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[174.93.89.182]) by smtp.gmail.com with ESMTPSA id t6sm2507659qti.2.2021.02.03.13.08.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 13:08:34 -0800 (PST) From: Peter Xu To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Wei Zhang , Matthew Wilcox , Linus Torvalds , Jason Gunthorpe , Gal Pressman , peterx@redhat.com, Christoph Hellwig , Andrea Arcangeli , Jan Kara , Kirill Shutemov , David Gibson , Mike Rapoport , Mike Kravetz , Kirill Tkhai , Jann Horn , Andrew Morton Subject: [PATCH 0/4] mm/hugetlb: Early cow on fork, and a few cleanups Date: Wed, 3 Feb 2021 16:08:28 -0500 Message-Id: <20210203210832.113685-1-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable 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: As reported by Gal [1], we still miss the code clip to handle early cow for= =0D hugetlb case, which is true. Again, it still feels odd to fork() after usi= ng a=0D few huge pages, especially if they're privately mapped to me.. However I d= o=0D agree with Gal and Jason in that we should still have that since that'll=0D complete the early cow on fork effort at least, and it'll still fix issues= =0D where buffers are not well under control and not easy to apply MADV_DONTFOR= K.=0D =0D The first two patches (1-2) are some cleanups I noticed when reading into t= he=0D hugetlb reserve map code. I think it's good to have but they're not necess= ary=0D for fixing the fork issue.=0D =0D The last two patches (3-4) is the real fix.=0D =0D I tested this with a fork() after some vfio-pci assignment, so I'm pretty s= ure=0D the page copy path could trigger well (page will be accounted right after t= he=0D fork()), but I didn't do data check since the card I assigned is some rando= m=0D nic. Gal, please feel free to try this if you have better way to verify th= e=0D series.=0D =0D https://github.com/xzpeter/linux/tree/fork-cow-pin-huge=0D =0D Please review, thanks!=0D =0D [1] https://lore.kernel.org/lkml/27564187-4a08-f187-5a84-3df50009f6ca@amazo= n.com/=0D =0D Peter Xu (4):=0D hugetlb: Dedup the code to add a new file_region=0D hugetlg: Break earlier in add_reservation_in_range() when we can=0D mm: Introduce page_needs_cow_for_dma() for deciding whether cow=0D hugetlb: Do early cow when page pinned on src mm=0D =0D include/linux/mm.h | 21 ++++++++=0D mm/huge_memory.c | 8 +--=0D mm/hugetlb.c | 129 ++++++++++++++++++++++++++++++++++-----------=0D mm/internal.h | 5 --=0D mm/memory.c | 7 +--=0D 5 files changed, 123 insertions(+), 47 deletions(-)=0D =0D --=20=0D 2.26.2=0D =0D