err) break; /* Check mountpoints.. */ - follow_mount(&next.mnt, &next.dentry); + __follow_mount(&next); + if (nd->mnt != next.mnt) + mntput(nd->mnt); err = -ENOENT; inode = next.dentry->d_inode; @@ -836,7 +855,9 @@ last_component: err = do_lookup(nd, &this, &next); if (err) break; - follow_mount(&next.mnt, &next.dentry); + __follow_mount(&next); + if (nd->mnt != next.mnt) + mntput(nd->mnt); inode = next.dentry->d_inode; if ((lookup_flags & LOOKUP_FOLLOW) && inode && inode->i_op && inode->i_op->follow_link) { |