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[174.93.89.182]) by smtp.gmail.com with ESMTPSA id z20sm17078830qki.93.2021.02.08.19.02.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Feb 2021 19:02:31 -0800 (PST) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Matthew Wilcox , Linus Torvalds , Kirill Tkhai , Mike Rapoport , David Gibson , Kirill Shutemov , Christoph Hellwig , Miaohe Lin , Gal Pressman , Jason Gunthorpe , Jann Horn , peterx@redhat.com, Jan Kara , Wei Zhang , Mike Kravetz , Andrea Arcangeli , Andrew Morton Subject: [PATCH v4 0/5] mm/hugetlb: Early cow on fork, and a few cleanups Date: Mon, 8 Feb 2021 22:02:24 -0500 Message-Id: <20210209030229.84991-1-peterx@redhat.com> X-Mailer: git-send-email 2.26.2 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v4:=0D - add r-b for Mike on the last patch, add some more commit message explains= =0D that why we don't need wr-protect trick=0D - fix one warning of unused var in copy_present_page() [Gal]=0D =0D v3:=0D - rebase to linux-next/akpm, switch to the new HPAGE helpers [MikeK]=0D - correct error check for alloc_huge_page(); test it this time to make sure= =0D fork() fails gracefully when overcommit [MikeK]=0D - move page copy out of pgtable lock: this changed quite a bit of the logic= in=0D the last patch, prealloc is dropped since I found it easier to understand= =0D without looping at all [MikeK]=0D =0D v2:=0D - pass in 1 to alloc_huge_page() last param [Mike]=0D - reduce comment, unify the comment in one place [Linus]=0D - add r-bs for Mike and Miaohe=0D =0D ---- original cover letter ----=0D =0D 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 (5):=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 mm: Use is_cow_mapping() across tree where proper=0D hugetlb: Do early cow when page pinned on src mm=0D =0D drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 4 +-=0D drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 2 +-=0D fs/proc/task_mmu.c | 2 -=0D include/linux/mm.h | 21 ++++=0D mm/huge_memory.c | 8 +-=0D mm/hugetlb.c | 123 +++++++++++++++------=0D mm/internal.h | 5 -=0D mm/memory.c | 8 +-=0D 8 files changed, 117 insertions(+), 56 deletions(-)=0D =0D -- =0D 2.26.2=0D =0D