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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1s2bQQ-00000002Ezr-38HW; Thu, 02 May 2024 18:44:58 +0000 Date: Thu, 2 May 2024 19:44:58 +0100 From: Matthew Wilcox To: Jason Gunthorpe Cc: John Hubbard , David Hildenbrand , Alistair Popple , Christoph Hellwig , Andrew Morton , LKML , linux-rdma@vger.kernel.org, linux-mm@kvack.org, Mike Marciniszyn , Leon Romanovsky , Artemy Kovalyov , Michael Guralnik , Pak Markthub Subject: Re: [RFC] RDMA/umem: pin_user_pages*() can temporarily fail due to migration glitches Message-ID: References: <20240501003117.257735-1-jhubbard@nvidia.com> <20240501121032.GA941030@nvidia.com> <87r0el3tfi.fsf@nvdebian.thelocal> <92289167-5655-4c51-8dfc-df7ae53fdb7b@redhat.com> <20240502183408.GC3341011@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240502183408.GC3341011@nvidia.com> X-Stat-Signature: uztqdbym6dtjns3qbzme98wp5gifb5m7 X-Rspamd-Queue-Id: 108DA14004B X-Rspamd-Server: rspam10 X-Rspam-User: X-HE-Tag: 1714675507-748901 X-HE-Meta: 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 IqxgIeMQ bdabcBRDuaFgpQPjikLRaO4EaRdOt3LxQaV1IxtHg28Z3ZwyAFNK6hD9gU4Z86MO0F6jFkstKmiU4x4izyAa/kBkZZB3bAIiFFWX9HH0lZ7SeVDhxF72IQlSXA6ausTQFrUzBu2wZLexhfEHJt7mo7uf8XCtsmsbCpNTobm+3AMjyW77bTO2S1GrZXQ== 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, May 02, 2024 at 03:34:08PM -0300, Jason Gunthorpe wrote: > IMHO pin_user_pages() should sleep and spin in an interruptable sleep killable, not interruptible. Otherwise SIGWINCH and SIGALRM can result an early return. > until we get all the migrations done. Not sure how hard it would be to > add some kind of proper waiting event sleep? ummmmm. We have a "has waiters" bit in the folio. So on every call to folio_put(), we could check that bit and wake up any waiters. I need to think about that; right now, we only use it for unlock and end_writeback. Making folio_put() heavier is, well, quite a lot of call-sites.