Commit 3bd8bc89 authored by Al Viro's avatar Al Viro
Browse files

step_into(): move fetching ->d_inode past handle_mounts() 



... and lose messing with it in __follow_mount_rcu()

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 4cb64024

fs/namei.c

+11 −20
Original line number Diff line number Diff line
@@ -1474,8 +1474,7 @@ EXPORT_SYMBOL(follow_down); 
 * Try to skip to top of mountpoint pile in rcuwalk mode.  Fail if

 * we meet a managed dentry that would need blocking.

 */

static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,

			       struct inode **inode)

static bool __follow_mount_rcu(struct nameidata *nd, struct path *path)

{

	struct dentry *dentry = path->dentry;

	unsigned int flags = dentry->d_flags;
@@ -1505,13 +1504,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, 
				dentry = path->dentry = mounted->mnt.mnt_root;

				nd->state |= ND_JUMPED;

				nd->next_seq = read_seqcount_begin(&dentry->d_seq);

				*inode = dentry->d_inode;

				/*

				 * 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.

				 */

				flags = dentry->d_flags;

				// makes sure that non-RCU pathwalk could reach

				// this state.
@@ -1527,7 +1519,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, 
}



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

			  struct path *path, struct inode **inode)

			  struct path *path)

{

	bool jumped;

	int ret;
@@ -1536,12 +1528,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, 
	path->dentry = dentry;

	if (nd->flags & LOOKUP_RCU) {

		unsigned int seq = nd->next_seq;

		*inode = dentry->d_inode;

		if (read_seqcount_retry(&dentry->d_seq, seq))

			return -ECHILD;

		if (unlikely(!*inode))

			return -ENOENT;

		if (likely(__follow_mount_rcu(nd, path, inode)))

		if (likely(__follow_mount_rcu(nd, path)))

			return 0;

		// *path and nd->next_seq might've been clobbered

		path->mnt = nd->path.mnt;
@@ -1561,8 +1548,6 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry, 
		dput(path->dentry);

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

			mntput(path->mnt);

	} else {

		*inode = d_backing_inode(path->dentry);

	}

	return ret;

}
@@ -1843,15 +1828,21 @@ static const char *step_into(struct nameidata *nd, int flags, 
{

	struct path path;

	struct inode *inode;

	int err = handle_mounts(nd, dentry, &path, &inode);

	int err = handle_mounts(nd, dentry, &path);



	if (err < 0)

		return ERR_PTR(err);

	inode = path.dentry->d_inode;

	if (likely(!d_is_symlink(path.dentry)) ||

	   ((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||

	   (flags & WALK_NOFOLLOW)) {

		/* not a symlink or should not follow */

		if (!(nd->flags & LOOKUP_RCU)) {

		if (nd->flags & LOOKUP_RCU) {

			if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))

				return ERR_PTR(-ECHILD);

			if (unlikely(!inode))

				return ERR_PTR(-ENOENT);

		} else {

			dput(nd->path.dentry);

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

				mntput(nd->path.mnt);