dm io: fix discard support

This patch fixes a crash by recognising discards in dm_io. Currently dm_mirror can send REQ_DISCARD bios if running over a discard-enabled device and without support in dm_io the system crashes badly. BUG: unable to handle kernel paging request at 00800000 IP: __bio_add_page.part.17+0xf5/0x1e0 ... bio_add_page+0x56/0x70 dispatch_io+0x1cf/0x240 [dm_mod] ? km_get_page+0x50/0x50 [dm_mod] ? vm_next_page+0x20/0x20 [dm_mod] ? mirror_flush+0x130/0x130 [dm_mirror] dm_io+0xdc/0x2b0 [dm_mod] ... Introduced in 2.6.38-rc1 by commit 5fc2ffe (dm raid1: support discard). Signed-off-by: Milan Broz <[email protected]> Cc: [email protected] Acked-by: Mike Snitzer <[email protected]> Signed-off-by: Alasdair G Kergon <[email protected]>
rtvt123 · Mar 7, 2012 · 0c535e0 · 0c535e0
1 parent 902c6a9
commit 0c535e0
Showing 1 changed file with 16 additions and 7 deletions.
diff --git a/drivers/md/dm-io.c b/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
@@ -305,20 +307,27 @@ 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;
 		bio->bi_end_io = endio;
 		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))