Re: [PATCH v3 4/6] alloc_tag: add accuracy based filtering to ioctl

[Abhishek Bapat]

Btw, Sashiko left a comment in this patch stating that the value of
"inaccurate" is echoed back to the user. But since it's an input-only
parameter, that is expected. Changing it in the kernel would be
unexpected. Hence, I will ignore that comment.

On Mon, Jun 8, 2026 at 1:55 PM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:
>
> On Mon, Jun 8, 2026 at 1:25 AM Hao Ge <hao.ge@xxxxxxxxx> wrote:
> >
> >
> > On 2026/6/8 14:22, Hao Ge wrote:
> > > Hi Abhishek
> > >
> > >
> > > On 2026/6/6 07:36, Abhishek Bapat wrote:
> > >> Extend the allocinfo filtering mechanism to allow users to filter tags
> > >> based on their accuracy.
> > >>
> > >> Signed-off-by: Abhishek Bapat <abhishekbapat@xxxxxxxxxx>
> > >> ---
> > >>   include/uapi/linux/alloc_tag.h | 3 +++
> > >>   lib/alloc_tag.c                | 8 ++++++++
> > >>   2 files changed, 11 insertions(+)
> > >>
> > >> diff --git a/include/uapi/linux/alloc_tag.h
> > >> b/include/uapi/linux/alloc_tag.h
> > >> index 0e648192df4d..42445bdb11c5 100644
> > >> --- a/include/uapi/linux/alloc_tag.h
> > >> +++ b/include/uapi/linux/alloc_tag.h
> > >> @@ -20,6 +20,7 @@ struct allocinfo_tag {
> > >>       char function[ALLOCINFO_STR_SIZE];
> > >>       char filename[ALLOCINFO_STR_SIZE];
> > >>       __u64 lineno;
> > >> +    __u64 inaccurate;
> > >
> > >
> > > I was wondering if it would make sense to define inaccurate as a flags
> > > field
> > >
> > > (e.g. __u64 flags with ALLOCINFO_TAG_F_INACCURATE (1 <<0)),
> > >
> > > so that only bit 0 is used today and the upper bits are reserved for
> > > future use,
> > >
> > > aligning with current kernel codebase.
> > >
> > > This design also allows for better extensibility if we need to
> > >
> > > add new flags for any reason in the future.
> > >
> > > We also need to add flag validity checks if we go this route.
> > >
> > And I've reviewed the issue reported by Sashiko, and I think it's valid.
> >
> > When we expand the allocinfo_tag_data structure
> >
> > struct allocinfo_tag_data{
> >
> >      char modname[64];
> >
> >      char function[64];
> >
> >      char filename[64];
> >
> >      __u64 lineno;
> >
> >      __u64 inaccurate;
> >
> >      __u64 bytes;
> >
> >      __u64 calls;
> >
> >      __u8 accurate;
> >    /* padding */
> >
> > }
> >
> > I think user space may see two fields related to inaccuracy.
>
> Yes but one field (inside allocinfo_tag) is the input parameter which
> user provides to specify the filtering criteria and the other is the
> returned tag information. It's similar to any other tag attribute
> which you can be included in the filters.
>
> >
> > How do you like these modifications?
