On Sat, Feb 21, 2026 at 12:45:25PM -0800, Eric Biggers wrote:
> Currently, all filesystems that support fsverity (ext4, f2fs, and btrfs)
> cache the Merkle tree in the pagecache at a 64K aligned offset after the
> end of the file data. This offset needs to be a multiple of the page
> size, which is guaranteed only when the page size is 64K or smaller.
>
> 64K was chosen to be the "largest reasonable page size". But it isn't
> the largest *possible* page size: the hexagon and powerpc ports of Linux
> support 256K pages, though that configuration is rarely used.
>
> For now, just disable support for FS_VERITY in these odd configurations
> to ensure it isn't used in cases where it would have incorrect behavior.
>
> Fixes: 671e67b47e9f ("fs-verity: add Kconfig and the helper functions for
> hashing")
> Reported-by: Christoph Hellwig <[email protected]>
> Closes: https://lore.kernel.org/r/[email protected]
> Signed-off-by: Eric Biggers <[email protected]>
> ---
> fs/verity/Kconfig | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig
> index 76d1c5971b82..b20882963ffb 100644
> --- a/fs/verity/Kconfig
> +++ b/fs/verity/Kconfig
> @@ -1,9 +1,12 @@
> # SPDX-License-Identifier: GPL-2.0
>
> config FS_VERITY
> bool "FS Verity (read-only file-based authenticity protection)"
> + # Filesystems cache the Merkle tree at a 64K aligned offset in the
> + # pagecache. That approach assumes the page size is at most 64K.
> + depends on PAGE_SHIFT <= 16
Makes sense to me, we have "depends on PAGE_SIZE_LESS_THAN_256KB" since
somebody tried to use btrfs on the 256K system.
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