[PATCH v6 06/31] shrinker: convert superblock shrinkers to new API

Glauber Costa
2013-05-12T18:13:27Z

From: Dave Chinner <dchinner@redhat.com>

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.

[ glommer: use mult_frac for fractional proportions, build fixes ]
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Glauber Costa <glommer@openvz.org>
Acked-by: Mel Gorman <mgorman@suse.de>
---
fs/dcache.c | 10 +++++---
fs/inode.c | 7 +++--
fs/internal.h | 2 ++
fs/super.c | 74 ++++++++++++++++++++++++++++++++---------------------
fs/xfs/xfs_icache.c | 4 +--
fs/xfs/xfs_icache.h | 2 +-
fs/xfs/xfs_super.c | 8 +++---
include/linux/fs.h | 8 ++----
8 files changed, 67 insertions(+), 48 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 868abf9..dc0069c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -856,11 +856,12 @@ 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, unsigned long nr_to_scan)
{
struct dentry *dentry;
LIST_HEAD(referenced);
LIST_HEAD(tmp);
+ long freed = 0;

relock:
spin_lock(&sb->s_dentry_lru_lock);
@@ -885,7 +886,8 @@ 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);
@@ -895,6 +897,7 @@ relock:
spin_unlock(&sb->s_dentry_lru_lock);

shrink_dentry_list(&tmp);
+ return freed;
}

/*
@@ -1275,9 +1278,8 @@ 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);
cond_resched();
}
diff --git a/fs/inode.c b/fs/inode.c
index 00d5fc3..730aea7 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -704,10 +704,11 @@ 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, unsigned 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);
@@ -777,6 +778,7 @@ 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);
@@ -787,6 +789,7 @@ 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 eaa75f7..bb7b6e4 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -110,6 +110,7 @@ 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, unsigned long nr_to_scan);
extern void inode_add_lru(struct inode *inode);

/*
@@ -125,6 +126,7 @@ 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, unsigned long nr_to_scan);

/*
* read_write.c
diff --git a/fs/super.c b/fs/super.c
index 0be75fb..9d2f2e9 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 +80,45 @@ 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 = mult_frac(sc->nr_to_scan, sb->s_nr_dentry_unused,
- total_objects);
- inodes = mult_frac(sc->nr_to_scan, sb->s_nr_inodes_unused,
- total_objects);
- if (fs_objects)
- fs_objects = mult_frac(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 = mult_frac(sc->nr_to_scan, sb->s_nr_dentry_unused,
+ total_objects);
+ inodes = mult_frac(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 = mult_frac(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 = vfs_pressure_ratio(total_objects);
drop_super(sb);
return total_objects;
@@ -217,7 +232,8 @@ 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..b35c311 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -1164,7 +1164,7 @@ 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)
@@ -1173,7 +1173,7 @@ xfs_reclaim_inodes_nr(
xfs_reclaim_work_queue(mp);
xfs_ail_push_all(mp->m_ail);

- xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
+ return xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
}

/*
diff --git a/fs/xfs/xfs_icache.h b/fs/xfs/xfs_icache.h
index e0f138c..2d6d2d3 100644
--- a/fs/xfs/xfs_icache.h
+++ b/fs/xfs/xfs_icache.h
@@ -31,7 +31,7 @@ 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_nr(struct xfs_mount *mp, int 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 ea341ce..1ff991b 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1523,19 +1523,19 @@ 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 67e1040..f5eabf9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1326,10 +1326,6 @@ 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);

/*
@@ -1616,8 +1612,8 @@ 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);
};

/*
--
1.8.1.4