linux-ext4 - Re: fsverity cleanups, speedup and memory usage optimization v2

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Message-ID: <20260122154215.GV26902@suse.cz>
Date: Thu, 22 Jan 2026 16:42:15 +0100
From: David Sterba <dsterba@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: Eric Biggers <ebiggers@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	David Sterba <dsterba@...e.com>, Theodore Ts'o <tytso@....edu>,
	Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
	Andrey Albershteyn <aalbersh@...hat.com>,
	"Matthew Wilcox (Oracle)" <willy@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
	fsverity@...ts.linux.dev
Subject: Re: fsverity cleanups, speedup and memory usage optimization v2

On Thu, Jan 22, 2026 at 09:21:56AM +0100, Christoph Hellwig wrote:
> Hi all,
> 
> this series has a hodge podge of fsverity enhances that I looked into as
> part of the review of the xfs fsverity support series.
> 
> The first part calls fsverity code from VFS code instead of requiring
> boilerplate in the file systems.  The first patch fixes a bug in btrfs
> as part of that, as btrfs was missing a check.  An xfstests
> test case for this was submitted already.
> 
> The middle part optimizes the fsverity read path by kicking off readahead
> for the fsverity hashes from the data read submission context, which in my
> simply testing showed huge benefits for sequential reads using dd.
> I haven't been able to get fio to run on a preallocated fio file, but
> I expect random read benefits would be significantly better than that
> still.
> 
> The last part avoids the need for a pointer in every inode for fsverity
> and instead uses a rhashtable lookup, which is once per read_folio or
> ->readahead invocation and for for btrfs another time for each bio
> completion.  Right now this does not increse the number of inodes in
> each slab, but for ext4 we are getting very close to that (within
> 16 bytes by my count).
> 
> Changes since v1:
>  - reorder to keep the most controversial part last
>  - drop moving the open handling to common code (for now)
>  - factor the page cache read code into common code
>  - reduce the number of hash lookups
>  - add a barrier in the fsverity_active that pairs with the cmpxchg
>    that sets the inode flag.
> 
> Diffstat:
>  fs/attr.c                    |   12 ++

For the btrfs changes

>  fs/btrfs/btrfs_inode.h       |    4 
>  fs/btrfs/extent_io.c         |   37 +++++---
>  fs/btrfs/inode.c             |   13 ---
>  fs/btrfs/verity.c            |   11 --

Acked-by: David Sterba <dsterba@...e.com>