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[46.135.84.71]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a80f414e4b6sm39584766b.151.2024.08.12.23.07.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Aug 2024 23:07:38 -0700 (PDT) Date: Tue, 13 Aug 2024 08:07:27 +0200 From: Mateusz Guzik To: Andrii Nakryiko Cc: linux-trace-kernel@vger.kernel.org, peterz@infradead.org, oleg@redhat.com, rostedt@goodmis.org, mhiramat@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, paulmck@kernel.org, willy@infradead.org, surenb@google.com, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH RFC v3 12/13] mm: add SLAB_TYPESAFE_BY_RCU to files_cache Message-ID: References: <20240813042917.506057-1-andrii@kernel.org> <20240813042917.506057-13-andrii@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240813042917.506057-13-andrii@kernel.org> X-Rspam-User: X-Rspamd-Queue-Id: 233F7A0023 X-Rspamd-Server: rspam01 X-Stat-Signature: r1cih65k3e77uscajt8nm9nmtyexjr4r X-HE-Tag: 1723529260-553890 X-HE-Meta: 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 PWTHR0vp 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 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: On Mon, Aug 12, 2024 at 09:29:16PM -0700, Andrii Nakryiko wrote: > Add RCU protection for file struct's backing memory by adding > SLAB_TYPESAFE_BY_RCU flag to files_cachep. This will allow to locklessly > access struct file's fields under RCU lock protection without having to > take much more expensive and contended locks. > > This is going to be used for lockless uprobe look up in the next patch. > > Suggested-by: Matthew Wilcox > Signed-off-by: Andrii Nakryiko > --- > kernel/fork.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 76ebafb956a6..91ecc32a491c 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -3157,8 +3157,8 @@ void __init proc_caches_init(void) > NULL); > files_cachep = kmem_cache_create("files_cache", > sizeof(struct files_struct), 0, > - SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, > - NULL); > + SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU| > + SLAB_ACCOUNT, NULL); > fs_cachep = kmem_cache_create("fs_cache", > sizeof(struct fs_struct), 0, > SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, Did you mean to add it to the cache backing 'struct file' allocations? That cache is created in fs/file_table.c and already has the flag: filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0, SLAB_TYPESAFE_BY_RCU | SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT, NULL); The cache you are modifying in this patch contains the fd array et al and is of no consequence to "uprobes: add speculative lockless VMA to inode resolution". iow this patch needs to be dropped