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Thu, 12 Nov 2026 11:21:39 +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 fxoaJEOh9WodfQAAD6G6ig (envelope-from ); Thu, 12 Nov 2026 11:21:39 +0000 Date: Thu, 12 Nov 2026 11:21:38 +0000 From: Pedro Falcato To: "Lorenzo Stoakes (ARM)" Cc: David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , David Rientjes , Shakeel Butt , Andrew Morton , Jann Horn , "Matthew Wilcox (Oracle)" , Jan Kara , Nhat Pham , Johannes Weiner , Zi Yan , Matthew Brost , Joshua Hahn , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Usama Arif , Kairui Song , Balbir Singh , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Kiryl Shutsemau , Yu-cheng Yu , Dave Hansen , Dennis Zhou , Tejun Heo , Christoph Lameter , Peng Fan , Josef Bacik , Chris Mason , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Borislav Petkov (AMD)" , Mark Brown , "Dennis Zhou (Facebook)" , Rick Edgecombe , stable@vger.kernel.org Subject: Re: [PATCH 01/13] mm/mmap: free gathered pages before MMF_OOM_SKIP Message-ID: References: <20261111-mason-migrate-et-al-fixes-v1-0-3d2454362e8d@kernel.org> <20261111-mason-migrate-et-al-fixes-v1-1-3d2454362e8d@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: <20261111-mason-migrate-et-al-fixes-v1-1-3d2454362e8d@kernel.org> X-Spamd-Result: default: False [-12.01 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; 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)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCPT_COUNT_TWELVE(0.00)[43]; MIME_TRACE(0.00)[0:+]; FREEMAIL_CC(0.00)[kernel.org,infradead.org,google.com,suse.com,linux.dev,linux-foundation.org,suse.cz,gmail.com,cmpxchg.org,nvidia.com,intel.com,sk.com,gourry.net,linux.alibaba.com,tencent.com,redhat.com,linux.intel.com,gentwo.org,nxp.com,fb.com,kvack.org,vger.kernel.org,alien8.de]; DKIM_TRACE(0.00)[suse.de:+]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[]; R_RATELIMIT(0.00)[to_ip_from(RLziudqfrzo6b7hzgpxksh1d9i)]; MISSING_XM_UA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -12.01 X-Spam-Level: X-Rspamd-Queue-Id: 83E481F74D On Wed, Nov 11, 2026 at 06:13:15PM +0000, Lorenzo Stoakes (ARM) wrote: > The OOM killer can quickly trigger again after having selected a > victim. That victim might not have freed its memory yet, but its mm will > be marked MMF_OOM_SKIP by this point, so the OOM killer will ignore it. > > This can cause the OOM killer to kill an innocent process when the first > might have freed enough memory to relieve the memory pressure. > > Fix the issue by freeing the memory before marking the mm MMF_OOM_SKIP. > > Note that the task which calls mmput() might not be the victim - if it > took a reference on the mm (e.g. ptrace), it may hold the last reference > and release it when it calls mmput(). > > Therefore we cannot rely on current to tell whether the mm belongs to an > OOM victim. Instead, partially revert commit b3541d912a84 ("mm: delete > unused MMF_OOM_VICTIM flag") to reinstate MMF_OOM_VICTIM, which > mark_oom_victim() sets on the victim's mm, and check that. > > Reported-by: Chris Mason > Fixes: bf3980c85212 ("mm: drop oom code from exit_mmap") > Cc: > Signed-off-by: Lorenzo Stoakes (ARM) Looks good, thank you! Reviewed-by: Pedro Falcato > --- > include/linux/mm_types.h | 2 ++ > include/linux/oom.h | 9 +++++++++ > mm/mmap.c | 9 ++++++++- > mm/oom_kill.c | 4 +++- > 4 files changed, 22 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 1ed35d258d2e..09e63ff12b04 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -2030,6 +2030,8 @@ enum { > #define MMF_TOPDOWN 31 /* mm searches top down by default */ > #define MMF_TOPDOWN_MASK BIT(MMF_TOPDOWN) > > +#define MMF_OOM_VICTIM 32 /* mm is the oom victim */ > + > #define MMF_INIT_LEGACY_MASK (MMF_DUMP_FILTER_MASK |\ > MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK |\ > MMF_VM_MERGE_ANY_MASK | MMF_TOPDOWN_MASK) > diff --git a/include/linux/oom.h b/include/linux/oom.h > index 00da05d227e6..a9390cb70541 100644 > --- a/include/linux/oom.h > +++ b/include/linux/oom.h > @@ -76,6 +76,15 @@ static inline bool tsk_is_oom_victim(struct task_struct * tsk) > return tsk->signal->oom_mm; > } > > +/* > + * Use this helper if tsk->mm != mm and the victim mm needs a special > + * handling. This is guaranteed to stay true after once set. > + */ > +static inline bool mm_is_oom_victim(struct mm_struct *mm) > +{ > + return mm_flags_test(MMF_OOM_VICTIM, mm); > +} > + > /* > * Checks whether a page fault on the given mm is still reliable. > * This is no longer true if the oom reaper started to reap the > diff --git a/mm/mmap.c b/mm/mmap.c > index 7618e72766a5..4cb18b217048 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1313,11 +1313,18 @@ void exit_mmap(struct mm_struct *mm) > /* update_hiwater_rss(mm) here? but nobody should be looking */ > /* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */ > unmap_vmas(&tlb, &unmap); > + > + /* > + * Free the memory before marking MMF_OOM_SKIP so a re-triggered OOM > + * killer will only skip this mm if it's already freed all it can. > + */ > + if (mm_is_oom_victim(mm)) > + tlb_flush_mmu(&tlb); I see there's a different tlb_flush_mmu() call below (in the actual function). Is tlb_flush_mmu() idempotent? -- Pedro