On Thu, Oct 17, 2019 at 10:28:00AM +0800, Qu Wenruo wrote:
> [BUG]
> For btrfs related events, there is a field for fsid, but perf never
> parse it correctly.
>
> # perf trace -e btrfs:qgroup_meta_convert xfs_io -f -c "pwrite 0 4k" \
> /mnt/btrfs/file1
> 0.000 xfs_io/77915 btrfs:qgroup_meta_reserve:(nil)U: refroot=5(FS_TREE) type=0x0 diff=2
> ^^^^^^ Not a correct UUID
> ...
>
> [CAUSE]
> The pretty_print() function doesn't handle the %pU format correctly.
> In fact it doesn't handle %pU as uuid at all.
>
> [FIX]
> Add a new function, print_uuid_arg(), to handle %pU correctly.
>
> Now perf trace can at least print fsid correctly:
> 0.000 xfs_io/79619 btrfs:qgroup_meta_reserve:23ad1511-dd83-47d4-a79c-e96625a15a6e refroot=5(FS_TREE) type=0x0 diff=2
>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> Changelog:
> v2:
> - Use more comment explaining the finetunings we skipped for %pU*
> - Use more elegant way to output uuid string
> ---
> tools/lib/traceevent/event-parse.c | 56 ++++++++++++++++++++++++++++++
> 1 file changed, 56 insertions(+)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index d948475585ce..3c9473f46efe 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -18,6 +18,7 @@
> #include <errno.h>
> #include <stdint.h>
> #include <limits.h>
> +#include <linux/uuid.h>
> #include <linux/time64.h>
>
> #include <netinet/in.h>
> @@ -4508,6 +4509,45 @@ get_bprint_format(void *data, int size __maybe_unused,
> return format;
> }
>
> +static void print_uuid_arg(struct trace_seq *s, void *data, int size,
> + struct tep_event *event, struct tep_print_arg *arg)
> +{
> + unsigned char *buf;
> + int i;
> +
> + if (arg->type != TEP_PRINT_FIELD) {
> + trace_seq_printf(s, "ARG TYPE NOT FIELID but %d", arg->type);
> + return;
> + }
> +
> + if (!arg->field.field) {
> + arg->field.field = tep_find_any_field(event, arg->field.name);
> + if (!arg->field.field) {
> + do_warning("%s: field %s not found",
> + __func__, arg->field.name);
> + return;
> + }
> + }
> + if (arg->field.field->size < 16) {
> + trace_seq_printf(s, "INVALID UUID: size have %u expect 16",
> + arg->field.field->size);
> + return;
> + }
So if there's an interest for very compact printing loop, something like
this produces the same output:
for (i = 0; i < 8; i++) {
printf("%02X", buf[i]);
printf("%02X", buf[i]);
if (1 <= i && i <= 4)
putchar('-');
}
"23ad 1511 - dd83 - 47d4 - a79c - e966 25a1 5a6e"
0 1 2 3 4 5 6 7
IOW, split into pairs and print dash after a few of them.
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