6 files changed, 121 insertions, 257 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 41e2085d430b..2762804a140d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -743,13 +743,11 @@ static void shrink_dentry_list(struct list_head *list)
  *
  * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
  */
-static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
+static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
 {
-        /* called from prune_dcache() and shrink_dcache_parent() */
         struct dentry *dentry;
         LIST_HEAD(referenced);
         LIST_HEAD(tmp);
-        int cnt = *count;
 
 relock:
         spin_lock(&dcache_lru_lock);
@@ -777,7 +775,7 @@ relock:
                 } else {
                         list_move_tail(&dentry->d_lru, &tmp);
                         spin_unlock(&dentry->d_lock);
-                        if (!--cnt)
+                        if (!--count)
                                 break;
                 }
                 cond_resched_lock(&dcache_lru_lock);
@@ -787,83 +785,22 @@ relock:
         spin_unlock(&dcache_lru_lock);
 
         shrink_dentry_list(&tmp);
-
-        *count = cnt;
 }
 
 /**
- * prune_dcache - shrink the dcache
- * @count: number of entries to try to free
+ * prune_dcache_sb - shrink the dcache
+ * @nr_to_scan: number of entries to try to free
  *
- * Shrink the dcache. This is done when we need more memory, or simply when we
- * need to unmount something (at which point we need to unuse all dentries).
+ * 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.
  *
- * This function may fail to free any resources if all the dentries are in use.
+ * This function may fail to free any resources if all the dentries are in
+ * use.
  */
-static void prune_dcache(int count)
+void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
 {
-        struct super_block *sb, *p = NULL;
-        int w_count;
-        int unused = dentry_stat.nr_unused;
-        int prune_ratio;
-        int pruned;
-
-        if (unused == 0 || count == 0)
-                return;
-        if (count >= unused)
-                prune_ratio = 1;
-        else
-                prune_ratio = unused / count;
-        spin_lock(&sb_lock);
-        list_for_each_entry(sb, &super_blocks, s_list) {
-                if (list_empty(&sb->s_instances))
-                        continue;
-                if (sb->s_nr_dentry_unused == 0)
-                        continue;
-                sb->s_count++;
-                /* Now, we reclaim unused dentrins with fairness.
-                 * We reclaim them same percentage from each superblock.
-                 * We calculate number of dentries to scan on this sb
-                 * as follows, but the implementation is arranged to avoid
-                 * overflows:
-                 * number of dentries to scan on this sb =
-                 * count * (number of dentries on this sb /
-                 * number of dentries in the machine)
-                 */
-                spin_unlock(&sb_lock);
-                if (prune_ratio != 1)
-                        w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
-                else
-                        w_count = sb->s_nr_dentry_unused;
-                pruned = w_count;
-                /*
-                 * We need to be sure this filesystem isn't being unmounted,
-                 * otherwise we could race with generic_shutdown_super(), and
-                 * end up holding a reference to an inode while the filesystem
-                 * is unmounted.  So we try to get s_umount, and make sure
-                 * s_root isn't NULL.
-                 */
-                if (down_read_trylock(&sb->s_umount)) {
-                        if ((sb->s_root != NULL) &&
-                            (!list_empty(&sb->s_dentry_lru))) {
-                                __shrink_dcache_sb(sb, &w_count,
-                                                DCACHE_REFERENCED);
-                                pruned -= w_count;
-                        }
-                        up_read(&sb->s_umount);
-                }
-                spin_lock(&sb_lock);
-                if (p)
-                        __put_super(p);
-                count -= pruned;
-                p = sb;
-                /* more work left to do? */
-                if (count <= 0)
-                        break;
-        }
-        if (p)
-                __put_super(p);
-        spin_unlock(&sb_lock);
+        __shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
 }
 
 /**
@@ -1238,42 +1175,10 @@ void shrink_dcache_parent(struct dentry * parent)
         int found;
 
         while ((found = select_parent(parent)) != 0)
-                __shrink_dcache_sb(sb, &found, 0);
+                __shrink_dcache_sb(sb, found, 0);
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
 
-/*
- * Scan `sc->nr_slab_to_reclaim' dentries and return the number which remain.
- *
- * We need to avoid reentering the filesystem if the caller is performing a
- * GFP_NOFS allocation attempt.  One example deadlock is:
- *
- * ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
- * prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
- * ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
- *
- * In this case we return -1 to tell the caller that we baled.
- */
-static int shrink_dcache_memory(struct shrinker *shrink,
-                                struct shrink_control *sc)
-{
-        int nr = sc->nr_to_scan;
-        gfp_t gfp_mask = sc->gfp_mask;
-
-        if (nr) {
-                if (!(gfp_mask & __GFP_FS))
-                        return -1;
-                prune_dcache(nr);
-        }
-
-        return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
-}
-
-static struct shrinker dcache_shrinker = {
-        .shrink = shrink_dcache_memory,
-        .seeks = DEFAULT_SEEKS,
-};
-
 /**
  * __d_alloc    -       allocate a dcache entry
  * @sb: filesystem it will belong to
@@ -3083,8 +2988,6 @@ static void __init dcache_init(void)
          */
         dentry_cache = KMEM_CACHE(dentry,
                 SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
-        
-        register_shrinker(&dcache_shrinker);
 
