2 files changed, 166 insertions, 3 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 81c02d63440b..74dcf19cfe68 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -547,6 +547,8 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
                                 rw = WRITE_FUA;
                         else
                                 rw = WRITE;
+                        if (test_and_clear_bit(R5_Discard, &sh->dev[i].flags))
+                                rw |= REQ_DISCARD;
                 } else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
                         rw = READ;
                 else if (test_and_clear_bit(R5_WantReplace,
@@ -1170,8 +1172,13 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
                                         set_bit(R5_WantFUA, &dev->flags);
                                 if (wbi->bi_rw & REQ_SYNC)
                                         set_bit(R5_SyncIO, &dev->flags);
-                                tx = async_copy_data(1, wbi, dev->page,
-                                        dev->sector, tx);
+                                if (wbi->bi_rw & REQ_DISCARD) {
+                                        memset(page_address(dev->page), 0,
+                                                STRIPE_SECTORS << 9);
+                                        set_bit(R5_Discard, &dev->flags);
+                                } else
+                                        tx = async_copy_data(1, wbi, dev->page,
+                                                dev->sector, tx);
                                 wbi = r5_next_bio(wbi, dev->sector);
                         }
                 }
@@ -1237,6 +1244,20 @@ ops_run_reconstruct5(struct stripe_head *sh, struct raid5_percpu *percpu,
         pr_debug("%s: stripe %llu\n", __func__,
                 (unsigned long long)sh->sector);
 
+        for (i = 0; i < sh->disks; i++) {
+                if (pd_idx == i)
+                        continue;
+                if (!test_bit(R5_Discard, &sh->dev[i].flags))
+                        break;
+        }
+        if (i >= sh->disks) {
+                atomic_inc(&sh->count);
+                memset(page_address(sh->dev[pd_idx].page), 0,
+                        STRIPE_SECTORS << 9);
+                set_bit(R5_Discard, &sh->dev[pd_idx].flags);
+                ops_complete_reconstruct(sh);
+                return;
+        }
         /* check if prexor is active which means only process blocks
          * that are part of a read-modify-write (written)
          */
@@ -1281,10 +1302,28 @@ ops_run_reconstruct6(struct stripe_head *sh, struct raid5_percpu *percpu,
 {
         struct async_submit_ctl submit;
         struct page **blocks = percpu->scribble;
-        int count;
+        int count, i;
 
         pr_debug("%s: stripe %llu\n", __func__, (unsigned long long)sh->sector);
 
+        for (i = 0; i < sh->disks; i++) {
+                if (sh->pd_idx == i || sh->qd_idx == i)
+                        continue;
+                if (!test_bit(R5_Discard, &sh->dev[i].flags))
+                        break;
+        }
+        if (i >= sh->disks) {
+                atomic_inc(&sh->count);
+                memset(page_address(sh->dev[sh->pd_idx].page), 0,
+                        STRIPE_SECTORS << 9);
+                memset(page_address(sh->dev[sh->qd_idx].page), 0,
+                        STRIPE_SECTORS << 9);
+                set_bit(R5_Discard, &sh->dev[sh->pd_idx].flags);
+                set_bit(R5_Discard, &sh->dev[sh->qd_idx].flags);
+                ops_complete_reconstruct(sh);
+                return;
+        }
+
         count = set_syndrome_sources(blocks, sh);
 
         atomic_inc(&sh->count);
@@ -4067,6 +4106,88 @@ static void release_stripe_plug(struct mddev *mddev,
                 release_stripe(sh);
 }
 
