[PATCH 2/2] blk-mq: fix schedule from atomic context

Ming Lei
2014-05-31T16:44:07Z

blk_mq_put_ctx() has to be called before io_schedule() in
bt_get().

This patch fixes the problem by taking similar approach from
percpu_ida allocation for the situation.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
block/blk-mq-tag.c | 48 +++++++++++++++++++++++++++++++-----------------
block/blk-mq-tag.h | 2 +-
block/blk-mq.c | 36 +++++++++++++++++++++++-------------
block/blk-mq.h | 23 +++++++++++++++++++++++
4 files changed, 78 insertions(+), 31 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index d90c4ae..1aab39f 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -221,8 +221,10 @@ static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt,
return bs;
}

-static int bt_get(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx,
- unsigned int *last_tag, gfp_t gfp)
+static int bt_get(struct blk_mq_alloc_data *data,
+ struct blk_mq_bitmap_tags *bt,
+ struct blk_mq_hw_ctx *hctx,
+ unsigned int *last_tag)
{
struct bt_wait_state *bs;
DEFINE_WAIT(wait);
@@ -232,7 +234,7 @@ static int bt_get(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx,
if (tag != -1)
return tag;

- if (!(gfp & __GFP_WAIT))
+ if (!(data->gfp & __GFP_WAIT))
return -1;

bs = bt_wait_ptr(bt, hctx);
@@ -249,50 +251,62 @@ static int bt_get(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx,
if (was_empty)
atomic_set(&bs->wait_cnt, bt->wake_cnt);

+ blk_mq_put_ctx(data->ctx);
+
io_schedule();
+
+ data->ctx = blk_mq_get_ctx(data->q);
+ data->hctx = data->q->mq_ops->map_queue(data->q,
+ data->ctx->cpu);
+ if (data->reserved) {
+ bt = &data->hctx->tags->breserved_tags;
+ } else {
+ last_tag = &data->ctx->last_tag;
+ hctx = data->hctx;
+ bt = &hctx->tags->bitmap_tags;
+ }
+ finish_wait(&bs->wait, &wait);
+ bs = bt_wait_ptr(bt, hctx);
} while (1);

finish_wait(&bs->wait, &wait);
return tag;
}

-static unsigned int __blk_mq_get_tag(struct blk_mq_tags *tags,
- struct blk_mq_hw_ctx *hctx,
- unsigned int *last_tag, gfp_t gfp)
+static unsigned int __blk_mq_get_tag(struct blk_mq_alloc_data *data)
{
int tag;

- tag = bt_get(&tags->bitmap_tags, hctx, last_tag, gfp);
+ tag = bt_get(data, &data->hctx->tags->bitmap_tags, data->hctx,
+ &data->ctx->last_tag);
if (tag >= 0)
- return tag + tags->nr_reserved_tags;
+ return tag + data->hctx->tags->nr_reserved_tags;

return BLK_MQ_TAG_FAIL;
}

-static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_tags *tags,
- gfp_t gfp)
+static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_alloc_data *data)
{
int tag, zero = 0;

- if (unlikely(!tags->nr_reserved_tags)) {
+ if (unlikely(!data->hctx->tags->nr_reserved_tags)) {
WARN_ON_ONCE(1);
return BLK_MQ_TAG_FAIL;
}

- tag = bt_get(&tags->breserved_tags, NULL, &zero, gfp);
+ tag = bt_get(data, &data->hctx->tags->breserved_tags, NULL, &zero);
if (tag < 0)
return BLK_MQ_TAG_FAIL;

return tag;
}

-unsigned int blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, unsigned int *last_tag,
- gfp_t gfp, bool reserved)
+unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
{
- if (!reserved)
- return __blk_mq_get_tag(hctx->tags, hctx, last_tag, gfp);
+ if (!data->reserved)
+ return __blk_mq_get_tag(data);

- return __blk_mq_get_reserved_tag(hctx->tags, gfp);
+ return __blk_mq_get_reserved_tag(data);
}

static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt)
diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h
index c959de5..98696a6 100644
--- a/block/blk-mq-tag.h
+++ b/block/blk-mq-tag.h
@@ -48,7 +48,7 @@ struct blk_mq_tags {
extern struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags, unsigned int reserved_tags, int node);
extern void blk_mq_free_tags(struct blk_mq_tags *tags);

-extern unsigned int blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, unsigned int *last_tag, gfp_t gfp, bool reserved);
+extern unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data);
extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, unsigned int tag, unsigned int *last_tag);
extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags);
extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index b9230c5..43eb315 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -210,24 +210,23 @@ static void blk_mq_rq_ctx_init(struct request_queue *q, struct blk_mq_ctx *ctx,
}

static struct request *
-__blk_mq_alloc_request(struct request_queue *q, struct blk_mq_hw_ctx *hctx,
- struct blk_mq_ctx *ctx, int rw, gfp_t gfp, bool reserved)
+__blk_mq_alloc_request(struct blk_mq_alloc_data *data, int rw)
{
struct request *rq;
unsigned int tag;

