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sbitmap: add __sbitmap_queue_get_batch()

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The block layer tag allocation batching still calls into sbitmap to get
each tag, but we can improve on that. Add __sbitmap_queue_get_batch(),
which returns a mask of tags all at once, along with an offset for
those tags.

An example return would be 0xff, where bits 0..7 are set, with
tag_offset == 128. The valid tags in this case would be 128..135.

A batch is specific to an individual sbitmap_map, hence it cannot be
larger than that. The requested number of tags is automatically reduced
to the max that can be satisfied with a single map.

On failure, 0 is returned. Caller should fall back to single tag
allocation at that point/

Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2021-10-09 13:02:23 -06:00
parent 8971a3b7f1
commit 9672b0d437
2 changed files with 64 additions and 0 deletions
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13
include/linux/sbitmap.h
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@@ -426,6 +426,19 @@ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth);
*/
int __sbitmap_queue_get(struct sbitmap_queue *sbq);
/**
* __sbitmap_queue_get_batch() - Try to allocate a batch of free bits
* @sbq: Bitmap queue to allocate from.
* @nr_tags: number of tags requested
* @offset: offset to add to returned bits
*
* Return: Mask of allocated tags, 0 if none are found. Each tag allocated is
* a bit in the mask returned, and the caller must add @offset to the value to
* get the absolute tag value.
*/
unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags,
unsigned int *offset);
/**
* __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct
* sbitmap_queue, limiting the depth used from each word, with preemption