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, 16 insertions, 12 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index a1470fda366c..fcc8ae75d874 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -76,7 +76,7 @@
 #include <linux/buffer_head.h>
 #include <linux/capability.h>
 #include <linux/quotaops.h>
-#include <linux/writeback.h> /* for inode_lock, oddly enough.. */
+#include "../internal.h" /* ugh */
 
 #include <asm/uaccess.h>
 
@@ -900,7 +900,7 @@ static void add_dquot_ref(struct super_block *sb, int type)
         int reserved = 0;
 #endif
 
-        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)) ||
@@ -915,19 +915,23 @@ static void add_dquot_ref(struct super_block *sb, int type)
 #endif
                 __iget(inode);
                 spin_unlock(&inode->i_lock);
-                spin_unlock(&inode_lock);
+                spin_unlock(&inode_sb_list_lock);
 
                 iput(old_inode);
                 __dquot_initialize(inode, type);
-                /* We hold a reference to 'inode' so it couldn't have been
-                 * removed from s_inodes list while we dropped the inode_lock.
-                 * We cannot iput the inode now as we can be holding the last
-                 * reference and we cannot iput it under inode_lock. So we
-                 * keep the reference and iput it later. */
+
+                /*
+                 * We hold a reference to 'inode' so it couldn't have been
+                 * removed from s_inodes list while we dropped the
+                 * inode_sb_list_lock We cannot iput the inode now as we can be
+                 * holding the last reference and we cannot iput it under
+                 * inode_sb_list_lock. So we keep the reference and iput it
+                 * later.
+                 */
                 old_inode = inode;
-                spin_lock(&inode_lock);
+                spin_lock(&inode_sb_list_lock);
         }
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_sb_list_lock);
         iput(old_inode);
 
 #ifdef CONFIG_QUOTA_DEBUG
@@ -1008,7 +1012,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
         struct inode *inode;
         int reserved = 0;
 
-        spin_lock(&inode_lock);
+        spin_lock(&inode_sb_list_lock);
         list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
                 /*
                  *  We have to scan also I_NEW inodes because they can already
@@ -1022,7 +1026,7 @@ static void remove_dquot_ref(struct super_block *sb, int type,
                         remove_inode_dquot_ref(inode, type, tofree_head);
                 }
         }
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_sb_list_lock);
 #ifdef CONFIG_QUOTA_DEBUG
         if (reserved) {
                 printk(KERN_WARNING "VFS (%s): Writes happened after quota"