         /* Hash may have been set up in dcache_init_early */
         if (!hashdist)
diff --git a/fs/inode.c b/fs/inode.c
index 0450e25aeda0..1fdbb64a952f 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -73,7 +73,7 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_wb_list_lock);
  *
  * We don't actually need it to protect anything in the umount path,
  * but only need to cycle through it to make sure any inode that
- * prune_icache took off the LRU list has been fully torn down by the
+ * prune_icache_sb took off the LRU list has been fully torn down by the
  * time we are past evict_inodes.
  */
 static DECLARE_RWSEM(iprune_sem);
@@ -544,7 +544,7 @@ void evict_inodes(struct super_block *sb)
         dispose_list(&dispose);
 
         /*
-         * Cycle through iprune_sem to make sure any inode that prune_icache
+         * Cycle through iprune_sem to make sure any inode that prune_icache_sb
          * moved off the list before we took the lock has been fully torn
          * down.
          */
@@ -612,9 +612,10 @@ 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 sb->s_inode_lru_lock by
- * dispose_list().
+ * 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().
  *
  * Any inodes which are pinned purely because of attached pagecache have their
  * pagecache removed.  If the inode has metadata buffers attached to
@@ -628,14 +629,15 @@ 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.
  */
-static void shrink_icache_sb(struct super_block *sb, int *nr_to_scan)
+void prune_icache_sb(struct super_block *sb, int nr_to_scan)
 {
         LIST_HEAD(freeable);
         int nr_scanned;
         unsigned long reap = 0;
 
+        down_read(&iprune_sem);
         spin_lock(&sb->s_inode_lru_lock);
-        for (nr_scanned = *nr_to_scan; nr_scanned >= 0; nr_scanned--) {
+        for (nr_scanned = nr_to_scan; nr_scanned >= 0; nr_scanned--) {
                 struct inode *inode;
 
                 if (list_empty(&sb->s_inode_lru))
@@ -707,111 +709,11 @@ static void shrink_icache_sb(struct super_block *sb, int *nr_to_scan)
         else
                 __count_vm_events(PGINODESTEAL, reap);
         spin_unlock(&sb->s_inode_lru_lock);
-        *nr_to_scan = nr_scanned;
 
         dispose_list(&freeable);
-}
-
-static void prune_icache(int count)
-{
-        struct super_block *sb, *p = NULL;
-        int w_count;
-        int unused = inodes_stat.nr_unused;
-        int prune_ratio;
-        int pruned;
-
-        if (unused == 0 || count == 0)
-                return;
-        down_read(&iprune_sem);
-        if (count >= unused)
-                prune_ratio = 1;
-        else
-                prune_ratio = unused / count;
-        spin_lock(&sb_lock);
-        list_for_each_entry(sb, &super_blocks, s_list) {
-                if (list_empty(&sb->s_instances))
-                        continue;
-                if (sb->s_nr_inodes_unused == 0)
-                        continue;
-                sb->s_count++;
-                /* Now, we reclaim unused dentrins with fairness.
-                 * We reclaim them same percentage from each superblock.
-                 * We calculate number of dentries to scan on this sb
-                 * as follows, but the implementation is arranged to avoid
-                 * overflows:
-                 * number of dentries to scan on this sb =
-                 * count * (number of dentries on this sb /
-                 * number of dentries in the machine)
-                 */
-                spin_unlock(&sb_lock);
-                if (prune_ratio != 1)
-                        w_count = (sb->s_nr_inodes_unused / prune_ratio) + 1;
-                else
-                        w_count = sb->s_nr_inodes_unused;
-                pruned = w_count;
-                /*
-                 * We need to be sure this filesystem isn't being unmounted,
-                 * otherwise we could race with generic_shutdown_super(), and
-                 * end up holding a reference to an inode while the filesystem
-                 * is unmounted.  So we try to get s_umount, and make sure
-                 * s_root isn't NULL.
-                 */
-                if (down_read_trylock(&sb->s_umount)) {
-                        if ((sb->s_root != NULL) &&
-                            (!list_empty(&sb->s_dentry_lru))) {
-                                shrink_icache_sb(sb, &w_count);
-                                pruned -= w_count;
-                        }
-                        up_read(&sb->s_umount);
-                }
-                spin_lock(&sb_lock);
-                if (p)
-                        __put_super(p);
-                count -= pruned;
-                p = sb;
-                /* more work left to do? */
-                if (count <= 0)
-                        break;
-        }
-        if (p)
-                __put_super(p);
-        spin_unlock(&sb_lock);
         up_read(&iprune_sem);
 }
 
