Merge branch 'work.autofs' into for-linus

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/Locking

@@ -20,7 +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);
+	int (*d_manage)(const struct path *, bool);
 	struct dentry *(*d_real)(struct dentry *, const struct inode *,
 				 unsigned int);
 

Documentation/filesystems/vfs.txt

@@ -948,7 +948,7 @@ 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);
+	int (*d_manage)(const struct path *, bool);
 	struct dentry *(*d_real)(struct dentry *, const struct inode *,
 				 unsigned int);
 };

fs/autofs4/autofs_i.h

@@ -145,7 +145,7 @@ void autofs4_free_ino(struct autofs_info *);
 
 /* Expiration */
 int is_autofs4_dentry(struct dentry *);
-int autofs4_expire_wait(struct dentry *dentry, int rcu_walk);
+int autofs4_expire_wait(const struct path *path, int rcu_walk);
 int autofs4_expire_run(struct super_block *, struct vfsmount *,
 		       struct autofs_sb_info *,
 		       struct autofs_packet_expire __user *);
@@ -217,7 +217,8 @@ static inline int autofs_prepare_pipe(struct file *pipe)
 
 /* Queue management functions */
 
-int autofs4_wait(struct autofs_sb_info *, struct dentry *, enum autofs_notify);
+int autofs4_wait(struct autofs_sb_info *,
+		 const struct path *, enum autofs_notify);
 int autofs4_wait_release(struct autofs_sb_info *, autofs_wqt_t, int);
 void autofs4_catatonic_mode(struct autofs_sb_info *);
 

fs/autofs4/dev-ioctl.c

@@ -468,7 +468,7 @@ static int autofs_dev_ioctl_requester(struct file *fp,
 	ino = autofs4_dentry_ino(path.dentry);
 	if (ino) {
 		err = 0;
-		autofs4_expire_wait(path.dentry, 0);
+		autofs4_expire_wait(&path, 0);
 		spin_lock(&sbi->fs_lock);
 		param->requester.uid =
 			from_kuid_munged(current_user_ns(), ino->uid);
@@ -575,7 +575,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
 
 		devid = new_encode_dev(dev);
 
-		err = have_submounts(path.dentry);
+		err = path_has_submounts(&path);
 
 		if (follow_down_one(&path))
 			magic = path.dentry->d_sb->s_magic;

fs/autofs4/expire.c

@@ -310,26 +310,29 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
 	now = jiffies;
 	timeout = sbi->exp_timeout;
 
-	spin_lock(&sbi->fs_lock);
-	ino = autofs4_dentry_ino(root);
-	/* No point expiring a pending mount */
-	if (ino->flags & AUTOFS_INF_PENDING)
-		goto out;
 	if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
+		spin_lock(&sbi->fs_lock);
+		ino = autofs4_dentry_ino(root);
+		/* No point expiring a pending mount */
+		if (ino->flags & AUTOFS_INF_PENDING) {
+			spin_unlock(&sbi->fs_lock);
+			goto out;
+		}
 		ino->flags |= AUTOFS_INF_WANT_EXPIRE;
 		spin_unlock(&sbi->fs_lock);
 		synchronize_rcu();
-		spin_lock(&sbi->fs_lock);
 		if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
+			spin_lock(&sbi->fs_lock);
 			ino->flags |= AUTOFS_INF_EXPIRING;
 			init_completion(&ino->expire_complete);
 			spin_unlock(&sbi->fs_lock);
 			return root;
 		}
+		spin_lock(&sbi->fs_lock);
 		ino->flags &= ~AUTOFS_INF_WANT_EXPIRE;
+		spin_unlock(&sbi->fs_lock);
 	}
 out:
-	spin_unlock(&sbi->fs_lock);
 	dput(root);
 
 	return NULL;
@@ -495,8 +498,9 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
 	return expired;
 }
 
-int autofs4_expire_wait(struct dentry *dentry, int rcu_walk)
+int autofs4_expire_wait(const struct path *path, int rcu_walk)
 {
+	struct dentry *dentry = path->dentry;
 	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 	struct autofs_info *ino = autofs4_dentry_ino(dentry);
 	int status;
@@ -525,7 +529,7 @@ int autofs4_expire_wait(struct dentry *dentry, int rcu_walk)
 
 		pr_debug("waiting for expire %p name=%pd\n", dentry, dentry);
 
