Commit 2aa38470 authored by Al Viro's avatar Al Viro
Browse files

non-RCU analogue of the previous commit 



new helper: choose_mountpoint().  Wrapper around choose_mountpoint_rcu(),
similar to lookup_mnt() vs. __lookup_mnt().  follow_dotdot() switched to
it.  Now we don't grab mount_lock exclusive anymore; note that the
primitive used non-RCU mount traversals in other direction (lookup_mnt())
doesn't bother with that either - it uses mount_lock seqcount instead.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 7ef482fa

fs/namei.c

+39 −17
Original line number Diff line number Diff line
@@ -605,10 +605,9 @@ static void terminate_walk(struct nameidata *nd) 
}



/* path_put is needed afterwards regardless of success or failure */

static bool legitimize_path(struct nameidata *nd,

			    struct path *path, unsigned seq)

static bool __legitimize_path(struct path *path, unsigned seq, unsigned mseq)

{

	int res = __legitimize_mnt(path->mnt, nd->m_seq);

	int res = __legitimize_mnt(path->mnt, mseq);

	if (unlikely(res)) {

		if (res > 0)

			path->mnt = NULL;
@@ -622,6 +621,12 @@ static bool legitimize_path(struct nameidata *nd, 
	return !read_seqcount_retry(&path->dentry->d_seq, seq);

}



static inline bool legitimize_path(struct nameidata *nd,

			    struct path *path, unsigned seq)

{

	return __legitimize_path(path, nd->m_seq, seq);

}



static bool legitimize_links(struct nameidata *nd)

{

	int i;
@@ -1154,6 +1159,31 @@ static bool choose_mountpoint_rcu(struct mount *m, const struct path *root, 
	return false;

}



static bool choose_mountpoint(struct mount *m, const struct path *root,

			      struct path *path)

{

	bool found;



	rcu_read_lock();

	while (1) {

		unsigned seq, mseq = read_seqbegin(&mount_lock);



		found = choose_mountpoint_rcu(m, root, path, &seq);

		if (unlikely(!found)) {

			if (!read_seqretry(&mount_lock, mseq))

				break;

		} else {

			if (likely(__legitimize_path(path, seq, mseq)))

				break;

			rcu_read_unlock();

			path_put(path);

			rcu_read_lock();

		}

	}

	rcu_read_unlock();

	return found;

}



/*

 * Perform an automount

 * - return -EISDIR to tell follow_managed() to stop and return the path we
@@ -1756,22 +1786,14 @@ static struct dentry *follow_dotdot(struct nameidata *nd, 
	if (path_equal(&nd->path, &nd->root))

		goto in_root;

	if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {

		struct path path = nd->path;

		path_get(&path);

		while (1) {

			if (!follow_up(&path)) {

				path_put(&path);

				goto in_root;

			}

			if (path_equal(&path, &nd->root)) {

				path_put(&path);

		struct path path;



		if (!choose_mountpoint(real_mount(nd->path.mnt),

				       &nd->root, &path))

			goto in_root;

			}

			if (path.dentry != nd->path.mnt->mnt_root)

				break;

		}

		path_put(&nd->path);

		nd->path = path;

		nd->inode = path.dentry->d_inode;

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

			return ERR_PTR(-EXDEV);

	}

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