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, 23 insertions, 20 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 389f5a247599..785b1ab23ff0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -34,10 +34,15 @@
  *   inode->i_state, inode->i_hash, __iget()
  * inode_lru_lock protects:
  *   inode_lru, inode->i_lru
+ * inode_sb_list_lock protects:
+ *   sb->s_inodes, inode->i_sb_list
  *
  * Lock ordering:
  * inode_lock
  *   inode->i_lock
+ *
+ * inode_sb_list_lock
+ *   inode->i_lock
  *     inode_lru_lock
  */
 
@@ -99,6 +104,8 @@ static struct hlist_head *inode_hashtable __read_mostly;
  */
 DEFINE_SPINLOCK(inode_lock);
 
+__cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
+
 /*
  * iprune_sem provides exclusion between the icache shrinking and the
  * umount path.
@@ -378,26 +385,23 @@ static void inode_lru_list_del(struct inode *inode)
         spin_unlock(&inode_lru_lock);
 }
 
-static inline void __inode_sb_list_add(struct inode *inode)
-{
-        list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
-}
-
 /**
  * inode_sb_list_add - add inode to the superblock list of inodes
  * @inode: inode to add
  */
 void inode_sb_list_add(struct inode *inode)
 {
-        spin_lock(&inode_lock);
-        __inode_sb_list_add(inode);
-        spin_unlock(&inode_lock);
+        spin_lock(&inode_sb_list_lock);
+        list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
+        spin_unlock(&inode_sb_list_lock);
 }
 EXPORT_SYMBOL_GPL(inode_sb_list_add);
 
-static inline void __inode_sb_list_del(struct inode *inode)
+static inline void inode_sb_list_del(struct inode *inode)
 {
+        spin_lock(&inode_sb_list_lock);
         list_del_init(&inode->i_sb_list);
+        spin_unlock(&inode_sb_list_lock);
 }
 
 static unsigned long hash(struct super_block *sb, unsigned long hashval)
@@ -481,9 +485,10 @@ static void evict(struct inode *inode)
 
         spin_lock(&inode_lock);
         list_del_init(&inode->i_wb_list);
-        __inode_sb_list_del(inode);
         spin_unlock(&inode_lock);
 
+        inode_sb_list_del(inode);
+
         if (op->evict_inode) {
                 op->evict_inode(inode);
         } else {
@@ -539,7 +544,7 @@ void evict_inodes(struct super_block *sb)
         struct inode *inode, *next;
         LIST_HEAD(dispose);
 
-        spin_lock(&inode_lock);
+        spin_lock(&inode_sb_list_lock);
         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
                 if (atomic_read(&inode->i_count))
                         continue;
@@ -555,7 +560,7 @@ void evict_inodes(struct super_block *sb)
                 spin_unlock(&inode->i_lock);
                 list_add(&inode->i_lru, &dispose);
         }
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_sb_list_lock);
 
         dispose_list(&dispose);
 
@@ -584,7 +589,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
         struct inode *inode, *next;
         LIST_HEAD(dispose);
 
-        spin_lock(&inode_lock);
+        spin_lock(&inode_sb_list_lock);
         list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
                 spin_lock(&inode->i_lock);
                 if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
@@ -607,7 +612,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
                 spin_unlock(&inode->i_lock);
                 list_add(&inode->i_lru, &dispose);
         }
-        spin_unlock(&inode_lock);
+        spin_unlock(&inode_sb_list_lock);
 
         dispose_list(&dispose);
 
@@ -867,16 +872,14 @@ struct inode *new_inode(struct super_block *sb)
 {
         struct inode *inode;
 
-        spin_lock_prefetch(&inode_lock);
+        spin_lock_prefetch(&inode_sb_list_lock);
 
         inode = alloc_inode(sb);
         if (inode) {
-                spin_lock(&inode_lock);
                 spin_lock(&inode->i_lock);
                 inode->i_state = 0;
                 spin_unlock(&inode->i_lock);
-                __inode_sb_list_add(inode);
-                spin_unlock(&inode_lock);
+                inode_sb_list_add(inode);
         }
         return inode;
 }
@@ -945,7 +948,7 @@ static struct inode *get_new_inode(struct super_block *sb,
                         inode->i_state = I_NEW;
                         hlist_add_head(&inode->i_hash, head);
                         spin_unlock(&inode->i_lock);
-                        __inode_sb_list_add(inode);
+                        inode_sb_list_add(inode);
                         spin_unlock(&inode_lock);
 
                         /* Return the locked inode with I_NEW set, the
@@ -994,7 +997,7 @@ static struct inode *get_new_inode_fast(struct super_block *sb,
                         inode->i_state = I_NEW;
                         hlist_add_head(&inode->i_hash, head);
                         spin_unlock(&inode->i_lock);
-                        __inode_sb_list_add(inode);
+                        inode_sb_list_add(inode);
                         spin_unlock(&inode_lock);
 
                         /* Return the locked inode with I_NEW set, the