diff mbox

[3/4] block: Dynamically allocate and refcount backing_dev_info

Message ID 20170131125429.14303-4-jack@suse.cz (mailing list archive)
State New, archived
Headers show

Commit Message

Jan Kara Jan. 31, 2017, 12:54 p.m. UTC 
Instead of storing backing_dev_info inside struct request_queue,
allocate it dynamically, reference count it, and free it when the last
reference is dropped. Currently only request_queue holds the reference
but in the following patch we add other users referencing
backing_dev_info.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 block/blk-core.c                 | 12 +++++-------
 block/blk-sysfs.c                |  2 +-
 include/linux/backing-dev-defs.h |  2 ++
 include/linux/backing-dev.h      | 10 +++++++++-
 include/linux/blkdev.h           |  1 -
 mm/backing-dev.c                 | 37 ++++++++++++++++++++++++++++++++++++-
 6 files changed, 53 insertions(+), 11 deletions(-)

Comments

Christoph Hellwig Feb. 1, 2017, 9:50 a.m. UTC | #1 
On Tue, Jan 31, 2017 at 01:54:28PM +0100, Jan Kara wrote:
> Instead of storing backing_dev_info inside struct request_queue,
> allocate it dynamically, reference count it, and free it when the last
> reference is dropped. Currently only request_queue holds the reference
> but in the following patch we add other users referencing
> backing_dev_info.

Do we really need the separate slab cache?  Otherwise this looks
fine to me.
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Jan Kara Feb. 1, 2017, 12:22 p.m. UTC | #2 
On Wed 01-02-17 01:50:07, Christoph Hellwig wrote:
> On Tue, Jan 31, 2017 at 01:54:28PM +0100, Jan Kara wrote:
> > Instead of storing backing_dev_info inside struct request_queue,
> > allocate it dynamically, reference count it, and free it when the last
> > reference is dropped. Currently only request_queue holds the reference
> > but in the following patch we add other users referencing
> > backing_dev_info.
> 
> Do we really need the separate slab cache?  Otherwise this looks
> fine to me.

Yeah, probably it is not worth it. I'll remove it.

								Honza
Jens Axboe Feb. 1, 2017, 10:45 p.m. UTC | #3 
On 02/01/2017 04:22 AM, Jan Kara wrote:
> On Wed 01-02-17 01:50:07, Christoph Hellwig wrote:
>> On Tue, Jan 31, 2017 at 01:54:28PM +0100, Jan Kara wrote:
>>> Instead of storing backing_dev_info inside struct request_queue,
>>> allocate it dynamically, reference count it, and free it when the last
>>> reference is dropped. Currently only request_queue holds the reference
>>> but in the following patch we add other users referencing
>>> backing_dev_info.
>>
>> Do we really need the separate slab cache?  Otherwise this looks
>> fine to me.
> 
> Yeah, probably it is not worth it. I'll remove it.

I agree on that, it should not be a hot path. Will you respin the series
after making this change? Would be great to get this queued up.
Jan Kara Feb. 2, 2017, 1:32 p.m. UTC | #4 
On Wed 01-02-17 14:45:20, Jens Axboe wrote:
> On 02/01/2017 04:22 AM, Jan Kara wrote:
> > On Wed 01-02-17 01:50:07, Christoph Hellwig wrote:
> >> On Tue, Jan 31, 2017 at 01:54:28PM +0100, Jan Kara wrote:
> >>> Instead of storing backing_dev_info inside struct request_queue,
> >>> allocate it dynamically, reference count it, and free it when the last
> >>> reference is dropped. Currently only request_queue holds the reference
> >>> but in the following patch we add other users referencing
> >>> backing_dev_info.
> >>
> >> Do we really need the separate slab cache?  Otherwise this looks
> >> fine to me.
> > 
> > Yeah, probably it is not worth it. I'll remove it.
> 
> I agree on that, it should not be a hot path. Will you respin the series
> after making this change? Would be great to get this queued up.

Yes, will send it later today. I was just waiting whether someone else does
not have more comments to the series.

								Honza
diff mbox

Patch

diff --git a/block/blk-core.c b/block/blk-core.c
index a9ff1b919ae7..545ccb4b96f3 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -693,7 +693,6 @@  static void blk_rq_timed_out_timer(unsigned long data)
 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 {
 	struct request_queue *q;
-	int err;
 
 	q = kmem_cache_alloc_node(blk_requestq_cachep,
 				gfp_mask | __GFP_ZERO, node_id);
@@ -708,17 +707,16 @@  struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 	if (!q->bio_split)
 		goto fail_id;
 
-	q->backing_dev_info = &q->_backing_dev_info;
+	q->backing_dev_info = bdi_alloc_node(gfp_mask, node_id);
+	if (!q->backing_dev_info)
+		goto fail_split;
+
 	q->backing_dev_info->ra_pages =
 			(VM_MAX_READAHEAD * 1024) / PAGE_SIZE;
 	q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK;
 	q->backing_dev_info->name = "block";
 	q->node = node_id;
 
