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Mon, 23 Jan 2023 19:51:05 -0500 (EST) Received: by box.shutemov.name (Postfix, from userid 1000) id F24B310942D; Tue, 24 Jan 2023 03:51:02 +0300 (+03) Date: Tue, 24 Jan 2023 03:51:02 +0300 From: "Kirill A. Shutemov" To: David Hildenbrand , g@box.shutemov.name Cc: Jann Horn , Andrew Morton , linux-mm@kvack.org, "Kirill A. Shutemov" , Zach O'Keefe , linux-kernel@vger.kernel.org, Yang Shi Subject: Re: [PATCH] mm/khugepaged: Fix ->anon_vma race Message-ID: <20230124005102.ow33h7tfmj5eqyr3@box.shutemov.name> References: <20230111133351.807024-1-jannh@google.com> <20230112085649.gvriasb2t5xwmxkm@box.shutemov.name> <20230115190654.mehtlyz2rxtg34sl@box.shutemov.name> <20230116123403.fiyv22esqgh7bzp3@box.shutemov.name> <5a7fdfa7-5b25-0ed4-2479-661d387b397b@redhat.com> <20230116134710.n4dgtrutt6rqif62@box.shutemov.name> <1b8696ec-e2be-7b7b-705c-e2dcabb2e8e5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1b8696ec-e2be-7b7b-705c-e2dcabb2e8e5@redhat.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7469F40014 X-Rspam-User: X-Stat-Signature: 5cbdoqw39cx1zdaqpnprnxjyicwg7qke X-HE-Tag: 1674521467-901633 X-HE-Meta: U2FsdGVkX18dpI+rS1JE6zyI12b+dhDpmQ1rSls6JGlgWIqyiWvZZLqoQFjYTQkoLu+rHq7g4zQh77mUj7VeY1u28nN0A8Ut+aWZp39RuKkAlSvy4BVmtLQ0JWn//sZzNyGHegBeXYzSWOOEuhGdGrqNV2K3sJxnQgjgjIdozUl4hptEEaRlnHKhH56GUkKTw3L6aO+9L0YTo4wDyAfuu9i9dpLd3d7MzQ2W+8pbaqKjp3ytLSivfdw2L/xY8HMKoQeHlNeol0CZ0wM5nRlrw5dkktehe80EYYbePt4z/PClS4u+BivqicacxzuQFjGJEuoXR5diGLXfFBcmWkeY8MPDdue1QdLqbzKn0g/gKxvxTha7z+DWjl+ZXuZE+R9605CeZie8YRT+ZgmcXwFu+ANafHviAtkWB1CddhG3oXSzzlOKV326g5glnRiyCrIGw4NH8mqGE3eHpNSAlQO+NNBdQmJHo5lMIAUEbMCUfoITICJIQDPAy9x4QGSp+mQH01p/x9PwTfrANKW5XHrVhfUHY6nGIaAJfGZpnmV9AHQ3WepnKB3zth77HWFkKWwrRHUhOMpSfSgSh7jWs4T1c04iR+OWC8Id1BFZzI+J90h+lGGxHCnNQb+fevK51SVA2KuRy+CgYBvR7ahYBfIDy2Cb6Rz+YLJmS0r/PCBikiFkUZOu3N3eGzAW/AtmZWR+dL4QMhF6SWrmDOX96bkRD7bjoXWO96ABG2ilgHh6/NOCPtNkA2+T8MlpaWQv8qo670d5GrZCY9NoNq+GGwVJFe7sfPzy+LYjwecjXZdNPvFELnF5TRz/vM9w0Tbt67vMkhYy5nMzPxRwW5VpCatX8YMLs+jsdQxcAYrxb+8oz5Tap7d3Jb4+PhC8ok7cD3+4npfCY0vTFfGeBKIcYq8iuThXuen08ikFuh6E1pJi017oR7mOPIPoYQR6sK1ZzUfbRBgKoroE1eaDcpjEI1c /vT4kgvt ZhLSMKHK2B5ueynKrnDH8wvs/igBWSOyEEKCe2rkZt6Y5tqwYMxQsbWq23AcSjFDTCvjLXy5VbiW3tzwpe6kNYtz8mi/56CXkXBDOreFVemo32Q0ZD+gJ0JZTqFwUvlG9V/hmWMvy2fq4o4hdG+WAY7SI4XzfxSFkDj4ou/y9Wo5xKXNgzFiJss+Asyl7MFYPH6heqVznHIg+xRcoOKz3HDx6R/HGr5cJ5VNoVVuORqzFZXJNXbNZ7ADi6jy2Xfu9CX3F0l4tT7KmIrIaokSMqNJoMNC47h/C2wJjDDwQ1IqCqXZ+hsvlh8OVkhSUWCIO0EShqsJ7W1PXcZEHK3L5BWgdb7OmY/B/BjnRGjs9eVSaSbHwIdPNEqzMKrlEIRmCWtIh 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: On Mon, Jan 23, 2023 at 12:07:05PM +0100, David Hildenbrand wrote: > > > commit bedf03416913d88c796288f9dca109a53608c745 > > > Author: Yang Shi > > > Date: Wed Sep 7 11:01:44 2022 -0700 > > > > > > powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush > > > The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will > > > move to use RCU instead of disabling local interrupts in fast-GUP. Using > > > an IPI is the old-styled way of serializing against fast-GUP although it > > > still works as expected now. > > > And fast-GUP now fixed the potential race with THP collapse by checking > > > whether PMD is changed or not. So IPI broadcast in radix pmd collapse > > > flush is not necessary anymore. But it is still needed for hash TLB. > > > > Okay. But I think tlb_remove_table_sync_one() belongs inside > > pmdp_collapse_flush(). Collapsing pmd table into huge page without > > serialization is a bug. They should not be separate. > > Agreed. But I wonder if it should be moved into a generic > pmdp_collapse_flush(), that calls an arch specific __pmdp_collapse_flush(). Um? There's no __pmdp_collapse_flush(). Architectural code overrides pmdp_collapse_flush() altogether. It has know how to serialize properly for the arch. -- Kiryl Shutsemau / Kirill A. Shutemov