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Wed, 26 Jul 2023 04:31:52 -0700 (PDT) Received: from google.com ([2401:fa00:8f:203:a2a4:d590:6375:66ba]) by smtp.gmail.com with ESMTPSA id y3-20020a1709029b8300b001b895336435sm12863278plp.21.2023.07.26.04.31.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Jul 2023 04:31:52 -0700 (PDT) Date: Wed, 26 Jul 2023 20:31:47 +0900 From: Sergey Senozhatsky To: Andrew Yang =?utf-8?B?KOaliuaZuuW8tyk=?= Cc: "senozhatsky@chromium.org" , "bigeasy@linutronix.de" , "linux-kernel@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "linux-mm@kvack.org" , wsd_upstream , Casper Li =?utf-8?B?KOadjuS4reamrik=?= , "akpm@linux-foundation.org" , "minchan@kernel.org" , "linux-arm-kernel@lists.infradead.org" , "matthias.bgg@gmail.com" , "angelogioacchino.delregno@collabora.com" Subject: Re: [PATCH] zsmalloc: Fix races between modifications of fullness and isolated Message-ID: <20230726113147.GK955071@google.com> References: <20230721063705.11455-1-andrew.yang@mediatek.com> <20230726031846.GJ955071@google.com> <42f1209a686404ffd0f9dff05ed10a8d23383a11.camel@mediatek.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <42f1209a686404ffd0f9dff05ed10a8d23383a11.camel@mediatek.com> X-Rspamd-Queue-Id: 2E36FC0016 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: q51jgodmjqoc49atkk6q8gdsboeghkty X-HE-Tag: 1690371113-611878 X-HE-Meta: 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 XCHIi261 CLGK9XKn16ZvuFRTxr7wpYeQdluKP9SJnOY9X0SEV4clXNJvwGq9fz5MyG1ZWvkhbHNnMDx+6KJ++jWlpqel6KWXKXLtL9OAnVEiKtWvwt7oMCcWfj2YseLD5x07+R8s3YZgVzyzwY28SE5x7Q02YXsG+vKcNAXS3X8lSY1+ifodOZfepPkKjapTP3UFc9FAdob2yKZdEH5mxQrKDuqCQukys1GvxeFkUJVu6Fh2GNbb8eqI/uO29oXR1XtWlzqaJ4I9NxQ6xbkk/rV75OMWlpKKMeM7zv42Bt9/NxUwx59C9iOKJUwUPzp3RXt4RpMgbNjOMCdwCpDvQTV4NzRApoCu4djCAZXPjBTUHPY77pzjgIq7FrTbhS+hUwhrOph2QX1M9AIEh979ahTOKGEW6zHUKb6yMG0rdK0uf8mLOuED5tgoyjaM90i70tutEQQ5SAfagQWP2iWVVirii+T3cLvAv3XnLyIQrU7T0IPBMEUgILMs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.001313, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (23/07/26 06:59), Andrew Yang (楊智強) wrote: > On Wed, 2023-07-26 at 12:18 +0900, Sergey Senozhatsky wrote: > > > > External email : Please do not click links or open attachments until > > you have verified the sender or the content. > > On (23/07/21 14:37), Andrew Yang wrote: > > > > > > Since fullness and isolated share the same unsigned int, > > > modifications of them should be protected by the same lock. > > > > > > Signed-off-by: Andrew Yang > > > Fixes: c4549b871102 ("zsmalloc: remove zspage isolation for > > migration") > > > > Have you observed issues in real life? That commit is more than a > > year > > and a half old, so I wonder. > > > Yes, we encountered many kernel exceptions of > VM_BUG_ON(zspage->isolated == 0) in dec_zspage_isolation() and > BUG_ON(!pages[1]) in zs_unmap_object() lately. Got it. > This issue only occurs when migration and reclamation occur at the > same time. With our memory stress test, we can reproduce this issue > several times a day. We have no idea why no one else encountered > this issue. BTW, we switched to the new kernel version with this > defect a few months ago. Yeah, pretty curious myself. > > > @@ -1858,8 +1860,8 @@ static int zs_page_migrate(struct page > > *newpage, struct page *page, > > > * Since we complete the data copy and set up new zspage > > structure, > > > * it's okay to release the pool's lock. > > > */ > > > > This comment should be moved too, because this is not where we unlock > > the > > pool anymore. > > > Okay, I will submit a new patch later. Thank you!