-	err = bdi_init(q->backing_dev_info);
-	if (err)
-		goto fail_split;
-
 	setup_timer(&q->backing_dev_info->laptop_mode_wb_timer,
 		    laptop_mode_timer_fn, (unsigned long) q);
 	setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
@@ -769,7 +767,7 @@  struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 fail_ref:
 	percpu_ref_exit(&q->q_usage_counter);
 fail_bdi:
-	bdi_destroy(q->backing_dev_info);
+	bdi_put(q->backing_dev_info);
 fail_split:
 	bioset_free(q->bio_split);
 fail_id:
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 64fb54c6b41c..4cbaa519ec2d 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -799,7 +799,7 @@  static void blk_release_queue(struct kobject *kobj)
 		container_of(kobj, struct request_queue, kobj);
 
 	wbt_exit(q);
-	bdi_exit(q->backing_dev_info);
+	bdi_put(q->backing_dev_info);
 	blkcg_exit_queue(q);
 
 	if (q->elevator) {
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index e850e76acaaf..ad955817916d 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -10,6 +10,7 @@ 
 #include <linux/flex_proportions.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
+#include <linux/kref.h>
 
 struct page;
 struct device;
@@ -144,6 +145,7 @@  struct backing_dev_info {
 
 	char *name;
 
+	struct kref refcnt;	/* Reference counter for the structure */
 	unsigned int capabilities; /* Device capabilities */
 	unsigned int min_ratio;
 	unsigned int max_ratio, max_prop_frac;
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 43b93a947e61..efb6ca992d05 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -18,7 +18,14 @@ 
 #include <linux/slab.h>
 
 int __must_check bdi_init(struct backing_dev_info *bdi);
-void bdi_exit(struct backing_dev_info *bdi);
+
+static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
+{
+	kref_get(&bdi->refcnt);
+	return bdi;
+}
+
+void bdi_put(struct backing_dev_info *bdi);
 
 __printf(3, 4)
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
@@ -29,6 +36,7 @@  void bdi_unregister(struct backing_dev_info *bdi);
 
 int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
 void bdi_destroy(struct backing_dev_info *bdi);
+struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id);
 
 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
 			bool range_cyclic, enum wb_reason reason);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 069e4a102a73..de85701cc699 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -433,7 +433,6 @@  struct request_queue {
 	struct delayed_work	delay_work;
 
 	struct backing_dev_info	*backing_dev_info;
-	struct backing_dev_info	_backing_dev_info;
 
 	/*
 	 * The queue owner gets to use this for whatever they like.
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 3bfed5ab2475..db7d33a898a8 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -20,6 +20,8 @@  struct backing_dev_info noop_backing_dev_info = {
 };
 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
 
+static struct kmem_cache *bdi_cachep;
+
 static struct class *bdi_class;
 
 /*
@@ -237,6 +239,9 @@  static __init int bdi_class_init(void)
 
 	bdi_class->dev_groups = bdi_dev_groups;
 	bdi_debug_init();
+
+	bdi_cachep = KMEM_CACHE(backing_dev_info, SLAB_PANIC);
+
 	return 0;
 }
 postcore_initcall(bdi_class_init);
@@ -776,6 +781,7 @@  int bdi_init(struct backing_dev_info *bdi)
 
 	bdi->dev = NULL;
 
+	kref_init(&bdi->refcnt);
 	bdi->min_ratio = 0;
 	bdi->max_ratio = 100;
 	bdi->max_prop_frac = FPROP_FRAC_BASE;
@@ -791,6 +797,21 @@  int bdi_init(struct backing_dev_info *bdi)
 }
 EXPORT_SYMBOL(bdi_init);
 
+struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id)
+{
+	struct backing_dev_info *bdi;
+
+	bdi = kmem_cache_alloc_node(bdi_cachep, gfp_mask | __GFP_ZERO, node_id);
+	if (!bdi)
+		return NULL;
+
+	if (bdi_init(bdi)) {
+		kmem_cache_free(bdi_cachep, bdi);
+		return NULL;
+	}
+	return bdi;
+}
+
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 		const char *fmt, ...)
 {
@@ -871,12 +892,26 @@  void bdi_unregister(struct backing_dev_info *bdi)
 	}
 }
 
-void bdi_exit(struct backing_dev_info *bdi)
+static void bdi_exit(struct backing_dev_info *bdi)
 {
 	WARN_ON_ONCE(bdi->dev);
 	wb_exit(&bdi->wb);
 }
 
+static void release_bdi(struct kref *ref)
+{
+	struct backing_dev_info *bdi =
+			container_of(ref, struct backing_dev_info, refcnt);
+
+	bdi_exit(bdi);
+	kmem_cache_free(bdi_cachep, bdi);
+}
+
+void bdi_put(struct backing_dev_info *bdi)
+{
+	kref_put(&bdi->refcnt, release_bdi);
+}
+
 void bdi_destroy(struct backing_dev_info *bdi)
 {
 	bdi_unregister(bdi);