1 files changed, 49 insertions, 8 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index a88948b8bd17..10ba92def3f6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -36,6 +36,7 @@
 #include <linux/bit_spinlock.h>
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
+#include <linux/ratelimit.h>
 #include "internal.h"
 
 /*
@@ -225,7 +226,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
 }
 
 /*
- * dentry_lru_(add|del|move_tail) must be called with d_lock held.
+ * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
@@ -245,6 +246,9 @@ static void __dentry_lru_del(struct dentry *dentry)
         dentry_stat.nr_unused--;
 }
 
+/*
+ * Remove a dentry with references from the LRU.
+ */
 static void dentry_lru_del(struct dentry *dentry)
 {
         if (!list_empty(&dentry->d_lru)) {
@@ -254,6 +258,23 @@ static void dentry_lru_del(struct dentry *dentry)
         }
 }
 
+/*
+ * Remove a dentry that is unreferenced and about to be pruned
+ * (unhashed and destroyed) from the LRU, and inform the file system.
+ * This wrapper should be called _prior_ to unhashing a victim dentry.
+ */
+static void dentry_lru_prune(struct dentry *dentry)
+{
+        if (!list_empty(&dentry->d_lru)) {
+                if (dentry->d_flags & DCACHE_OP_PRUNE)
+                        dentry->d_op->d_prune(dentry);
+
+                spin_lock(&dcache_lru_lock);
+                __dentry_lru_del(dentry);
+                spin_unlock(&dcache_lru_lock);
+        }
+}
+
 static void dentry_lru_move_tail(struct dentry *dentry)
 {
         spin_lock(&dcache_lru_lock);
@@ -403,8 +424,12 @@ relock:
 
         if (ref)
                 dentry->d_count--;
-        /* if dentry was on the d_lru list delete it from there */
-        dentry_lru_del(dentry);
+        /*
+         * if dentry was on the d_lru list delete it from there.
+         * inform the fs via d_prune that this dentry is about to be
+         * unhashed and destroyed.
+         */
+        dentry_lru_prune(dentry);
         /* if it was on the hash then remove it */
         __d_drop(dentry);
         return d_kill(dentry, parent);
@@ -522,9 +547,11 @@ int d_invalidate(struct dentry * dentry)
          * would make it unreachable from the root,
          * we might still populate it if it was a
          * working directory or similar).
+         * We also need to leave mountpoints alone,
+         * directory or not.
          */
-        if (dentry->d_count > 1) {
-                if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
+        if (dentry->d_count > 1 && dentry->d_inode) {
+                if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
                         spin_unlock(&dentry->d_lock);
                         return -EBUSY;
                 }
@@ -854,8 +881,12 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
                 do {
                         struct inode *inode;
 
-                        /* detach from the system */
-                        dentry_lru_del(dentry);
+                        /*
+                         * remove the dentry from the lru, and inform
+                         * the fs that this dentry is about to be
+                         * unhashed and destroyed.
+                         */
+                        dentry_lru_prune(dentry);
                         __d_shrink(dentry);
 
                         if (dentry->d_count != 0) {
@@ -1283,6 +1314,8 @@ void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
                 dentry->d_flags |= DCACHE_OP_REVALIDATE;
         if (op->d_delete)
                 dentry->d_flags |= DCACHE_OP_DELETE;
+        if (op->d_prune)
+                dentry->d_flags |= DCACHE_OP_PRUNE;
 
 }
 EXPORT_SYMBOL(d_set_d_op);
@@ -2351,8 +2384,16 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
                                 actual = __d_unalias(inode, dentry, alias);
                         }
                         write_sequnlock(&rename_lock);
-                        if (IS_ERR(actual))
+                        if (IS_ERR(actual)) {
+                                if (PTR_ERR(actual) == -ELOOP)
+                                        pr_warn_ratelimited(
+                                                "VFS: Lookup of '%s' in %s %s"
+                                                " would have caused loop\n",
+                                                dentry->d_name.name,
+                                                inode->i_sb->s_type->name,
+                                                inode->i_sb->s_id);
                                 dput(alias);
+                        }
                         goto out_nolock;
                 }
         }