-		status = autofs4_wait(sbi, dentry, NFY_NONE);
+		status = autofs4_wait(sbi, path, NFY_NONE);
 		wait_for_completion(&ino->expire_complete);
 
 		pr_debug("expire done status=%d\n", status);
@@ -592,11 +596,12 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 
 	if (dentry) {
 		struct autofs_info *ino = autofs4_dentry_ino(dentry);
+		const struct path path = { .mnt = mnt, .dentry = dentry };
 
 		/* This is synchronous because it makes the daemon a
 		 * little easier
 		 */
-		ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
+		ret = autofs4_wait(sbi, &path, NFY_EXPIRE);
 
 		spin_lock(&sbi->fs_lock);
 		/* avoid rapid-fire expire attempts if expiry fails */

fs/autofs4/root.c

@@ -32,7 +32,7 @@ static int autofs4_dir_open(struct inode *inode, struct file *file);
 static struct dentry *autofs4_lookup(struct inode *,
 				     struct dentry *, unsigned int);
 static struct vfsmount *autofs4_d_automount(struct path *);
-static int autofs4_d_manage(struct dentry *, bool);
+static int autofs4_d_manage(const struct path *, bool);
 static void autofs4_dentry_release(struct dentry *);
 
 const struct file_operations autofs4_root_operations = {
@@ -123,7 +123,7 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
 	 * it.
 	 */
 	spin_lock(&sbi->lookup_lock);
-	if (!d_mountpoint(dentry) && simple_empty(dentry)) {
+	if (!path_is_mountpoint(&file->f_path) && simple_empty(dentry)) {
 		spin_unlock(&sbi->lookup_lock);
 		return -ENOENT;
 	}
@@ -269,39 +269,41 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry,
 	return NULL;
 }
 
-static int autofs4_mount_wait(struct dentry *dentry, bool rcu_walk)
+static int autofs4_mount_wait(const struct path *path, bool rcu_walk)
 {
-	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-	struct autofs_info *ino = autofs4_dentry_ino(dentry);
+	struct autofs_sb_info *sbi = autofs4_sbi(path->dentry->d_sb);
+	struct autofs_info *ino = autofs4_dentry_ino(path->dentry);
 	int status = 0;
 
 	if (ino->flags & AUTOFS_INF_PENDING) {
 		if (rcu_walk)
 			return -ECHILD;
-		pr_debug("waiting for mount name=%pd\n", dentry);
-		status = autofs4_wait(sbi, dentry, NFY_MOUNT);
+		pr_debug("waiting for mount name=%pd\n", path->dentry);
+		status = autofs4_wait(sbi, path, NFY_MOUNT);
 		pr_debug("mount wait done status=%d\n", status);
 	}
 	ino->last_used = jiffies;
 	return status;
 }
 
-static int do_expire_wait(struct dentry *dentry, bool rcu_walk)
+static int do_expire_wait(const struct path *path, bool rcu_walk)
 {
+	struct dentry *dentry = path->dentry;
 	struct dentry *expiring;
 
 	expiring = autofs4_lookup_expiring(dentry, rcu_walk);
 	if (IS_ERR(expiring))
 		return PTR_ERR(expiring);
 	if (!expiring)
-		return autofs4_expire_wait(dentry, rcu_walk);
+		return autofs4_expire_wait(path, rcu_walk);
 	else {
+		const struct path this = { .mnt = path->mnt, .dentry = expiring };
 		/*
 		 * If we are racing with expire the request might not
 		 * be quite complete, but the directory has been removed
 		 * so it must have been successful, just wait for it.
 		 */
-		autofs4_expire_wait(expiring, 0);
+		autofs4_expire_wait(&this, 0);
 		autofs4_del_expiring(expiring);
 		dput(expiring);
 	}
@@ -354,7 +356,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 	 * and the directory was removed, so just go ahead and try
 	 * the mount.
 	 */
-	status = do_expire_wait(dentry, 0);
+	status = do_expire_wait(path, 0);
 	if (status && status != -EAGAIN)
 		return NULL;
 
