Re: [PATCH v6 16/22] xfs: remove unwritten extents after preallocations in fsverity metadata

Darrick J. Wong
2026-03-31T23:36:06Z

On Tue, Mar 31, 2026 at 11:28:17PM +0200, Andrey Albershteyn wrote:
> XFS preallocates spaces during writes. In normal I/O this space, if
> unused, is removed by truncate. For files with fsverity XFS does not use
> truncate as fsverity metadata is stored past EOF.
>
> After we're done with writing fsverity metadata iterate over extents in
> that region and remove any unwritten ones. These would be left overs in
> the holes in the merkle tree and past fsverity descriptor.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>

/me is ok with this
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/xfs/xfs_fsverity.c | 67 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 67 insertions(+)
>
> diff --git a/fs/xfs/xfs_fsverity.c b/fs/xfs/xfs_fsverity.c
> index 5a6a48fcf843..b193009a1bdb 100644
> --- a/fs/xfs/xfs_fsverity.c
> +++ b/fs/xfs/xfs_fsverity.c
> @@ -21,6 +21,8 @@
> #include "xfs_iomap.h"
> #include "xfs_error.h"
> #include "xfs_health.h"
> +#include "xfs_bmap.h"
> +#include "xfs_bmap_util.h"
> #include <linux/fsverity.h>
> #include <linux/iomap.h>
> #include <linux/pagemap.h>
> @@ -173,6 +175,63 @@ xfs_fsverity_delete_metadata(
> return error;
> }
>
> +static int
> +xfs_fsverity_cancel_unwritten(
> + struct xfs_inode *ip,
> + xfs_fileoff_t start,
> + xfs_fileoff_t end)
> +{
> + struct xfs_mount *mp = ip->i_mount;
> + struct xfs_trans *tp;
> + xfs_fileoff_t offset_fsb = XFS_B_TO_FSB(mp, start);
> + xfs_fileoff_t end_fsb = XFS_B_TO_FSB(mp, end);
> + struct xfs_bmbt_irec imap;
> + int nimaps;
> + int error = 0;
> + int done;
> +
> +
> + while (offset_fsb < end_fsb) {
> + nimaps = 1;
> +
> + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0, 0,
> + 0, &tp);
> + if (error)
> + return error;
> +
> + xfs_ilock(ip, XFS_ILOCK_EXCL);
> + error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
> + &imap, &nimaps, 0);
> + if (error)
> + goto out_cancel;
> +
> + if (nimaps == 0)
> + goto out_cancel;
> +
> + if (imap.br_state == XFS_EXT_UNWRITTEN) {
> + xfs_trans_ijoin(tp, ip, 0);
> +
> + error = xfs_bunmapi(tp, ip, imap.br_startoff,
> + imap.br_blockcount, 0, 1, &done);
> + if (error)
> + goto out_cancel;
> +
> + error = xfs_trans_commit(tp);
> + } else {
> + xfs_trans_cancel(tp);
> + }
> + xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +
> + offset_fsb = imap.br_startoff + imap.br_blockcount;
> + }
> +
> + return error;
> +out_cancel:
> + xfs_trans_cancel(tp);
> + xfs_iunlock(ip, XFS_ILOCK_EXCL);
> + return error;
> +}
> +
>
> /*
> * Prepare to enable fsverity by clearing old metadata.
> @@ -248,6 +307,14 @@ xfs_fsverity_end_enable(
> if (error)
> goto out;
>
> + /*
> + * Remove unwritten extents left by COW preallocations and write
> + * preallocation in the merkle tree holes and past descriptor
> + */
> + error = xfs_fsverity_cancel_unwritten(ip, range_start, LLONG_MAX);
> + if (error)
> + goto out;
> +
> /*
> * Proactively drop any delayed allocations in COW fork, the fsverity
> * files are read-only
> --
> 2.51.2
>
>