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Tue, 12 Nov 2024 07:13:07 +0100 Message-ID: <5afdbcb2-99ee-48de-88a6-afe910329a04@gmx.com> Date: Tue, 12 Nov 2024 16:43:03 +1030 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: About using on-stack fsdata pointer for write_begin() and write_end() callbacks To: Christoph Hellwig Cc: Qu Wenruo , linux-fsdevel@vger.kernel.org, linux-btrfs References: <561428e6-3f71-48cb-bd73-46cc21789f6f@gmx.com> <03f86d46-0de3-4c7b-901f-1ae16b554186@gmx.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1YAUJEP5a sQAKCRDCPZHzoSX+qF+mB/9gXu9C3BV0omDZBDWevJHxpWpOwQ8DxZEbk9b9LcrQlWdhFhyn xi+l5lRziV9ZGyYXp7N35a9t7GQJndMCFUWYoEa+1NCuxDs6bslfrCaGEGG/+wd6oIPb85xo naxnQ+SQtYLUFbU77WkUPaaIU8hH2BAfn9ZSDX9lIxheQE8ZYGGmo4wYpnN7/hSXALD7+oun tZljjGNT1o+/B8WVZtw/YZuCuHgZeaFdhcV2jsz7+iGb+LsqzHuznrXqbyUQgQT9kn8ZYFNW 7tf+LNxXuwedzRag4fxtR+5GVvJ41Oh/eygp8VqiMAtnFYaSlb9sjia1Mh+m+OBFeuXjgGlG VvQFzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCZxF1gQUJEP5a0gAK CRDCPZHzoSX+qHGpB/kB8A7M7KGL5qzat+jBRoLwB0Y3Zax0QWuANVdZM3eJDlKJKJ4HKzjo B2Pcn4JXL2apSan2uJftaMbNQbwotvabLXkE7cPpnppnBq7iovmBw++/d8zQjLQLWInQ5kNq Vmi36kmq8o5c0f97QVjMryHlmSlEZ2Wwc1kURAe4lsRG2dNeAd4CAqmTw0cMIrR6R/Dpt3ma +8oGXJOmwWuDFKNV4G2XLKcghqrtcRf2zAGNogg3KulCykHHripG3kPKsb7fYVcSQtlt5R6v HZStaZBzw4PcDiaAF3pPDBd+0fIKS6BlpeNRSFG94RYrt84Qw77JWDOAZsyNfEIEE0J6LSR/ In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:XbzuunYOiECzoD6U/Ln2CEUBWH6EPDnjWB9SAbG+Hb722uZ3tlK wbhK5vjElCEXzFgZ9wCNwSB/bDSbqm5YUBbrUaxkieOjbgjhb7pUtCllufjmLYtC7KLhfOx RVX/HT01wScWTHMuSv8TWAMFf1ybktuZ+gyU9nNAFDvkuxD7xhW77pP/OBWwusS3ZNrJNJB JahoAMQqwcUEMfwAOOB5g== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:9HYwuqvUoLI=;53WFSLChFmWPMiBYpPARAg1IhiB Yw88J3o1lY0E7XXj/lvyndujFmVlDcE/Ggw6Ck8ZtarPY6ox4GDbnINN5HM80HgjX+eEdI77s gzgp1CjdY9aOpFe/gpyx3ZQTHr1IsO719r8Aq+/3P2ndJZtUuNTUYkv9dpEwlf6l6/zXjithJ HEQ/qxJUwiJyQ8erz2Hp4lMEPS9bxfW0BSIvb1dsja0LwZ7EJAZbHdKvPe8aXxtc5SE8ZUXXF 9+bqBFZiNMqMxD5Xmcht2ihWPQyTpNNTd06M7ZXdPrFBX2FyA9c9Y8TUznpE1bCdeK0zbyRI6 36cTAcrYaP8TijHPE8WtavAfSJrIQImGulSJHlo4w8S+DX4eK2ewh6n7wFNlsV5OlbxYXGuTv HrAnGRyLyG10Aq8wNS/Np/qBFcCiB+TsW5mEknEsUe4DaeBuqBb8V7Bry3FO1SyDs95mEq+aB YnDYfiYO0h9uUzHHh24myQRnaj8UisrHuTLER8WydsAaA2WOQQ5hMCEhFvFxU++Hi2PpTY+9q YDFiZbX6za9P+8BG4FR3fBo+6ea0Z1982/gSTkzdh4Ms8eWC0JZt/6hElAiu1P6u/IrWwlKNo Bv05ahoN03VlNNFu1eBzABI5YUOKc0iPnNPWY2PmlzpTCZWIVdlPsswBGIPgLtTgYI3bgpREz xSZE4S5aIxXw9Vo5pQ3+uzY2cCZF7YIoc+2G6a52fVvwlDKuWOejLJnHhTb6sDrESaOEvn4Nf nDUe5uZZ1QJwkwXE2svoXEQnqwQXWzNv9PEjCFeaersRrFQze0VGQyZjwLuXZuNg7ZGLP6t2V pTwwLcisytAZlW7kOrdQZz+VIFcOJobqRqM8/h1zHz62ptiCdJi5QFYuaZRyAput+p9YkZI6o vmBJBe7URf7uHCugDxldkVYsg8qhfMkY7d5dNuU8J+MgRPUlCLKog2Hmj =E5=9C=A8 2024/11/12 16:36, Christoph Hellwig =E5=86=99=E9=81=93: > On Tue, Nov 12, 2024 at 04:33:56PM +1030, Qu Wenruo wrote: >> IIRC it's related to the get_user_page() shenanigans but not 100% sure. > > While there might be a few stragglers left, everyone should be using > pin_user_pages when manipulating page contents. The long tolerated > just pin and mark dirty is officially a bug now. Great to know that. > >> I'm talking about the iomap_set_range_dirty() call inside >> iomap_writepage_map(), for the "if (i_blocks_per_folio() > 1)" branch. > > That does not set the page dirty. It propagatates the per-folio > dirty state into the per-block dirty bitmap allocated in the line > above. I know, I just want to say it's marking the whole folio to be written back= . And in that out-of-band case, shouldn't we error out now instead of marking the range to be written back? Especially such out-of-band folio is unstable and can lead to other problems, like content change halfway and causing csum mismatch. And if that's the case, I think it will be much easier for btrfs to get rid of its cow fixup workaround. Thanks, Qu