dcache: convert to use new lru list infrastructure
authorDave Chinner <dchinner@redhat.com>
Wed, 28 Aug 2013 00:18:00 +0000 (10:18 +1000)
committerAl Viro <viro@zeniv.linux.org.uk>
Tue, 10 Sep 2013 22:56:30 +0000 (18:56 -0400)
[glommer@openvz.org: don't reintroduce double decrement of nr_unused_dentries, adapted for new LRU return codes]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Rientjes <rientjes@google.com>
Cc: Gleb Natapov <gleb@redhat.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: J. Bruce Fields <bfields@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Kent Overstreet <koverstreet@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
fs/dcache.c
fs/super.c
include/linux/fs.h

index 77d466b13fefceb29aa8f2d8c40dbd5e3ec7e7ec..38a4a03499a28cb2ca6a268f6d0f044a658992c2 100644 (file)
@@ -37,6 +37,7 @@
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
 #include <linux/ratelimit.h>
+#include <linux/list_lru.h>
 #include "internal.h"
 #include "mount.h"
 
@@ -356,28 +357,17 @@ static void dentry_unlink_inode(struct dentry * dentry)
 }
 
 /*
- * dentry_lru_(add|del|move_list) must be called with d_lock held.
+ * dentry_lru_(add|del)_list) must be called with d_lock held.
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
        if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {
-               spin_lock(&dentry->d_sb->s_dentry_lru_lock);
+               if (list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
+                       this_cpu_inc(nr_dentry_unused);
                dentry->d_flags |= DCACHE_LRU_LIST;
-               list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
-               dentry->d_sb->s_nr_dentry_unused++;
-               this_cpu_inc(nr_dentry_unused);
-               spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
        }
 }
 
-static void __dentry_lru_del(struct dentry *dentry)
-{
-       list_del_init(&dentry->d_lru);
-       dentry->d_flags &= ~DCACHE_LRU_LIST;
-       dentry->d_sb->s_nr_dentry_unused--;
-       this_cpu_dec(nr_dentry_unused);
-}
-
 /*
  * Remove a dentry with references from the LRU.
  *
@@ -393,27 +383,9 @@ static void dentry_lru_del(struct dentry *dentry)
                return;
        }
 
-       if (!list_empty(&dentry->d_lru)) {
-               spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-               __dentry_lru_del(dentry);
-               spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
-       }
-}
-
-static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
-{
-       BUG_ON(dentry->d_flags & DCACHE_SHRINK_LIST);
-
-       spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-       if (list_empty(&dentry->d_lru)) {
-               dentry->d_flags |= DCACHE_LRU_LIST;
-               list_add_tail(&dentry->d_lru, list);
-       } else {
-               list_move_tail(&dentry->d_lru, list);
-               dentry->d_sb->s_nr_dentry_unused--;
+       if (list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
                this_cpu_dec(nr_dentry_unused);
-       }
-       spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
+       dentry->d_flags &= ~DCACHE_LRU_LIST;
 }
 
 /**
@@ -901,12 +873,72 @@ static void shrink_dentry_list(struct list_head *list)
        rcu_read_unlock();
 }
 
