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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id j26-20020a0cae9a000000b0064f3d5cbbb6sm2926202qvd.114.2023.08.23.09.41.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Aug 2023 09:41:03 -0700 (PDT) Date: Wed, 23 Aug 2023 12:41:00 -0400 From: Peter Xu To: Hugh Dickins Cc: Andrew Morton , Edward Liaw , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH mm-hotfixes-unstable] shmem: fix smaps BUG sleeping while atomic Message-ID: References: <6fe3b3ec-abdf-332f-5c23-6a3b3a3b11a9@google.com> MIME-Version: 1.0 In-Reply-To: <6fe3b3ec-abdf-332f-5c23-6a3b3a3b11a9@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Queue-Id: D6D7610001C X-Rspam-User: X-Stat-Signature: k1ygukebwtcdg1yot3shz4qsgksnbku9 X-Rspamd-Server: rspam03 X-HE-Tag: 1692808866-735511 X-HE-Meta: U2FsdGVkX1+M+MBmBn+JPcjFFKTjtaQats+zhmdTPlDjx/o0lpzpWlfOFegXV7sAtc6VomB/ZwmnfArRQdH3I3723GsV1rXUmKb/303XpC3zkCB7e3nBENXk07ug73lq/QPhXa/vntPIpqEpO5MEyiOl38D76lVv5YWp1Kzr8BFQQN8Nhw9Mt2qIAg5IUjrtbMRVEVQbFveLO2cJ09TueZQ0rG/xfbNT1O0/PCvMYJNxTBbuyRISyNyBzA5EeyOTHCPTQyIc0pNlUgQ46uD3COyM53HDVTrnGRbBcWUWWRgMEJfvRkHRaTZ01fKS78lVtEvYBbJw0wm2e2SDVceteWnnCrPlSF4xEa5ffqLcPHEwNcY2eEx+CxsfUgNfYNLBZDEIbwGYKTL8aIxYn9GJgz2xTpY90soGDPm5aEO1s3/liPjfazNc4w3l3BiiCnuO4Ur7uJhEp5YfeD+Tz3TmlZ1dW09cbgMVdc4wYbNggMaAZyQ+codhe7kLHFcws+LWOIZ2Mo3YgTHukCr0jZISs+Bo6AFA6p1spjwtVH5mMGeP5J9eBN2uOdFdiuQ8F+vfBp+77sZSHh/5CfDmJeSSDXIA48IfDdWhW1KBX0ot6W/FuhmixedYYLyAo45NWJLoLIPdQDEndNHKeCUj5WdQeYxJ3pjjtJO0piFeakZRGBJGyCJRl6mvwO02Vr16kGEIftRQYkpJSiTRAb+GK5lRMA0n4aR2vSl+cFKRXuBd36T6NCUlHe1J90OOzYEsuGSAzmf9/aB9srS34FUEEXdqpcOIqakO1wHGaP9Eqa35QHiwIoVr1RVH7GKg+nhtZQQfutK6ycSx9AClt2rWV3HUuWNAyB2Z5saW+1mdvKbBUK7WfWmOCI8VEXhCRovk02p6IZRqv269Ym6Rmzd2WKr1P8pd4EsD6zoWYsxuTERNaG0/MdV5kmykMSvGDkTGW19zr8KlgWTyMU3j3OEgjL3 UUjtMTN9 SNAlHZLSSk7O6QHTAQSsT4zXu9rAhFXPQkHgINEuArCISC5pWFJZ+phY3EMojposJaLVsxRnIHHHUKNiyk6bKsgt4mEsrtR9DlypkpAgIksint2kxelABri2aQPyDBAGNczSC5xNT6OzSCZIjJCeQ2HQ70yCUe4ATXTUppI9JIK/G2saobgBm0EgykOWuH4tdh1F+C3RFrGNxLVqaMQ1eKlMD1qzN6fJoEEjBbm6YzeAXvGYLeKVYJo6KzTDwvV2b9SAIT1r3b7qatsR4cD2hAc5lAXSzcp6y8iz64tLN5Le8nGMTDM4rsqS31TrScnSUNXYvyQ2YHvLMrWuSY2Gx9Ikb0NhgD8xfOocEQTbJRM10LyG9jLlvUmxjHLhzWcRE8IKtv2lqeIN3I2zrXrq6SOgQQXlcadPvRiCZSo/GhmWkItjtbHA0rX0zb4FLsnGhVmX12Bxfak2coplzRVtIT7NxzVidRPujFQrHO2ad0s6LC7c= 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 Tue, Aug 22, 2023 at 10:14:47PM -0700, Hugh Dickins wrote: > smaps_pte_hole_lookup() is calling shmem_partial_swap_usage() with page > table lock held: but shmem_partial_swap_usage() does cond_resched_rcu() > if need_resched(): "BUG: sleeping function called from invalid context". > > Since shmem_partial_swap_usage() is designed to count across a range, but > smaps_pte_hole_lookup() only calls it for a single page slot, just break > out of the loop on the last or only page, before checking need_resched(). > > Fixes: 230100321518 ("mm/smaps: simplify shmem handling of pte holes") > Signed-off-by: Hugh Dickins > Cc: stable@vger.kernel.org # 5.16+ Oops.. thanks Hugh. Acked-by: Peter Xu -- Peter Xu