+static void make_discard_request(struct mddev *mddev, struct bio *bi)
+{
+        struct r5conf *conf = mddev->private;
+        sector_t logical_sector, last_sector;
+        struct stripe_head *sh;
+        int remaining;
+        int stripe_sectors;
+
+        if (mddev->reshape_position != MaxSector)
+                /* Skip discard while reshape is happening */
+                return;
+
+        logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
+        last_sector = bi->bi_sector + (bi->bi_size>>9);
+
+        bi->bi_next = NULL;
+        bi->bi_phys_segments = 1; /* over-loaded to count active stripes */
+
+        stripe_sectors = conf->chunk_sectors *
+                (conf->raid_disks - conf->max_degraded);
+        logical_sector = DIV_ROUND_UP_SECTOR_T(logical_sector,
+                                               stripe_sectors);
+        sector_div(last_sector, stripe_sectors);
+
+        logical_sector *= conf->chunk_sectors;
+        last_sector *= conf->chunk_sectors;
+
+        for (; logical_sector < last_sector;
+             logical_sector += STRIPE_SECTORS) {
+                DEFINE_WAIT(w);
+                int d;
+        again:
+                sh = get_active_stripe(conf, logical_sector, 0, 0, 0);
+                prepare_to_wait(&conf->wait_for_overlap, &w,
+                                TASK_UNINTERRUPTIBLE);
+                spin_lock_irq(&sh->stripe_lock);
+                for (d = 0; d < conf->raid_disks; d++) {
+                        if (d == sh->pd_idx || d == sh->qd_idx)
+                                continue;
+                        if (sh->dev[d].towrite || sh->dev[d].toread) {
+                                set_bit(R5_Overlap, &sh->dev[d].flags);
+                                spin_unlock_irq(&sh->stripe_lock);
+                                release_stripe(sh);
+                                schedule();
+                                goto again;
+                        }
+                }
+                finish_wait(&conf->wait_for_overlap, &w);
+                for (d = 0; d < conf->raid_disks; d++) {
+                        if (d == sh->pd_idx || d == sh->qd_idx)
+                                continue;
+                        sh->dev[d].towrite = bi;
+                        set_bit(R5_OVERWRITE, &sh->dev[d].flags);
+                        raid5_inc_bi_active_stripes(bi);
+                }
+                spin_unlock_irq(&sh->stripe_lock);
+                if (conf->mddev->bitmap) {
+                        for (d = 0;
+                             d < conf->raid_disks - conf->max_degraded;
+                             d++)
+                                bitmap_startwrite(mddev->bitmap,
+                                                  sh->sector,
+                                                  STRIPE_SECTORS,
+                                                  0);
+                        sh->bm_seq = conf->seq_flush + 1;
+                        set_bit(STRIPE_BIT_DELAY, &sh->state);
+                }
+
+                set_bit(STRIPE_HANDLE, &sh->state);
+                clear_bit(STRIPE_DELAYED, &sh->state);
+                if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+                        atomic_inc(&conf->preread_active_stripes);
+                release_stripe_plug(mddev, sh);
+        }
+
+        remaining = raid5_dec_bi_active_stripes(bi);
+        if (remaining == 0) {
+                md_write_end(mddev);
+                bio_endio(bi, 0);
+        }
+}
+
 static void make_request(struct mddev *mddev, struct bio * bi)
 {
         struct r5conf *conf = mddev->private;
@@ -4089,6 +4210,11 @@ static void make_request(struct mddev *mddev, struct bio * bi)
              chunk_aligned_read(mddev,bi))
                 return;
 
+        if (unlikely(bi->bi_rw & REQ_DISCARD)) {
+                make_discard_request(mddev, bi);
+                return;
+        }
+
         logical_sector = bi->bi_sector & ~((sector_t)STRIPE_SECTORS-1);
         last_sector = bi->bi_sector + (bi->bi_size>>9);
         bi->bi_next = NULL;
@@ -5362,6 +5488,7 @@ static int run(struct mddev *mddev)
 
         if (mddev->queue) {
                 int chunk_size;
+                bool discard_supported = true;
                 /* read-ahead size must cover two whole stripes, which
                  * is 2 * (datadisks) * chunksize where 'n' is the
                  * number of raid devices
@@ -5381,13 +5508,48 @@ static int run(struct mddev *mddev)
                 blk_queue_io_min(mddev->queue, chunk_size);
                 blk_queue_io_opt(mddev->queue, chunk_size *
                                  (conf->raid_disks - conf->max_degraded));
+                /*
+                 * We can only discard a whole stripe. It doesn't make sense to
+                 * discard data disk but write parity disk
+                 */
+                stripe = stripe * PAGE_SIZE;
+                mddev->queue->limits.discard_alignment = stripe;
+                mddev->queue->limits.discard_granularity = stripe;
+                /*
+                 * unaligned part of discard request will be ignored, so can't
+                 * guarantee discard_zerors_data
+                 */
+                mddev->queue->limits.discard_zeroes_data = 0;
 
                 rdev_for_each(rdev, mddev) {
                         disk_stack_limits(mddev->gendisk, rdev->bdev,
                                           rdev->data_offset << 9);
                         disk_stack_limits(mddev->gendisk, rdev->bdev,
                                           rdev->new_data_offset << 9);
+                        /*
+                         * discard_zeroes_data is required, otherwise data
+                         * could be lost. Consider a scenario: discard a stripe
+                         * (the stripe could be inconsistent if
+                         * discard_zeroes_data is 0); write one disk of the
+                         * stripe (the stripe could be inconsistent again
+                         * depending on which disks are used to calculate
+                         * parity); the disk is broken; The stripe data of this
+                         * disk is lost.
+                         */
+                        if (!blk_queue_discard(bdev_get_queue(rdev->bdev)) ||
+                            !bdev_get_queue(rdev->bdev)->
+                                                limits.discard_zeroes_data)
+                                discard_supported = false;
                 }
+
+                if (discard_supported &&
+                   mddev->queue->limits.max_discard_sectors >= stripe &&
+                   mddev->queue->limits.discard_granularity >= stripe)
+                        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD,
+                                                mddev->queue);
+                else
+                        queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD,
+                                                mddev->queue);
         }
 
         return 0;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index a9fc24901eda..18b2c4a8a1fd 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -298,6 +298,7 @@ enum r5dev_flags {
         R5_WantReplace, /* We need to update the replacement, we have read
                          * data in, and now is a good time to write it out.
                          */
+        R5_Discard,     /* Discard the stripe */
 };
 
 /*