@@ -362,7 +364,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 	spin_lock(&sbi->fs_lock);
 	if (ino->flags & AUTOFS_INF_PENDING) {
 		spin_unlock(&sbi->fs_lock);
-		status = autofs4_mount_wait(dentry, 0);
+		status = autofs4_mount_wait(path, 0);
 		if (status)
 			return ERR_PTR(status);
 		goto done;
@@ -370,28 +372,28 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 
 	/*
 	 * If the dentry is a symlink it's equivalent to a directory
-	 * having d_mountpoint() true, so there's no need to call back
-	 * to the daemon.
+	 * having path_is_mountpoint() true, so there's no need to call
+	 * back to the daemon.
 	 */
 	if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
 		spin_unlock(&sbi->fs_lock);
 		goto done;
 	}
 
-	if (!d_mountpoint(dentry)) {
+	if (!path_is_mountpoint(path)) {
 		/*
 		 * It's possible that user space hasn't removed directories
 		 * after umounting a rootless multi-mount, although it
-		 * should. For v5 have_submounts() is sufficient to handle
-		 * this because the leaves of the directory tree under the
-		 * mount never trigger mounts themselves (they have an autofs
-		 * trigger mount mounted on them). But v4 pseudo direct mounts
-		 * do need the leaves to trigger mounts. In this case we
-		 * have no choice but to use the list_empty() check and
+		 * should. For v5 path_has_submounts() is sufficient to
+		 * handle this because the leaves of the directory tree under
+		 * the mount never trigger mounts themselves (they have an
+		 * autofs trigger mount mounted on them). But v4 pseudo direct
+		 * mounts do need the leaves to trigger mounts. In this case
+		 * we have no choice but to use the list_empty() check and
 		 * require user space behave.
 		 */
 		if (sbi->version > 4) {
-			if (have_submounts(dentry)) {
+			if (path_has_submounts(path)) {
 				spin_unlock(&sbi->fs_lock);
 				goto done;
 			}
@@ -403,7 +405,7 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 		}
 		ino->flags |= AUTOFS_INF_PENDING;
 		spin_unlock(&sbi->fs_lock);
-		status = autofs4_mount_wait(dentry, 0);
+		status = autofs4_mount_wait(path, 0);
 		spin_lock(&sbi->fs_lock);
 		ino->flags &= ~AUTOFS_INF_PENDING;
 		if (status) {
@@ -421,8 +423,9 @@ static struct vfsmount *autofs4_d_automount(struct path *path)
 	return NULL;
 }
 
-static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
+static int autofs4_d_manage(const struct path *path, bool rcu_walk)
 {
+	struct dentry *dentry = path->dentry;
 	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
 	struct autofs_info *ino = autofs4_dentry_ino(dentry);
 	int status;
@@ -431,20 +434,20 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
 
 	/* The daemon never waits. */
 	if (autofs4_oz_mode(sbi)) {
-		if (!d_mountpoint(dentry))
+		if (!path_is_mountpoint(path))
 			return -EISDIR;
 		return 0;
 	}
 
 	/* Wait for pending expires */
-	if (do_expire_wait(dentry, rcu_walk) == -ECHILD)
+	if (do_expire_wait(path, rcu_walk) == -ECHILD)
 		return -ECHILD;
 
 	/*
 	 * This dentry may be under construction so wait on mount
 	 * completion.
 	 */
-	status = autofs4_mount_wait(dentry, rcu_walk);
+	status = autofs4_mount_wait(path, rcu_walk);
 	if (status)
 		return status;
 
