Commit ea936aeb authored by Al Viro's avatar Al Viro
Browse files

massage __follow_mount_rcu() a bit 



make the loop more similar to that in follow_managed(), with
explicit tracking of flags, etc.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent c108837e

fs/namei.c

+35 −35
Original line number Diff line number Diff line
@@ -1269,12 +1269,6 @@ int follow_down_one(struct path *path) 
}

EXPORT_SYMBOL(follow_down_one);



static inline int managed_dentry_rcu(const struct path *path)

{

	return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?

		path->dentry->d_op->d_manage(path, true) : 0;

}



/*

 * Try to skip to top of mountpoint pile in rcuwalk mode.  Fail if

 * we meet a managed dentry that would need blocking.
@@ -1282,43 +1276,49 @@ static inline int managed_dentry_rcu(const struct path *path) 
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,

			       struct inode **inode, unsigned *seqp)

{

	struct dentry *dentry = path->dentry;

	unsigned int flags = dentry->d_flags;



	if (likely(!(flags & DCACHE_MANAGED_DENTRY)))

		return true;



	if (unlikely(nd->flags & LOOKUP_NO_XDEV))

		return false;



	for (;;) {

		struct mount *mounted;

		/*

		 * Don't forget we might have a non-mountpoint managed dentry

		 * that wants to block transit.

		 */

		switch (managed_dentry_rcu(path)) {

		case -ECHILD:

		default:

			return false;

		case -EISDIR:

			return true;

		case 0:

			break;

		if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {

			int res = dentry->d_op->d_manage(path, true);

			if (res)

				return res == -EISDIR;

			flags = dentry->d_flags;

		}



		if (!d_mountpoint(path->dentry))

			return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);



		mounted = __lookup_mnt(path->mnt, path->dentry);

		if (!mounted)

			break;

		if (unlikely(nd->flags & LOOKUP_NO_XDEV))

			return false;

		if (flags & DCACHE_MOUNTED) {

			struct mount *mounted = __lookup_mnt(path->mnt, dentry);

			if (mounted) {

				path->mnt = &mounted->mnt;

		path->dentry = mounted->mnt.mnt_root;

				dentry = path->dentry = mounted->mnt.mnt_root;

				nd->flags |= LOOKUP_JUMPED;

		*seqp = read_seqcount_begin(&path->dentry->d_seq);

				*seqp = read_seqcount_begin(&dentry->d_seq);

				*inode = dentry->d_inode;

				/*

		 * Update the inode too. We don't need to re-check the

		 * dentry sequence number here after this d_inode read,

		 * because a mount-point is always pinned.

				 * We don't need to re-check ->d_seq after this

				 * ->d_inode read - there will be an RCU delay

				 * between mount hash removal and ->mnt_root

				 * becoming unpinned.

				 */

		*inode = path->dentry->d_inode;

				flags = dentry->d_flags;

				continue;

			}

			if (read_seqretry(&mount_lock, nd->m_seq))

				return false;

		}

		return !(flags & DCACHE_NEED_AUTOMOUNT);

	}

	return !read_seqretry(&mount_lock, nd->m_seq) &&

		!(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);

}



static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,