blktrace: add support for REQ_OP_WRITE_ZEROES tracing

Currently, REQ_OP_WRITE_ZEROES operations are not handled in the
blktrace infrastructure, resulting in incorrect or missing operation
labels in ftrace blktrace output. This manifests as write-zeroes
operations appearing with incorrect labels like "N" instead of a
proper "WZ" designation.

This patch adds complete support for REQ_OP_WRITE_ZEROES across the
blktrace infrastructure:

Add BLK_TC_WRITE_ZEROES trace category in blktrace_api.h and update
BLK_TC_END_V2 marker accordingly
Map REQ_OP_WRITE_ZEROES to BLK_TC_WRITE_ZEROES in __blk_add_trace()
to ensure proper trace event categorization
Update fill_rwbs() to generate "WZ" label for write-zeroes operations
in ftrace output, making them easily identifiable
Add "write-zeroes" string mapping in act_to_str array for debugfs
filter interface
Update blk_fill_rwbs() to handle REQ_OP_WRITE_ZEROES for block layer
event tracing

With this fix, write-zeroes operations are now correctly traced and
displayed.

===========================================================
BEFORE THIS PATCH
===========================================================
blkdiscard -z -o 0 -l 40960 /dev/nvme0n1
   blkdiscard-3809 [030] .....  1212.253701: block_bio_queue: 259,0 NS 0 + 80 [blkdiscard]
   blkdiscard-3809 [030] .....  1212.253703: block_getrq: 259,0 NS 0 + 80 [blkdiscard]
   blkdiscard-3809 [030] .....  1212.253704: block_io_start: 259,0 NS 40960 () 0 + 80 be,0,4 [blkdiscard]
   blkdiscard-3809 [030] .....  1212.253704: block_plug: [blkdiscard]
   blkdiscard-3809 [030] .....  1212.253706: block_unplug: [blkdiscard] 1
   blkdiscard-3809 [030] .....  1212.253706: block_rq_insert: 259,0 NS 40960 () 0 + 80 be,0,4 [blkdiscard]
kworker/30:1H-566  [030] .....  1212.253726: block_rq_issue: 259,0 NS 40960 () 0 + 80 be,0,4 [kworker/30:1H]
       <idle>-0    [030] d.h1.  1212.253957: block_rq_complete: 259,0 NS () 0 + 80 be,0,4 [0]
       <idle>-0    [030] dNh1.  1212.253960: block_io_done: 259,0 NS 0 () 0 + 0 none,0,0 [swapper/30]

Trace Event Breakdown:
 Event             | Device | Op  | Sector | Sectors | Byte Size | Calculation

 block_bio_queue   | 259,0  | NS  | 0      | 80      | -         | 80 × 512 = 40,960
 block_getrq       | 259,0  | NS  | 0      | 80      | -         | 80 × 512 = 40,960
 block_io_start    | 259,0  | NS  | 0      | 80      | 40960     | Direct from trace
 block_rq_insert   | 259,0  | NS  | 0      | 80      | 40960     | Direct from trace
 block_rq_issue    | 259,0  | NS  | 0      | 80      | 40960     | Direct from trace
 block_rq_complete | 259,0  | NS  | 0      | 80      | -         | 80 × 512 = 40,960
 block_io_done     | 259,0  | NS  | 0      | 0       | 0         | Completion (no data)

  Total Bytes Transferred: Sectors: 80 Bytes: 80 × 512 = 40,960 bytes

===========================================================
AFTER THIS PATCH
===========================================================
blkdiscard -z -o 0 -l 40960 /dev/nvme0n1

   blkdiscard-2477 [020] .....   960.989131: block_bio_queue: 259,0 WZS 0 + 80 [blkdiscard]
   blkdiscard-2477 [020] .....   960.989134: block_getrq: 259,0 WZS 0 + 80 [blkdiscard]
   blkdiscard-2477 [020] .....   960.989135: block_io_start: 259,0 WZS 40960 () 0 + 80 be,0,4 [blkdiscard]
   blkdiscard-2477 [020] .....   960.989138: block_plug: [blkdiscard]
   blkdiscard-2477 [020] .....   960.989140: block_unplug: [blkdiscard] 1
   blkdiscard-2477 [020] .....   960.989141: block_rq_insert: 259,0 WZS 40960 () 0 + 80 be,0,4 [blkdiscard]
kworker/20:1H-736  [020] .....   960.989166: block_rq_issue: 259,0 WZS 40960 () 0 + 80 be,0,4 [kworker/20:1H]
       <idle>-0    [020] d.h1.   960.989476: block_rq_complete: 259,0 WZS () 0 + 80 be,0,4 [0]
       <idle>-0    [020] dNh1.   960.989482: block_io_done: 259,0 WZS 0 () 0 + 0 none,0,0 [swapper/20]

