diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 5f0c52a07386ff849c7fb2078669df9e87fa8cdf..cbf98b989b11fa8358a9ac1965c58987012f5adf 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -20,6 +20,7 @@ prototypes:
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
struct vfsmount *(*d_automount)(struct path *path);
+ int (*d_manage)(struct dentry *, bool);
locking rules:
rename_lock ->d_lock may block rcu-walk
@@ -31,6 +32,7 @@ d_release: no no yes no
d_iput: no no yes no
d_dname: no no no no
d_automount: no no yes no
+d_manage: no no yes no
--------------------------- inode_operations ---------------------------
prototypes:
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 726a4f6fa3c932dc5566c743e081f2f4c6b61e02..4682586b147a8495f7add164662c0d2dec928d7b 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -865,6 +865,7 @@ struct dentry_operations {
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
+ int (*d_manage)(struct dentry *, bool);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
@@ -938,12 +939,30 @@ struct dentry_operations {
target and the parent VFS mount record to provide inheritable mount
parameters. NULL should be returned if someone else managed to make
the automount first. If the automount failed, then an error code
- should be returned.
+ should be returned. If -EISDIR is returned, then the directory will
+ be treated as an ordinary directory and returned to pathwalk to
+ continue walking.
This function is only used if DCACHE_NEED_AUTOMOUNT is set on the
dentry. This is set by __d_instantiate() if S_AUTOMOUNT is set on the
inode being added.
+ d_manage: called to allow the filesystem to manage the transition from a
+ dentry (optional). This allows autofs, for example, to hold up clients
+ waiting to explore behind a 'mountpoint' whilst letting the daemon go
+ past and construct the subtree there. 0 should be returned to let the
+ calling process continue. -EISDIR can be returned to tell pathwalk to
+ use this directory as an ordinary directory and to ignore anything
+ mounted on it and not to check the automount flag. Any other error
+ code will abort pathwalk completely.
+
+ If the 'mounting_here' parameter is true, then namespace_sem is being
+ held by the caller and the function should not initiate any mounts or
+ unmounts that it will then wait for.
+
+ This function is only used if DCACHE_MANAGE_TRANSIT is set on the
+ dentry being transited from.
+
Example :
static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
diff --git a/drivers/staging/autofs/dirhash.c b/drivers/staging/autofs/dirhash.c
index d3f42c8325f7fafcd05d2a610efb1d738706e55f..a08bd735503599b85b80c45d9152a4339f029484 100644
--- a/drivers/staging/autofs/dirhash.c
+++ b/drivers/staging/autofs/dirhash.c
@@ -88,14 +88,13 @@ struct autofs_dir_ent *autofs_expire(struct super_block *sb,
}
path.mnt = mnt;
path_get(&path);
- if (!follow_down(&path)) {
+ if (!follow_down_one(&path)) {
path_put(&path);
DPRINTK(("autofs: not expirable\
(not a mounted directory): %s\n", ent->name));
continue;
}
- while (d_mountpoint(path.dentry) && follow_down(&path))
- ;
+ follow_down(&path, false); // TODO: need to check error
umount_ok = may_umount(path.mnt);
path_put(&path);
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index e83c0336e7b58a9cbcb4bea29f819d31ffc755a3..f3e891d57a2c9b26088a2edd2afe743153b4e046 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -273,10 +273,7 @@ static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
default:
mntput(newmnt);
break;
diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 0fffe1c24cecf354b620cafcbffc002a6318093c..eb67953452bb28a799999a5f6e56a292c87fd659 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -229,19 +229,6 @@ int autofs4_wait(struct autofs_sb_info *,struct dentry *, enum autofs_notify);
int autofs4_wait_release(struct autofs_sb_info *,autofs_wqt_t,int);
void autofs4_catatonic_mode(struct autofs_sb_info *);
-static inline int autofs4_follow_mount(struct path *path)
-{
- int res = 0;
-
- while (d_mountpoint(path->dentry)) {
- int followed = follow_down(path);
- if (!followed)
- break;
- res = 1;
- }
- return res;
-}
-
static inline u32 autofs4_get_dev(struct autofs_sb_info *sbi)
{
return new_encode_dev(sbi->sb->s_dev);
diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index eff9a419469a3d1661f4ad64d674b8db4370ae09..1442da4860e5ef6ad303fd5868fa70c68a5601a6 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -551,7 +551,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
err = have_submounts(path.dentry);
- if (follow_down(&path))
+ if (follow_down_one(&path))
magic = path.mnt->mnt_sb->s_magic;
}
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
index cc1d013659051401f49afe701e835eb732a31ed7..6a930b90d38983e542070ed9b7c3b157398c9751 100644
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -56,7 +56,7 @@ static int autofs4_mount_busy(struct vfsmount *mnt, struct dentry *dentry)
path_get(&path);
- if (!follow_down(&path))
+ if (!follow_down_one(&path))
goto done;
if (is_autofs4_dentry(path.dentry)) {
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 651e4ef563b1c1c0ed6f21904e27999d0e80e1c0..20225636a4e9ac92ecfe6bfcc18fc8db9530d3c7 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -234,7 +234,7 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
nd->flags);
/*
* For an expire of a covered direct or offset mount we need
- * to break out of follow_down() at the autofs mount trigger
+ * to break out of follow_down_one() at the autofs mount trigger
* (d_mounted--), so we can see the expiring flag, and manage
* the blocking and following here until the expire is completed.
