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[PATCH 05/19] shrinker: convert superblock shrinkers to new API

To: glommer@xxxxxxxxxxxxx
Subject: [PATCH 05/19] shrinker: convert superblock shrinkers to new API
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 28 Nov 2012 10:14:32 +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>

Convert superblock shrinker to use the new count/scan API, and
propagate the API changes through to the filesystem callouts. The
filesystem callouts already use a count/scan API, so it's just
changing counters to longs to match the VM API.

This requires the dentry and inode shrinker callouts to be converted
to the count/scan API. This is mainly a mechanical change.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/dcache.c         |   10 +++++---
 fs/inode.c          |    7 +++--
 fs/internal.h       |    3 +++
 fs/super.c          |   71 ++++++++++++++++++++++++++++++---------------------
 fs/xfs/xfs_icache.c |   17 +++++++-----
 fs/xfs/xfs_icache.h |    4 +--
 fs/xfs/xfs_super.c  |    8 +++---
 include/linux/fs.h  |    8 ++----
 8 files changed, 74 insertions(+), 54 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 0124a84..ca647b8 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -892,11 +892,12 @@ static void shrink_dentry_list(struct list_head *list)
  * This function may fail to free any resources if all the dentries are in
  * use.
  */
-void prune_dcache_sb(struct super_block *sb, int count)
+long prune_dcache_sb(struct super_block *sb, long nr_to_scan)
 {
        struct dentry *dentry;
        LIST_HEAD(referenced);
        LIST_HEAD(tmp);
+       long freed = 0;
 
 relock:
        spin_lock(&sb->s_dentry_lru_lock);
@@ -921,7 +922,8 @@ relock:
                        this_cpu_dec(nr_dentry_unused);
                        sb->s_nr_dentry_unused--;
                        spin_unlock(&dentry->d_lock);
-                       if (!--count)
+                       freed++;
+                       if (!--nr_to_scan)
                                break;
                }
                cond_resched_lock(&sb->s_dentry_lru_lock);
@@ -931,6 +933,7 @@ relock:
        spin_unlock(&sb->s_dentry_lru_lock);
 
        shrink_dentry_list(&tmp);
+       return freed;
 }
 
 /*
@@ -1317,9 +1320,8 @@ rename_retry:
 void shrink_dcache_parent(struct dentry * parent)
 {
        LIST_HEAD(dispose);
-       int found;
 
-       while ((found = select_parent(parent, &dispose)) != 0)
+       while (select_parent(parent, &dispose))
                shrink_dentry_list(&dispose);
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
diff --git a/fs/inode.c b/fs/inode.c
index c9fb382..3624ae0 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -691,10 +691,11 @@ 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.
  */
-void prune_icache_sb(struct super_block *sb, int nr_to_scan)
+long prune_icache_sb(struct super_block *sb, long nr_to_scan)
 {
        LIST_HEAD(freeable);
-       int nr_scanned;
+       long nr_scanned;
+       long freed = 0;
        unsigned long reap = 0;
 
        spin_lock(&sb->s_inode_lru_lock);
@@ -764,6 +765,7 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan)
                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);
@@ -774,6 +776,7 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan)
                current->reclaim_state->reclaimed_slab += reap;
 
        dispose_list(&freeable);
+       return freed;
 }
 
 static void __wait_on_freeing_inode(struct inode *inode);
diff --git a/fs/internal.h b/fs/internal.h
index 916b7cb..7d7908b 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -110,6 +110,8 @@ extern int open_check_o_direct(struct file *f);
  * inode.c
  */
 extern spinlock_t inode_sb_list_lock;
+extern long prune_icache_sb(struct super_block *sb, long nr_to_scan);
+
 
 /*
  * fs-writeback.c
@@ -124,3 +126,4 @@ extern int invalidate_inodes(struct super_block *, bool);
  * dcache.c
  */
 extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
+extern long prune_dcache_sb(struct super_block *sb, long nr_to_scan);
diff --git a/fs/super.c b/fs/super.c
index 21abf02..fda6f12 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -53,11 +53,14 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {
  * 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)
+static long super_cache_scan(struct shrinker *shrink, struct shrink_control 
*sc)
 {
        struct super_block *sb;
-       int     fs_objects = 0;
-       int     total_objects;
+       long    fs_objects = 0;
+       long    total_objects;
+       long    freed = 0;
+       long    dentries;
+       long    inodes;
 
        sb = container_of(shrink, struct super_block, s_shrink);
 
@@ -65,7 +68,7 @@ static int prune_super(struct shrinker *shrink, struct 
shrink_control *sc)
         * 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))
+       if (!(sc->gfp_mask & __GFP_FS))
                return -1;
 
        if (!grab_super_passive(sb))
@@ -77,33 +80,42 @@ static int prune_super(struct shrinker *shrink, struct 
shrink_control *sc)
        total_objects = sb->s_nr_dentry_unused +
                        sb->s_nr_inodes_unused + fs_objects + 1;
 
-       if (sc->nr_to_scan) {
-               int     dentries;
-               int     inodes;
-
-               /* 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;
-               if (fs_objects)
-                       fs_objects = (sc->nr_to_scan * fs_objects) /
-                                                       total_objects;
-               /*
-                * prune the dcache first as the icache is pinned by it, then
-                * prune the icache, followed by the filesystem specific caches
-                */
-               prune_dcache_sb(sb, dentries);
-               prune_icache_sb(sb, inodes);
+       /* 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;
 
