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authorDan Williams <dan.j.williams@intel.com>2022-11-03 17:31:00 -0700
committerDan Williams <dan.j.williams@intel.com>2022-11-04 16:03:43 -0700
commit8f401ec1c8975eabfe4c089de91cbe058deabf71 (patch)
treecc1d28f74278adbc2279efa2a926194f16b6f0f4 /drivers/cxl
parente4f6dfa9ef756a3934a4caf618b1e86e9e8e21d0 (diff)
cxl/region: Recycle region ids
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: 779dd20cfb56 ("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>
Diffstat (limited to 'drivers/cxl')
-rw-r--r--drivers/cxl/core/region.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index c0253de74945..f9ae5ad284ff 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -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;