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>

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index d90c4aeb7dd38c02582d8f8e88f0e176dd9118be..1aab39f71d9544c89e82c9540050bc40a83d3eed 100644 (file)
--- 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 c959de58d2a55fba4c9c248d871cfa3fd3e66f16..98696a65d4d45243d45a406c866c1cf93ff89c97 100644 (file)
--- 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 b9230c522c6bc5d2d79d869de5853f96657b1412..43eb3156e1107e8946d4a8d2a2c7e3c1e3b0bea9 100644 (file)
--- 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 57a7968e47b3418b4ee852ba3398e0e7eb5abc60..26460884c6cd835202e90b2d5985c827495ca626 100644 (file)
--- 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