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authorAkinobu Mita <akinobu.mita@gmail.com>2015-09-26 20:09:23 +0300
committerJens Axboe <axboe@fb.com>2015-09-29 20:32:50 +0300
commit5778322e67ed34dc9f391a4a5cbcbb856071ceba (patch)
tree142b9e7ac2a85dc3ee7cfd403f53b56cb2921957 /block/blk-mq-cpumap.c
parent0e6263682014d480b8d7b8c10287f4536066b54f (diff)
downloadlinux-5778322e67ed34dc9f391a4a5cbcbb856071ceba.tar.xz
blk-mq: avoid inserting requests before establishing new mapping
Notifier callbacks for CPU_ONLINE action can be run on the other CPU than the CPU which was just onlined. So it is possible for the process running on the just onlined CPU to insert request and run hw queue before establishing new mapping which is done by blk_mq_queue_reinit_notify(). This can cause a problem when the CPU has just been onlined first time since the request queue was initialized. At this time ctx->index_hw for the CPU, which is the index in hctx->ctxs[] for this ctx, is still zero before blk_mq_queue_reinit_notify() is called by notifier callbacks for CPU_ONLINE action. For example, there is a single hw queue (hctx) and two CPU queues (ctx0 for CPU0, and ctx1 for CPU1). Now CPU1 is just onlined and a request is inserted into ctx1->rq_list and set bit0 in pending bitmap as ctx1->index_hw is still zero. And then while running hw queue, flush_busy_ctxs() finds bit0 is set in pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list. But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list is ignored. Fix it by ensuring that new mapping is established before onlined cpu starts running. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Reviewed-by: Ming Lei <tom.leiming@gmail.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Ming Lei <tom.leiming@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq-cpumap.c')
-rw-r--r--block/blk-mq-cpumap.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 1e28ddb656b8..8764c241e5bb 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -31,7 +31,8 @@ static int get_first_sibling(unsigned int cpu)
return cpu;
}
-int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
+int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
+ const struct cpumask *online_mask)
{
unsigned int i, nr_cpus, nr_uniq_cpus, queue, first_sibling;
cpumask_var_t cpus;
@@ -41,7 +42,7 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
cpumask_clear(cpus);
nr_cpus = nr_uniq_cpus = 0;
- for_each_online_cpu(i) {
+ for_each_cpu(i, online_mask) {
nr_cpus++;
first_sibling = get_first_sibling(i);
if (!cpumask_test_cpu(first_sibling, cpus))
@@ -51,7 +52,7 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
queue = 0;
for_each_possible_cpu(i) {
- if (!cpu_online(i)) {
+ if (!cpumask_test_cpu(i, online_mask)) {
map[i] = 0;
continue;
}
@@ -95,7 +96,7 @@ unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set)
if (!map)
return NULL;
- if (!blk_mq_update_queue_map(map, set->nr_hw_queues))
+ if (!blk_mq_update_queue_map(map, set->nr_hw_queues, cpu_online_mask))
return map;
kfree(map);