1 files changed, 51 insertions, 3 deletions

diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index 5ad9231c8700..dad32f8bce7d 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -37,6 +37,13 @@ struct dm_kcopyd_client {
         unsigned int nr_pages;
         unsigned int nr_free_pages;
 
+        /*
+         * Block devices to unplug.
+         * Non-NULL pointer means that a block device has some pending requests
+         * and needs to be unplugged.
+         */
+        struct block_device *unplug[2];
+
         struct dm_io_client *io_client;
 
         wait_queue_head_t destroyq;
@@ -308,6 +315,31 @@ static int run_complete_job(struct kcopyd_job *job)
         return 0;
 }
 
+/*
+ * Unplug the block device at the specified index.
+ */
+static void unplug(struct dm_kcopyd_client *kc, int rw)
+{
+        if (kc->unplug[rw] != NULL) {
+                blk_unplug(bdev_get_queue(kc->unplug[rw]));
+                kc->unplug[rw] = NULL;
+        }
+}
+
+/*
+ * Prepare block device unplug. If there's another device
+ * to be unplugged at the same array index, we unplug that
+ * device first.
+ */
+static void prepare_unplug(struct dm_kcopyd_client *kc, int rw,
+                           struct block_device *bdev)
+{
+        if (likely(kc->unplug[rw] == bdev))
+                return;
+        unplug(kc, rw);
+        kc->unplug[rw] = bdev;
+}
+
 static void complete_io(unsigned long error, void *context)
 {
         struct kcopyd_job *job = (struct kcopyd_job *) context;
@@ -345,7 +377,7 @@ static int run_io_job(struct kcopyd_job *job)
 {
         int r;
         struct dm_io_request io_req = {
-                .bi_rw = job->rw | REQ_UNPLUG,
+                .bi_rw = job->rw,
                 .mem.type = DM_IO_PAGE_LIST,
                 .mem.ptr.pl = job->pages,
                 .mem.offset = job->offset,
@@ -354,10 +386,16 @@ static int run_io_job(struct kcopyd_job *job)
                 .client = job->kc->io_client,
         };
 
-        if (job->rw == READ)
+        if (job->rw == READ) {
                 r = dm_io(&io_req, 1, &job->source, NULL);
-        else
+                prepare_unplug(job->kc, READ, job->source.bdev);
+        } else {
+                if (job->num_dests > 1)
+                        io_req.bi_rw |= REQ_UNPLUG;
                 r = dm_io(&io_req, job->num_dests, job->dests, NULL);
+                if (!(io_req.bi_rw & REQ_UNPLUG))
+                        prepare_unplug(job->kc, WRITE, job->dests[0].bdev);
+        }
 
         return r;
 }
@@ -435,10 +473,18 @@ static void do_work(struct work_struct *work)
          * Pages jobs when successful will jump onto the io jobs
          * list.  io jobs call wake when they complete and it all
          * starts again.
+         *
+         * Note that io_jobs add block devices to the unplug array,
+         * this array is cleared with "unplug" calls. It is thus
+         * forbidden to run complete_jobs after io_jobs and before
+         * unplug because the block device could be destroyed in
+         * job completion callback.
          */
         process_jobs(&kc->complete_jobs, kc, run_complete_job);
         process_jobs(&kc->pages_jobs, kc, run_pages_job);
         process_jobs(&kc->io_jobs, kc, run_io_job);
+        unplug(kc, READ);
+        unplug(kc, WRITE);
 }
 
 /*
@@ -619,6 +665,8 @@ int dm_kcopyd_client_create(unsigned int nr_pages,
         INIT_LIST_HEAD(&kc->io_jobs);
         INIT_LIST_HEAD(&kc->pages_jobs);
 
+        memset(kc->unplug, 0, sizeof(kc->unplug));
+
         kc->job_pool = mempool_create_slab_pool(MIN_JOBS, _job_cache);
         if (!kc->job_pool)
                 goto bad_slab;