From 061478438d04779181c2ce4d7ffeeca343a70a98 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Wed, 14 Jul 2021 21:26:52 -0700 Subject: mm/page_alloc: further fix __alloc_pages_bulk() return value The author of commit b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after checking populated elements") was possibly confused by the mixture of return values throughout the function. The API contract is clear that the function "Returns the number of pages on the list or array." It does not list zero as a unique return value with a special meaning. Therefore zero is a plausible return value only if @nr_pages is zero or less. Clean up the return logic to make it clear that the returned value is always the total number of pages in the array/list, not the number of pages that were allocated during this call. The only change in behavior with this patch is the value returned if prepare_alloc_pages() fails. To match the API contract, the number of pages currently in the array/list is returned in this case. The call site in __page_pool_alloc_pages_slow() also seems to be confused on this matter. It should be attended to by someone who is familiar with that code. [mel@techsingularity.net: Return nr_populated if 0 pages are requested] Link: https://lkml.kernel.org/r/20210713152100.10381-4-mgorman@techsingularity.net Signed-off-by: Chuck Lever Signed-off-by: Mel Gorman Acked-by: Jesper Dangaard Brouer Cc: Desmond Cheong Zhi Xi Cc: Zhang Qiang Cc: Yanfei Xu Cc: Matteo Croce Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) (limited to 'mm') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 4d79e357a4ba..3e97e68aef7a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5221,9 +5221,6 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, unsigned int alloc_flags = ALLOC_WMARK_LOW; int nr_populated = 0, nr_account = 0; - if (unlikely(nr_pages <= 0)) - return 0; - /* * Skip populated array elements to determine if any pages need * to be allocated before disabling IRQs. @@ -5231,9 +5228,13 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, while (page_array && nr_populated < nr_pages && page_array[nr_populated]) nr_populated++; + /* No pages requested? */ + if (unlikely(nr_pages <= 0)) + goto out; + /* Already populated array? */ if (unlikely(page_array && nr_pages - nr_populated == 0)) - return nr_populated; + goto out; /* Use the single page allocator for one page. */ if (nr_pages - nr_populated == 1) @@ -5255,7 +5256,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, gfp &= gfp_allowed_mask; alloc_gfp = gfp; if (!prepare_alloc_pages(gfp, 0, preferred_nid, nodemask, &ac, &alloc_gfp, &alloc_flags)) - return nr_populated; + goto out; gfp = alloc_gfp; /* Find an allowed local zone that meets the low watermark. */ @@ -5323,6 +5324,7 @@ unsigned long __alloc_pages_bulk(gfp_t gfp, int preferred_nid, __count_zid_vm_events(PGALLOC, zone_idx(zone), nr_account); zone_statistics(ac.preferred_zoneref->zone, zone, nr_account); +out: return nr_populated; failed_irq: @@ -5338,7 +5340,7 @@ failed: nr_populated++; } - return nr_populated; + goto out; } EXPORT_SYMBOL_GPL(__alloc_pages_bulk); -- cgit v1.2.3