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[PATCH 07/19] inode: convert inode lru list to generic lru list code.

To: glommer@xxxxxxxxxxxxx
Subject: [PATCH 07/19] inode: convert inode lru list to generic lru list code.
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 28 Nov 2012 10:14:34 +1100
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, xfs@xxxxxxxxxxx
In-reply-to: <1354058086-27937-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1354058086-27937-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/inode.c         |  173 +++++++++++++++++++++-------------------------------
 fs/super.c         |   11 ++--
 include/linux/fs.h |    6 +-
 3 files changed, 75 insertions(+), 115 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 3624ae0..2662305 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -17,6 +17,7 @@
 #include <linux/prefetch.h>
 #include <linux/buffer_head.h> /* for inode_has_buffers */
 #include <linux/ratelimit.h>
+#include <linux/list_lru.h>
 #include "internal.h"
 
 /*
@@ -24,7 +25,7 @@
  *
  * inode->i_lock protects:
  *   inode->i_state, inode->i_hash, __iget()
- * inode->i_sb->s_inode_lru_lock protects:
+ * Inode LRU list locks protect:
  *   inode->i_sb->s_inode_lru, inode->i_lru
  * inode_sb_list_lock protects:
  *   sb->s_inodes, inode->i_sb_list
@@ -37,7 +38,7 @@
  *
  * inode_sb_list_lock
  *   inode->i_lock
- *     inode->i_sb->s_inode_lru_lock
+ *     Inode LRU list locks
  *
  * bdi->wb.list_lock
  *   inode->i_lock
@@ -399,24 +400,14 @@ EXPORT_SYMBOL(ihold);
 
 static void inode_lru_list_add(struct inode *inode)
 {
-       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++;
+       if (list_lru_add(&inode->i_sb->s_inode_lru, &inode->i_lru))
                this_cpu_inc(nr_unused);
-       }
-       spin_unlock(&inode->i_sb->s_inode_lru_lock);
 }
 
 static void inode_lru_list_del(struct inode *inode)
 {
-       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--;
+       if (list_lru_del(&inode->i_sb->s_inode_lru, &inode->i_lru))
                this_cpu_dec(nr_unused);
-       }
-       spin_unlock(&inode->i_sb->s_inode_lru_lock);
 }
 
 /**
@@ -660,24 +651,8 @@ int invalidate_inodes(struct super_block *sb, bool 
kill_dirty)
        return busy;
 }
 
-static int can_unuse(struct inode *inode)
-{
-       if (inode->i_state & ~I_REFERENCED)
-               return 0;
-       if (inode_has_buffers(inode))
-               return 0;
-       if (atomic_read(&inode->i_count))
-               return 0;
-       if (inode->i_data.nrpages)
-               return 0;
-       return 1;
-}
-
 /*
- * Walk the superblock inode LRU for freeable inodes and attempt to free them.
- * This is called from the superblock shrinker function with a number of inodes
- * to trim from the LRU. Inodes to be freed are moved to a temporary list and
- * then are freed outside inode_lock by dispose_list().
+ * Isolate the inode from the LRU in preparation for freeing it.
  *
  * Any inodes which are pinned purely because of attached pagecache have their
  * pagecache removed.  If the inode has metadata buffers attached to
@@ -691,90 +666,78 @@ static int can_unuse(struct inode *inode)
  * LRU does not have strict ordering. Hence we don't want to reclaim inodes
  * with this flag set because they are the inodes that are out of order.
  */
-long prune_icache_sb(struct super_block *sb, long nr_to_scan)
+static int inode_lru_isolate(struct list_head *item, spinlock_t *lru_lock,
+                               void *arg)
 {
-       LIST_HEAD(freeable);
-       long nr_scanned;
-       long freed = 0;
-       unsigned long reap = 0;
+       struct list_head *freeable = arg;
+       struct inode    *inode = container_of(item, struct inode, i_lru);
 
