linux-kernel - [PATCH 1/2] slab: make GFP_SLAB_BUG_MASK information more human readable

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Date:	Fri, 10 Jun 2016 10:43:19 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Cristopher Lameter <clameter@....com>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <js1304@...il.com>,
	Pekka Enberg <penberg@...nel.org>, <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>
Subject: [PATCH 1/2] slab: make GFP_SLAB_BUG_MASK information more human readable

From: Michal Hocko <mhocko@...e.com>

printk offers %pGg for quite some time so let's use it to get a human
readable list of invalid flags.

The original output would be
[  429.191962] gfp: 2

after the change
[  429.191962] Unexpected gfp: 0x2 (__GFP_HIGHMEM)

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 mm/slab.c | 3 ++-
 mm/slub.c | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 763096a247f6..03fb724d6e48 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2686,7 +2686,8 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep,
 	 * critical path in kmem_cache_alloc().
 	 */
 	if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-		pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK);
+		gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
+		pr_emerg("Unexpected gfp: %#x (%pGg)\n", invalid_mask, &invalid_mask);
 		BUG();
 	}
 	local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
diff --git a/mm/slub.c b/mm/slub.c
index cbf4e0e07d41..dd5a9eee7df5 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1628,7 +1628,8 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
 {
 	if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-		pr_emerg("gfp: %u\n", flags & GFP_SLAB_BUG_MASK);
+		gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
+		pr_emerg("Unexpected gfp: %#x (%pGg)\n", invalid_mask, &invalid_mask);
 		BUG();
 	}
 
-- 
2.8.1