Signed-off-by: Josef Bacik <redacted>
---
fs/namei.c             |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/dcache.h |    1 +
2 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index e3c4f11..a1bff4f 100644
--- a/fs/namei.c
+++ b/fs/namei.c

@@ -1198,6 +1198,29 @@ static struct dentry *d_alloc_and_lookup(struct dentry *parent,

}

/*
+ * We already have a dentry, but require a lookup to be performed on the parent
+ * directory to fill in d_inode. Returns the new dentry, or ERR_PTR on error.
+ * parent->d_inode->i_mutex must be held. d_lookup must have verified that no
+ * child exists while under i_mutex.
+ */
+static struct dentry *d_inode_lookup(struct dentry *parent, struct dentry *dentry,
+				     struct nameidata *nd)
+{
+	struct inode *inode = parent->d_inode;
+	struct dentry *old;
+
+	/* Don't create child dentry for a dead directory. */
+	if (unlikely(IS_DEADDIR(inode)))
+		return ERR_PTR(-ENOENT);
+
+	old = inode->i_op->lookup(inode, dentry, nd);
+	if (unlikely(old)) {
+		dput(dentry);
+		dentry = old;
+	}
+	return dentry;
+}
+/*
*  It's more convoluted than I'd like it to be, but... it's still fairly
*  small and for now I'd prefer to have fast path as straight as possible.
*  It _is_ time-critical.

@@ -1236,6 +1259,13 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,

				goto unlazy;
			}
		}
+		if (unlikely(dentry->d_flags & DCACHE_NEED_LOOKUP)) {
+			if (nameidata_dentry_drop_rcu(nd, dentry))
+				return -ECHILD;
+			dput(dentry);
+			dentry = NULL;
+			goto retry;
+		}
		path->mnt = mnt;
		path->dentry = dentry;
		if (likely(__follow_mount_rcu(nd, path, inode, false)))

@@ -1250,6 +1280,12 @@ unlazy:

		}
	} else {
		dentry = __d_lookup(parent, name);
+		if (unlikely(!dentry))
+			goto retry;
+		if (unlikely(dentry->d_flags & DCACHE_NEED_LOOKUP)) {
+			dput(dentry);
+			dentry = NULL;
+		}
	}

retry:

@@ -1268,6 +1304,18 @@ retry:

			/* known good */
			need_reval = 0;
			status = 1;
+		} else if (unlikely(dentry->d_flags & DCACHE_NEED_LOOKUP)) {
+			struct dentry *old;
+
+			dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
+			dentry = d_inode_lookup(parent, dentry, nd);

+			if (IS_ERR(dentry)) {
+				mutex_unlock(&dir->i_mutex);
+				return PTR_ERR(dentry);
+			}
+			/* known good */
+			need_reval = 0;
+			status = 1;
		}
		mutex_unlock(&dir->i_mutex);
	}

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 19d90a5..a8b2457 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h

@@ -216,6 +216,7 @@ struct dentry_operations {

#define DCACHE_MOUNTED		0x10000	/* is a mountpoint */
#define DCACHE_NEED_AUTOMOUNT	0x20000	/* handle automount on this dir */
#define DCACHE_MANAGE_TRANSIT	0x40000	/* manage transit from this dirent */
+#define DCACHE_NEED_LOOKUP	0x80000 /* dentry requires i_op->lookup */
#define DCACHE_MANAGED_DENTRY \
	(DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)

-- 
1.7.2.3

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