[PATCH v8 17/22] xfs: remove unwritten extents after preallocations in fsverity metadata

Andrey Albershteyn
2026-04-20T11:48:25Z

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>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
---
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 68d9736d19d9..ef5cf97ad700 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