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Mon, 08 Sep 2025 18:00:22 -0700 (PDT) From: Alexei Starovoitov To: bpf@vger.kernel.org, linux-mm@kvack.org Cc: vbabka@suse.cz, harry.yoo@oracle.com, shakeel.butt@linux.dev, mhocko@suse.com, bigeasy@linutronix.de, andrii@kernel.org, memxor@gmail.com, akpm@linux-foundation.org, peterz@infradead.org, rostedt@goodmis.org, hannes@cmpxchg.org Subject: [PATCH slab v5 5/6] slab: Reuse first bit for OBJEXTS_ALLOC_FAIL Date: Mon, 8 Sep 2025 18:00:06 -0700 Message-Id: <20250909010007.1660-6-alexei.starovoitov@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20250909010007.1660-1-alexei.starovoitov@gmail.com> References: <20250909010007.1660-1-alexei.starovoitov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 69F98160019 X-Rspamd-Server: rspam05 X-Stat-Signature: dgtrgt95d3orongx7ry7t7wijzpwfkts X-Rspam-User: X-HE-Tag: 1757379624-885302 X-HE-Meta: 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 XwbrEI/c tQMuyARtv3HqnknHBL4up5h7YXv3S9AS2f3kmXKDACWESTdkpzGgdF5kBixiEs3X8HK5lztaTF4MkiTCN9dBiiafQWp7wlecA0Xcv 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: List-Subscribe: List-Unsubscribe: From: Alexei Starovoitov Since the combination of valid upper bits in slab->obj_exts with OBJEXTS_ALLOC_FAIL bit can never happen, use OBJEXTS_ALLOC_FAIL == (1ull << 0) as a magic sentinel instead of (1ull << 2) to free up bit 2. Signed-off-by: Alexei Starovoitov --- include/linux/memcontrol.h | 10 ++++++++-- mm/slub.c | 2 +- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 785173aa0739..d254c0b96d0d 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -341,17 +341,23 @@ enum page_memcg_data_flags { __NR_MEMCG_DATA_FLAGS = (1UL << 2), }; +#define __OBJEXTS_ALLOC_FAIL MEMCG_DATA_OBJEXTS #define __FIRST_OBJEXT_FLAG __NR_MEMCG_DATA_FLAGS #else /* CONFIG_MEMCG */ +#define __OBJEXTS_ALLOC_FAIL (1UL << 0) #define __FIRST_OBJEXT_FLAG (1UL << 0) #endif /* CONFIG_MEMCG */ enum objext_flags { - /* slabobj_ext vector failed to allocate */ - OBJEXTS_ALLOC_FAIL = __FIRST_OBJEXT_FLAG, + /* + * Use bit 0 with zero other bits to signal that slabobj_ext vector + * failed to allocate. The same bit 0 with valid upper bits means + * MEMCG_DATA_OBJEXTS. + */ + OBJEXTS_ALLOC_FAIL = __OBJEXTS_ALLOC_FAIL, /* the next bit after the last actual flag */ __NR_OBJEXTS_FLAGS = (__FIRST_OBJEXT_FLAG << 1), }; diff --git a/mm/slub.c b/mm/slub.c index 212161dc0f29..61841ba72120 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2051,7 +2051,7 @@ static inline void handle_failed_objexts_alloc(unsigned long obj_exts, * objects with no tag reference. Mark all references in this * vector as empty to avoid warnings later on. */ - if (obj_exts & OBJEXTS_ALLOC_FAIL) { + if (obj_exts == OBJEXTS_ALLOC_FAIL) { unsigned int i; for (i = 0; i < objects; i++) -- 2.47.3