Trace Event Breakdown:
 Event             | Device | Op  | Sector | Sectors | Byte Size | Calculation

 block_bio_queue   | 259,0  | WZS | 0      | 80      | -         | 80 × 512 = 40,960
 block_getrq       | 259,0  | WZS | 0      | 80      | -         | 80 × 512 = 40,960
 block_io_start    | 259,0  | WZS | 0      | 80      | 40960     | Direct from trace
 block_rq_insert   | 259,0  | WZS | 0      | 80      | 40960     | Direct from trace
 block_rq_issue    | 259,0  | WZS | 0      | 80      | 40960     | Direct from trace
 block_rq_complete | 259,0  | WZS | 0      | 80      | -         | 80 × 512 = 40,960
 block_io_done     | 259,0  | WZS | 0      | 0       | 0         | Completion (no data)

  Total Bytes Transferred: Sectors: 80 Bytes: 80 × 512 = 40,960 bytes

Tested with ftrace blktrace on NVMe devices using blkdiscard with
the -z (write-zeroes) flag.

Signed-off-by: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/uapi/linux/blktrace_api.h b/include/uapi/linux/blktrace_api.h
index 30f3d25893657255603fcbea9d033b977212be95..7c092d9f3aa4a5cfde144a77833e12000dd62f57 100644 (file)
--- a/include/uapi/linux/blktrace_api.h
+++ b/include/uapi/linux/blktrace_api.h
@@ -35,7 +35,9 @@ enum blktrace_cat {
        BLK_TC_ZONE_OPEN        = 1ull << 20,   /* zone open */
        BLK_TC_ZONE_CLOSE       = 1ull << 21,   /* zone close */
 
-       BLK_TC_END_V2           = 1ull << 21,
+       BLK_TC_WRITE_ZEROES     = 1ull << 22,   /* write-zeroes */
+
+       BLK_TC_END_V2           = 1ull << 22,
 };
 
 #define BLK_TC_SHIFT           (16)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index e4f26ddb7ee215791c6b6fe360bb079f238b6443..af8cbc8e1a7c9c87ac5b5a57aef419acbc2bf54e 100644 (file)
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -360,6 +360,9 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
        case REQ_OP_ZONE_CLOSE:
                what |= BLK_TC_ACT(BLK_TC_ZONE_CLOSE);
                break;
+       case REQ_OP_WRITE_ZEROES:
+               what |= BLK_TC_ACT(BLK_TC_WRITE_ZEROES);
+               break;
        default:
                break;
        }
@@ -1408,7 +1411,10 @@ static void fill_rwbs(char *rwbs, const struct blk_io_trace2 *t)
 
        if (tc & BLK_TC_DISCARD)
                rwbs[i++] = 'D';
-       else if (tc & BLK_TC_WRITE)
+       else if (tc & BLK_TC_WRITE_ZEROES) {
+               rwbs[i++] = 'W';
+               rwbs[i++] = 'Z';
+       } else if (tc & BLK_TC_WRITE)
                rwbs[i++] = 'W';
        else if (t->bytes)
                rwbs[i++] = 'R';
@@ -1951,6 +1957,7 @@ static const struct {
        { BLK_TC_DISCARD,       "discard"       },
        { BLK_TC_DRV_DATA,      "drv_data"      },
        { BLK_TC_FUA,           "fua"           },
+       { BLK_TC_WRITE_ZEROES,  "write-zeroes"  },
 };
 
 static int blk_trace_str2mask(const char *str)
@@ -2164,6 +2171,10 @@ void blk_fill_rwbs(char *rwbs, blk_opf_t opf)
                rwbs[i++] = 'Z';
                rwbs[i++] = 'C';
                break;
+       case REQ_OP_WRITE_ZEROES:
+               rwbs[i++] = 'W';
+               rwbs[i++] = 'Z';
+               break;
        default:
                rwbs[i++] = 'N';
        }