> >
> >
> > diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h
> > --- a/include/uapi/linux/alloc_tag.h
> > +++ b/include/uapi/linux/alloc_tag.h
> > @@ -20,7 +20,6 @@ struct allocinfo_tag {
> >       char function[ALLOCINFO_STR_SIZE];
> >       char filename[ALLOCINFO_STR_SIZE];
> >       __u64 lineno;
> > -    __u64 inaccurate;
> >   };
> >
> >   /* The alignment ensures 32-bit compatible interfaces are not broken */
> > @@ -40,7 +39,7 @@ enum {
> >       ALLOCINFO_FILTER_FUNCTION,
> >       ALLOCINFO_FILTER_FILENAME,
> >       ALLOCINFO_FILTER_LINENO,
> > -    ALLOCINFO_FILTER_INACCURATE,
> > +    ALLOCINFO_FILTER_FLAGS,
> >       ALLOCINFO_FILTER_MIN_SIZE,
> >       ALLOCINFO_FILTER_MAX_SIZE,
> >       __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE
> > @@ -50,16 +49,20 @@ enum {
> >   #define ALLOCINFO_FILTER_MASK_FUNCTION        (1 <<
> > ALLOCINFO_FILTER_FUNCTION)
> >   #define ALLOCINFO_FILTER_MASK_FILENAME        (1 <<
> > ALLOCINFO_FILTER_FILENAME)
> >   #define ALLOCINFO_FILTER_MASK_LINENO        (1 << ALLOCINFO_FILTER_LINENO)
> > -#define ALLOCINFO_FILTER_MASK_INACCURATE    (1 <<
> > ALLOCINFO_FILTER_INACCURATE)
> > +#define ALLOCINFO_FILTER_MASK_FLAGS        (1 << ALLOCINFO_FILTER_FLAGS)
> >   #define ALLOCINFO_FILTER_MASK_MIN_SIZE        (1 <<
> > ALLOCINFO_FILTER_MIN_SIZE)
> >   #define ALLOCINFO_FILTER_MASK_MAX_SIZE        (1 <<
> > ALLOCINFO_FILTER_MAX_SIZE)
> >
> >   #define ALLOCINFO_FILTER_MASKS \
> >       ((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1)
> >
> > +#define ALLOCINFO_FILTER_F_INACCURATE    (1ULL << 0)
> > +#define ALLOCINFO_FILTER_FLAGS_ALL ALLOCINFO_FILTER_F_INACCURATE
> > +
> >   struct allocinfo_filter {
> >       __u64 mask; /* bitmask of the filter fields used */
> >       struct allocinfo_tag fields;
> > +    __u64 flags; /* bitmask of ALLOCINFO_FILTER_F_* */
> >       __u64 min_size;
> >       __u64 max_size;
> >   };
> > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> > --- a/lib/alloc_tag.c
> > +++ b/lib/alloc_tag.c
> > @@ -249,8 +249,6 @@ static bool matches_filter(struct codetag *ct,
> > struct allocinfo_filter *filter,
> >                  struct alloc_tag_counters *counters,
> >                  bool *fetched_counters)
> >   {
> > -    bool inaccurate;
> > -
> >       if (!filter || !filter->mask)
> >           return true;
> >
> > @@ -277,10 +275,11 @@ static bool matches_filter(struct codetag *ct,
> > struct allocinfo_filter *filter,
> >           ct->lineno != filter->fields.lineno)
> >           return false;
> >
> > -    if (filter->mask & ALLOCINFO_FILTER_MASK_INACCURATE) {
> > -        inaccurate = !!(ct->flags & CODETAG_FLAG_INACCURATE);
> > -        if (inaccurate != !!(filter->fields.inaccurate))
> > -            return false;
> > +    if (filter->mask & ALLOCINFO_FILTER_MASK_FLAGS) {
> > +        if (filter->flags & ALLOCINFO_FILTER_F_INACCURATE) {
> > +            if (!(ct->flags & CODETAG_FLAG_INACCURATE))
>
> How would you filter records which have only accurate data?
>
> Overall I would prefer ALLOCINFO_FILTER_MASK_INACCURATE rather than
> ALLOCINFO_FILTER_MASK_FLAGS. The fact that this attribute is a
> single-bit flag is a technical detail. It's still a tag attribuite
> like file and module names and IMO deserves its own filter.
