linux-kernel - Re: weird allocation pattern in alloc_ila

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Date:   Fri, 6 Jan 2017 13:16:42 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tom Herbert <tom@...bertland.com>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: weird allocation pattern in alloc_ila_locks

I was thinking about the rhashtable which was the source of the c&p and
it can be simplified as well.
---
>From 555543604f5f020284ea85d928d52f6a55fde7ca Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.com>
Date: Fri, 6 Jan 2017 13:12:31 +0100
Subject: [PATCH] rhashtable: simplify a strange allocation pattern

alloc_bucket_locks allocation pattern is quite unusual. We are
preferring vmalloc when CONFIG_NUMA is enabled which doesn't make much
sense because there is no special NUMA locality handled in that code
path. Let's just simplify the code and use kvmalloc helper, which is a
transparent way to use kmalloc with vmalloc fallback, if the caller
is allowed to block and use the flag otherwise.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 lib/rhashtable.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 32d0ad058380..4d3886b6ab7d 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -77,16 +77,9 @@ static int alloc_bucket_locks(struct rhashtable *ht, struct bucket_table *tbl,
 	size = min_t(unsigned int, size, tbl->size >> 1);
 
 	if (sizeof(spinlock_t) != 0) {
-		tbl->locks = NULL;
-#ifdef CONFIG_NUMA
-		if (size * sizeof(spinlock_t) > PAGE_SIZE &&
-		    gfp == GFP_KERNEL)
-			tbl->locks = vmalloc(size * sizeof(spinlock_t));
-#endif
-		if (gfp != GFP_KERNEL)
-			gfp |= __GFP_NOWARN | __GFP_NORETRY;
-
-		if (!tbl->locks)
+		if (gfpflags_allow_blocking(gfp_))
+			tbl->locks = kvmalloc(size * sizeof(spinlock_t), gfp);
+		else
 			tbl->locks = kmalloc_array(size, sizeof(spinlock_t),
 						   gfp);
 		if (!tbl->locks)
-- 
2.11.0

-- 
Michal Hocko
SUSE Labs