-/*
- * shrink_icache_memory() will attempt to reclaim some unused inodes.  Here,
- * "unused" means that no dentries are referring to the inodes: the files are
- * not open and the dcache references to those inodes have already been
- * reclaimed.
- *
- * This function is passed the number of inodes to scan, and it returns the
- * total number of remaining possibly-reclaimable inodes.
- */
-static int shrink_icache_memory(struct shrinker *shrink,
-                                struct shrink_control *sc)
-{
-        int nr = sc->nr_to_scan;
-        gfp_t gfp_mask = sc->gfp_mask;
-
-        if (nr) {
-                /*
-                 * Nasty deadlock avoidance.  We may hold various FS locks,
-                 * and we don't want to recurse into the FS that called us
-                 * in clear_inode() and friends..
-                 */
-                if (!(gfp_mask & __GFP_FS))
-                        return -1;
-                prune_icache(nr);
-        }
-        return (get_nr_inodes_unused() / 100) * sysctl_vfs_cache_pressure;
-}
-
-static struct shrinker icache_shrinker = {
-        .shrink = shrink_icache_memory,
-        .seeks = DEFAULT_SEEKS,
-};
-
 static void __wait_on_freeing_inode(struct inode *inode);
 /*
  * Called with the inode lock held.
@@ -1691,7 +1593,6 @@ void __init inode_init(void)
                                          (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
                                          SLAB_MEM_SPREAD),
                                          init_once);
-        register_shrinker(&icache_shrinker);
 
         /* Hash may have been set up in inode_init_early */
         if (!hashdist)
diff --git a/fs/super.c b/fs/super.c
index e63c754447ce..37a75410079e 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -38,6 +38,48 @@
 LIST_HEAD(super_blocks);
 DEFINE_SPINLOCK(sb_lock);
 
+/*
+ * One thing we have to be careful of with a per-sb shrinker is that we don't
+ * drop the last active reference to the superblock from within the shrinker.
+ * If that happens we could trigger unregistering the shrinker from within the
+ * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
+ * take a passive reference to the superblock to avoid this from occurring.
+ */
+static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
+{
+        struct super_block *sb;
+        int count;
+
+        sb = container_of(shrink, struct super_block, s_shrink);
+
+        /*
+         * Deadlock avoidance.  We may hold various FS locks, and we don't want
+         * to recurse into the FS that called us in clear_inode() and friends..
+         */
+        if (sc->nr_to_scan && !(sc->gfp_mask & __GFP_FS))
+                return -1;
+
+        if (!grab_super_passive(sb))
+                return -1;
+
+        if (sc->nr_to_scan) {
+                /* proportion the scan between the two caches */
+                int total;
+
+                total = sb->s_nr_dentry_unused + sb->s_nr_inodes_unused + 1;
+                count = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total;
+
+                /* prune dcache first as icache is pinned by it */
+                prune_dcache_sb(sb, count);
+                prune_icache_sb(sb, sc->nr_to_scan - count);
+        }
+
+        count = ((sb->s_nr_dentry_unused + sb->s_nr_inodes_unused) / 100)
+                                                * sysctl_vfs_cache_pressure;
+        drop_super(sb);
+        return count;
+}
+
 /**
  *      alloc_super     -       create new superblock
  *      @type:  filesystem type superblock should belong to
@@ -116,6 +158,9 @@ static struct super_block *alloc_super(struct file_system_type *type)
                 s->s_op = &default_op;
                 s->s_time_gran = 1000000000;
                 s->cleancache_poolid = -1;
+
+                s->s_shrink.seeks = DEFAULT_SEEKS;
+                s->s_shrink.shrink = prune_super;
         }
 out:
         return s;
@@ -183,6 +228,10 @@ void deactivate_locked_super(struct super_block *s)
         if (atomic_dec_and_test(&s->s_active)) {
                 cleancache_flush_fs(s);
                 fs->kill_sb(s);
+
+                /* caches are now gone, we can safely kill the shrinker now */
+                unregister_shrinker(&s->s_shrink);
+
                 /*
                  * We need to call rcu_barrier so all the delayed rcu free
                  * inodes are flushed before we release the fs module.
@@ -311,7 +360,6 @@ void generic_shutdown_super(struct super_block *sb)
 {
         const struct super_operations *sop = sb->s_op;
 