@@ -460,7 +463,7 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
 
 		if (ino->flags & AUTOFS_INF_WANT_EXPIRE)
 			return 0;
-		if (d_mountpoint(dentry))
+		if (path_is_mountpoint(path))
 			return 0;
 		inode = d_inode_rcu(dentry);
 		if (inode && S_ISLNK(inode->i_mode))
@@ -487,7 +490,7 @@ static int autofs4_d_manage(struct dentry *dentry, bool rcu_walk)
 		 * we can avoid needless calls ->d_automount() and avoid
 		 * an incorrect ELOOP error return.
 		 */
-		if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
+		if ((!path_is_mountpoint(path) && !simple_empty(dentry)) ||
 		    (d_really_is_positive(dentry) && d_is_symlink(dentry)))
 			status = -EISDIR;
 	}

fs/autofs4/waitq.c

@@ -250,8 +250,9 @@ autofs4_find_wait(struct autofs_sb_info *sbi, const struct qstr *qstr)
 static int validate_request(struct autofs_wait_queue **wait,
 			    struct autofs_sb_info *sbi,
 			    const struct qstr *qstr,
-			    struct dentry *dentry, enum autofs_notify notify)
+			    const struct path *path, enum autofs_notify notify)
 {
+	struct dentry *dentry = path->dentry;
 	struct autofs_wait_queue *wq;
 	struct autofs_info *ino;
 
@@ -314,6 +315,7 @@ static int validate_request(struct autofs_wait_queue **wait,
 	 */
 	if (notify == NFY_MOUNT) {
 		struct dentry *new = NULL;
+		struct path this;
 		int valid = 1;
 
 		/*
@@ -333,7 +335,9 @@ static int validate_request(struct autofs_wait_queue **wait,
 					dentry = new;
 			}
 		}
-		if (have_submounts(dentry))
+		this.mnt = path->mnt;
+		this.dentry = dentry;
+		if (path_has_submounts(&this))
 			valid = 0;
 
 		if (new)
@@ -345,8 +349,9 @@ static int validate_request(struct autofs_wait_queue **wait,
 }
 
 int autofs4_wait(struct autofs_sb_info *sbi,
-		 struct dentry *dentry, enum autofs_notify notify)
+		 const struct path *path, enum autofs_notify notify)
 {
+	struct dentry *dentry = path->dentry;
 	struct autofs_wait_queue *wq;
 	struct qstr qstr;
 	char *name;
@@ -405,7 +410,7 @@ int autofs4_wait(struct autofs_sb_info *sbi,
 		return -EINTR;
 	}
 
-	ret = validate_request(&wq, sbi, &qstr, dentry, notify);
+	ret = validate_request(&wq, sbi, &qstr, path, notify);
 	if (ret <= 0) {
 		if (ret != -EINTR)
 			mutex_unlock(&sbi->wq_mutex);

fs/dcache.c

@@ -1273,38 +1273,44 @@ static void d_walk(struct dentry *parent, void *data,
 	goto again;
 }
 
-/*
- * Search for at least 1 mount point in the dentry's subdirs.
- * We descend to the next level whenever the d_subdirs
- * list is non-empty and continue searching.
- */
+struct check_mount {
+	struct vfsmount *mnt;
+	unsigned int mounted;
+};
 
-static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
+static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
 {
-	int *ret = data;
-	if (d_mountpoint(dentry)) {
-		*ret = 1;
+	struct check_mount *info = data;
+	struct path path = { .mnt = info->mnt, .dentry = dentry };
+
+	if (likely(!d_mountpoint(dentry)))
+		return D_WALK_CONTINUE;
+	if (__path_is_mountpoint(&path)) {
+		info->mounted = 1;
 		return D_WALK_QUIT;
 	}
 	return D_WALK_CONTINUE;
 }
 
 /**
- * have_submounts - check for mounts over a dentry
- * @parent: dentry to check.
+ * path_has_submounts - check for mounts over a dentry in the
+ *                      current namespace.
+ * @parent: path to check.
  *
  * Return true if the parent or its subdirectories contain
- * a mount point
+ * a mount point in the current namespace.
  */
-int have_submounts(struct dentry *parent)
+int path_has_submounts(const struct path *parent)
 {
-	int ret = 0;
+	struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
 
-	d_walk(parent, &ret, check_mount, NULL);
+	read_seqlock_excl(&mount_lock);
+	d_walk(parent->dentry, &data, path_check_mount, NULL);
+	read_sequnlock_excl(&mount_lock);
 
-	return ret;
+	return data.mounted;
 }
-EXPORT_SYMBOL(have_submounts);
+EXPORT_SYMBOL(path_has_submounts);
 
