fs: dcache scale d_unhashed

Protect d_unhashed(dentry) condition with d_lock. This means keeping
DCACHE_UNHASHED bit in synch with hash manipulations.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

1 files changed, 20 insertions, 9 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index b9d25d83e228..433e7139c23a 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -16,6 +16,11 @@
 
 #include <asm/uaccess.h>
 
+static inline int simple_positive(struct dentry *dentry)
+{
+        return dentry->d_inode && !d_unhashed(dentry);
+}
+
 int simple_getattr(struct vfsmount *mnt, struct dentry *dentry,
                    struct kstat *stat)
 {
@@ -100,8 +105,10 @@ loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
                         while (n && p != &file->f_path.dentry->d_subdirs) {
                                 struct dentry *next;
                                 next = list_entry(p, struct dentry, d_u.d_child);
-                                if (!d_unhashed(next) && next->d_inode)
+                                spin_lock(&next->d_lock);
+                                if (simple_positive(next))
                                         n--;
+                                spin_unlock(&next->d_lock);
                                 p = p->next;
                         }
                         list_add_tail(&cursor->d_u.d_child, p);
@@ -155,9 +162,13 @@ int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
                         for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
                                 struct dentry *next;
                                 next = list_entry(p, struct dentry, d_u.d_child);
-                                if (d_unhashed(next) || !next->d_inode)
+                                spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
+                                if (!simple_positive(next)) {
+                                        spin_unlock(&next->d_lock);
                                         continue;
+                                }
 
+                                spin_unlock(&next->d_lock);
                                 spin_unlock(&dcache_lock);
                                 if (filldir(dirent, next->d_name.name, 
                                             next->d_name.len, filp->f_pos, 
@@ -259,20 +270,20 @@ int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *den
         return 0;
 }
 
-static inline int simple_positive(struct dentry *dentry)
-{
-        return dentry->d_inode && !d_unhashed(dentry);
-}
-
 int simple_empty(struct dentry *dentry)
 {
         struct dentry *child;
         int ret = 0;
 
         spin_lock(&dcache_lock);
-        list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child)
-                if (simple_positive(child))
+        list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
+                spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+                if (simple_positive(child)) {
+                        spin_unlock(&child->d_lock);
                         goto out;
+                }
+                spin_unlock(&child->d_lock);
+        }
         ret = 1;
 out:
         spin_unlock(&dcache_lock);