From 708e55c42fbe91dce978103da6d5d975e691c1a2 Mon Sep 17 00:00:00 2001
From: Milan Broz <mbroz@redhat.com>
Date: Wed, 7 Mar 2012 19:09:37 +0000
Subject: [PATCH] --- yaml --- r: 288326 b: refs/heads/master c:
 0c535e0d6f463365c29623350dbd91642363c39b h: refs/heads/master v: v3

---
 [refs]                   |  2 +-
 trunk/drivers/md/dm-io.c | 23 ++++++++++++++++-------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index 4198d316af6b..60d8d41ddf7c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 902c6a96a7cb9c50d2a8aed1788efad0a5d8f04c
+refs/heads/master: 0c535e0d6f463365c29623350dbd91642363c39b
diff --git a/trunk/drivers/md/dm-io.c b/trunk/drivers/md/dm-io.c
index ad2eba40e319..ea5dd289fe2a 100644
--- a/trunk/drivers/md/dm-io.c
+++ b/trunk/drivers/md/dm-io.c
@@ -296,6 +296,8 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
 	unsigned offset;
 	unsigned num_bvecs;
 	sector_t remaining = where->count;
+	struct request_queue *q = bdev_get_queue(where->bdev);
+	sector_t discard_sectors;
 
 	/*
 	 * where->count may be zero if rw holds a flush and we need to
@@ -305,9 +307,12 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
 		/*
 		 * Allocate a suitably sized-bio.
 		 */
-		num_bvecs = dm_sector_div_up(remaining,
-					     (PAGE_SIZE >> SECTOR_SHIFT));
-		num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
+		if (rw & REQ_DISCARD)
+			num_bvecs = 1;
+		else
+			num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
+					  dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
+
 		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
 		bio->bi_sector = where->sector + (where->count - remaining);
 		bio->bi_bdev = where->bdev;
@@ -315,10 +320,14 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
 		bio->bi_destructor = dm_bio_destructor;
 		store_io_and_region_in_bio(bio, io, region);
 
-		/*
-		 * Try and add as many pages as possible.
-		 */
-		while (remaining) {
+		if (rw & REQ_DISCARD) {
+			discard_sectors = min_t(sector_t, q->limits.max_discard_sectors, remaining);
+			bio->bi_size = discard_sectors << SECTOR_SHIFT;
+			remaining -= discard_sectors;
+		} else while (remaining) {
+			/*
+			 * Try and add as many pages as possible.
+			 */
 			dp->get_page(dp, &page, &len, &offset);
 			len = min(len, to_bytes(remaining));
 			if (!bio_add_page(bio, page, len, offset))