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Wed, 15 Jan 2025 07:58:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id ZC2XJsJqh2dicQAAD6G6ig (envelope-from ); Wed, 15 Jan 2025 07:58:58 +0000 Message-ID: Date: Wed, 15 Jan 2025 08:58:58 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 16/17] mm: make vma cache SLAB_TYPESAFE_BY_RCU To: Suren Baghdasaryan , Wei Yang , willy@infradead.org Cc: akpm@linux-foundation.org, peterz@infradead.org, liam.howlett@oracle.com, lorenzo.stoakes@oracle.com, david.laight.linux@gmail.com, mhocko@suse.com, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, lokeshgidra@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, klarasmodin@gmail.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20250111042604.3230628-1-surenb@google.com> <20250111042604.3230628-17-surenb@google.com> <20250115022703.hqbqdqawvqgrfgxb@master> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-2.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_ENVRCPT(0.00)[gmail.com,sina.com]; RCVD_TLS_ALL(0.00)[]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; TAGGED_RCPT(0.00)[]; RCPT_COUNT_TWELVE(0.00)[34]; FREEMAIL_TO(0.00)[google.com,gmail.com,infradead.org]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[linux-foundation.org,infradead.org,oracle.com,gmail.com,suse.com,cmpxchg.org,intel.com,techsingularity.net,redhat.com,stgolabs.net,kernel.org,sina.com,google.com,linux.dev,soleen.com,lwn.net,vger.kernel.org,kvack.org,android.com]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; R_RATELIMIT(0.00)[to_ip_from(RLumbhs4xhzuuihrchnpuyb6qu)] X-Spam-Score: -2.80 X-Spam-Flag: NO On 1/15/25 04:15, Suren Baghdasaryan wrote: > On Tue, Jan 14, 2025 at 6:27 PM Wei Yang wrote: >> >> On Fri, Jan 10, 2025 at 08:26:03PM -0800, Suren Baghdasaryan wrote: >> >> >diff --git a/kernel/fork.c b/kernel/fork.c >> >index 9d9275783cf8..151b40627c14 100644 >> >--- a/kernel/fork.c >> >+++ b/kernel/fork.c >> >@@ -449,6 +449,42 @@ struct vm_area_struct *vm_area_alloc(struct mm_struct *mm) >> > return vma; >> > } >> > >> >+static void vm_area_init_from(const struct vm_area_struct *src, >> >+ struct vm_area_struct *dest) >> >+{ >> >+ dest->vm_mm = src->vm_mm; >> >+ dest->vm_ops = src->vm_ops; >> >+ dest->vm_start = src->vm_start; >> >+ dest->vm_end = src->vm_end; >> >+ dest->anon_vma = src->anon_vma; >> >+ dest->vm_pgoff = src->vm_pgoff; >> >+ dest->vm_file = src->vm_file; >> >+ dest->vm_private_data = src->vm_private_data; >> >+ vm_flags_init(dest, src->vm_flags); >> >+ memcpy(&dest->vm_page_prot, &src->vm_page_prot, >> >+ sizeof(dest->vm_page_prot)); >> >+ /* >> >+ * src->shared.rb may be modified concurrently when called from >> >+ * dup_mmap(), but the clone will reinitialize it. >> >+ */ >> >+ data_race(memcpy(&dest->shared, &src->shared, sizeof(dest->shared))); >> >+ memcpy(&dest->vm_userfaultfd_ctx, &src->vm_userfaultfd_ctx, >> >+ sizeof(dest->vm_userfaultfd_ctx)); >> >+#ifdef CONFIG_ANON_VMA_NAME >> >+ dest->anon_name = src->anon_name; >> >+#endif >> >+#ifdef CONFIG_SWAP >> >+ memcpy(&dest->swap_readahead_info, &src->swap_readahead_info, >> >+ sizeof(dest->swap_readahead_info)); >> >+#endif >> >+#ifndef CONFIG_MMU >> >+ dest->vm_region = src->vm_region; >> >+#endif >> >+#ifdef CONFIG_NUMA >> >+ dest->vm_policy = src->vm_policy; >> >+#endif >> >+} >> >> Would this be difficult to maintain? We should make sure not miss or overwrite >> anything. > > Yeah, it is less maintainable than a simple memcpy() but I did not > find a better alternative. Willy knows one but refuses to share it :( > I added a warning above the struct > vm_area_struct definition to update this function every time we change > that structure. Not sure if there is anything else I can do to help > with this. > >> >> -- >> Wei Yang >> Help you, Help me