fs: move i_sb_list out from under inode_lock

Protect the per-sb inode list with a new global lock
inode_sb_list_lock and use it to protect the list manipulations and
traversals. This lock replaces the inode_lock as the inodes on the
list can be validity checked while holding the inode->i_lock and
hence the inode_lock is no longer needed to protect the list.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index 6c6f73ba0868..98b77c89494c 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -8,6 +8,7 @@
 #include <linux/writeback.h>
 #include <linux/sysctl.h>
 #include <linux/gfp.h>
+#include "internal.h"
 
 /* A global variable is a bit ugly, but it keeps the code simple */
 int sysctl_drop_caches;
@@ -16,7 +17,7 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
 {
         struct inode *inode, *toput_inode = NULL;
 
-        spin_lock(&inode_lock);
+        spin_lock(&inode_sb_list_lock);
         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
                 spin_lock(&inode->i_lock);
                 if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
@@ -26,13 +27,13 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
                 }
                 __iget(inode);
                 spin_unlock(&inode->i_lock);
-                spin_unlock(&inode_lock);
+                spin_unlock(&inode_sb_list_lock);
                 invalidate_mapping_pages(inode->i_mapping, 0, -1);
                 iput(toput_inode);
                 toput_inode = inode;
-                spin_lock(&inode_lock);
+                spin_lock(&inode_sb_list_lock);
         }
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_sb_list_lock);
         iput(toput_inode);
 }