Re: [PATCH v4 1/3] mm: slab/slub: Add check_slab_flags function to check for valid flags

[Vlastimil Babka]

On 12/5/18 6:48 AM, Nicolas Boichat wrote:
> Remove duplicated code between slab and slub, and will make it
> easier to make the test more complicated in the next commits.
> 
> Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")

Well, not really. Patch 3 does that and yeah this will be a prerequisity
for a clean stable backport, but we don't tag all prerequisities like
this, I think?

> Signed-off-by: Nicolas Boichat 

Acked-by: Vlastimil Babka 
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[PATCH v4 1/3] mm: slab/slub: Add check_slab_flags function to check for valid flags

[Nicolas Boichat]

Remove duplicated code between slab and slub, and will make it
easier to make the test more complicated in the next commits.

Fixes: ad67f5a6545f ("arm64: replace ZONE_DMA with ZONE_DMA32")
Signed-off-by: Nicolas Boichat 
---
 mm/internal.h | 18 --
 mm/slab.c |  8 +---
 mm/slub.c |  8 +---
 3 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index f0c9ccde3bdb9e..a2ee82a0cd44ae 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -33,8 +33,22 @@
 /* Control allocation cpuset and node placement constraints */
 #define GFP_CONSTRAINT_MASK (__GFP_HARDWALL|__GFP_THISNODE)
 
-/* Do not use these with a slab allocator */
-#define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
+/* Check for flags that must not be used with a slab allocator */
+static inline gfp_t check_slab_flags(gfp_t flags)
+{
+   gfp_t bug_mask = __GFP_DMA32 | __GFP_HIGHMEM | ~__GFP_BITS_MASK;
+
+   if (unlikely(flags & bug_mask)) {
+   gfp_t invalid_mask = flags & bug_mask;
+
+   flags &= ~bug_mask;
+   pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x 
(%pGg). Fix your code!\n",
+   invalid_mask, _mask, flags, );
+   dump_stack();
+   }
+
+   return flags;
+}
 
 void page_writeback_init(void);
 
diff --git a/mm/slab.c b/mm/slab.c
index 73fe23e649c91a..65a774f05e7836 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2643,13 +2643,7 @@ static struct page *cache_grow_begin(struct kmem_cache 
*cachep,
 * Be lazy and only check for valid flags here,  keeping it out of the
 * critical path in kmem_cache_alloc().
 */
-   if (unlikely(flags & GFP_SLAB_BUG_MASK)) {
-   gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
-   flags &= ~GFP_SLAB_BUG_MASK;
-   pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x 
(%pGg). Fix your code!\n",
-   invalid_mask, _mask, flags, );
-   dump_stack();
-   }
+   flags = check_slab_flags(flags);
WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO));
local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK);
 
diff --git a/mm/slub.c b/mm/slub.c
index c229a9b7dd5448..21a3f6866da472 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1685,13 +1685,7 @@ 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)) {
-   gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK;
-   flags &= ~GFP_SLAB_BUG_MASK;
-   pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x 
(%pGg). Fix your code!\n",
-   invalid_mask, _mask, flags, );
-   dump_stack();
-   }
+   flags = check_slab_flags(flags);
 
return allocate_slab(s,
flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node);
-- 
2.20.0.rc1.387.gf8505762e3-goog

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