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From: Vlastimil Babka <vbabka@suse.cz>
Subject: [PATCH v2 0/3] cleanup of SLAB_ flags
Date: Fri, 23 Feb 2024 19:27:16 +0100
Message-Id: <20240223-slab-cleanup-flags-v2-0-02f1753e8303@suse.cz>
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To: Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, 
 David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, 
 Andrew Morton <akpm@linux-foundation.org>, 
 Roman Gushchin <roman.gushchin@linux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@gmail.com>, 
 Andrey Ryabinin <ryabinin.a.a@gmail.com>, 
 Alexander Potapenko <glider@google.com>, 
 Andrey Konovalov <andreyknvl@gmail.com>, Dmitry Vyukov <dvyukov@google.com>, 
 Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Zheng Yejian <zhengyejian1@huawei.com>, 
 Xiongwei Song <xiongwei.song@windriver.com>, 
 Chengming Zhou <chengming.zhou@linux.dev>, linux-mm@kvack.org, 
 linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, 
 Vlastimil Babka <vbabka@suse.cz>, Steven Rostedt <rostedt@goodmis.org>

This started by the report that SLAB_MEM_SPREAD flag is dead (Patch 1).
Then in the alloc profiling series we realized it's too easy to reuse an
existing SLAB_ flag's value when defining a new one, by mistake.
Thus let the compiler do that for us via a new helper enum (Patch 2).
When checking if more flags are dead or could be removed, didn't spot
any, but found out the SLAB_KASAN handling of preventing cache merging
can be simplified since we now have an explicit SLAB_NO_MERGE (Patch 3).

The SLAB_MEM_SPREAD flag is now marked as unused and for removal, and
has a value of 0 so it's a no-op. Patches to remove its usage can/will
be submitted to respective subsystems independently of this series - the
flag is already dead as of v6.8-rc1 with SLAB removed. The removal of
dead cpuset_do_slab_mem_spread() code can also be submitted
independently.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
Changes in v2:
- Collect R-b, T-b (thanks!)
- Unify all disabled flags's value to a sparse-happy zero with a new macro (lkp/sparse).
- Rename __SF_BIT to __SLAB_FLAG_BIT (Roman Gushchin)
- Rewrod kasan_cache_create() comment (Andrey Konovalov)
- Link to v1: https://lore.kernel.org/r/20240220-slab-cleanup-flags-v1-0-e657e373944a@suse.cz

---
Vlastimil Babka (3):
      mm, slab: deprecate SLAB_MEM_SPREAD flag
      mm, slab: use an enum to define SLAB_ cache creation flags
      mm, slab, kasan: replace kasan_never_merge() with SLAB_NO_MERGE

 include/linux/kasan.h |  6 ----
 include/linux/slab.h  | 97 ++++++++++++++++++++++++++++++++++++---------------
 mm/kasan/generic.c    | 22 ++++--------
 mm/slab.h             |  1 -
 mm/slab_common.c      |  2 +-
 mm/slub.c             |  6 ++--
 6 files changed, 79 insertions(+), 55 deletions(-)
---
base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d
change-id: 20240219-slab-cleanup-flags-c864415ecc8e

Best regards,
-- 
Vlastimil Babka <vbabka@suse.cz>