+static enum lru_status
+dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
+{
+       struct list_head *freeable = arg;
+       struct dentry   *dentry = container_of(item, struct dentry, d_lru);
+
+
+       /*
+        * we are inverting the lru lock/dentry->d_lock here,
+        * so use a trylock. If we fail to get the lock, just skip
+        * it
+        */
+       if (!spin_trylock(&dentry->d_lock))
+               return LRU_SKIP;
+
+       /*
+        * Referenced dentries are still in use. If they have active
+        * counts, just remove them from the LRU. Otherwise give them
+        * another pass through the LRU.
+        */
+       if (dentry->d_lockref.count) {
+               list_del_init(&dentry->d_lru);
+               spin_unlock(&dentry->d_lock);
+               return LRU_REMOVED;
+       }
+
+       if (dentry->d_flags & DCACHE_REFERENCED) {
+               dentry->d_flags &= ~DCACHE_REFERENCED;
+               spin_unlock(&dentry->d_lock);
+
+               /*
+                * The list move itself will be made by the common LRU code. At
+                * this point, we've dropped the dentry->d_lock but keep the
+                * lru lock. This is safe to do, since every list movement is
+                * protected by the lru lock even if both locks are held.
+                *
+                * This is guaranteed by the fact that all LRU management
+                * functions are intermediated by the LRU API calls like
+                * list_lru_add and list_lru_del. List movement in this file
+                * only ever occur through this functions or through callbacks
+                * like this one, that are called from the LRU API.
+                *
+                * The only exceptions to this are functions like
+                * shrink_dentry_list, and code that first checks for the
+                * DCACHE_SHRINK_LIST flag.  Those are guaranteed to be
+                * operating only with stack provided lists after they are
+                * properly isolated from the main list.  It is thus, always a
+                * local access.
+                */
+               return LRU_ROTATE;
+       }
+
+       dentry->d_flags |= DCACHE_SHRINK_LIST;
+       list_move_tail(&dentry->d_lru, freeable);
+       this_cpu_dec(nr_dentry_unused);
+       spin_unlock(&dentry->d_lock);
+
+       return LRU_REMOVED;
+}
+
 /**
  * prune_dcache_sb - shrink the dcache
  * @sb: superblock
- * @count: number of entries to try to free
+ * @nr_to_scan : number of entries to try to free
  *
- * Attempt to shrink the superblock dcache LRU by @count entries. This is
+ * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
  * done when we need more memory an called from the superblock shrinker
  * function.
  *
@@ -915,45 +947,12 @@ static void shrink_dentry_list(struct list_head *list)
  */
 long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan)
 {
-       struct dentry *dentry;
-       LIST_HEAD(referenced);
-       LIST_HEAD(tmp);
-       long freed = 0;
+       LIST_HEAD(dispose);
+       long freed;
 
-relock:
-       spin_lock(&sb->s_dentry_lru_lock);
-       while (!list_empty(&sb->s_dentry_lru)) {
-               dentry = list_entry(sb->s_dentry_lru.prev,
-                               struct dentry, d_lru);
-               BUG_ON(dentry->d_sb != sb);
-
-               if (!spin_trylock(&dentry->d_lock)) {
-                       spin_unlock(&sb->s_dentry_lru_lock);
-                       cpu_relax();
-                       goto relock;
-               }
-
-               if (dentry->d_flags & DCACHE_REFERENCED) {
-                       dentry->d_flags &= ~DCACHE_REFERENCED;
-                       list_move(&dentry->d_lru, &referenced);
-                       spin_unlock(&dentry->d_lock);
-               } else {
-                       list_move(&dentry->d_lru, &tmp);
-                       dentry->d_flags |= DCACHE_SHRINK_LIST;
-                       this_cpu_dec(nr_dentry_unused);
-                       sb->s_nr_dentry_unused--;
-                       spin_unlock(&dentry->d_lock);
-                       freed++;
-                       if (!--nr_to_scan)
-                               break;
-               }
-               cond_resched_lock(&sb->s_dentry_lru_lock);
-       }
-       if (!list_empty(&referenced))
-               list_splice(&referenced, &sb->s_dentry_lru);
-       spin_unlock(&sb->s_dentry_lru_lock);
-
-       shrink_dentry_list(&tmp);
+       freed = list_lru_walk(&sb->s_dentry_lru, dentry_lru_isolate,
+                             &dispose, nr_to_scan);
+       shrink_dentry_list(&dispose);
        return freed;
 }
 
@@ -987,24 +986,10 @@ shrink_dcache_list(
  */
 void shrink_dcache_sb(struct super_block *sb)
 {
-       LIST_HEAD(tmp);
-
-       spin_lock(&sb->s_dentry_lru_lock);
-       while (!list_empty(&sb->s_dentry_lru)) {
-               /*
-                * account for removal here so we don't need to handle it later
-                * even though the dentry is no longer on the lru list.
-                */
-               list_splice_init(&sb->s_dentry_lru, &tmp);
-               this_cpu_sub(nr_dentry_unused, sb->s_nr_dentry_unused);
-               sb->s_nr_dentry_unused = 0;
-               spin_unlock(&sb->s_dentry_lru_lock);
+       long disposed;
 
