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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id r15-20020ac85e8f000000b00403214e8862sm1027423qtx.33.2023.06.28.09.47.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jun 2023 09:47:15 -0700 (PDT) Date: Wed, 28 Jun 2023 12:47:13 -0400 From: Peter Xu To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, ying.huang@intel.com, david@redhat.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Subject: Re: [PATCH v4 6/6] mm: handle userfaults under VMA lock Message-ID: References: <20230628071800.544800-1-surenb@google.com> <20230628071800.544800-7-surenb@google.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: 18BC4160022 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 3bzsqegt65okh3kkmp6wf6c85wuehq8o X-HE-Tag: 1687970838-757750 X-HE-Meta: U2FsdGVkX1+pa3Eubc/jUlW+MlqvYBGA3eOrekn+GMZIW1efr5ntIHyRCE+eFFI8iXcmuvQRqMwVCO8fPbSTNe2EH1gGfQFc+OeR4Y2vKBPSn5oD/Xn+RJKmS0ioS6UtzVJ43wMY1t5hzowemYKL2GyQ1AsD7e153yUeC8kkHbkUXWX/xNQXZgNfTsLtOIQLNvJqSxcDlHso/2A6KNijNAu7Y91UFEztBRxyYruqEuQLOVXr4lNShhl+AnsZG6KP3o08DqhgxZ+uAMubsHe8I9h0A+ws5wMWpNA+0zLc24UKNmvkBtlWt5kO/HY5wbNozFJBEzyXMONDP+oxABhZfTirAlHUGdb1CWe3IBVxxm85xX9O2avNNxZnuZd38k/QK69fHwT7wmCgu95XhOeqrOjrb2KmFHsczB3GWeUXJuEBM7NFDvGevf0whxZL7KueRn/h8ghF5VL8mgI4HfPOZkD69Oz/EQGHKiHCYeJhspM4eCuaQWB0fpIy32McqeBXVe+sAo1eb8CoIcqN5GC3YAh5hAuQXT+gjEruV/q0P1sfogjD1g/mqlYxqrqmmhw+uCJwaQFzGdxFZ+bag5eQaa6Acw1mO6PfZur0ZURqgLW7jJMdBQrp85ssdoANYPmFmHTPCKV3DqrkjKCwCfXP3KS6mW00/Nn9WPg5JQzHiB53kCUoJAvI6ckeOSL8F0kg3wgpL8790Ta5MfxFXs5NYbHNgSWCsbYberbVUX+ve1zD8aIHYfvY/pxvlyGrsl3hgn6GG0bHcKcepgBL1rAlR0C+mbxK2mWEcY1mexZ/hcGJg+nrsj7NRxurMe2BunyHvjkQszMUbiMYsx2LIXT7cOF8MzSsmthYKXLm4285QXa/nLDVyFBbfF6WgM0Y+KycpvMfi+AX6yDji/lL/DcG68GXa5fbKBEF9nzr9SWAxwFRZE5/B2E2zvjISDdqQ17jEYxIcO9E9KLBB/dDi5K jIKxe1R4 SAYQF9xTUfTeYzpSeO26ZDI9ybqYyBG7VrsKVePGn+TcP+Aqo858TflaSchTPxBTxz2xkA9XTiAhNzuEG3Xt7CqwMedoUbzXogRRa9+MRMH+QnZ+OWNBue1/FxlUHzLUgi17XI7AMop+0sLRQ5qaRCazbzjbv2I4NGRP2Ja/5eGL0GHi7pk12iMBg/rqs/la/tL1Jiwtq38QF+DYecHuAR8dBw3DjxyvWc1L6WOnUuniZIoiekl/oisRN0ga5269tgR6VrC3xLCM4DdlzCTakSwj4x4L2S5Z1qDAZbZ+KvEFUQds+H0Sc1DmMd/Qni4c2mnfkMzoM8gjNVquFaDMuU/YB8Xo9tUK6K9J/g/4yPeUJ1o4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000045, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Jun 28, 2023 at 09:22:24AM -0700, Suren Baghdasaryan wrote: > Ack. I was not sure if the ctx->mm would always be the same as vmf->mm. Feel free to look at the entrance of handle_userfault(), where there's: struct vm_area_struct *vma = vmf->vma; struct mm_struct *mm = vma->vm_mm; struct userfaultfd_ctx *ctx; ... ctx = vma->vm_userfaultfd_ctx.ctx; ... BUG_ON(ctx->mm != mm); ... So I think we should be safe. Thanks, -- Peter Xu