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Date: Thu, 26 Feb 2026 14:07:14 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Tal Zussman <tz2294@columbia.edu>
Cc: Jens Axboe <axboe@kernel.dk>,
	"Tigran A. Aivazian" <aivazian.tigran@gmail.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	Namjae Jeon <linkinjeon@kernel.org>,
	Sungjong Seo <sj1557.seo@samsung.com>,
	Yuezhang Mo <yuezhang.mo@sony.com>,
	Dave Kleikamp <shaggy@kernel.org>,
	Ryusuke Konishi <konishi.ryusuke@gmail.com>,
	Viacheslav Dubeyko <slava@dubeyko.com>,
	Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
	Bob Copeland <me@bobcopeland.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
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	ntfs3@lists.linux.dev, linux-karma-devel@lists.sourceforge.net,
	linux-mm@kvack.org
Subject: Re: [PATCH RFC v2 2/2] block: enable RWF_DONTCACHE for block devices
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References: <20260225-blk-dontcache-v2-0-70e7ac4f7108@columbia.edu>
 <20260225-blk-dontcache-v2-2-70e7ac4f7108@columbia.edu>
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> --- a/fs/bfs/file.c
> +++ b/fs/bfs/file.c
> @@ -177,7 +177,7 @@ static int bfs_write_begin(const struct kiocb *iocb,
>  {
>  	int ret;
>  
> -	ret = block_write_begin(mapping, pos, len, foliop, bfs_get_block);
> +	ret = block_write_begin(iocb, mapping, pos, len, foliop, bfs_get_block);

Please don't change the prototoype for block_write_begin and thus
cause churn for all these legacy file systems.  Add a new
block_write_begin_iocb, and use that in the block code and to implement
block_write_begin.

And avoid the overly long line there to keep the code readable.

Note that you also need to cover the !CONFIG_BUFFER_HEAD case.