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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: A9D4F1C002C X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: q8jg7f14hutjrpekwctu7wq9coo6ra45 X-HE-Tag: 1701354816-145236 X-HE-Meta: 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 nhR7Zd53 g+AYyrTFrlI4Rf/SBZLG8MDJerTVFe8CxG8SSIEBGuvB9g4k9NmePwBVGJeZuIpEGF/uj764R0xaEg1kxGgVzNQnPD9TeRA+MOYy/NacrHXWo331t7hYpD/Gx7ptj7fpXx8zNjiSl2wmqRAO0s+VuRodr4O6rJQ023NDZ 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 Thu, Nov 30, 2023 at 02:43:48PM +0100, David Hildenbrand wrote: > On 30.11.23 14:32, Alexandru Elisei wrote: > > Hi, > > > > On Thu, Nov 30, 2023 at 01:49:34PM +0100, David Hildenbrand wrote: > > > > > > + > > > > > > +out_retry: > > > > > > + put_page(page); > > > > > > + if (vmf->flags & FAULT_FLAG_VMA_LOCK) > > > > > > + vma_end_read(vma); > > > > > > + if (fault_flag_allow_retry_first(vmf->flags)) { > > > > > > + err = VM_FAULT_RETRY; > > > > > > + } else { > > > > > > + /* Replay the fault. */ > > > > > > + err = 0; > > > > > > > > > > Hello! > > > > > > > > > > Unfortunately, if the page continues to be pinned, it seems like fault will continue to occur. > > > > > I guess it makes system stability issue. (but I'm not familiar with that, so please let me know if I'm mistaken!) > > > > > > > > > > How about migrating the page when migration problem repeats. > > > > > > > > Yes, I had the same though in the previous iteration of the series, the > > > > page was migrated out of the VMA if tag storage couldn't be reserved. > > > > > > > > Only short term pins are allowed on MIGRATE_CMA pages, so I expect that the > > > > pin will be released before the fault is replayed. Because of this, and > > > > because it makes the code simpler, I chose not to migrate the page if tag > > > > storage couldn't be reserved. > > > > > > There are still some cases that are theoretically problematic: vmsplice() > > > can pin pages forever and doesn't use FOLL_LONGTERM yet. > > > > > > All these things also affect other users that rely on movability (e.g., CMA, > > > memory hotunplug). > > > > I wasn't aware of that, thank you for the information. Then to ensure that the > > process doesn't hang by replying the loop indefinitely, I'll migrate the page if > > tag storage cannot be reserved. Looking over the code again, I think I can reuse > > the same function that migrates tag storage pages out of the MTE VMA (added in > > patch #21), so no major changes needed. > > It's going to be interesting if migrating that page fails because it is > pinned :/ I imagine that having both the page **and** its tag storage pinned longterm without FOLL_LONGTERM is going to be exceedingly rare. Am I mistaken in believing that the problematic vmsplice() behaviour is recognized as something that needs to be fixed? Thanks, Alex > > -- > Cheers, > > David / dhildenb >