-               if (fs_objects && sb->s_op->free_cached_objects) {
-                       sb->s_op->free_cached_objects(sb, fs_objects);
-                       fs_objects = sb->s_op->nr_cached_objects(sb);
-               }
-               total_objects = sb->s_nr_dentry_unused +
-                               sb->s_nr_inodes_unused + fs_objects;
+       /*
+        * prune the dcache first as the icache is pinned by it, then
+        * prune the icache, followed by the filesystem specific caches
+        */
+       freed = prune_dcache_sb(sb, dentries);
+       freed += prune_icache_sb(sb, inodes);
+
+       if (fs_objects) {
+               fs_objects = (sc->nr_to_scan * fs_objects) / total_objects;
+               freed += sb->s_op->free_cached_objects(sb, fs_objects);
        }
 
+       drop_super(sb);
+       return freed;
+}
+
+static long super_cache_count(struct shrinker *shrink, struct shrink_control 
*sc)
+{
+       struct super_block *sb;
+       long    total_objects = 0;
+
+       sb = container_of(shrink, struct super_block, s_shrink);
+
+       if (!grab_super_passive(sb))
+               return -1;
+
+       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 += sb->s_nr_inodes_unused;
+
        total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
        drop_super(sb);
        return total_objects;
@@ -217,7 +229,8 @@ static struct super_block *alloc_super(struct 
file_system_type *type, int flags)
                s->cleancache_poolid = -1;
 
                s->s_shrink.seeks = DEFAULT_SEEKS;
-               s->s_shrink.shrink = prune_super;
+               s->s_shrink.scan_objects = super_cache_scan;
+               s->s_shrink.count_objects = super_cache_count;
                s->s_shrink.batch = 1024;
        }
 out:
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 96e344e..2f91e2b 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1029,7 +1029,7 @@ STATIC int
 xfs_reclaim_inodes_ag(
        struct xfs_mount        *mp,
        int                     flags,
-       int                     *nr_to_scan)
+       long                    *nr_to_scan)
 {
        struct xfs_perag        *pag;
        int                     error = 0;
@@ -1150,7 +1150,7 @@ xfs_reclaim_inodes(
        xfs_mount_t     *mp,
        int             mode)
 {
-       int             nr_to_scan = INT_MAX;
+       long            nr_to_scan = LONG_MAX;
 
        return xfs_reclaim_inodes_ag(mp, mode, &nr_to_scan);
 }
@@ -1164,29 +1164,32 @@ xfs_reclaim_inodes(
  * them to be cleaned, which we hope will not be very long due to the
  * background walker having already kicked the IO off on those dirty inodes.
  */
-void
+long
 xfs_reclaim_inodes_nr(
        struct xfs_mount        *mp,
-       int                     nr_to_scan)
+       long                    nr_to_scan)
 {
+       long nr = nr_to_scan;
+
        /* kick background reclaimer and push the AIL */
        xfs_reclaim_work_queue(mp);
        xfs_ail_push_all(mp->m_ail);
 
-       xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
+       xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr);
+       return nr_to_scan - nr;
 }
 
 /*
  * Return the number of reclaimable inodes in the filesystem for
  * the shrinker to determine how much to reclaim.
  */
-int
+long
 xfs_reclaim_inodes_count(
        struct xfs_mount        *mp)
 {
        struct xfs_perag        *pag;
        xfs_agnumber_t          ag = 0;
-       int                     reclaimable = 0;
+       long                    reclaimable = 0;
 
        while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
                ag = pag->pag_agno + 1;
diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h
index e0f138c..c860d07 100644
--- a/fs/xfs/xfs_icache.h
+++ b/fs/xfs/xfs_icache.h
@@ -30,8 +30,8 @@ int xfs_iget(struct xfs_mount *mp, struct xfs_trans *tp, 
xfs_ino_t ino,
 void xfs_reclaim_worker(struct work_struct *work);
 
 int xfs_reclaim_inodes(struct xfs_mount *mp, int mode);
-int xfs_reclaim_inodes_count(struct xfs_mount *mp);
-void xfs_reclaim_inodes_nr(struct xfs_mount *mp, int nr_to_scan);
+long xfs_reclaim_inodes_count(struct xfs_mount *mp);
+long xfs_reclaim_inodes_nr(struct xfs_mount *mp, long nr_to_scan);
 
 void xfs_inode_set_reclaim_tag(struct xfs_inode *ip);
 
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index ab8839b..00aa61d 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1514,19 +1514,19 @@ xfs_fs_mount(
        return mount_bdev(fs_type, flags, dev_name, data, xfs_fs_fill_super);
 }
 
-static int
+static long
 xfs_fs_nr_cached_objects(
        struct super_block      *sb)
 {
        return xfs_reclaim_inodes_count(XFS_M(sb));
 }
 
-static void
+static long
 xfs_fs_free_cached_objects(
        struct super_block      *sb,
-       int                     nr_to_scan)
+       long                    nr_to_scan)
 {
-       xfs_reclaim_inodes_nr(XFS_M(sb), nr_to_scan);
+       return xfs_reclaim_inodes_nr(XFS_M(sb), nr_to_scan);
 }
 
 static const struct super_operations xfs_super_operations = {
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0845283..13833e3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1325,10 +1325,6 @@ struct super_block {
        int s_readonly_remount;
 };
 
-/* 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);
 
 /*
@@ -1621,8 +1617,8 @@ struct super_operations {
        ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, 
loff_t);
 #endif
        int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
-       int (*nr_cached_objects)(struct super_block *);
-       void (*free_cached_objects)(struct super_block *, int);
+       long (*nr_cached_objects)(struct super_block *);
+       long (*free_cached_objects)(struct super_block *, long);
 };
 
 /*
-- 
1.7.10

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