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 <[email protected]>
> Signed-off-by: Andrey Albershteyn <[email protected]>

/me is ok with this
Reviewed-by: "Darrick J. Wong" <[email protected]>

--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
> 
> 


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