[Crash-utility] [PATCH v2] Handle blk_mq_ctx member changes for kernels v5.16-rc1~75^2~44

[Lianbo Jiang]

Kernel commit <9a14d6ce4135> ("block: remove debugfs blk_mq_ctx
dispatched/merged/completed attributes") removed the member
rq_dispatched and rq_completed from struct blk_mq_ctx. Without
this patch, crash will fail with the following error:

crash> dev -d
MAJOR GENDISK            NAME       REQUEST_QUEUE      TOTAL ASYNC  SYNC

dev: invalid structure member offset: blk_mq_ctx_rq_dispatched
     FILE: dev.c  LINE: 4229  FUNCTION: get_one_mctx_diskio()

Signed-off-by: Lianbo Jiang <lijiang at redhat.com>
---
change since v1:
[1] display prompt information "(not supported)" instead of the
statistical result if kernel does not support it

 dev.c | 56 ++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 38 insertions(+), 18 deletions(-)

diff --git a/dev.c b/dev.c
index effe789f38d8..c5e38e1c5376 100644
--- a/dev.c
+++ b/dev.c
@@ -4246,6 +4246,10 @@ get_mq_diskio(unsigned long q, unsigned long *mq_count)
 	unsigned long mctx_addr;
 	struct diskio tmp;
 
+	if (!MEMBER_EXISTS("blk_mq_ctx", "rq_dispatched") &&
+		!MEMBER_EXISTS("blk_mq_ctx", "rq_completed"))
+		return;
+
 	memset(&tmp, 0x00, sizeof(struct diskio));
 
 	readmem(q + OFFSET(request_queue_queue_ctx), KVADDR, &queue_ctx,
@@ -4475,24 +4479,40 @@ display_one_diskio(struct iter *i, unsigned long gendisk, ulong flags)
 		&& (io.read + io.write == 0))
 		return;
 
-	fprintf(fp, "%s%s%s  %s%s%s%s  %s%5d%s%s%s%s%s",
-		mkstring(buf0, 5, RJUST|INT_DEC, (char *)(unsigned long)major),
-		space(MINSPACE),
-		mkstring(buf1, VADDR_PRLEN, LJUST|LONG_HEX, (char *)gendisk),
-		space(MINSPACE),
-		mkstring(buf2, 10, LJUST, disk_name),
-		space(MINSPACE),
-		mkstring(buf3, VADDR_PRLEN <= 11 ? 11 : VADDR_PRLEN,
-			 LJUST|LONG_HEX, (char *)queue_addr),
-		space(MINSPACE),
-		io.read + io.write,
-		space(MINSPACE),
-		mkstring(buf4, 5, RJUST|INT_DEC,
-			(char *)(unsigned long)io.read),
-		space(MINSPACE),
-		mkstring(buf5, 5, RJUST|INT_DEC,
-			(char *)(unsigned long)io.write),
-		space(MINSPACE));
+	if (!MEMBER_EXISTS("blk_mq_ctx", "rq_dispatched") &&
+		!MEMBER_EXISTS("blk_mq_ctx", "rq_completed"))
+		fprintf(fp, "%s%s%s  %s%s%s%s  %s%s%s",
+			mkstring(buf0, 5, RJUST|INT_DEC, (char *)(unsigned long)major),
+			space(MINSPACE),
+			mkstring(buf1, VADDR_PRLEN, LJUST|LONG_HEX, (char *)gendisk),
+			space(MINSPACE),
+			mkstring(buf2, 10, LJUST, disk_name),
+			space(MINSPACE),
+			mkstring(buf3, VADDR_PRLEN <= 11 ? 11 : VADDR_PRLEN,
+				 LJUST|LONG_HEX, (char *)queue_addr),
+			space(MINSPACE),
+			mkstring(buf4, 16, LJUST, "(not supported)"),
+			space(MINSPACE));
+
+	else
+		fprintf(fp, "%s%s%s  %s%s%s%s  %s%5d%s%s%s%s%s",
+			mkstring(buf0, 5, RJUST|INT_DEC, (char *)(unsigned long)major),
+			space(MINSPACE),
+			mkstring(buf1, VADDR_PRLEN, LJUST|LONG_HEX, (char *)gendisk),
+			space(MINSPACE),
+			mkstring(buf2, 10, LJUST, disk_name),
+			space(MINSPACE),
+			mkstring(buf3, VADDR_PRLEN <= 11 ? 11 : VADDR_PRLEN,
+				 LJUST|LONG_HEX, (char *)queue_addr),
+			space(MINSPACE),
+			io.read + io.write,
+			space(MINSPACE),
+			mkstring(buf4, 5, RJUST|INT_DEC,
+				(char *)(unsigned long)io.read),
+			space(MINSPACE),
+			mkstring(buf5, 5, RJUST|INT_DEC,
+				(char *)(unsigned long)io.write),
+			space(MINSPACE));
 
 	if (VALID_MEMBER(request_queue_in_flight)) {
 		if (!use_mq_interface(queue_addr)) {
-- 
2.20.1