linux-kernel - Re: [PATCH 0/1] Add 16K Support for f2fs

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Message-ID: <20230816023417.GA899@sol.localdomain>
Date:   Tue, 15 Aug 2023 19:34:17 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Daniel Rosenberg <drosen@...gle.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        Jaegeuk Kim <jaegeuk@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] Add 16K Support for f2fs

On Tue, Aug 15, 2023 at 06:14:31PM -0700, Daniel Rosenberg via Linux-f2fs-devel wrote:
> F2fs filesystems currently have two large restrictions around block size.
> The block size must equal the page size, and the block size must be 4096.
> 
> The following patch, along with the associated f2fs-tools patch set, relax the
> latter restriction, allowing you to use 16K block size f2fs on a 16K page size
> system. It does not allow mounting 4K block size f2fs on a 16k page system.
> 
> Doing that would require a lot more work, requiring a refactor of all block
> sized struct similar to the userspace patches, as well as handling the block
> reading/writing at sub page boundaries. As far as I know, buffer_heads are
> still the main way this is handled in other filesystems. Is there a different
> option there? I know there's a general desire to move away from buffer_heads,
> but I don't know of any replacements covering that use case. And it would feel
> a bit silly to not be able to read older filesystems from a 16k system...

iomap is the replacement for buffer heads.  See https://lwn.net/Articles/935934

- Eric