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Tue, 02 May 2023 11:33:26 -0700 (PDT) MIME-Version: 1.0 References: <20230501165450.15352-1-surenb@google.com> <20230501165450.15352-10-surenb@google.com> <20230502145014.24b28e64@meshulam.tesarici.cz> In-Reply-To: <20230502145014.24b28e64@meshulam.tesarici.cz> From: Suren Baghdasaryan Date: Tue, 2 May 2023 11:33:15 -0700 Message-ID: Subject: Re: [PATCH 09/40] mm: introduce __GFP_NO_OBJ_EXT flag to selectively prevent slabobj_ext creation To: =?UTF-8?B?UGV0ciBUZXNhxZnDrWs=?= Cc: akpm@linux-foundation.org, kent.overstreet@linux.dev, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, ldufour@linux.ibm.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, keescook@chromium.org, ndesaulniers@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 2, 2023 at 5:50=E2=80=AFAM Petr Tesa=C5=99=C3=ADk wrote: > > On Mon, 1 May 2023 09:54:19 -0700 > Suren Baghdasaryan wrote: > > > Introduce __GFP_NO_OBJ_EXT flag in order to prevent recursive allocatio= ns > > when allocating slabobj_ext on a slab. > > > > Signed-off-by: Suren Baghdasaryan > > --- > > include/linux/gfp_types.h | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/gfp_types.h b/include/linux/gfp_types.h > > index 6583a58670c5..aab1959130f9 100644 > > --- a/include/linux/gfp_types.h > > +++ b/include/linux/gfp_types.h > > @@ -53,8 +53,13 @@ typedef unsigned int __bitwise gfp_t; > > #define ___GFP_SKIP_ZERO 0 > > #define ___GFP_SKIP_KASAN 0 > > #endif > > +#ifdef CONFIG_SLAB_OBJ_EXT > > +#define ___GFP_NO_OBJ_EXT 0x4000000u > > +#else > > +#define ___GFP_NO_OBJ_EXT 0 > > +#endif > > #ifdef CONFIG_LOCKDEP > > -#define ___GFP_NOLOCKDEP 0x4000000u > > +#define ___GFP_NOLOCKDEP 0x8000000u > > So now we have two flags that depend on config options, but the first > one is always allocated in fact. I wonder if you could use an enum to > let the compiler allocate bits. Something similar to what Muchun Song > did with section flags. > > See commit ed7802dd48f7a507213cbb95bb4c6f1fe134eb5d for reference. Thanks for the reference. I'll take a closer look and will try to clean it = up. > > > #else > > #define ___GFP_NOLOCKDEP 0 > > #endif > > @@ -99,12 +104,15 @@ typedef unsigned int __bitwise gfp_t; > > * node with no fallbacks or placement policy enforcements. > > * > > * %__GFP_ACCOUNT causes the allocation to be accounted to kmemcg. > > + * > > + * %__GFP_NO_OBJ_EXT causes slab allocation to have no object > > extension. */ > > #define __GFP_RECLAIMABLE ((__force gfp_t)___GFP_RECLAIMABLE) > > #define __GFP_WRITE ((__force gfp_t)___GFP_WRITE) > > #define __GFP_HARDWALL ((__force gfp_t)___GFP_HARDWALL) > > #define __GFP_THISNODE ((__force gfp_t)___GFP_THISNODE) > > #define __GFP_ACCOUNT ((__force gfp_t)___GFP_ACCOUNT) > > +#define __GFP_NO_OBJ_EXT ((__force gfp_t)___GFP_NO_OBJ_EXT) > > > > /** > > * DOC: Watermark modifiers > > @@ -249,7 +257,7 @@ typedef unsigned int __bitwise gfp_t; > > #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) > > > > /* Room for N __GFP_FOO bits */ > > -#define __GFP_BITS_SHIFT (26 + IS_ENABLED(CONFIG_LOCKDEP)) > > +#define __GFP_BITS_SHIFT (27 + IS_ENABLED(CONFIG_LOCKDEP)) > > If the above suggestion is implemented, this could be changed to > something like __GFP_LAST_BIT (the enum's last identifier). Ack. Thanks for reviewing! Suren. > > Petr T