1 files changed, 21 insertions, 14 deletions

diff --git a/fs/inode.c b/fs/inode.c
index b2ba83d2c4e1..76582b06ab97 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/backing-dev.h>
 #include <linux/wait.h>
+#include <linux/rwsem.h>
 #include <linux/hash.h>
 #include <linux/swap.h>
 #include <linux/security.h>
@@ -87,14 +88,18 @@ static struct hlist_head *inode_hashtable __read_mostly;
 DEFINE_SPINLOCK(inode_lock);
 
 /*
- * iprune_mutex provides exclusion between the kswapd or try_to_free_pages
+ * iprune_sem provides exclusion between the kswapd or try_to_free_pages
  * icache shrinking path, and the umount path.  Without this exclusion,
  * by the time prune_icache calls iput for the inode whose pages it has
  * been invalidating, or by the time it calls clear_inode & destroy_inode
  * from its final dispose_list, the struct super_block they refer to
  * (for inode->i_sb->s_op) may already have been freed and reused.
+ *
+ * We make this an rwsem because the fastpath is icache shrinking. In
+ * some cases a filesystem may be doing a significant amount of work in
+ * its inode reclaim code, so this should improve parallelism.
  */
-static DEFINE_MUTEX(iprune_mutex);
+static DECLARE_RWSEM(iprune_sem);
 
 /*
  * Statistics gathering..
@@ -123,7 +128,7 @@ static void wake_up_inode(struct inode *inode)
 int inode_init_always(struct super_block *sb, struct inode *inode)
 {
         static const struct address_space_operations empty_aops;
-        static struct inode_operations empty_iops;
+        static const struct inode_operations empty_iops;
         static const struct file_operations empty_fops;
         struct address_space *const mapping = &inode->i_data;
 
@@ -381,7 +386,7 @@ static int invalidate_list(struct list_head *head, struct list_head *dispose)
                 /*
                  * We can reschedule here without worrying about the list's
                  * consistency because the per-sb list of inodes must not
-                 * change during umount anymore, and because iprune_mutex keeps
+                 * change during umount anymore, and because iprune_sem keeps
                  * shrink_icache_memory() away.
                  */
                 cond_resched_lock(&inode_lock);
@@ -420,7 +425,7 @@ int invalidate_inodes(struct super_block *sb)
         int busy;
         LIST_HEAD(throw_away);
 
-        mutex_lock(&iprune_mutex);
+        down_write(&iprune_sem);
         spin_lock(&inode_lock);
         inotify_unmount_inodes(&sb->s_inodes);
         fsnotify_unmount_inodes(&sb->s_inodes);
@@ -428,7 +433,7 @@ int invalidate_inodes(struct super_block *sb)
         spin_unlock(&inode_lock);
 
         dispose_list(&throw_away);
-        mutex_unlock(&iprune_mutex);
+        up_write(&iprune_sem);
 
         return busy;
 }
@@ -467,7 +472,7 @@ static void prune_icache(int nr_to_scan)
         int nr_scanned;
         unsigned long reap = 0;
 
-        mutex_lock(&iprune_mutex);
+        down_read(&iprune_sem);
         spin_lock(&inode_lock);
         for (nr_scanned = 0; nr_scanned < nr_to_scan; nr_scanned++) {
                 struct inode *inode;
@@ -509,7 +514,7 @@ static void prune_icache(int nr_to_scan)
         spin_unlock(&inode_lock);
 
         dispose_list(&freeable);
-        mutex_unlock(&iprune_mutex);
+        up_read(&iprune_sem);
 }
 
 /*
@@ -695,13 +700,15 @@ void unlock_new_inode(struct inode *inode)
         }
 #endif
         /*
-         * This is special!  We do not need the spinlock
-         * when clearing I_LOCK, because we're guaranteed
-         * that nobody else tries to do anything about the
-         * state of the inode when it is locked, as we
-         * just created it (so there can be no old holders
-         * that haven't tested I_LOCK).
+         * This is special!  We do not need the spinlock when clearing I_LOCK,
+         * because we're guaranteed that nobody else tries to do anything about
+         * the state of the inode when it is locked, as we just created it (so
+         * there can be no old holders that haven't tested I_LOCK).
+         * However we must emit the memory barrier so that other CPUs reliably
+         * see the clearing of I_LOCK after the other inode initialisation has
+         * completed.
          */
+        smp_mb();
         WARN_ON((inode->i_state & (I_LOCK|I_NEW)) != (I_LOCK|I_NEW));
         inode->i_state &= ~(I_LOCK|I_NEW);
         wake_up_inode(inode);