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List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC] btrfs: get rid of btrfs_(alloc|free)_compr_folio() To: Boris Burkov , David Sterba Cc: Qu Wenruo , linux-btrfs@vger.kernel.org References: <20260305025611.GC5735@twin.jikos.cz> <20260305174609.GC926642@zen.localdomain> 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 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zhCyDYdv29TUzjG1MxJG+uBBPG8a+UYmNnRYAGAmlkjN8g10G2PbGubKwQTg8TG+NfJB8RVNK CsZEfF++SfFIOcFhA0JMI299p/TxlwoPi+xaODahtp5QgQ80eF0vInPTJT82IuDs6yNFY0Ejh mBIb6ZG9Cdl1EVfqXXLdLGzYtlEIlNaUKBWi18/zWOO2qBEDxBItX8nsT2pQ== =E5=9C=A8 2026/3/6 04:16, Boris Burkov =E5=86=99=E9=81=93: [...] >> So I stand by the reason of the pool but with the evolution of folios >> and bs < ps the cost could be too high. I can still see the pool for a >> subset of the combinations for some common scenario like 4K block size >> on 64K page host (e.g. ARM). >> >=20 > FWIW, we do already see issues with allocation in compressed IO in > production, so I am hesitant to support this change. May I ask how frequent the problem is, and what's the CPU arch? Finally is it only happening after commit 6f706f34fc4c ("btrfs: switch=20 to btrfs_compress_bio() interface for compressed writes"), aka v7.0 kernel= . I tried my best locally to introduce extra ASSERT()s to make sure every=20 folio inside a compressed bio has a ref of 1, but it hasn't yet=20 triggered inside zlib_compress_bio(). Thanks, Qu >=20 > On the one hand, we have the issues so the pool is not completely saving > us anyway. On the other hand, removing it seems likely to make this wors= e > in the way that you predict, Dave. >=20 > If we do move forward with this, I will try to watch such errors closely > on the first release of a kernel without the pool. >=20 > Thanks, > Boris >=20 >>> And hopefully this will address David's recent crash (as usual I'm not >>> able to reproduce locally). >> >> I'll run the test with this patch. >=20