[PATCH net-next 05/12] mm: Make the page_frag_cache allocator handle __GFP_ZERO itself

[David Howells]

Make the page_frag_cache allocator handle __GFP_ZERO itself rather than
passing it off to the page allocator.  There may be a mix of callers, some
specifying __GFP_ZERO and some not - and even if all specify __GFP_ZERO, we
might refurbish the page, in which case the returned memory doesn't get
cleared.

This is a potential bug in the nvme over TCP driver.

Signed-off-by: David Howells <dhowells at redhat.com>
cc: "David S. Miller" <davem at davemloft.net>
cc: Eric Dumazet <edumazet at google.com>
cc: Jakub Kicinski <kuba at kernel.org>
cc: Paolo Abeni <pabeni at redhat.com>
cc: Jens Axboe <axboe at kernel.dk>
cc: Jeroen de Borst <jeroendb at google.com>
cc: Catherine Sullivan <csully at google.com>
cc: Shailend Chand <shailend at google.com>
cc: Felix Fietkau <nbd at nbd.name>
cc: John Crispin <john at phrozen.org>
cc: Sean Wang <sean.wang at mediatek.com>
cc: Mark Lee <Mark-MC.Lee at mediatek.com>
cc: Lorenzo Bianconi <lorenzo at kernel.org>
cc: Matthias Brugger <matthias.bgg at gmail.com>
cc: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
cc: Keith Busch <kbusch at kernel.org>
cc: Jens Axboe <axboe at fb.com>
cc: Christoph Hellwig <hch at lst.de>
cc: Sagi Grimberg <sagi at grimberg.me>
cc: Chaitanya Kulkarni <kch at nvidia.com>
cc: Andrew Morton <akpm at linux-foundation.org>
cc: Matthew Wilcox <willy at infradead.org>
cc: netdev at vger.kernel.org
cc: linux-arm-kernel at lists.infradead.org
cc: linux-mediatek at lists.infradead.org
cc: linux-nvme at lists.infradead.org
cc: linux-mm at kvack.org
---
 mm/page_frag_alloc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/page_frag_alloc.c b/mm/page_frag_alloc.c
index ffd68bfb677d..2b73c7f5d9a9 100644
--- a/mm/page_frag_alloc.c
+++ b/mm/page_frag_alloc.c
@@ -23,7 +23,10 @@ static struct folio *page_frag_cache_refill(struct page_frag_cache *nc,
 					    gfp_t gfp_mask)
 {
 	struct folio *folio = NULL;
-	gfp_t gfp = gfp_mask;
+	gfp_t gfp;
+
+	gfp_mask &= ~__GFP_ZERO;
+	gfp = gfp_mask;
 
 #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
 	gfp_mask |= __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC;
@@ -71,6 +74,7 @@ void *page_frag_alloc_align(struct page_frag_cache *nc,
 {
 	struct folio *folio = nc->folio;
 	size_t offset;
+	void *p;
 
 	WARN_ON_ONCE(!is_power_of_2(align));
 
@@ -133,7 +137,10 @@ void *page_frag_alloc_align(struct page_frag_cache *nc,
 	offset &= ~(align - 1);
 	nc->offset = offset;
 
-	return folio_address(folio) + offset;
+	p = folio_address(folio) + offset;
+	if (gfp_mask & __GFP_ZERO)
+		return memset(p, 0, fragsz);
+	return p;
 }
 EXPORT_SYMBOL(page_frag_alloc_align);