-
         if (sb->s_root) {
                 shrink_dcache_for_umount(sb);
                 sync_filesystem(sb);
@@ -399,6 +447,7 @@ retry:
         list_add(&s->s_instances, &type->fs_supers);
         spin_unlock(&sb_lock);
         get_filesystem(type);
+        register_shrinker(&s->s_shrink);
         return s;
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 460d2cc21ec6..d7f35e90b84a 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -393,6 +393,7 @@ struct inodes_stat_t {
 #include <linux/semaphore.h>
 #include <linux/fiemap.h>
 #include <linux/rculist_bl.h>
+#include <linux/shrinker.h>
 #include <linux/atomic.h>
 
 #include <asm/byteorder.h>
@@ -1444,8 +1445,14 @@ struct super_block {
          * Saved pool identifier for cleancache (-1 means none)
          */
         int cleancache_poolid;
+
+        struct shrinker s_shrink;       /* per-sb shrinker handle */
 };
 
+/* superblock cache pruning functions */
+extern void prune_icache_sb(struct super_block *sb, int nr_to_scan);
+extern void prune_dcache_sb(struct super_block *sb, int nr_to_scan);
+
 extern struct timespec current_fs_time(struct super_block *sb);
 
 /*
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9b9777ac726d..e3a1a9eec0b1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -15,6 +15,7 @@
 #include <linux/range.h>
 #include <linux/pfn.h>
 #include <linux/bit_spinlock.h>
+#include <linux/shrinker.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -1121,45 +1122,6 @@ static inline void sync_mm_rss(struct task_struct *task, struct mm_struct *mm)
 }
 #endif
 
-/*
- * This struct is used to pass information from page reclaim to the shrinkers.
- * We consolidate the values for easier extention later.
- */
-struct shrink_control {
-        gfp_t gfp_mask;
-
-        /* How many slab objects shrinker() should scan and try to reclaim */
-        unsigned long nr_to_scan;
-};
-
-/*
- * A callback you can register to apply pressure to ageable caches.
- *
- * 'sc' is passed shrink_control which includes a count 'nr_to_scan'
- * and a 'gfpmask'.  It should look through the least-recently-used
- * 'nr_to_scan' entries and attempt to free them up.  It should return
- * the number of objects which remain in the cache.  If it returns -1, it means
- * it cannot do any scanning at this time (eg. there is a risk of deadlock).
- *
- * The 'gfpmask' refers to the allocation we are currently trying to
- * fulfil.
- *
- * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
- * querying the cache size, so a fastpath for that case is appropriate.
- */
-struct shrinker {
-        int (*shrink)(struct shrinker *, struct shrink_control *sc);
-        int seeks;      /* seeks to recreate an obj */
-        long batch;     /* reclaim batch size, 0 = default */
-
-        /* These are for internal use */
-        struct list_head list;
-        long nr;        /* objs pending delete */
-};
-#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
-extern void register_shrinker(struct shrinker *);
-extern void unregister_shrinker(struct shrinker *);
-
 int vma_wants_writenotify(struct vm_area_struct *vma);
 
 extern pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
new file mode 100644
index 000000000000..790651b4e5ba
--- /dev/null
+++ b/include/linux/shrinker.h
@@ -0,0 +1,42 @@
+#ifndef _LINUX_SHRINKER_H
+#define _LINUX_SHRINKER_H
+
+/*
+ * This struct is used to pass information from page reclaim to the shrinkers.
+ * We consolidate the values for easier extention later.
+ */
+struct shrink_control {
+        gfp_t gfp_mask;
+
+        /* How many slab objects shrinker() should scan and try to reclaim */
+        unsigned long nr_to_scan;
+};
+
+/*
+ * A callback you can register to apply pressure to ageable caches.
+ *
+ * 'sc' is passed shrink_control which includes a count 'nr_to_scan'
+ * and a 'gfpmask'.  It should look through the least-recently-used
+ * 'nr_to_scan' entries and attempt to free them up.  It should return
+ * the number of objects which remain in the cache.  If it returns -1, it means
+ * it cannot do any scanning at this time (eg. there is a risk of deadlock).
+ *
+ * The 'gfpmask' refers to the allocation we are currently trying to
+ * fulfil.
+ *
+ * Note that 'shrink' will be passed nr_to_scan == 0 when the VM is
+ * querying the cache size, so a fastpath for that case is appropriate.
+ */
+struct shrinker {
+        int (*shrink)(struct shrinker *, struct shrink_control *sc);
+        int seeks;      /* seeks to recreate an obj */
+        long batch;     /* reclaim batch size, 0 = default */
+
+        /* These are for internal use */
+        struct list_head list;
+        long nr;        /* objs pending delete */
+};
+#define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
+extern void register_shrinker(struct shrinker *);
+extern void unregister_shrinker(struct shrinker *);
+#endif