3 files changed, 72 insertions, 14 deletions

diff --git a/fs/namei.c b/fs/namei.c
index cd43ff89fbaa..c7c6b255db2c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1827,6 +1827,20 @@ static struct dentry *lookup_slow(const struct qstr *name,
 	return res;
 }
 
+static struct dentry *lookup_slow_killable(const struct qstr *name,
+					   struct dentry *dir,
+					   unsigned int flags)
+{
+	struct inode *inode = dir->d_inode;
+	struct dentry *res;
+
+	if (inode_lock_shared_killable(inode))
+		return ERR_PTR(-EINTR);
+	res = __lookup_slow(name, dir, flags);
+	inode_unlock_shared(inode);
+	return res;
+}
+
 static inline int may_lookup(struct mnt_idmap *idmap,
 			     struct nameidata *restrict nd)
 {
@@ -3011,6 +3025,47 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap, struct qstr *name,
 EXPORT_SYMBOL(lookup_one_unlocked);
 
 /**
+ * lookup_one_positive_killable - lookup single pathname component
+ * @idmap:	idmap of the mount the lookup is performed from
+ * @name:	qstr olding pathname component to lookup
+ * @base:	base directory to lookup from
+ *
+ * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
+ * known positive or ERR_PTR(). This is what most of the users want.
+ *
+ * Note that pinned negative with unlocked parent _can_ become positive at any
+ * time, so callers of lookup_one_unlocked() need to be very careful; pinned
+ * positives have >d_inode stable, so this one avoids such problems.
+ *
+ * This can be used for in-kernel filesystem clients such as file servers.
+ *
+ * It should be called without the parent i_rwsem held, and will take
+ * the i_rwsem itself if necessary.  If a fatal signal is pending or
+ * delivered, it will return %-EINTR if the lock is needed.
+ */
+struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
+					    struct qstr *name,
+					    struct dentry *base)
+{
+	int err;
+	struct dentry *ret;
+
+	err = lookup_one_common(idmap, name, base);
+	if (err)
+		return ERR_PTR(err);
+
+	ret = lookup_dcache(name, base, 0);
+	if (!ret)
+		ret = lookup_slow_killable(name, base, 0);
+	if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
+		dput(ret);
+		ret = ERR_PTR(-ENOENT);
+	}
+	return ret;
+}
+EXPORT_SYMBOL(lookup_one_positive_killable);
+
+/**
  * lookup_one_positive_unlocked - lookup single pathname component
  * @idmap:	idmap of the mount the lookup is performed from
  * @name:	qstr holding pathname component to lookup
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index b65cdfce31ce..15cb06fa0c9a 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -270,26 +270,26 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
 
 static int ovl_check_whiteouts(const struct path *path, struct ovl_readdir_data *rdd)
 {
-	int err;
+	int err = 0;
 	struct dentry *dentry, *dir = path->dentry;
 	const struct cred *old_cred;
 
 	old_cred = ovl_override_creds(rdd->dentry->d_sb);
 
-	err = down_write_killable(&dir->d_inode->i_rwsem);
-	if (!err) {
-		while (rdd->first_maybe_whiteout) {
-			struct ovl_cache_entry *p =
-				rdd->first_maybe_whiteout;
-			rdd->first_maybe_whiteout = p->next_maybe_whiteout;
-			dentry = lookup_one(mnt_idmap(path->mnt),
-					    &QSTR_LEN(p->name, p->len), dir);
-			if (!IS_ERR(dentry)) {
-				p->is_whiteout = ovl_is_whiteout(dentry);
-				dput(dentry);
-			}
+	while (rdd->first_maybe_whiteout) {
+		struct ovl_cache_entry *p =
+			rdd->first_maybe_whiteout;
+		rdd->first_maybe_whiteout = p->next_maybe_whiteout;
+		dentry = lookup_one_positive_killable(mnt_idmap(path->mnt),
+						      &QSTR_LEN(p->name, p->len),
+						      dir);
+		if (!IS_ERR(dentry)) {
+			p->is_whiteout = ovl_is_whiteout(dentry);
+			dput(dentry);
+		} else if (PTR_ERR(dentry) == -EINTR) {
+			err = -EINTR;
+			break;
 		}
-		inode_unlock(dir->d_inode);
 	}
 	ovl_revert_creds(old_cred);
 
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 5d085428e471..551a1a01e5e7 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -80,6 +80,9 @@ struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
 struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 					    struct qstr *name,
 					    struct dentry *base);
+struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
+					    struct qstr *name,
+					    struct dentry *base);
 
 extern int follow_down_one(struct path *);
 extern int follow_down(struct path *path, unsigned int flags);