*/
@@ -243,7 +243,7 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
if (ino->flags & AUTOFS_INF_EXPIRING) {
spin_unlock(&sbi->fs_lock);
/* Follow down to our covering mount. */
- if (!follow_down(&nd->path))
+ if (!follow_down_one(&nd->path))
goto done;
goto follow;
}
@@ -292,11 +292,10 @@ follow:
* multi-mount with no root offset so we don't need
* to follow it.
*/
- if (d_mountpoint(dentry)) {
- if (!autofs4_follow_mount(&nd->path)) {
- status = -ENOENT;
+ if (d_managed(dentry)) {
+ status = follow_down(&nd->path, false);
+ if (status < 0)
goto out_error;
- }
}
done:
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index c68a056f27fd52e29764c3a5524b4e4393a0e586..83479cf63f963a27d445715cb809fa15a0ef1627 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -273,10 +273,7 @@ static int add_mount_helper(struct vfsmount *newmnt, struct nameidata *nd,
break;
case -EBUSY:
/* someone else made a mount here whilst we were busy */
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
default:
mntput(newmnt);
break;
diff --git a/fs/namei.c b/fs/namei.c
index 16109da68bbffdd3f45035a3da6abe6a3db1c826..9d3033dc22e9cd7637364a545c29b104c93f9fdd 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -960,6 +960,7 @@ static int follow_automount(struct path *path, unsigned flags,
/*
* Handle a dentry that is managed in some way.
+ * - Flagged for transit management (autofs)
* - Flagged as mountpoint
* - Flagged as automount point
*
@@ -979,6 +980,16 @@ static int follow_managed(struct path *path, unsigned flags)
while (managed = ACCESS_ONCE(path->dentry->d_flags),
managed &= DCACHE_MANAGED_DENTRY,
unlikely(managed != 0)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held. */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(path->dentry, false);
+ if (ret < 0)
+ return ret == -EISDIR ? 0 : ret;
+ }
+
/* Transit to a mounted filesystem. */
if (managed & DCACHE_MOUNTED) {
struct vfsmount *mounted = lookup_mnt(path);
@@ -1012,7 +1023,7 @@ static int follow_managed(struct path *path, unsigned flags)
return 0;
}
-int follow_down(struct path *path)
+int follow_down_one(struct path *path)
{
struct vfsmount *mounted;
@@ -1029,14 +1040,19 @@ int follow_down(struct path *path)
/*
* Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
- * meet an automount point and we're not walking to "..". True is returned to
+ * meet a managed dentry and we're not walking to "..". True is returned to
* continue, false to abort.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, bool reverse_transit)
{
+ unsigned abort_mask =
+ reverse_transit ? 0 : DCACHE_MANAGE_TRANSIT;
+
while (d_mountpoint(path->dentry)) {
struct vfsmount *mounted;
+ if (path->dentry->d_flags & abort_mask)
+ return true;
mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted)
break;
@@ -1086,6 +1102,57 @@ static int follow_dotdot_rcu(struct nameidata *nd)
return 0;
}
+/*
+ * Follow down to the covering mount currently visible to userspace. At each
+ * point, the filesystem owning that dentry may be queried as to whether the
+ * caller is permitted to proceed or not.
+ *
+ * Care must be taken as namespace_sem may be held (indicated by mounting_here
+ * being true).
+ */
+int follow_down(struct path *path, bool mounting_here)
+{
+ unsigned managed;
+ int ret;
+
+ while (managed = ACCESS_ONCE(path->dentry->d_flags),
+ unlikely(managed & DCACHE_MANAGED_DENTRY)) {
+ /* Allow the filesystem to manage the transit without i_mutex
+ * being held.
+ *
+ * We indicate to the filesystem if someone is trying to mount
+ * something here. This gives autofs the chance to deny anyone
+ * other than its daemon the right to mount on its
+ * superstructure.
+ *
+ * The filesystem may sleep at this point.
