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[032/163] mm, slub: make reclaim_account attribute read-only

Message ID 20200807061848.vF8DVDKGT%akpm@linux-foundation.org
State New
Headers show
Series [001/163] mm/memory.c: avoid access flag update TLB flush for retried page fault | expand

Commit Message

Andrew Morton Aug. 7, 2020, 6:18 a.m. UTC
From: Vlastimil Babka <vbabka@suse.cz>
Subject: mm, slub: make reclaim_account attribute read-only

The attribute reflects the SLAB_RECLAIM_ACCOUNT cache flag.  It's not
clear why this attribute was writable in the first place, as it's tied to
how the cache is used by its creator, it's not a user tunable. 

- it affects slab merging, but that's not being checked while toggled
- if affects whether __GFP_RECLAIMABLE flag is used to allocate page, but
  the runtime toggle doesn't update allocflags
- it affects cache_vmstat_idx() so runtime toggling might lead to incosistency

Thus make it read-only.

Link: http://lkml.kernel.org/r/20200610163135.17364-6-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Jann Horn <jannh@google.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

 mm/slub.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)
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--- a/mm/slub.c~mm-slub-make-reclaim_account-attribute-read-only
+++ a/mm/slub.c
@@ -5207,16 +5207,7 @@  static ssize_t reclaim_account_show(stru
 	return sprintf(buf, "%d\n", !!(s->flags & SLAB_RECLAIM_ACCOUNT));
-static ssize_t reclaim_account_store(struct kmem_cache *s,
-				const char *buf, size_t length)
-	s->flags &= ~SLAB_RECLAIM_ACCOUNT;
-	if (buf[0] == '1')
-		s->flags |= SLAB_RECLAIM_ACCOUNT;
-	return length;
 static ssize_t hwcache_align_show(struct kmem_cache *s, char *buf)