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b=lQuCOS3d1ws7UGlowjuxi/xIeEVlvuM4bUkrEBOZ6HkXbSiLWY26/U34wGWnYFniJ axYfRytTmC1LQ+BYWNolzK2224KO0LrAZ2rKKXxlY5FbBOsqYN7VsljtLj0FvniKxr LS/rMna4q5if94a2rREaCbeBLCVSl5PX+YLn7+YrtyqHzBi6Kuagxsjh8w7/OvitQD BIZkFRoUeUT9rwEWSTqu54KZUlz8lXSTrSUKXu59nSImUPgXD5pr56/hxYYaM92ynZ lMXpVgbnLfaCJ/pGaL10KWxrIT4yRU/QZixdsZMjzkeNiJnmGkzn4BDUC8TtlIb5nS 2VkepP6EHTkaQ== Message-ID: <365d8e50-5aeb-45e9-97a3-87d0024cdc5f@kernel.org> Date: Tue, 28 Jul 2026 19:41:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 06/13] mm/slab: abstract slabobj_ext.ref access Content-Language: en-US To: Harry Yoo Cc: Suren Baghdasaryan , Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20260727-b4-objext_split-v3-0-c29ef0f1f257@kernel.org> <20260727-b4-objext_split-v3-6-c29ef0f1f257@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 1BB44100008 X-Stat-Signature: 4baqxqqmgf5ex55h9zem1dtmpuo4yxbw X-Rspam-User: X-HE-Tag: 1785260480-792885 X-HE-Meta: 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 v4k5MLH8 z5CvpMCX7bHDFPAWVA2vDtMXknhhnwzry2/BJ2eO+PzAobjA9LT15IYkMZd0ui8cm7D0SouYz5Ot91Yp/kBCOycO0iAnK6M9EMVNuK8qruj6IB+PUUIcGjYWkpXVKM28rRdPdm7QDthJlgpkm2swHsbTNjndZKvZTkiuwNspvvE5pbZeB9ThL+vq2L1og5fx7+RJ0dABDCgcUeVtruU8mdwpW+u54eTjchgTCxVGve2KHXs2vGVvrwYiXGKwP3QOUdyfLXOzT5+O/9gbFus6orvXCV9FDm1TuvJa07Jy2EtWnT6jV/Io2lYEmLkffZYC/WznLszgZQyyJjVaLsNWDRaYkyk9gTv2wmj07 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/28/26 15:41, Harry Yoo wrote: > On Mon, Jul 27, 2026 at 02:54:00PM +0200, Vlastimil Babka (SUSE) wrote: >> In preparation for changes to the structure, abstract access to the ref >> field with a slab_obj_ext_codetag_ref() function. Rename the field to >> _ctref to make an unexpected direct access a compile error. >> >> No functional change intended. >> >> Reviewed-by: Suren Baghdasaryan >> Reviewed-by: Hao Li >> Signed-off-by: Vlastimil Babka (SUSE) >> --- > > Looks good to me, > Reviewed-by: Harry Yoo (Oracle) > > With a suggestion: it would be nice to have debug warnings > that trigger when slab_obj_ext_codetag_ref() is compiled but > not supposed to be called. > > e.g.) for kfence objects, or later in the series when we > reduce slabobj_ext memory (!slab_obj_ext_has_codetag()) > > Similarly, it would be nice (later in the series) to have a warning > in slab_obj_ext_objcg() when slab_needs_objcg() returns false. OK good idea but we can't do it right now as the helpers are introduced later. So for 9/13 mm/slab: introduce slab_obj_ext_has_codetag(): diff --git a/mm/slab.h b/mm/slab.h index 8f352d9f4d91..fbad99da093c 100644 --- a/mm/slab.h +++ b/mm/slab.h @@ -726,6 +726,8 @@ static inline void slab_obj_ext_set_objcg(struct slabobj_ext *obj_ext, static inline union codetag_ref * slab_obj_ext_codetag_ref(struct slab *slab, struct slabobj_ext *obj_ext) { + VM_WARN_ON_ONCE(!slab_obj_ext_has_codetag()); + if (IS_ENABLED(CONFIG_MEMCG)) obj_ext += 1; ... and for objcg we would need to start passing slab pointer to slab_obj_ext_objcg() and slab_obj_ext_set_objcg(). Hmm... >> mm/slab.h | 10 +++++++++- >> mm/slub.c | 42 ++++++++++++++++++++++++++++-------------- >> 2 files changed, 37 insertions(+), 15 deletions(-)