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;
> + 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.
> + 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);
bool ida_exists(struct ida *ida, unsigned int id)
{
return ida_find_first_range(ida, id, id) == id;
}
int ida_find_first(struct ida *ida)
{
return ida_find_first_range(ida, 0, ~0);
}
_min and _max variations of the latter would align with existing
ida_alloc variants, but maybe no need to add them preemptively.
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,
Alex
> +
> /**
> * ida_free() - Release an allocated ID.
> * @ida: IDA handle.