- tag = blk_mq_get_tag(hctx, &ctx->last_tag, gfp, reserved);
+ tag = blk_mq_get_tag(data);
if (tag != BLK_MQ_TAG_FAIL) {
- rq = hctx->tags->rqs[tag];
+ rq = data->hctx->tags->rqs[tag];

rq->cmd_flags = 0;
- if (blk_mq_tag_busy(hctx)) {
+ if (blk_mq_tag_busy(data->hctx)) {
rq->cmd_flags = REQ_MQ_INFLIGHT;
- atomic_inc(&hctx->nr_active);
+ atomic_inc(&data->hctx->nr_active);
}

rq->tag = tag;
- blk_mq_rq_ctx_init(q, ctx, rq, rw);
+ blk_mq_rq_ctx_init(data->q, data->ctx, rq, rw);
return rq;
}

@@ -240,22 +239,27 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw, gfp_t gfp,
struct blk_mq_ctx *ctx;
struct blk_mq_hw_ctx *hctx;
struct request *rq;
+ struct blk_mq_alloc_data alloc_data;

if (blk_mq_queue_enter(q))
return NULL;

ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
+ blk_mq_set_alloc_data(&alloc_data, q, gfp & ~__GFP_WAIT,
+ reserved, ctx, hctx);

- rq = __blk_mq_alloc_request(q, hctx, ctx, rw, gfp & ~__GFP_WAIT,
- reserved);
+ rq = __blk_mq_alloc_request(&alloc_data, rw);
if (!rq && (gfp & __GFP_WAIT)) {
__blk_mq_run_hw_queue(hctx);
blk_mq_put_ctx(ctx);

ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
- rq = __blk_mq_alloc_request(q, hctx, ctx, rw, gfp, reserved);
+ blk_mq_set_alloc_data(&alloc_data, q, gfp, reserved, ctx,
+ hctx);
+ rq = __blk_mq_alloc_request(&alloc_data, rw);
+ ctx = alloc_data.ctx;
}
blk_mq_put_ctx(ctx);
return rq;
@@ -1136,6 +1140,7 @@ static struct request *blk_mq_map_request(struct request_queue *q,
struct blk_mq_ctx *ctx;
struct request *rq;
int rw = bio_data_dir(bio);
+ struct blk_mq_alloc_data alloc_data;

if (unlikely(blk_mq_queue_enter(q))) {
bio_endio(bio, -EIO);
@@ -1149,7 +1154,9 @@ static struct request *blk_mq_map_request(struct request_queue *q,
rw |= REQ_SYNC;

trace_block_getrq(q, bio, rw);
- rq = __blk_mq_alloc_request(q, hctx, ctx, rw, GFP_ATOMIC, false);
+ blk_mq_set_alloc_data(&alloc_data, q, GFP_ATOMIC, false, ctx,
+ hctx);
+ rq = __blk_mq_alloc_request(&alloc_data, rw);
if (unlikely(!rq)) {
__blk_mq_run_hw_queue(hctx);
blk_mq_put_ctx(ctx);
@@ -1157,8 +1164,11 @@ static struct request *blk_mq_map_request(struct request_queue *q,

ctx = blk_mq_get_ctx(q);
hctx = q->mq_ops->map_queue(q, ctx->cpu);
- rq = __blk_mq_alloc_request(q, hctx, ctx, rw,
- __GFP_WAIT|GFP_ATOMIC, false);
+ blk_mq_set_alloc_data(&alloc_data, q,
+ __GFP_WAIT|GFP_ATOMIC, false, ctx, hctx);
+ rq = __blk_mq_alloc_request(&alloc_data, rw);
+ ctx = alloc_data.ctx;
+ hctx = alloc_data.hctx;
}

hctx->queued++;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 57a7968..2646088 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -91,4 +91,27 @@ static inline void blk_mq_put_ctx(struct blk_mq_ctx *ctx)
put_cpu();
}

+struct blk_mq_alloc_data {
+ /* input parameter */
+ struct request_queue *q;
+ gfp_t gfp;
+ bool reserved;
+
+ /* input & output parameter */
+ struct blk_mq_ctx *ctx;
+ struct blk_mq_hw_ctx *hctx;
+};
+
+static inline void blk_mq_set_alloc_data(struct blk_mq_alloc_data *data,
+ struct request_queue *q, gfp_t gfp, bool reserved,
+ struct blk_mq_ctx *ctx,
+ struct blk_mq_hw_ctx *hctx)
+{
+ data->q = q;
+ data->gfp = gfp;
+ data->reserved = reserved;
+ data->ctx = ctx;
+ data->hctx = hctx;
+}
+
#endif
--
1.7.9.5