John Garry <john.g.garry@xxxxxxxxxx> writes:
> On 03/04/2025 06:28, Ritesh Harjani (IBM) wrote:
>> Filesystems like XFS can implement atomic write I/O using either REQ_ATOMIC
>> flag set in the bio or via CoW operation. It will be useful if we have a
>> flag in trace events to distinguish between the two.
>
> I suppose that this could be useful. So far I test with block driver
> traces, i.e. NVMe or SCSI internal traces, just to ensure that we see
> the requests sent as expected
>
Right.
> This patch adds
>> char 'a' to rwbs field of the trace events if REQ_ATOMIC flag is set in
>> the bio.
>
> All others use uppercase characters, so I suggest that you continue to
> use that.
It will be good to know on whether only uppercase characters are allowed
or we are good with smallcase characters too?
> Since 'A' is already used, how about 'U' for untorn? Or 'T'
> for aTOMic :)
>
If 'a' is not allowed, then we can change it to 'T' maybe.
-ritesh
>>
>> <W/ REQ_ATOMIC>
>> =================
>> xfs_io-1107 [002] ..... 406.206441: block_rq_issue: 8,48 WSa 16384 () 768 + 32 none,0,0 [xfs_io]
>> <idle>-0 [002] ..s1. 406.209918: block_rq_complete: 8,48 WSa () 768 + 32 none,0,0 [0]
>>
>> <W/O REQ_ATOMIC>
>> ===============
>> xfs_io-1108 [002] ..... 411.212317: block_rq_issue: 8,48 WS 16384 () 1024 + 32 none,0,0 [xfs_io]
>> <idle>-0 [002] ..s1. 411.215842: block_rq_complete: 8,48 WS () 1024 + 32 none,0,0 [0]
>>
>> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
>> ---
>> include/trace/events/block.h | 2 +-
>> kernel/trace/blktrace.c | 2 ++
>> 2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/trace/events/block.h b/include/trace/events/block.h
>> index bd0ea07338eb..de538b110ea1 100644
>> --- a/include/trace/events/block.h
>> +++ b/include/trace/events/block.h
>> @@ -11,7 +11,7 @@
>> #include <linux/tracepoint.h>
>> #include <uapi/linux/ioprio.h>
>>
>> -#define RWBS_LEN 8
>> +#define RWBS_LEN 9
>>
>> #define IOPRIO_CLASS_STRINGS \
>> { IOPRIO_CLASS_NONE, "none" }, \
>> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
>> index 3679a6d18934..6badf296ab2b 100644
>> --- a/kernel/trace/blktrace.c
>> +++ b/kernel/trace/blktrace.c
>> @@ -1896,6 +1896,8 @@ void blk_fill_rwbs(char *rwbs, blk_opf_t opf)
>> rwbs[i++] = 'S';
>> if (opf & REQ_META)
>> rwbs[i++] = 'M';
>> + if (opf & REQ_ATOMIC)
>> + rwbs[i++] = 'a';
>>
>> rwbs[i] = '\0';
>> }
>> --
>> 2.48.1
>>