+ */
+ if (managed & DCACHE_MANAGE_TRANSIT) {
+ BUG_ON(!path->dentry->d_op);
+ BUG_ON(!path->dentry->d_op->d_manage);
+ ret = path->dentry->d_op->d_manage(path->dentry, mounting_here);
+ if (ret < 0)
+ return ret == -EISDIR ? 0 : ret;
+ }
+
+ /* Transit to a mounted filesystem. */
+ if (managed & DCACHE_MOUNTED) {
+ struct vfsmount *mounted = lookup_mnt(path);
+ if (!mounted)
+ break;
+ dput(path->dentry);
+ mntput(path->mnt);
+ path->mnt = mounted;
+ path->dentry = dget(mounted->mnt_root);
+ continue;
+ }
+
+ /* Don't handle automount points here */
+ break;
+ }
+ return 0;
+}
+
/*
* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
*/
@@ -3530,6 +3597,7 @@ const struct inode_operations page_symlink_inode_operations = {
};
EXPORT_SYMBOL(user_path_at);
+EXPORT_SYMBOL(follow_down_one);
EXPORT_SYMBOL(follow_down);
EXPORT_SYMBOL(follow_up);
EXPORT_SYMBOL(get_write_access); /* binfmt_aout */
diff --git a/fs/namespace.c b/fs/namespace.c
index 3ddfd9046c449199a8f75ffcaf54761dde37fa73..d94ccd6ddafd6be52b1c13fc325041cded2aec82 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1844,9 +1844,10 @@ static int do_move_mount(struct path *path, char *old_name)
return err;
down_write(&namespace_sem);
- while (d_mountpoint(path->dentry) &&
- follow_down(path))
- ;
+ err = follow_down(path, true);
+ if (err < 0)
+ goto out;
+
err = -EINVAL;
if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
goto out;
@@ -1940,9 +1941,10 @@ int do_add_mount(struct vfsmount *newmnt, struct path *path,
down_write(&namespace_sem);
/* Something was mounted here while we slept */
- while (d_mountpoint(path->dentry) &&
- follow_down(path))
- ;
+ err = follow_down(path, true);
+ if (err < 0)
+ goto unlock;
+
err = -EINVAL;
if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
goto unlock;
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 74aaf3963c101ab1775e1efd3f544d0ac310273c..bfcb933e5755cb346ece178809bbbb6ddea4003d 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -176,10 +176,7 @@ out_err:
path_put(&nd->path);
goto out;
out_follow:
- while (d_mountpoint(nd->path.dentry) &&
- follow_down(&nd->path))
- ;
- err = 0;
+ err = follow_down(&nd->path, false);
goto out;
}
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 230b79fbf0051be98df5bc5067a2f6f8f18b3b8a..0f79e33a65d75311f0beace5b3ce334e71468463 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -88,8 +88,9 @@ nfsd_cross_mnt(struct svc_rqst *rqstp, struct dentry **dpp,
.dentry = dget(dentry)};
int err = 0;
- while (d_mountpoint(path.dentry) && follow_down(&path))
- ;
+ err = follow_down(&path, false);
+ if (err < 0)
+ goto out;
exp2 = rqst_exp_get_by_name(rqstp, &path);
if (IS_ERR(exp2)) {
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index ee6c26d142c3f94a5f089af62592175ae556031d..1a87760d65322b2d0528886b3232d2707f725532 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -168,6 +168,7 @@ struct dentry_operations {
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
+ int (*d_manage)(struct dentry *, bool);
} ____cacheline_aligned;
/*
@@ -214,8 +215,9 @@ struct dentry_operations {
#define DCACHE_MOUNTED 0x10000 /* is a mountpoint */
#define DCACHE_NEED_AUTOMOUNT 0x20000 /* handle automount on this dir */
+#define DCACHE_MANAGE_TRANSIT 0x40000 /* manage transit from this dirent */
#define DCACHE_MANAGED_DENTRY \
- (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT)
+ (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)
extern seqlock_t rename_lock;
@@ -404,7 +406,12 @@ static inline void dont_mount(struct dentry *dentry)
extern void dput(struct dentry *);
-static inline int d_mountpoint(struct dentry *dentry)
+static inline bool d_managed(struct dentry *dentry)
+{
+ return dentry->d_flags & DCACHE_MANAGED_DENTRY;
+}
+
+static inline bool d_mountpoint(struct dentry *dentry)
{
return dentry->d_flags & DCACHE_MOUNTED;
}
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 18d06add0a40b91d5ab5cf7254fc7cfbb47f527f..8ef2c789c2a8962f67bb25045cf4887078870749 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -79,7 +79,8 @@ extern struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
-extern int follow_down(struct path *);
+extern int follow_down_one(struct path *);
+extern int follow_down(struct path *, bool);
extern int follow_up(struct path *);
extern struct dentry *lock_rename(struct dentry *, struct dentry *);