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b=ZAhQRSX6NzlLGAY/qPz0H4PP+wZMAT4cbhasXTr9LPMVhLDazTFWANcO/zyvKqUfZpsCqO t/i/H+jtjJbuO9X04Dozym7Yh7hc6dhQ9pV1XE1Zo0zSLcOdIwVpQpxEx0hrnhCWMFDuUi gw32/Yoqug6gvcCCS5fJbnUrpJpM+bs= X-Stat-Signature: c7waekarp96amn4ekdoyzzm97rqfg34g X-Rspamd-Queue-Id: 4482214004E Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=igORDamf; spf=pass (imf23.hostedemail.com: domain of apopple@nvidia.com designates 40.107.223.54 as permitted sender) smtp.mailfrom=apopple@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1659572070-948641 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: Andrew Morton writes: > On Tue, 2 Aug 2022 10:30:12 +1000 Alistair Popple wrote: > >> When pinning pages with FOLL_LONGTERM check_and_migrate_movable_pages() >> is called to migrate pages out of zones which should not contain any >> longterm pinned pages. >> >> When migration succeeds all pages will have been unpinned so pinning >> needs to be retried. This is indicated by returning zero. When all pages >> are in the correct zone the number of pinned pages is returned. >> >> However migration can also fail, in which case pages are unpinned and >> -ENOMEM is returned. However if the failure was due to not being unable >> to isolate a page zero is returned. This leads to indefinite looping in >> __gup_longterm_locked(). >> >> Fix this by simplifying the return codes such that zero indicates all >> pages were successfully pinned in the correct zone while errors indicate >> either pages were migrated and pinning should be retried or that >> migration has failed and therefore the pinning operation should fail. >> >> This fixes the indefinite looping on page isolation failure by failing >> the pin operation instead of retrying indefinitely. >> > > Are we able to identify a Fixes: for this? Presumably something in the > series "Add MEMORY_DEVICE_COHERENT for coherent device memory mapping"? It seems the infinite loop was desired behaviour so I will re-spin this as a pure clean-up.