blk-mq: fix schedule from atomic context

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>
Signed-off-by: Jens Axboe <axboe@fb.com>

4 files changed, 78 insertions, 31 deletions

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index d90c4aeb7dd3..1aab39f71d95 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 c959de58d2a5..98696a65d4d4 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 b9230c522c6b..43eb3156e110 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 57a7968e47b3..26460884c6cd 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