>
>
>
> > +                return false;
> > +        }
> >       }
> >
> >       if (filter->mask & (ALLOCINFO_FILTER_MASK_MIN_SIZE |
> > ALLOCINFO_FILTER_MASK_MAX_SIZE)) {
> > @@ -318,6 +317,10 @@ static int allocinfo_ioctl_get_at(struct seq_file
> > *m, void __user *arg)
> >       if (params.filter.mask & ~ALLOCINFO_FILTER_MASKS)
> >           return -EINVAL;
> >
> > +    if ((params.filter.mask & ALLOCINFO_FILTER_MASK_FLAGS) &&
> > +        (params.filter.flags & ~ALLOCINFO_FILTER_FLAGS_ALL))
> > +        return -EINVAL;
> > +
> >       if ((params.filter.mask & ALLOCINFO_FILTER_MASK_MIN_SIZE) &&
> >           (params.filter.mask & ALLOCINFO_FILTER_MASK_MAX_SIZE) &&
> >           params.filter.min_size > params.filter.max_size)
> >
> >
> > Thanks
> >
> > Best Regards
> >
> > Hao
> >
> >
> > >
> > > Thanks
> > >
> > > Best Regards
> > >
> > > Hao
> > >
> > >
> > >>   };
> > >>     /* The alignment ensures 32-bit compatible interfaces are not
> > >> broken */
> > >> @@ -39,6 +40,7 @@ enum {
> > >>       ALLOCINFO_FILTER_FUNCTION,
> > >>       ALLOCINFO_FILTER_FILENAME,
> > >>       ALLOCINFO_FILTER_LINENO,
> > >> +    ALLOCINFO_FILTER_INACCURATE,
> > >>       ALLOCINFO_FILTER_MIN_SIZE,
> > >>       ALLOCINFO_FILTER_MAX_SIZE,
> > >>       __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE
> > >> @@ -48,6 +50,7 @@ enum {
> > >>   #define ALLOCINFO_FILTER_MASK_FUNCTION        (1 <<
> > >> ALLOCINFO_FILTER_FUNCTION)
> > >>   #define ALLOCINFO_FILTER_MASK_FILENAME        (1 <<
> > >> ALLOCINFO_FILTER_FILENAME)
> > >>   #define ALLOCINFO_FILTER_MASK_LINENO        (1 <<
> > >> ALLOCINFO_FILTER_LINENO)
> > >> +#define ALLOCINFO_FILTER_MASK_INACCURATE    (1 <<
> > >> ALLOCINFO_FILTER_INACCURATE)
> > >>   #define ALLOCINFO_FILTER_MASK_MIN_SIZE        (1 <<
> > >> ALLOCINFO_FILTER_MIN_SIZE)
> > >>   #define ALLOCINFO_FILTER_MASK_MAX_SIZE        (1 <<
> > >> ALLOCINFO_FILTER_MAX_SIZE)
> > >>   diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> > >> index ddc6946f56ab..cbcd12c4ef9c 100644
> > >> --- a/lib/alloc_tag.c
> > >> +++ b/lib/alloc_tag.c
> > >> @@ -249,6 +249,8 @@ static bool matches_filter(struct codetag *ct,
> > >> struct allocinfo_filter *filter,
> > >>                  struct alloc_tag_counters *counters,
> > >>                  bool *fetched_counters)
> > >>   {
> > >> +    bool inaccurate;
> > >> +
> > >>       if (!filter || !filter->mask)
> > >>           return true;
> > >>   @@ -275,6 +277,12 @@ static bool matches_filter(struct codetag *ct,
> > >> struct allocinfo_filter *filter,
> > >>           ct->lineno != filter->fields.lineno)
> > >>           return false;
> > >>   +    if (filter->mask & ALLOCINFO_FILTER_MASK_INACCURATE) {
> > >> +        inaccurate = !!(ct->flags & CODETAG_FLAG_INACCURATE);
> > >> +        if (inaccurate != !!(filter->fields.inaccurate))
> > >> +            return false;
> > >> +    }
> > >> +
> > >>       if (filter->mask & (ALLOCINFO_FILTER_MASK_MIN_SIZE |
> > >> ALLOCINFO_FILTER_MASK_MAX_SIZE)) {
> > >>           if (!*fetched_counters) {
> > >>               *counters = allocinfo_prefetch_counters(ct);