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cxl/region: Recycle region ids

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At region creation time the next region-id is atomically cached so that
there is predictability of region device names. If that region is
destroyed and then a new one is created the region id increments. That
ends up looking like a memory leak, or is otherwise surprising that
identifiers roll forward even after destroying all previously created
regions.

Try to reuse rather than free old region ids at region release time.

While this fixes a cosmetic issue, the needlessly advancing memory
region-id gives the appearance of a memory leak, hence the "Fixes" tag,
but no "Cc: stable" tag.

Cc: Ben Widawsky <bwidawsk@kernel.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Fixes: 779dd20cfb ("cxl/region: Add region creation support")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/166752186062.947915.13200195701224993317.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams 2022-11-03 17:31:00 -07:00
parent e4f6dfa9ef
commit 8f401ec1c8
1 changed files with 20 additions and 0 deletions
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20
drivers/cxl/core/region.c
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@ -1534,9 +1534,24 @@ static const struct attribute_group *region_groups[] = {
static void cxl_region_release(struct device *dev)
{
struct cxl_root_decoder *cxlrd = to_cxl_root_decoder(dev->parent);
struct cxl_region *cxlr = to_cxl_region(dev);
int id = atomic_read(&cxlrd->region_id);
/*
* Try to reuse the recently idled id rather than the cached
* next id to prevent the region id space from increasing
* unnecessarily.
*/
if (cxlr->id < id)
if (atomic_try_cmpxchg(&cxlrd->region_id, &id, cxlr->id)) {
memregion_free(id);
goto out;
}
memregion_free(cxlr->id);
out:
put_device(dev->parent);
kfree(cxlr);
}
@ -1598,6 +1613,11 @@ static struct cxl_region *cxl_region_alloc(struct cxl_root_decoder *cxlrd, int i
device_initialize(dev);
lockdep_set_class(&dev->mutex, &cxl_region_key);
dev->parent = &cxlrd->cxlsd.cxld.dev;
/*
* Keep root decoder pinned through cxl_region_release to fixup
* region id allocations
*/
get_device(dev->parent);
device_set_pm_not_required(dev);
dev->bus = &cxl_bus_type;
dev->type = &cxl_region_type;