blk-mq: respect rq_affinity

The blk-mq code is using it's own version of the I/O completion affinity
tunables, which causes a few issues:

 - the rq_affinity sysfs file doesn't work for blk-mq devices, even if it
   still is present, thus breaking existing tuning setups.
 - the rq_affinity = 1 mode, which is the defauly for legacy request based
   drivers isn't implemented at all.
 - blk-mq drivers don't implement any completion affinity with the default
   flag settings.

This patches removes the blk-mq ipi_redirect flag and sysfs file, as well
as the internal BLK_MQ_F_SHOULD_IPI flag and replaces it with code that
respects the queue-wide rq_affinity flags and also implements the
rq_affinity = 1 mode.

This means I/O completion affinity can now only be tuned block-queue wide
instead of per context, which seems more sensible to me anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

4 files changed, 6 insertions, 46 deletions

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 9176a6984857..8145b5b25b4b 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -203,42 +203,6 @@ static ssize_t blk_mq_hw_sysfs_rq_list_show(struct blk_mq_hw_ctx *hctx,
         return ret;
 }
 
-static ssize_t blk_mq_hw_sysfs_ipi_show(struct blk_mq_hw_ctx *hctx, char *page)
-{
-        ssize_t ret;
-
-        spin_lock(&hctx->lock);
-        ret = sprintf(page, "%u\n", !!(hctx->flags & BLK_MQ_F_SHOULD_IPI));
-        spin_unlock(&hctx->lock);
-
-        return ret;
-}
-
-static ssize_t blk_mq_hw_sysfs_ipi_store(struct blk_mq_hw_ctx *hctx,
-                                         const char *page, size_t len)
-{
-        struct blk_mq_ctx *ctx;
-        unsigned long ret;
-        unsigned int i;
-
-        if (kstrtoul(page, 10, &ret)) {
-                pr_err("blk-mq-sysfs: invalid input '%s'\n", page);
-                return -EINVAL;
-        }
-
-        spin_lock(&hctx->lock);
-        if (ret)
-                hctx->flags |= BLK_MQ_F_SHOULD_IPI;
-        else
-                hctx->flags &= ~BLK_MQ_F_SHOULD_IPI;
-        spin_unlock(&hctx->lock);
-
-        hctx_for_each_ctx(hctx, ctx, i)
-                ctx->ipi_redirect = !!ret;
-
-        return len;
-}
-
 static ssize_t blk_mq_hw_sysfs_tags_show(struct blk_mq_hw_ctx *hctx, char *page)
 {
         return blk_mq_tag_sysfs_show(hctx->tags, page);
@@ -307,11 +271,6 @@ static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_pending = {
         .attr = {.name = "pending", .mode = S_IRUGO },
         .show = blk_mq_hw_sysfs_rq_list_show,
 };
-static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_ipi = {
-        .attr = {.name = "ipi_redirect", .mode = S_IRUGO | S_IWUSR},
-        .show = blk_mq_hw_sysfs_ipi_show,
-        .store = blk_mq_hw_sysfs_ipi_store,
-};
 static struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_tags = {
         .attr = {.name = "tags", .mode = S_IRUGO },
         .show = blk_mq_hw_sysfs_tags_show,
@@ -326,7 +285,6 @@ static struct attribute *default_hw_ctx_attrs[] = {
         &blk_mq_hw_sysfs_run.attr,
         &blk_mq_hw_sysfs_dispatched.attr,
         &blk_mq_hw_sysfs_pending.attr,
-        &blk_mq_hw_sysfs_ipi.attr,
         &blk_mq_hw_sysfs_tags.attr,
         &blk_mq_hw_sysfs_cpus.attr,
         NULL,
diff --git a/block/blk-mq.c b/block/blk-mq.c
index a84112c94e74..f2e92eb92803 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -326,15 +326,19 @@ static void __blk_mq_complete_request_remote(void *data)
 void __blk_mq_complete_request(struct request *rq)
 {
         struct blk_mq_ctx *ctx = rq->mq_ctx;
+        bool shared = false;
         int cpu;
 
-        if (!ctx->ipi_redirect) {
+        if (!test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags)) {
                 rq->q->softirq_done_fn(rq);
                 return;
         }
 
         cpu = get_cpu();
-        if (cpu != ctx->cpu && cpu_online(ctx->cpu)) {
+        if (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags))
+                shared = cpus_share_cache(cpu, ctx->cpu);
+
+        if (cpu != ctx->cpu && !shared && cpu_online(ctx->cpu)) {
                 rq->csd.func = __blk_mq_complete_request_remote;
                 rq->csd.info = rq;
                 rq->csd.flags = 0;
diff --git a/block/blk-mq.h b/block/blk-mq.h
index b41a784de50d..1ae364ceaf8b 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -11,7 +11,6 @@ struct blk_mq_ctx {
 
         unsigned int            cpu;
         unsigned int            index_hw;
-        unsigned int            ipi_redirect;
 
         /* incremented at dispatch time */
         unsigned long           rq_dispatched[2];
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ab469d525894..3b561d651a02 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -122,7 +122,6 @@ enum {
 
         BLK_MQ_F_SHOULD_MERGE   = 1 << 0,
         BLK_MQ_F_SHOULD_SORT    = 1 << 1,
-        BLK_MQ_F_SHOULD_IPI     = 1 << 2,
 
         BLK_MQ_S_STOPPED        = 0,