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

Commit Message

Andrew Morton Aug. 7, 2020, 6:18 a.m. UTC

From: Vlastimil Babka <[e-mail]>
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. 
Furthermore:

- 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
  of NR_SLAB_RECLAIMABLE and NR_SLAB_UNRECLAIMABLE

Thus make it read-only.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Vlastimil Babka <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Acked-by: Roman Gushchin <[e-mail]>
Cc: Christoph Lameter <[e-mail]>
Cc: Jann Horn <[e-mail]>
Cc: Vijayanand Jitta <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Pekka Enberg <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/slub.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

Patch

--- 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;
-}
-SLAB_ATTR(reclaim_account);
+SLAB_ATTR_RO(reclaim_account);
 
 static ssize_t hwcache_align_show(struct kmem_cache *s, char *buf)
 {