[PATCH 2/4] md/raid10: prepare r10bio allocation width tracking

["Chen Cheng" <chencheng@fnnas.com>]

From: Chen Cheng <chencheng@fnnas.com>

Record how many devs[] slots each r10bio was allocated with.

Keep the active r10bio pool in a separate object that carries its width.
This keeps the allocation width separate from the per-request width stored
in used_nr_devs and prepares the pool for replacement during reshape.
---
 drivers/md/raid10.c | 40 +++++++++++++++++++++++++++-------------
 drivers/md/raid10.h |  8 +++++++-
 2 files changed, 34 insertions(+), 14 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index e93933632893..b447903fbdc6 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -103,14 +103,22 @@ static inline struct r10bio *get_resync_r10bio(struct bio *bio)
 	return get_resync_pages(bio)->raid_bio;
 }
 
-static void * r10bio_pool_alloc(gfp_t gfp_flags, void *data)
+static void *r10bio_pool_alloc(gfp_t gfp_flags, void *data)
 {
-	struct r10conf *conf = data;
-	int size = offsetof(struct r10bio, devs[conf->geo.raid_disks]);
+	struct r10bio_pool *pool = data;
+	int size = offsetof(struct r10bio, devs[pool->nr_devs]);
+	struct r10bio *r10_bio = kzalloc(size, gfp_flags);
+
+	if (r10_bio)
+		r10_bio->alloc_nr_devs = pool->nr_devs;
+	return r10_bio;
+}
 
-	/* allocate a r10bio with room for raid_disks entries in the
-	 * bios array */
-	return kzalloc(size, gfp_flags);
+static int init_r10bio_pool(struct r10bio_pool *pool, unsigned int nr_devs)
+{
+	pool->nr_devs = nr_devs;
+	return mempool_init(&pool->pool, NR_RAID_BIOS, r10bio_pool_alloc,
+			    rbio_pool_free, pool);
 }
 
 #define RESYNC_SECTORS (RESYNC_BLOCK_SIZE >> 9)
@@ -137,7 +145,7 @@ static void * r10buf_pool_alloc(gfp_t gfp_flags, void *data)
 	int nalloc, nalloc_rp;
 	struct resync_pages *rps;
 
-	r10_bio = r10bio_pool_alloc(gfp_flags, conf);
+	r10_bio = r10bio_pool_alloc(gfp_flags, conf->r10bio_pool);
 	if (!r10_bio)
 		return NULL;
 
@@ -277,7 +285,7 @@ static void free_r10bio(struct r10bio *r10_bio)
 	struct r10conf *conf = r10_bio->mddev->private;
 
 	put_all_bios(conf, r10_bio);
-	mempool_free(r10_bio, &conf->r10bio_pool);
+	mempool_free(r10_bio, &conf->r10bio_pool->pool);
 }
 
 static void put_buf(struct r10bio *r10_bio)
@@ -1531,7 +1539,7 @@ static void __make_request(struct mddev *mddev, struct bio *bio, int sectors)
 	struct r10conf *conf = mddev->private;
 	struct r10bio *r10_bio;
 
-	r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
+	r10_bio = mempool_alloc(&conf->r10bio_pool->pool, GFP_NOIO);
 
 	r10_bio->master_bio = bio;
 	r10_bio->sectors = sectors;
@@ -1724,7 +1732,7 @@ static int raid10_handle_discard(struct mddev *mddev, struct bio *bio)
 				(last_stripe_index << geo->chunk_shift);
 
 retry_discard:
-	r10_bio = mempool_alloc(&conf->r10bio_pool, GFP_NOIO);
+	r10_bio = mempool_alloc(&conf->r10bio_pool->pool, GFP_NOIO);
 	r10_bio->mddev = mddev;
 	r10_bio->state = 0;
 	r10_bio->sectors = 0;
@@ -3825,7 +3833,10 @@ static void raid10_free_conf(struct r10conf *conf)
 	if (!conf)
 		return;
 
-	mempool_exit(&conf->r10bio_pool);
+	if (conf->r10bio_pool) {
+		mempool_exit(&conf->r10bio_pool->pool);
+		kfree(conf->r10bio_pool);
+	}
 	kfree(conf->mirrors);
 	kfree(conf->mirrors_old);
 	kfree(conf->mirrors_new);
@@ -3870,10 +3881,13 @@ static struct r10conf *setup_conf(struct mddev *mddev)
 	if (!conf->tmppage)
 		goto out;
 
+	conf->r10bio_pool = kzalloc_obj(struct r10bio_pool);
+	if (!conf->r10bio_pool)
+		goto out;
+
 	conf->geo = geo;
 	conf->copies = copies;
-	err = mempool_init(&conf->r10bio_pool, NR_RAID_BIOS, r10bio_pool_alloc,
-			   rbio_pool_free, conf);
+	err = init_r10bio_pool(conf->r10bio_pool, conf->geo.raid_disks);
 	if (err)
 		goto out;
 
diff --git a/drivers/md/raid10.h b/drivers/md/raid10.h
index 92e8743023e6..8fa4e54c444c 100644
--- a/drivers/md/raid10.h
+++ b/drivers/md/raid10.h
@@ -20,6 +20,11 @@ struct raid10_info {
 	sector_t	head_position;
 };
 
+struct r10bio_pool {
+	mempool_t	pool;
+	unsigned int	nr_devs;
+};
+
 struct r10conf {
 	struct mddev		*mddev;
 	struct raid10_info	*mirrors;
@@ -87,7 +92,7 @@ struct r10conf {
 						   */
 	wait_queue_head_t	wait_barrier;
 
-	mempool_t		r10bio_pool;
+	struct r10bio_pool	*r10bio_pool;
 	mempool_t		r10buf_pool;
 	struct page		*tmppage;
 	struct bio_set		bio_split;
@@ -128,6 +133,7 @@ struct r10bio {
 	 */
 	int			read_slot;
 	unsigned int		used_nr_devs;
+	unsigned int		alloc_nr_devs;
 
 	struct list_head	retry_list;
 	/*
-- 
2.53.0