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authorAl Viro <viro@www.linux.org.uk>2005-06-06 13:36:05 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-06 14:42:25 -0700
commit463ffb2e9d39c2a3fd8c3c1d4a34e01f2078f972 (patch)
treee5d9b39aca2a546bf2b832c5a2a7066e34f9c1b5 /fs
parentd671d5e51400aab03c713a16ce3545aa81ad7b1c (diff)
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[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>
Diffstat (limited to 'fs')
-rw-r--r--fs/namei.c25
1 files changed, 23 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 3d08478d3130..23a1ad467976 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) {