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Mon, 17 Apr 2023 04:31:47 -0700 (PDT) MIME-Version: 1.0 References: <20230304034835.2082479-1-senozhatsky@chromium.org> <20230416151853.GK25053@google.com> <20230417024446.GL25053@google.com> <20230417035232.GM25053@google.com> <20230417111243.GN25053@google.com> <20230417112421.GO25053@google.com> In-Reply-To: <20230417112421.GO25053@google.com> From: Yosry Ahmed Date: Mon, 17 Apr 2023 04:31:11 -0700 Message-ID: Subject: Re: [PATCHv4 0/4] zsmalloc: fine-grained fullness and new compaction algorithm To: Sergey Senozhatsky Cc: Yu Zhao , Minchan Kim , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5FC05140022 X-Stat-Signature: wrxd9gpp8saj9zxhzouh1fm5bwusszfe X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1681731109-882096 X-HE-Meta: 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 z5+Td1L9 OTDD57YHFPd4dr8LujTcEild2F9TLwR1kRh4sQW4GPua/nX/Hpm9uh5gxskcY9WKyhGkU9LS35oc9jdDbt01LBB429Gl3sW+GMl9/sSOl8mj31UUFTxCGgtYfYt0uBOtwcBTnG/9CA2vKLCUkxdlqRCb0YFkv6BdsEEcD/NjOfTE0sQ2EsXaxYObvuAgbkstVEBdSpB80zPA0oy9ZLSE5X63W8JlDxct7Q5fkEduDaJaP+7ON/UWMPKRTOF/HdIHJ3Btd0fTRwo05NUn5loGONtoq+KtwPPne+Q185aPobM4QCVTC9k+emKq1Ktl5PjSJNvTNkN9vDbe0jVuQ+vdgq7xVe5YqyDnA+ZQO 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, Apr 17, 2023 at 4:24=E2=80=AFAM Sergey Senozhatsky wrote: > > On (23/04/17 04:16), Yosry Ahmed wrote: > > > That's a good question to which I don't have an answer. We can list_a= dd() > > > the same zspage twice, unlocking the pool after first list_add() so t= hat > > > another process (including another zs_compact()) can do something to = that > > > zspage. The answer is somewhere between these lines, I guess. > > > > But the first list_add() is (in this case) the correct add, so we > > expect other processes to be able to access the zspage after the first > > list_add() anyway, right? > > Correct. Compaction also can unlock pool->lock and schedule() so that > another process can access the source zspage, when compaction gets > scheduled it can attempt putback/unlock the same zspage one more time > (the zspage may not even exist at this point, I assume). Good point, that could very well be where the corruption is coming from. Thanks for pointing this out.