-       spin_lock(&sb->s_inode_lru_lock);
-       for (nr_scanned = nr_to_scan; nr_scanned >= 0; nr_scanned--) {
-               struct inode *inode;
+       /*
+        * we are inverting the lru lock/inode->i_lock here, so use a trylock.
+        * If we fail to get the lock, just skip it.
+        */
+       if (!spin_trylock(&inode->i_lock))
+               return 2;
 
-               if (list_empty(&sb->s_inode_lru))
-                       break;
+       /*
+        * Referenced or dirty inodes are still in use. Give them another pass
+        * through the LRU as we canot reclaim them now.
+        */
+       if (atomic_read(&inode->i_count) ||
+           (inode->i_state & ~I_REFERENCED)) {
+               list_del_init(&inode->i_lru);
+               spin_unlock(&inode->i_lock);
+               this_cpu_dec(nr_unused);
+               return 0;
+       }
 
-               inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
+       /* recently referenced inodes get one more pass */
+       if (inode->i_state & I_REFERENCED) {
+               inode->i_state &= ~I_REFERENCED;
+               spin_unlock(&inode->i_lock);
+               return 1;
+       }
 
-               /*
-                * 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.
-                */
-               if (!spin_trylock(&inode->i_lock)) {
-                       list_move_tail(&inode->i_lru, &sb->s_inode_lru);
-                       continue;
+       if (inode_has_buffers(inode) || inode->i_data.nrpages) {
+               __iget(inode);
+               spin_unlock(&inode->i_lock);
+               spin_unlock(lru_lock);
+               if (remove_inode_buffers(inode)) {
+                       unsigned long reap;
+                       reap = invalidate_mapping_pages(&inode->i_data, 0, -1);
+                       if (current_is_kswapd())
+                               __count_vm_events(KSWAPD_INODESTEAL, reap);
+                       else
+                               __count_vm_events(PGINODESTEAL, reap);
+                       if (current->reclaim_state)
+                               current->reclaim_state->reclaimed_slab += reap;
                }
+               iput(inode);
+               return 3;
+       }
 
-               /*
-                * Referenced or dirty inodes are still in use. Give them
-                * another pass through the LRU as we canot reclaim them now.
-                */
-               if (atomic_read(&inode->i_count) ||
-                   (inode->i_state & ~I_REFERENCED)) {
-                       list_del_init(&inode->i_lru);
-                       spin_unlock(&inode->i_lock);
-                       sb->s_nr_inodes_unused--;
-                       this_cpu_dec(nr_unused);
-                       continue;
-               }
+       WARN_ON(inode->i_state & I_NEW);
+       inode->i_state |= I_FREEING;
+       spin_unlock(&inode->i_lock);
 
-               /* recently referenced inodes get one more pass */
-               if (inode->i_state & I_REFERENCED) {
-                       inode->i_state &= ~I_REFERENCED;
-                       list_move(&inode->i_lru, &sb->s_inode_lru);
-                       spin_unlock(&inode->i_lock);
-                       continue;
-               }
-               if (inode_has_buffers(inode) || inode->i_data.nrpages) {
-                       __iget(inode);
-                       spin_unlock(&inode->i_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(&sb->s_inode_lru_lock);
-
-                       if (inode != list_entry(sb->s_inode_lru.next,
-                                               struct inode, i_lru))
-                               continue;       /* wrong inode or list_empty */
-                       /* avoid lock inversions with trylock */
-                       if (!spin_trylock(&inode->i_lock))
-                               continue;
-                       if (!can_unuse(inode)) {
-                               spin_unlock(&inode->i_lock);
-                               continue;
-                       }
-               }
-               WARN_ON(inode->i_state & I_NEW);
-               inode->i_state |= I_FREEING;
-               spin_unlock(&inode->i_lock);
+       list_move(&inode->i_lru, freeable);
+       this_cpu_dec(nr_unused);
+       return 0;
+}
 
