The patch titled
Subject: mm/cma: expose all pages to the buddy if activation of an area fails
has been added to the -mm tree. Its filename is
mm-cma-expose-all-pages-to-the-buddy-if-activation-of-an-area-fails.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-cma-expose-all-pages-to-the-buddy-if-activation-of-an-area-fails.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-cma-expose-all-pages-to-the-buddy-if-activation-of-an-area-fails.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/cma: expose all pages to the buddy if activation of an area fails
Right now, if activation fails, we might already have exposed some pages
to the buddy for CMA use (although they will never get actually used by
CMA), and some pages won't be exposed to the buddy at all.
Let's check for "single zone" early and on error, don't expose any pages
for CMA use - instead, expose them to the buddy available for any use.
Simply call free_reserved_page() on every single page - easier than going
via free_reserved_area(), converting back and forth between pfns and virt
addresses.
In addition, make sure to fixup totalcma_pages properly.
Example: 6 GiB QEMU VM with "... hugetlb_cma=2G movablecore=20% ...":
[ 0.006891] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node
[ 0.006893] cma: Reserved 2048 MiB at 0x0000000100000000
[ 0.006893] hugetlb_cma: reserved 2048 MiB on node 0
...
[ 0.175433] cma: CMA area hugetlb0 could not be activated
Before this patch:
# cat /proc/meminfo
MemTotal: 5867348 kB
MemFree: 5692808 kB
MemAvailable: 5542516 kB
...
CmaTotal: 2097152 kB
CmaFree: 1884160 kB
After this patch:
# cat /proc/meminfo
MemTotal: 6077308 kB
MemFree: 5904208 kB
MemAvailable: 5747968 kB
...
CmaTotal: 0 kB
CmaFree: 0 kB
Note: cma_init_reserved_mem() makes sure that we always cover full
pageblocks / MAX_ORDER - 1 pages.
Link: https://lkml.kernel.org/r/20210127101813.6370-2-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/cma.c | 43 +++++++++++++++++++++----------------------
1 file changed, 21 insertions(+), 22 deletions(-)
--- a/mm/cma.c~mm-cma-expose-all-pages-to-the-buddy-if-activation-of-an-area-fails
+++ a/mm/cma.c
@@ -94,34 +94,29 @@ static void cma_clear_bitmap(struct cma
static void __init cma_activate_area(struct cma *cma)
{
- unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
- unsigned i = cma->count >> pageblock_order;
+ unsigned long base_pfn = cma->base_pfn, pfn;
struct zone *zone;
cma->bitmap = bitmap_zalloc(cma_bitmap_maxno(cma), GFP_KERNEL);
if (!cma->bitmap)
goto out_error;
- WARN_ON_ONCE(!pfn_valid(pfn));
- zone = page_zone(pfn_to_page(pfn));
-
- do {
- unsigned j;
-
- base_pfn = pfn;
- for (j = pageblock_nr_pages; j; --j, pfn++) {
- WARN_ON_ONCE(!pfn_valid(pfn));
- /*
- * alloc_contig_range requires the pfn range
- * specified to be in the same zone. Make this
- * simple by forcing the entire CMA resv range
- * to be in the same zone.
- */
- if (page_zone(pfn_to_page(pfn)) != zone)
- goto not_in_zone;
- }
- init_cma_reserved_pageblock(pfn_to_page(base_pfn));
- } while (--i);
+ /*
+ * alloc_contig_range() requires the pfn range specified to be in the
+ * same zone. Simplify by forcing the entire CMA resv range to be in the
+ * same zone.
+ */
+ WARN_ON_ONCE(!pfn_valid(base_pfn));
+ zone = page_zone(pfn_to_page(base_pfn));
+ for (pfn = base_pfn + 1; pfn < base_pfn + cma->count; pfn++) {
+ WARN_ON_ONCE(!pfn_valid(pfn));
+ if (page_zone(pfn_to_page(pfn)) != zone)
+ goto not_in_zone;
+ }
+
+ for (pfn = base_pfn; pfn < base_pfn + cma->count;
+ pfn += pageblock_nr_pages)
+ init_cma_reserved_pageblock(pfn_to_page(pfn));
mutex_init(&cma->lock);
@@ -135,6 +130,10 @@ static void __init cma_activate_area(str
not_in_zone:
bitmap_free(cma->bitmap);
out_error:
+ /* Expose all pages to the buddy, they are useless for CMA. */
+ for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++)
+ free_reserved_page(pfn_to_page(pfn));
+ totalcma_pages -= cma->count;
cma->count = 0;
pr_err("CMA area %s could not be activated\n", cma->name);
return;
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
video-fbdev-acornfb-remove-free_unused_pages.patch
mm-simplify-free_highmem_page-and-free_reserved_page.patch
mm-cma-expose-all-pages-to-the-buddy-if-activation-of-an-area-fails.patch
mm-page_alloc-count-cma-pages-per-zone-and-print-them-in-proc-zoneinfo.patch
mm-memory_hotplug-memhp_merge_resource-mhp_merge_resource.patch
