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Mon, 26 Oct 2026 13:04:33 +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 XqdMAeFP32rTXAAAD6G6ig (envelope-from ); Mon, 26 Oct 2026 13:04:33 +0000 Date: Mon, 26 Oct 2026 13:04:31 +0000 From: Pedro Falcato To: "Lorenzo Stoakes (ARM)" Cc: Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Davidlohr Bueso , SJ Park , Kees Cook , Colin Cross , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 3/4] mm/madvise: preserve VMA_SOFTDIRTY_BIT when changing anonymous names Message-ID: References: <20261023-fix-vma-atomic-v1-0-8ff4fae1fc85@kernel.org> <20261023-fix-vma-atomic-v1-3-8ff4fae1fc85@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023-fix-vma-atomic-v1-3-8ff4fae1fc85@kernel.org> X-Spamd-Result: default: False [-13.51 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; MIME_TRACE(0.00)[0:+]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:email,suse.de:dkim]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -13.51 X-Spam-Level: X-Rspamd-Queue-Id: 768DD22263 On Fri, Oct 23, 2026 at 02:47:29PM +0100, Lorenzo Stoakes (ARM) wrote: > From: "David Hildenbrand (Arm)" > > When changing the anonymous VMA name, madvise_update_vma() calls > vma_modify_name() to possibly merge with adjacent VMAs. We don't call > vma_modify_flags() and consequently don't obtain the new VMA flags. > > Later in the function we update the VMA flags to the stale new_vma_flags > we obtained before. This can result in us losing the VMA_SOFTDIRTY_BIT > flag set on a VMA we just merged with. > > There is no need to update the VMA flags at all, so just exit early. This > skips calling khugepaged_enter_vma(), but since the flags didn't change > this is fine. > > Fixes: 9a10064f5625 ("mm: add a field to store names for private anonymous memory") > Cc: > Signed-off-by: David Hildenbrand (Arm) > Reviewed-by: Lorenzo Stoakes (ARM) > [ ljs - Minor edit of commit message, rebased ] > Signed-off-by: Lorenzo Stoakes (ARM) Reviewed-by: Pedro Falcato > --- > mm/madvise.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index b2e00efcaa54..e9fa4f71efea 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -177,6 +177,9 @@ static int madvise_update_vma(vm_flags_t new_flags, > > /* vm_flags is protected by the mmap_lock held in write mode. */ > vma_start_write(vma); > + if (set_new_anon_name) > + return replace_anon_vma_name(vma, anon_name); This looks non-obvious and brittle, maybe have a comment here? Or some more clever solution. -- Pedro