 /*
  * Called by mount code to set a mountpoint and check if the mountpoint is

fs/mount.h

@@ -94,6 +94,12 @@ extern struct mount *__lookup_mnt_last(struct vfsmount *, struct dentry *);
 extern int __legitimize_mnt(struct vfsmount *, unsigned);
 extern bool legitimize_mnt(struct vfsmount *, unsigned);
 
+static inline bool __path_is_mountpoint(const struct path *path)
+{
+	struct mount *m = __lookup_mnt(path->mnt, path->dentry);
+	return m && likely(!(m->mnt.mnt_flags & MNT_SYNC_UMOUNT));
+}
+
 extern void __detach_mounts(struct dentry *dentry);
 
 static inline void detach_mounts(struct dentry *dentry)

fs/namei.c

@@ -1200,7 +1200,7 @@ static int follow_managed(struct path *path, struct nameidata *nd)
 		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);
+			ret = path->dentry->d_op->d_manage(path, false);
 			if (ret < 0)
 				break;
 		}
@@ -1263,10 +1263,10 @@ int follow_down_one(struct path *path)
 }
 EXPORT_SYMBOL(follow_down_one);
 
-static inline int managed_dentry_rcu(struct dentry *dentry)
+static inline int managed_dentry_rcu(const struct path *path)
 {
-	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
-		dentry->d_op->d_manage(dentry, true) : 0;
+	return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
+		path->dentry->d_op->d_manage(path, true) : 0;
 }
 
 /*
@@ -1282,7 +1282,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
 		 * Don't forget we might have a non-mountpoint managed dentry
 		 * that wants to block transit.
 		 */
-		switch (managed_dentry_rcu(path->dentry)) {
+		switch (managed_dentry_rcu(path)) {
 		case -ECHILD:
 		default:
 			return false;
@@ -1392,8 +1392,7 @@ int follow_down(struct path *path)
 		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);
+			ret = path->dentry->d_op->d_manage(path, false);
 			if (ret < 0)
 				return ret == -EISDIR ? 0 : ret;
 		}

fs/namespace.c

@@ -1159,6 +1159,35 @@ struct vfsmount *mntget(struct vfsmount *mnt)
 }
 EXPORT_SYMBOL(mntget);
 
+/* path_is_mountpoint() - Check if path is a mount in the current
+ *                          namespace.
+ *
+ *  d_mountpoint() can only be used reliably to establish if a dentry is
+ *  not mounted in any namespace and that common case is handled inline.
+ *  d_mountpoint() isn't aware of the possibility there may be multiple
+ *  mounts using a given dentry in a different namespace. This function
+ *  checks if the passed in path is a mountpoint rather than the dentry
+ *  alone.
+ */
+bool path_is_mountpoint(const struct path *path)
+{
+	unsigned seq;
+	bool res;
+
+	if (!d_mountpoint(path->dentry))
+		return false;
+
+	rcu_read_lock();
+	do {
+		seq = read_seqbegin(&mount_lock);
+		res = __path_is_mountpoint(path);
+	} while (read_seqretry(&mount_lock, seq));
+	rcu_read_unlock();
+
+	return res;
+}
+EXPORT_SYMBOL(path_is_mountpoint);
+
 struct vfsmount *mnt_clone_internal(const struct path *path)
 {
 	struct mount *p;

include/linux/dcache.h

@@ -139,7 +139,7 @@ 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);
+	int (*d_manage)(const struct path *, bool);
 	struct dentry *(*d_real)(struct dentry *, const struct inode *,
 				 unsigned int);
 } ____cacheline_aligned;
@@ -254,7 +254,7 @@ extern struct dentry *d_find_alias(struct inode *);
 extern void d_prune_aliases(struct inode *);
 
 /* test whether we have any submounts in a subdir tree */
-extern int have_submounts(struct dentry *);
+extern int path_has_submounts(const struct path *);
 
 /*
  * This adds the entry to the hash queues.

include/linux/mount.h

@@ -98,4 +98,6 @@ extern dev_t name_to_dev_t(const char *name);
 
 extern unsigned int sysctl_mount_max;
 
+extern bool path_is_mountpoint(const struct path *path);
+
 #endif /* _LINUX_MOUNT_H */