-               list_move(&inode->i_lru, &freeable);
-               sb->s_nr_inodes_unused--;
-               this_cpu_dec(nr_unused);
-               freed++;
-       }
-       if (current_is_kswapd())
-               __count_vm_events(KSWAPD_INODESTEAL, reap);
-       else
-               __count_vm_events(PGINODESTEAL, reap);
-       spin_unlock(&sb->s_inode_lru_lock);
-       if (current->reclaim_state)
-               current->reclaim_state->reclaimed_slab += reap;
+/*
+ * Walk the superblock inode LRU for freeable inodes and attempt to free them.
+ * This is called from the superblock shrinker function with a number of inodes
+ * to trim from the LRU. Inodes to be freed are moved to a temporary list and
+ * then are freed outside inode_lock by dispose_list().
+ */
+long prune_icache_sb(struct super_block *sb, long nr_to_scan)
+{
+       LIST_HEAD(freeable);
+       long freed;
 
+       freed = list_lru_walk(&sb->s_inode_lru, inode_lru_isolate,
+                                               &freeable, nr_to_scan);
        dispose_list(&freeable);
        return freed;
 }
diff --git a/fs/super.c b/fs/super.c
index fda6f12..a2f09c8 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -77,12 +77,12 @@ static long super_cache_scan(struct shrinker *shrink, 
struct shrink_control *sc)
        if (sb->s_op && sb->s_op->nr_cached_objects)
                fs_objects = sb->s_op->nr_cached_objects(sb);
 
-       total_objects = sb->s_nr_dentry_unused +
-                       sb->s_nr_inodes_unused + fs_objects + 1;
+       inodes = list_lru_count(&sb->s_inode_lru);
+       total_objects = sb->s_nr_dentry_unused + inodes + fs_objects + 1;
 
        /* proportion the scan between the caches */
        dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total_objects;
-       inodes = (sc->nr_to_scan * sb->s_nr_inodes_unused) / total_objects;
+       inodes = (sc->nr_to_scan * inodes) / total_objects;
 
        /*
         * prune the dcache first as the icache is pinned by it, then
@@ -114,7 +114,7 @@ static long super_cache_count(struct shrinker *shrink, 
struct shrink_control *sc
                total_objects = sb->s_op->nr_cached_objects(sb);
 
        total_objects += sb->s_nr_dentry_unused;
-       total_objects += sb->s_nr_inodes_unused;
+       total_objects += list_lru_count(&sb->s_inode_lru);
 
        total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
        drop_super(sb);
@@ -195,8 +195,7 @@ static struct super_block *alloc_super(struct 
file_system_type *type, int flags)
                INIT_LIST_HEAD(&s->s_inodes);
                INIT_LIST_HEAD(&s->s_dentry_lru);
                spin_lock_init(&s->s_dentry_lru_lock);
-               INIT_LIST_HEAD(&s->s_inode_lru);
-               spin_lock_init(&s->s_inode_lru_lock);
+               list_lru_init(&s->s_inode_lru);
                INIT_LIST_HEAD(&s->s_mounts);
                init_rwsem(&s->s_umount);
                lockdep_set_class(&s->s_umount, &type->s_umount_key);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 13833e3..36b7db5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -10,6 +10,7 @@
 #include <linux/stat.h>
 #include <linux/cache.h>
 #include <linux/list.h>
+#include <linux/list_lru.h>
 #include <linux/radix-tree.h>
 #include <linux/rbtree.h>
 #include <linux/init.h>
@@ -1268,10 +1269,7 @@ struct super_block {
        struct list_head        s_dentry_lru;   /* unused dentry lru */
        int                     s_nr_dentry_unused;     /* # of dentry on lru */
 
-       /* 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 */
+       struct list_lru         s_inode_lru ____cacheline_aligned_in_smp;
 
        struct block_device     *s_bdev;
        struct backing_dev_info *s_bdi;
-- 
1.7.10

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