From 14891b8c5748d6d56565e9504d1a7da93a7c395f Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Thu, 3 Nov 2022 17:31:00 -0700 Subject: [PATCH] cxl/region: Recycle region ids [ Upstream commit 8f401ec1c8975eabfe4c089de91cbe058deabf71 ] 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 Cc: Jonathan Cameron Fixes: 779dd20cfb56 ("cxl/region: Add region creation support") Reviewed-by: Dave Jiang Reviewed-by: Vishal Verma Link: https://lore.kernel.org/r/166752186062.947915.13200195701224993317.stgit@dwillia2-xfh.jf.intel.com Signed-off-by: Dan Williams Signed-off-by: Sasha Levin --- drivers/cxl/core/region.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index 6b7fb955a05ac..78344e4d4215b 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -1533,9 +1533,24 @@ 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); } @@ -1597,6 +1612,11 @@ 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; -- 2.47.3