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List:       linux-mm-commits
Subject:    + slub-disable-tracing-and-failslab-for-merged-slabs.patch added to -mm tree
From:       akpm () linux-foundation ! org
Date:       2014-08-29 19:56:05
Message-ID: 5400dad5.rIy2xs4Zuxb8xsi0%akpm () linux-foundation ! org
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The patch titled
     Subject: slub: disable tracing and failslab for merged slabs
has been added to the -mm tree.  Its filename is
     slub-disable-tracing-and-failslab-for-merged-slabs.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/slub-disable-tracing-and-failslab-for-merged-slabs.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/slub-disable-tracing-and-failslab-for-merged-slabs.patch

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------------------------------------------------------
From: Christoph Lameter <cl@linux.com>
Subject: slub: disable tracing and failslab for merged slabs

Tracing of mergeable slabs as well as uses of failslab are confusing since
the objects of multiple slab caches will be affected.  Moreover this
creates a situation where a mergeable slab will become unmergeable.

If tracing or failslab testing is desired then it may be best to switch
merging off for starters.

Signed-off-by: Christoph Lameter <cl@linux.com>
Tested-by: WANG Chao <chaowang@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slub.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

diff -puN mm/slub.c~slub-disable-tracing-and-failslab-for-merged-slabs mm/slub.c
--- a/mm/slub.c~slub-disable-tracing-and-failslab-for-merged-slabs
+++ a/mm/slub.c
@@ -4604,6 +4604,14 @@ static ssize_t trace_show(struct kmem_ca
 static ssize_t trace_store(struct kmem_cache *s, const char *buf,
 							size_t length)
 {
+	/*
+	 * Tracing a merged cache is going to give confusing results
+	 * as well as cause other issues like converting a mergeable
+	 * cache into an umergeable one.
+	 */
+	if (s->refcount > 1)
+		return -EINVAL;
+
 	s->flags &= ~SLAB_TRACE;
 	if (buf[0] == '1') {
 		s->flags &= ~__CMPXCHG_DOUBLE;
@@ -4721,6 +4729,9 @@ static ssize_t failslab_show(struct kmem
 static ssize_t failslab_store(struct kmem_cache *s, const char *buf,
 							size_t length)
 {
+	if (s->refcount > 1)
+		return -EINVAL;
+
 	s->flags &= ~SLAB_FAILSLAB;
 	if (buf[0] == '1')
 		s->flags |= SLAB_FAILSLAB;
_

Patches currently in -mm which might be from cl@linux.com are

origin.patch
mm-slab_commonc-suppress-warning.patch
mm-slab_common-move-kmem_cache-definition-to-internal-header.patch
mm-slb-always-track-caller-in-kmalloc_node_track_caller.patch
mm-slab-move-cache_flusharray-out-of-unlikelytext-section.patch
mm-slab-noinline-__ac_put_obj.patch
mm-slab-factor-out-unlikely-part-of-cache_free_alien.patch
slub-disable-tracing-and-failslab-for-merged-slabs.patch
mm-thp-dont-hold-mmap_sem-in-khugepaged-when-allocating-thp.patch
mm-compaction-defer-each-zone-individually-instead-of-preferred-zone.patch
mm-compaction-defer-each-zone-individually-instead-of-preferred-zone-fix.patch
mm-compaction-do-not-count-compact_stall-if-all-zones-skipped-compaction.patch
mm-compaction-do-not-recheck-suitable_migration_target-under-lock.patch
mm-compaction-move-pageblock-checks-up-from-isolate_migratepages_range.patch
mm-compaction-reduce-zone-checking-frequency-in-the-migration-scanner.patch
mm-compaction-khugepaged-should-not-give-up-due-to-need_resched.patch
mm-compaction-khugepaged-should-not-give-up-due-to-need_resched-fix.patch
mm-compaction-periodically-drop-lock-and-restore-irqs-in-scanners.patch
mm-compaction-skip-rechecks-when-lock-was-already-held.patch
mm-compaction-remember-position-within-pageblock-in-free-pages-scanner.patch
mm-compaction-skip-buddy-pages-by-their-order-in-the-migrate-scanner.patch
mm-rename-allocflags_to_migratetype-for-clarity.patch
mm-compaction-pass-gfp-mask-to-compact_control.patch
mm-use-__seq_open_private-instead-of-seq_open.patch
vmstat-on-demand-vmstat-workers-v8.patch
vmstat-on-demand-vmstat-workers-v8-do-not-open-code-alloc_cpumask_var.patch
vmstat-on-demand-vmstat-workers-v8-fix-2.patch
linux-next.patch

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