linux-kernel - [PATCH] alloc_tag: Handle incomplete bulk allocations in vm_module_tags

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Message-ID: <20250409195448.3697351-1-tjmercier@google.com>
Date: Wed,  9 Apr 2025 19:54:47 +0000
From: "T.J. Mercier" <tjmercier@...gle.com>
To: Suren Baghdasaryan <surenb@...gle.com>, Kent Overstreet <kent.overstreet@...ux.dev>, 
	Andrew Morton <akpm@...ux-foundation.org>
Cc: "T.J. Mercier" <tjmercier@...gle.com>, Janghyuck Kim <janghyuck.kim@...sung.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH] alloc_tag: Handle incomplete bulk allocations in vm_module_tags_populate

alloc_pages_bulk_node may partially succeed and allocate fewer than the
requested nr_pages. There are several conditions under which this can
occur, but we have encountered the case where CONFIG_PAGE_OWNER is
enabled causing all bulk allocations to always fallback to single page
allocations due to commit 187ad460b841 ("mm/page_alloc: avoid page
allocator recursion with pagesets.lock held").

Currently vm_module_tags_populate immediately fails when
alloc_pages_bulk_node returns fewer than the requested number of pages.
This patch causes vm_module_tags_populate to retry bulk allocations for
the remaining memory instead.

Reported-by: Janghyuck Kim <janghyuck.kim@...sung.com>
Signed-off-by: T.J. Mercier <tjmercier@...gle.com>
---
 lib/alloc_tag.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 1d893e313614..25ecc1334b67 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -422,11 +422,20 @@ static int vm_module_tags_populate(void)
 		unsigned long old_shadow_end = ALIGN(phys_end, MODULE_ALIGN);
 		unsigned long new_shadow_end = ALIGN(new_end, MODULE_ALIGN);
 		unsigned long more_pages;
-		unsigned long nr;
+		unsigned long nr = 0;
 
 		more_pages = ALIGN(new_end - phys_end, PAGE_SIZE) >> PAGE_SHIFT;
-		nr = alloc_pages_bulk_node(GFP_KERNEL | __GFP_NOWARN,
-					   NUMA_NO_NODE, more_pages, next_page);
+		while (nr < more_pages) {
+			unsigned long allocated;
+
+			allocated = alloc_pages_bulk_node(GFP_KERNEL | __GFP_NOWARN,
+				NUMA_NO_NODE, more_pages - nr, next_page + nr);
+
+			if (!allocated)
+				break;
+			nr += allocated;
+		}
+
 		if (nr < more_pages ||
 		    vmap_pages_range(phys_end, phys_end + (nr << PAGE_SHIFT), PAGE_KERNEL,
 				     next_page, PAGE_SHIFT) < 0) {
-- 
2.49.0.504.g3bcea36a83-goog