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Thu, 13 Jul 2023 20:18:04 -0700 (PDT) MIME-Version: 1.0 References: <20230711202047.3818697-1-willy@infradead.org> <20230711202047.3818697-5-willy@infradead.org> In-Reply-To: <20230711202047.3818697-5-willy@infradead.org> From: Suren Baghdasaryan Date: Thu, 13 Jul 2023 20:17:53 -0700 Message-ID: Subject: Re: [PATCH v2 4/9] mm: Move FAULT_FLAG_VMA_LOCK check into handle_pte_fault() To: "Matthew Wilcox (Oracle)" Cc: linux-mm@kvack.org, Arjun Roy , Eric Dumazet , linux-fsdevel@vger.kernel.org, Punit Agrawal Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: ck1w5prioziia33sj1xni5qj7njkaxsx X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1176B160003 X-HE-Tag: 1689304684-441063 X-HE-Meta: U2FsdGVkX1/cjoo8UgYL54spuX0aEEuNI7NSQRbsm1unKt75kIOHH1YpxLilZyOeqYiIMivoJOzMHOHZDyZg1rGWdri6J5dacAt7VSaNipO56t5/OxVKtswycbPgqTR9rOwut2XLw7abkDcfU/wGcw3RXms7J8TfiEkBDbxikoic5Iv4jdqJTYJ1PUxaira3WaRUt1pBXMD5ahNnUbhhOFL0UjlDtWqquzfBCj2yKcXeK2C9JjTImDkGcz3wTuBLuRC4sA39vM2HJSwLLc97q2KCNTTRmMVNNVndxYa6us9IlJhHiG0YyABeCobMPttbRzjmm4ayKNpyvA+v1TKCqwvxwEglHoUZh/FNBzmGiuv2gFJQ0mZ6h9V0qmIwSOfRFvhCXB3821TTbm0nYflab3/syoJfpqb+p74V2GjAPVeBtxulhYZhYfMOL+GKXzi9jFGzKDj4ED65jo2aK2t1ewBShCWuag28M+CILE1CGd17N8AaC6GCtVAltkwtsKTPoQ4E+iyPTHfQWseOvcro5zAEmnK1NIyWItA2eCVWzGSPKHWBRzZSPcwUQqgv8MANp4TW3vV8BN/JrWUJBIkI4NB5E/8lV1H7bOgR56QI4gFedCeunCOJ1EfeWgkESQoT1W3kWtB4K69k4LzMa7MPw9NYRad4HQv6+/qUA+sEz0fKLt/NQobHXxYyuqehqBerRgnKmIbcSs86wwKsZTuUAxjVg1+RNq9GAhpGtx0ydSjmgrgddwtOQolDf3adtSPYqjLER6gbDzkxvHZqAKc5P89FwUQylNHybbG33kgAO3jqPr/mahNMJ+JJHgndC2gWRh477o328XWWeDAX7UGp3NsavNMKXqSpo68P0WAIq39B23yxDWtvvmfyGUufLNOU3H5W5wwjPYqU7C5ehIMXdiTUJgt31qPH1pD59sbu3RS4xACFERteHCjz8c1darMpLHBtBRZJhPNh0cu5isk 4a+h/0IT EfOepOL6TvySU1O2Os96u4nSQAaoBHFkBY8RpXQM3gJ9f8bQ/JtjNro3VznUaNmXi8CVg5BYxdXMZJjXTzGaBi/h7fz7CYO7aV5vgkTTULPoi7lEcJxu8QbFjJdCt25ebE12zqP7vOghC7SMODOmegMwaawaQgLRa5RR+wD1kBR7WuXEGMsp7WaGnaHNVlcCKl9jhVN0PFyl4AbeT29C8gxxl6G7CmP0py5G5oXKhL8u9YmrtCSIfB92gGGSpc4qRCxAX9vhmAwRzVtClt+vghkfS+Ma45kJD7ctjvV0v7dJcVDgNtGfRUehwj5x3InbfgWGIu0wxoPZphssWfTfLAWon2e7oKVt9OXFL X-Bogosity: Ham, tests=bogofilter, spamicity=0.002589, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jul 11, 2023 at 1:20=E2=80=AFPM Matthew Wilcox (Oracle) wrote: > > Push the check down from __handle_mm_fault(). There's a mild upside to > this patch in that we'll allocate the page tables while under the VMA > lock rather than the mmap lock, reducing the hold time on the mmap lock, > since the retry will find the page tables already populated. > > Signed-off-by: Matthew Wilcox (Oracle) Took some time but seems safe to me... Reviewed-by: Suren Baghdasaryan > --- > mm/memory.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 6eda5c5f2069..52f7fdd78380 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4924,6 +4924,11 @@ static vm_fault_t handle_pte_fault(struct vm_fault= *vmf) > { > pte_t entry; > > + if ((vmf->flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vmf->= vma)) { > + vma_end_read(vmf->vma); > + return VM_FAULT_RETRY; > + } > + > if (unlikely(pmd_none(*vmf->pmd))) { > /* > * Leave __pte_alloc() until later: because vm_ops->fault= may > @@ -5020,11 +5025,6 @@ static vm_fault_t __handle_mm_fault(struct vm_area= _struct *vma, > p4d_t *p4d; > vm_fault_t ret; > > - if ((flags & FAULT_FLAG_VMA_LOCK) && !vma_is_anonymous(vma)) { > - vma_end_read(vma); > - return VM_FAULT_RETRY; > - } > - > pgd =3D pgd_offset(mm, address); > p4d =3D p4d_alloc(mm, pgd, address); > if (!p4d) > -- > 2.39.2 >