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[PATCH 07/12] inode: move to per-sb LRU locks

To: linux-fsdevel@xxxxxxxxxxxxxxx
Subject: [PATCH 07/12] inode: move to per-sb LRU locks
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 2 Jun 2011 17:01:02 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <1306998067-27659-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1306998067-27659-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

With the inode LRUs moving to per-sb structures, there is no longer
a need for a global inode_lru_lock. The locking can be made more
fine-grained by moving to a per-sb LRU lock, isolating the LRU
operations of different filesytsems completely from each other.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/inode.c         |   27 +++++++++++++--------------
 fs/super.c         |    1 +
 include/linux/fs.h |    3 ++-
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index e039115..667a29c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -33,7 +33,7 @@
  *
  * inode->i_lock protects:
  *   inode->i_state, inode->i_hash, __iget()
- * inode_lru_lock protects:
+ * inode->i_sb->s_inode_lru_lock protects:
  *   inode->i_sb->s_inode_lru, inode->i_lru
  * inode_sb_list_lock protects:
  *   sb->s_inodes, inode->i_sb_list
@@ -46,7 +46,7 @@
  *
  * inode_sb_list_lock
  *   inode->i_lock
- *     inode_lru_lock
+ *     inode->i_sb->s_inode_lru_lock
  *
  * inode_wb_list_lock
  *   inode->i_lock
@@ -64,8 +64,6 @@ static unsigned int i_hash_shift __read_mostly;
 static struct hlist_head *inode_hashtable __read_mostly;
 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
 
-static DEFINE_SPINLOCK(inode_lru_lock);
-
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
 __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_wb_list_lock);
 
@@ -342,24 +340,24 @@ EXPORT_SYMBOL(ihold);
 
 static void inode_lru_list_add(struct inode *inode)
 {
-       spin_lock(&inode_lru_lock);
+       spin_lock(&inode->i_sb->s_inode_lru_lock);
        if (list_empty(&inode->i_lru)) {
                list_add(&inode->i_lru, &inode->i_sb->s_inode_lru);
                inode->i_sb->s_nr_inodes_unused++;
                this_cpu_inc(nr_unused);
        }
-       spin_unlock(&inode_lru_lock);
+       spin_unlock(&inode->i_sb->s_inode_lru_lock);
 }
 
 static void inode_lru_list_del(struct inode *inode)
 {
-       spin_lock(&inode_lru_lock);
+       spin_lock(&inode->i_sb->s_inode_lru_lock);
        if (!list_empty(&inode->i_lru)) {
                list_del_init(&inode->i_lru);
                inode->i_sb->s_nr_inodes_unused--;
                this_cpu_dec(nr_unused);
        }
-       spin_unlock(&inode_lru_lock);
+       spin_unlock(&inode->i_sb->s_inode_lru_lock);
 }
 
 /**
@@ -608,7 +606,8 @@ static int can_unuse(struct inode *inode)
 
 /*
  * Scan `goal' inodes on the unused list for freeable ones. They are moved to a
- * temporary list and then are freed outside inode_lru_lock by dispose_list().
+ * temporary list and then are freed outside sb->s_inode_lru_lock by
+ * dispose_list().
  *
  * Any inodes which are pinned purely because of attached pagecache have their
  * pagecache removed.  If the inode has metadata buffers attached to
@@ -628,7 +627,7 @@ static void shrink_icache_sb(struct super_block *sb, int 
*nr_to_scan)
        int nr_scanned;
        unsigned long reap = 0;
 
-       spin_lock(&inode_lru_lock);
+       spin_lock(&sb->s_inode_lru_lock);
        for (nr_scanned = *nr_to_scan; nr_scanned >= 0; nr_scanned--) {
                struct inode *inode;
 
@@ -638,7 +637,7 @@ static void shrink_icache_sb(struct super_block *sb, int 
*nr_to_scan)
                inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
 
                /*
-                * we are inverting the inode_lru_lock/inode->i_lock here,
+                * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
                 * so use a trylock. If we fail to get the lock, just move the
                 * inode to the back of the list so we don't spin on it.
                 */
@@ -670,12 +669,12 @@ static void shrink_icache_sb(struct super_block *sb, int 
*nr_to_scan)
                if (inode_has_buffers(inode) || inode->i_data.nrpages) {
                        __iget(inode);
                        spin_unlock(&inode->i_lock);
-                       spin_unlock(&inode_lru_lock);
+                       spin_unlock(&sb->s_inode_lru_lock);
                        if (remove_inode_buffers(inode))
                                reap += invalidate_mapping_pages(&inode->i_data,
                                                                0, -1);
                        iput(inode);
-                       spin_lock(&inode_lru_lock);
+                       spin_lock(&sb->s_inode_lru_lock);
 
                        if (inode != list_entry(sb->s_inode_lru.next,
                                                struct inode, i_lru))
@@ -700,7 +699,7 @@ static void shrink_icache_sb(struct super_block *sb, int 
*nr_to_scan)
                __count_vm_events(KSWAPD_INODESTEAL, reap);
        else
                __count_vm_events(PGINODESTEAL, reap);
-       spin_unlock(&inode_lru_lock);
+       spin_unlock(&sb->s_inode_lru_lock);
        *nr_to_scan = nr_scanned;
 
        dispose_list(&freeable);
diff --git a/fs/super.c b/fs/super.c
index ef7caf7..9c3fa1f 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -78,6 +78,7 @@ static struct super_block *alloc_super(struct 
file_system_type *type)
                INIT_LIST_HEAD(&s->s_inodes);
                INIT_LIST_HEAD(&s->s_dentry_lru);
                INIT_LIST_HEAD(&s->s_inode_lru);
+               spin_lock_init(&s->s_inode_lru_lock);
                init_rwsem(&s->s_umount);
                mutex_init(&s->s_lock);
                lockdep_set_class(&s->s_umount, &type->s_umount_key);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a96071d..bbd478e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1393,7 +1393,8 @@ struct super_block {
        struct list_head        s_dentry_lru;   /* unused dentry lru */
        int                     s_nr_dentry_unused;     /* # of dentry on lru */
 
-       /* inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
+       /* s_inode_lru_lock protects s_inode_lru and s_nr_inodes_unused */
+       spinlock_t              s_inode_lru_lock ____cacheline_aligned_in_smp;
        struct list_head        s_inode_lru;            /* unused inode lru */
        int                     s_nr_inodes_unused;     /* # of inodes on lru */
 
-- 
1.7.5.1

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