[dm-devel] [PATCH] block: fix infinite loop if the device loses discard capability

Mikulas Patocka mpatocka at redhat.com
Tue Jul 3 17:34:22 UTC 2018


If __blkdev_issue_discard is in progress and a device mapper device is
reloaded with a table that doesn't support discard,
q->limits.max_discard_sectors is set to zero. This results in infinite
loop in __blkdev_issue_discard.

This patch checks if max_discard_sectors is zero and aborts with
-EOPNOTSUPP.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Tested-by: Zdenek Kabelac <mpatocka at redhat.com>
Cc: stable at vger.kernel.org

---
 block/blk-lib.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

Index: linux-2.6/block/blk-lib.c
===================================================================
--- linux-2.6.orig/block/blk-lib.c	2018-06-18 01:08:49.500000000 +0200
+++ linux-2.6/block/blk-lib.c	2018-06-29 20:09:27.670000000 +0200
@@ -68,6 +68,8 @@ int __blkdev_issue_discard(struct block_
 		 */
 		req_sects = min_t(sector_t, nr_sects,
 					q->limits.max_discard_sectors);
+		if (!req_sects)
+			goto fail;
 		if (req_sects > UINT_MAX >> 9)
 			req_sects = UINT_MAX >> 9;
 
@@ -105,6 +107,14 @@ int __blkdev_issue_discard(struct block_
 
 	*biop = bio;
 	return 0;
+
+fail:
+	if (bio) {
+		submit_bio_wait(bio);
+		bio_put(bio);
+	}
+	*biop = NULL;
+	return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL(__blkdev_issue_discard);
 




More information about the dm-devel mailing list