linux-kernel - Re: [linux-next][bock] [bisected c20cfc27a] WARNING: CPU: 22 PID: 0 at block/blk-core.c:2655 .blk_update

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Date:   Wed, 10 May 2017 19:55:06 +0200
From:   Christoph Hellwig <hch@....de>
To:     Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
Cc:     Christoph Hellwig <hch@....de>, Jens Axboe <axboe@...nel.dk>,
        sachinp <sachinp@...ux.vnet.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [linux-next][bock] [bisected c20cfc27a] WARNING: CPU: 22 PID:
        0 at block/blk-core.c:2655 .blk_update_request+0x4f8/0x500

Hi Abdul,

can you test the patch below?  I'll try to create a way to inject
short WRITE SAME commands using qemu next, but I thought I'd give
you a chance to try it as well.

---
diff --git a/block/blk-core.c b/block/blk-core.c
index c580b0138a7f..c7068520794b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2644,8 +2644,6 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
 		return false;
 	}
 
-	WARN_ON_ONCE(req->rq_flags & RQF_SPECIAL_PAYLOAD);
-
 	req->__data_len -= total_bytes;
 
 	/* update sector only for requests with clear definition of sector */
@@ -2658,17 +2656,19 @@ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
 		req->cmd_flags |= req->bio->bi_opf & REQ_FAILFAST_MASK;
 	}
 
-	/*
-	 * If total number of sectors is less than the first segment
-	 * size, something has gone terribly wrong.
-	 */
-	if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
-		blk_dump_rq_flags(req, "request botched");
-		req->__data_len = blk_rq_cur_bytes(req);
-	}
+	if (!(req->rq_flags & RQF_SPECIAL_PAYLOAD)) {
+		/*
+		 * If total number of sectors is less than the first segment
+		 * size, something has gone terribly wrong.
+		 */
+		if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
+			blk_dump_rq_flags(req, "request botched");
+			req->__data_len = blk_rq_cur_bytes(req);
+		}
 
-	/* recalculate the number of segments */
-	blk_recalc_rq_segments(req);
+		/* recalculate the number of segments */
+		blk_recalc_rq_segments(req);
+	}
 
 	return true;
 }