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[70.31.26.132]) by smtp.gmail.com with ESMTPSA id i22-20020a05620a075600b006bb82221013sm12295147qki.0.2022.12.15.10.45.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Dec 2022 10:45:10 -0800 (PST) Date: Thu, 15 Dec 2022 13:45:08 -0500 From: Peter Xu To: James Houghton Cc: Mike Kravetz , Muchun Song , David Hildenbrand , David Rientjes , Axel Rasmussen , Mina Almasry , Zach O'Keefe , Manish Mishra , Naoya Horiguchi , "Dr . David Alan Gilbert" , "Matthew Wilcox (Oracle)" , Vlastimil Babka , Baolin Wang , Miaohe Lin , Yang Shi , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 24/47] hugetlb: update page_vma_mapped to do high-granularity walks Message-ID: References: <20221021163703.3218176-1-jthoughton@google.com> <20221021163703.3218176-25-jthoughton@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-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 05CDAC001C X-Stat-Signature: 7pi3txdu1yr3o3xmwtmnjeujkox9dq3g X-HE-Tag: 1671129916-16335 X-HE-Meta: U2FsdGVkX18O6TWVpDJ1lMfhffklCIHQVXNeM0uYaL92pf5OExn+0FR8L51DpMiEX5X3r7+LUsVGhnh6s/Mu85XNwdiK2IOIMMXn5BfMC4V8bqpXDKZndBhfd0GwE4YvkLw58dN8kmof0nJjZ+F4e1jhA5u2hPDx9xt4AF+IqXZOZGQ+KRlM4NPOy0fn+DbUTq0mDAncqlUQG3wJ5gKqUhxX4FezqJo5uJCxJbzsiWVm+kN/cRJh8Z1eKLClFHdtIWN9bJoLhaZmkcpxVpjZ8mw/dV10vHRT5OVNe9ytSkdWWJzrU3InZdeGSsKaWLRu9Tv12YqXV74JWRvPH8JHL220TbCOTWu+OfS3GXYRpHTTPr0siILdhYbQIR3XvHw9PlUIA06Ap5zktUdlqRIVpJxhJsv5TPmdwGDiCJ5kWUTPDBPDEebqG7TVchRSSzSNrD5+aTdJANMPghvpz9h2Kof3w3GIvY7aQ1/EddWVhbPL7i8kdGdPgdazYDCnMHBtzauha8E0qgqz0AaQqboIpu1+arhuyuIwc2cS+B3XLgBfWn0azJQtqaEXVxSTFYu+KNd5BgZ4iiHS7FrTS4kmbHkG2A8+aZx+I9vNkDhKh3TsppXQ/N+xLhEaVIfMQ7AhlzpXKQSbs/v5rbTLJWUwiAoblRW/wFwK+d785OVAOMgTHLT5LTlbeQUAOlfBsrtc0Irdfdo5Lx68ZWYIB2+FLucLArRjytODXWb0fZrmemSuwRZClCU8BItnz7lNaAJh2fveqJQsMfpj5kN13DshTJnCPLZ1cNP1JwUVOZR/jsIOxSUAgg/3PpUBGVLzsB1gJ9Jo4+OFb8QDXbXFYIx5WKSGcydHz2efiMEl5ALmvvEhqvTaArGBDiFJ3mWqK7vMFEjVvmD2dw6qNOqCZZEydpc4201FuNXQqB1vL6qeF/wsRII9FQR5Se7pUxeF09K1/ZhnhNbsN1tnMLgsDMZ tXhujSgm ogj5Wv/1HVpKptd1DM7g8n8G6QkoMXGHUMckWNBxFqteZarRrzkppLOCGMc4q8ayrBCtCwpjU1Jz9dCRTh3v5AFcVj/HGKNcmMqBHRr9wH5XvPUvz6AmVDGEi27TB0/UqlGe1zYrzT17u6jGfSXxI8mfEjg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi, James, On Thu, Dec 15, 2022 at 12:49:18PM -0500, James Houghton wrote: > > @@ -166,19 +167,57 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) [...] > I realize that I can't do this -- we're already holding the > i_mmap_rwsem, and we have to take the VMA lock first. It seems like > we're always holding it for writing in this case, so if I make > hugetlb_collapse taking the i_mmap_rwsem for reading, this will be > safe. > > Peter, you looked at this recently [1] -- do you know if we're always > holding i_mmap_rwsem *for writing* here? > > [1] https://lore.kernel.org/linux-mm/20221209170100.973970-10-peterx@redhat.com/ I think so, an analysis is in previous v2 in one of my reply to John: https://lore.kernel.org/all/Y5JjTPTxCWSklCan@x1n/ No hurt to double check, though. -- Peter Xu