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Fri, 13 Sep 2024 07:47:24 +0200 Message-ID: <85888aaa-c8f5-453b-8344-6cabc82f537e@gmx.com> Date: Fri, 13 Sep 2024 15:17:19 +0930 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: [PATCH] btrfs: scrub: skip PREALLOC extents on RAID stripe-tree To: Johannes Thumshirn , Johannes Thumshirn , Chris Mason , Josef Bacik , David Sterba , "open list:BTRFS FILE SYSTEM" , open list Cc: WenRuo Qu References: <20240912143312.14442-1-jth@kernel.org> <958f5586-c37a-4836-87a2-4530428b0a4e@wdc.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+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: <958f5586-c37a-4836-87a2-4530428b0a4e@wdc.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:5wVcUuI1GXMVxdeNkUQATjTvVBMzNLFpNPQ8eIwvXFTUdatVbaC sl5NfNe3OkDrLxe0fKW79BS0rmo9JVBEIVHXQEnZ6WGHd95T8LqiTTKl2e9tfXciW/BPC9f dCUOK5dLbSWmT6mPnHcmFSKCzZRxwAPFSXNQznJTvPEauqaAgVseGc8mcYivD1soR2ERWiK oxl9qyG5l/peJTDwmCT6w== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:yF2iUk9ITAQ=;GK0xtzAmesKahR10OBPz2IsDzNp VNqDA1MrCgijWpnK/6estQTuClGDIOMUFZYdoO3T1CaJ8exKElbSdJn8BtHTKaZS8AXlZhnvL yLm7b7Y3WQd2l+woQtejeNtcLtdcNUKSQ0UJIyjhLIPXwx+XmzOMFwBTni2h7MTRJ7nos91/X skSRbFdpR1LPjwYSfctmJ3pk048C5H87g/nbS7RDwJB8prDDp1/m/GeP9YXVlD/gNutIj8oxi UAgijv1gHQ62A77aZpeAQbZ8rbfbVFPFt1/b1o51AkmWeIkkQ7IlP2t4vrmlncZbcpKXtODz9 G3G6dpaEz64drk5E2iWo3EzhMio4uYQ6qkj5I4SdYvWO6dRo9c45AT4+CiYXPHGGssFdOtfB+ PwnPOTUtRekgAeySkcJvaIJoslwUCIzn0DZsw4NNEvnURqMkbmEEUzLGmuchzcLyHPasylvrr HZr5LD7OQJpUuCOAcUMqMpvEXNIvJmCVoVFEmfNezWGauSwQfAI3/ojN9Fh3MHqEcMrXxcEs2 9zhbaXPYFHnBTO67l2yuqiyW5alRI83/cHljz3I9LeK+8mkec5aZs8lQnePDTPHgqPxvsn9Yp U4KI0j2IcWFmjWKL8AFiHHRa4ZUrcAzZpRP5eHF/Sjx2iCVu5cFFczftqKUbSQ1itprjfpE/5 qVw2MiyHBEBt5VyhWJbz4FuO0SbEJgcYowmGE1AjCLQBrBvVZ8WlR2CImHTcbj3M3SdX3A2P8 V8/c1gxdD4soMfgb6CdKV63V05QL8V1l1R03Ngde8I3iE/AORuBmMnNbUqG/gbgqRk6B/ZKin MOeC2pld7s6UC59VfK8Ur8Fg== =E5=9C=A8 2024/9/13 15:12, Johannes Thumshirn =E5=86=99=E9=81=93: > On 12.09.24 23:32, Qu Wenruo wrote: >> >> >> =E5=9C=A8 2024/9/13 00:03, Johannes Thumshirn =E5=86=99=E9=81=93: >>> From: Johannes Thumshirn >>> >>> When scrubbing a RAID stripe-tree based filesystem with preallocated >>> extents, the btrfs_map_block() called by >>> scrub_submit_extent_sector_read() will return ENOENT, because there is >>> no RAID stripe-tree entry for preallocated extents. This then causes >>> the sector to be marked as a sector with an I/O error. >>> >>> To prevent this false alert don't mark secotors for that >>> btrfs_map_block() returned an ENOENT as I/O errors but skip them. >>> >>> This results for example in errors in fstests' btrfs/060 .. btrfs/074 >>> which all perform fsstress and scrub operations. Whit this fix, these >>> errors are gone and the tests pass again. >>> >>> Cc: Qu Wenru >> >> My concern is, ENOENT can be some real problems other than PREALLOC. >> I'd prefer this to be the last-resort method. > > Hm but what else could create an entry in the extent tree without having > it in the stripe tree? I can't really think of a situation creating this > layout. My concern is that, if by some other bug that certain writes didn't create needed RST entry, we will always treat them as preallocated during scrub. Thus it may be better to have a way to distinguish a real missing entry and preallocated extents. > > >> Would it be possible to create an RST entry for preallocated operations >> manually? E.g. without creating a dummy OE, but just insert the needed >> RST entries into RST tree at fallocate time? > > Let me give it a try. But I'm a bit less happy to do so, as RST already > increases the write amplification. Well, write amplification is always a big problem for btrfs... Thanks, Qu