-               shrink_dcache_list(&tmp);
-
-               spin_lock(&sb->s_dentry_lru_lock);
-       }
-       spin_unlock(&sb->s_dentry_lru_lock);
+       disposed = list_lru_dispose_all(&sb->s_dentry_lru, shrink_dcache_list);
+       this_cpu_sub(nr_dentry_unused, disposed);
 }
 EXPORT_SYMBOL(shrink_dcache_sb);
 
@@ -1366,7 +1351,8 @@ static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
        if (dentry->d_lockref.count) {
                dentry_lru_del(dentry);
        } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
-               dentry_lru_move_list(dentry, &data->dispose);
+               dentry_lru_del(dentry);
+               list_add_tail(&dentry->d_lru, &data->dispose);
                dentry->d_flags |= DCACHE_SHRINK_LIST;
                data->found++;
                ret = D_WALK_NORETRY;
index aa7995d73bcc2bf18eb83efa111842c79efaa90b..cd3c2cd9144dba80657d5bf3bf9ecb1555d08b56 100644 (file)
@@ -79,11 +79,11 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
                fs_objects = sb->s_op->nr_cached_objects(sb);
 
        inodes = list_lru_count(&sb->s_inode_lru);
-       total_objects = sb->s_nr_dentry_unused + inodes + fs_objects + 1;
+       dentries = list_lru_count(&sb->s_dentry_lru);
+       total_objects = dentries + inodes + fs_objects + 1;
 
        /* proportion the scan between the caches */
-       dentries = mult_frac(sc->nr_to_scan, sb->s_nr_dentry_unused,
-                                                               total_objects);
+       dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
        inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
 
        /*
@@ -117,7 +117,7 @@ static unsigned long super_cache_count(struct shrinker *shrink,
        if (sb->s_op && sb->s_op->nr_cached_objects)
                total_objects = sb->s_op->nr_cached_objects(sb);
 
-       total_objects += sb->s_nr_dentry_unused;
+       total_objects += list_lru_count(&sb->s_dentry_lru);
        total_objects += list_lru_count(&sb->s_inode_lru);
 
        total_objects = vfs_pressure_ratio(total_objects);
@@ -191,8 +191,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
                INIT_HLIST_NODE(&s->s_instances);
                INIT_HLIST_BL_HEAD(&s->s_anon);
                INIT_LIST_HEAD(&s->s_inodes);
-               INIT_LIST_HEAD(&s->s_dentry_lru);
-               spin_lock_init(&s->s_dentry_lru_lock);
+               list_lru_init(&s->s_dentry_lru);
                list_lru_init(&s->s_inode_lru);
                INIT_LIST_HEAD(&s->s_mounts);
                init_rwsem(&s->s_umount);
index e04786569c2828d74ba4eaf86e4b354ce438abd0..36e45df87f6eca94f5b5c56af5fd696c5cf57b4c 100644 (file)
@@ -1270,14 +1270,6 @@ struct super_block {
        struct list_head        s_files;
 #endif
        struct list_head        s_mounts;       /* list of mounts; _not_ for fs use */
-
-       /* s_dentry_lru_lock protects s_dentry_lru and s_nr_dentry_unused */
-       spinlock_t              s_dentry_lru_lock ____cacheline_aligned_in_smp;
-       struct list_head        s_dentry_lru;   /* unused dentry lru */
-       long                    s_nr_dentry_unused;     /* # of dentry on lru */
-
-       struct list_lru         s_inode_lru ____cacheline_aligned_in_smp;
-
        struct block_device     *s_bdev;
        struct backing_dev_info *s_bdi;
        struct mtd_info         *s_mtd;
@@ -1331,6 +1323,13 @@ struct super_block {
 
        /* AIO completions deferred from interrupt context */
        struct workqueue_struct *s_dio_done_wq;
+
+       /*
+        * Keep the lru lists last in the structure so they always sit on their
+        * own individual cachelines.
+        */
+       struct list_lru         s_dentry_lru ____cacheline_aligned_in_smp;
+       struct list_lru         s_inode_lru ____cacheline_aligned_in_smp;
 };
 
 extern struct timespec current_fs_time(struct super_block *sb);