On Thu, 18 Apr 2024 15:02:46 +0800
Yi Liu <yi.l.liu@xxxxxxxxx> wrote:
> On 2024/4/17 00:03, Alex Williamson wrote:
> > On Fri, 12 Apr 2024 01:21:18 -0700
> > Yi Liu <yi.l.liu@xxxxxxxxx> wrote:
> >
> >> There is no helpers for user to check if a given ID is allocated or not,
> >> neither a helper to loop all the allocated IDs in an IDA and do something
> >> for cleanup. With the two needs, a helper to get the lowest allocated ID
> >> of a range can help to achieve it.
> >>
> >> Caller can check if a given ID is allocated or not by:
> >> int id = 200, rc;
> >>
> >> rc = ida_get_lowest(&ida, id, id);
> >> if (rc == id)
> >> //id 200 is used
> >> else
> >> //id 200 is not used
> >>
> >> Caller can iterate all allocated IDs by:
> >> int id = 0;
> >>
> >> while (!ida_is_empty(&pasid_ida)) {
> >> id = ida_get_lowest(pasid_ida, id, INT_MAX);
> >> if (id < 0)
> >> break;
> >> //anything to do with the allocated ID
> >> ida_free(pasid_ida, pasid);
> >> }
> >>
> >> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> >> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> >> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
> >> ---
> >> include/linux/idr.h | 1 +
> >> lib/idr.c | 67 +++++++++++++++++++++++++++++++++++++++++++++
> >> 2 files changed, 68 insertions(+)
> >>
> >> diff --git a/include/linux/idr.h b/include/linux/idr.h
> >> index da5f5fa4a3a6..1dae71d4a75d 100644
> >> --- a/include/linux/idr.h
> >> +++ b/include/linux/idr.h
> >> @@ -257,6 +257,7 @@ struct ida {
> >> int ida_alloc_range(struct ida *, unsigned int min, unsigned int max, gfp_t);
> >> void ida_free(struct ida *, unsigned int id);
> >> void ida_destroy(struct ida *ida);
> >> +int ida_get_lowest(struct ida *ida, unsigned int min, unsigned int max);
> >>
> >> /**
> >> * ida_alloc() - Allocate an unused ID.
> >> diff --git a/lib/idr.c b/lib/idr.c
> >> index da36054c3ca0..03e461242fe2 100644
> >> --- a/lib/idr.c
> >> +++ b/lib/idr.c
> >> @@ -476,6 +476,73 @@ int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max,
> >> }
> >> EXPORT_SYMBOL(ida_alloc_range);
> >>
> >> +/**
> >> + * ida_get_lowest - Get the lowest used ID.
> >> + * @ida: IDA handle.
> >> + * @min: Lowest ID to get.
> >> + * @max: Highest ID to get.
> >> + *
> >> + * Get the lowest used ID between @min and @max, inclusive. The returned
> >> + * ID will not exceed %INT_MAX, even if @max is larger.
> >> + *
> >> + * Context: Any context. Takes and releases the xa_lock.
> >> + * Return: The lowest used ID, or errno if no used ID is found.
> >> + */
> >> +int ida_get_lowest(struct ida *ida, unsigned int min, unsigned int max)
> >> +{
> >> + unsigned long index = min / IDA_BITMAP_BITS;
> >> + unsigned int offset = min % IDA_BITMAP_BITS;
> >> + unsigned long *addr, size, bit;
> >> + unsigned long flags;
> >> + void *entry;
> >> + int ret;
> >> +
> >> + if (min >= INT_MAX)
> >> + return -EINVAL;
> >> + if (max >= INT_MAX)
> >> + max = INT_MAX;
> >> +
> >
> > Could these be made consistent with the test in ida_alloc_range(), ie:
> >
> > if ((int)min < 0)
> > return -EINVAL;
> > if ((int)max < 0)
> > max = INT_MAX;
> >
>
> sure.
>
> >> + xa_lock_irqsave(&ida->xa, flags);
> >> +
> >> + entry = xa_find(&ida->xa, &index, max / IDA_BITMAP_BITS, XA_PRESENT);
> >> + if (!entry) {
> >> + ret = -ENOTTY;
> >
> > -ENOENT? Same for all below too.
>
> I see.
>
> >> + goto err_unlock;
> >> + }
> >> +
> >> + if (index > min / IDA_BITMAP_BITS)
> >> + offset = 0;
> >> + if (index * IDA_BITMAP_BITS + offset > max) {
> >> + ret = -ENOTTY;
> >> + goto err_unlock;
> >> + }
> >> +
> >> + if (xa_is_value(entry)) {
> >> + unsigned long tmp = xa_to_value(entry);
> >> +
> >> + addr = &tmp;
> >> + size = BITS_PER_XA_VALUE;
> >> + } else {
> >> + addr = ((struct ida_bitmap *)entry)->bitmap;
> >> + size = IDA_BITMAP_BITS;
> >> + }
> >> +
> >> + bit = find_next_bit(addr, size, offset);
> >> +
> >> + xa_unlock_irqrestore(&ida->xa, flags);
> >> +
> >> + if (bit == size ||
> >> + index * IDA_BITMAP_BITS + bit > max)
> >> + return -ENOTTY;
> >> +
> >> + return index * IDA_BITMAP_BITS + bit;
> >> +
> >> +err_unlock:
> >> + xa_unlock_irqrestore(&ida->xa, flags);
> >> + return ret;
> >> +}
> >> +EXPORT_SYMBOL(ida_get_lowest);
> >
> > The API is a bit awkward to me, I wonder if it might be helped with
> > some renaming and wrappers...
> >
> > int ida_find_first_range(struct ida *ida, unsigned int min, unsigned int max);
>
> ok.
>
> > bool ida_exists(struct ida *ida, unsigned int id)
> > {
> > return ida_find_first_range(ida, id, id) == id;
> > }
>
> this does helps in next patch.
>
> >
> > int ida_find_first(struct ida *ida)
> > {
> > return ida_find_first_range(ida, 0, ~0);
> > }
> >
>
> perhaps it can be added in future. This series has two usages. One is to
> check if a given ID is allocated. This can be covered by your ida_exists().
> Another usage is to loop each IDs, do detach and free. This can still use
> the ida_find_first_range() like the example in the commit message. The
> first loop starts from 0, and next would start from the last found ID.
> This may be more efficient than starts from 0 in every loop.
>
>
> > _min and _max variations of the latter would align with existing
> > ida_alloc variants, but maybe no need to add them preemptively.
>
> yes.
>
> > Possibly an ida_for_each() could be useful in the use case of
> > disassociating each id, but not required for the brute force iterative
> > method. Thanks,
>
> yep. maybe we can start with the below code, no need for ida_for_each()
> today.
>
>
> int id = 0;
>
> while (!ida_is_empty(&pasid_ida)) {
> id = ida_find_first_range(pasid_ida, id, INT_MAX);
You've actually already justified the _min function here:
static inline int ida_find_first_min(struct ida *ida, unsigned int min)
{
return ida_find_first_range(ida, min, ~0);
}
Thanks,
Alex
> if (unlikely(WARN_ON(id < 0))
> break;
> iommufd_device_pasid_detach();
> ida_free(pasid_ida, pasid);
> }
>
> >
> >> +
> >> /**
> >> * ida_free() - Release an allocated ID.
> >> * @ida: IDA handle.
> >
>
