[PATCH RFC 02/10] xfs: Refactor xfs_reflink_end_cow_extent()

John Garry
2025-02-04T12:02:13Z

Refactor xfs_reflink_end_cow_extent() into separate parts which process
the CoW range and commit the transaction.

This refactoring will be used in future for when it is required to commit
a range of extents as a single transaction, similar to how it was done
pre-commit d6f215f359637.

Signed-off-by: John Garry <john.g.garry@oracle.com>
---
fs/xfs/xfs_reflink.c | 79 +++++++++++++++++++++++++++-----------------
1 file changed, 48 insertions(+), 31 deletions(-)

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 59f7fc16eb80..580469668334 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -786,35 +786,20 @@ xfs_reflink_update_quota(
* requirements as low as possible.
*/
STATIC int
-xfs_reflink_end_cow_extent(
+xfs_reflink_end_cow_extent_locked(
struct xfs_inode *ip,
xfs_fileoff_t *offset_fsb,
- xfs_fileoff_t end_fsb)
+ xfs_fileoff_t end_fsb,
+ struct xfs_trans *tp,
+ bool *commit)
{
struct xfs_iext_cursor icur;
struct xfs_bmbt_irec got, del, data;
- struct xfs_mount *mp = ip->i_mount;
- struct xfs_trans *tp;
struct xfs_ifork *ifp = xfs_ifork_ptr(ip, XFS_COW_FORK);
- unsigned int resblks;
int nmaps;
bool isrt = XFS_IS_REALTIME_INODE(ip);
int error;

- resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
- error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
- XFS_TRANS_RESERVE, &tp);
- if (error)
- return error;
-
- /*
- * Lock the inode. We have to ijoin without automatic unlock because
- * the lead transaction is the refcountbt record deletion; the data
- * fork update follows as a deferred log item.
- */
- xfs_ilock(ip, XFS_ILOCK_EXCL);
- xfs_trans_ijoin(tp, ip, 0);
-
/*
* In case of racing, overlapping AIO writes no COW extents might be
* left by the time I/O completes for the loser of the race. In that
@@ -823,7 +808,7 @@ xfs_reflink_end_cow_extent(
if (!xfs_iext_lookup_extent(ip, ifp, *offset_fsb, &icur, &got) ||
got.br_startoff >= end_fsb) {
*offset_fsb = end_fsb;
- goto out_cancel;
+ return 0;
}

/*
@@ -837,7 +822,7 @@ xfs_reflink_end_cow_extent(
if (!xfs_iext_next_extent(ifp, &icur, &got) ||
got.br_startoff >= end_fsb) {
*offset_fsb = end_fsb;
- goto out_cancel;
+ return 0;
}
}
del = got;
@@ -846,14 +831,14 @@ xfs_reflink_end_cow_extent(
error = xfs_iext_count_extend(tp, ip, XFS_DATA_FORK,
XFS_IEXT_REFLINK_END_COW_CNT);
if (error)
- goto out_cancel;
+ return error;

/* Grab the corresponding mapping in the data fork. */
nmaps = 1;
error = xfs_bmapi_read(ip, del.br_startoff, del.br_blockcount, &data,
&nmaps, 0);
if (error)
- goto out_cancel;
+ return error;

/* We can only remap the smaller of the two extent sizes. */
data.br_blockcount = min(data.br_blockcount, del.br_blockcount);
@@ -882,7 +867,7 @@ xfs_reflink_end_cow_extent(
error = xfs_bunmapi(NULL, ip, data.br_startoff,
data.br_blockcount, 0, 1, &done);
if (error)
- goto out_cancel;
+ return error;
ASSERT(done);
}

@@ -899,17 +884,49 @@ xfs_reflink_end_cow_extent(
/* Remove the mapping from the CoW fork. */
xfs_bmap_del_extent_cow(ip, &icur, &got, &del);

- error = xfs_trans_commit(tp);
- xfs_iunlock(ip, XFS_ILOCK_EXCL);
- if (error)
- return error;
-
/* Update the caller about how much progress we made. */
*offset_fsb = del.br_startoff + del.br_blockcount;
+ *commit = true;
return 0;
+}

-out_cancel:
- xfs_trans_cancel(tp);
+
+/*
+ * Remap part of the CoW fork into the data fork.
+ *
+ * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
+ * into the data fork; this function will remap what it can (at the end of the
+ * range) and update @end_fsb appropriately. Each remap gets its own
+ * transaction because we can end up merging and splitting bmbt blocks for
+ * every remap operation and we'd like to keep the block reservation
+ * requirements as low as possible.
+ */
+STATIC int
+xfs_reflink_end_cow_extent(
+ struct xfs_inode *ip,
+ xfs_fileoff_t *offset_fsb,
+ xfs_fileoff_t end_fsb)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ unsigned int resblks;
+ int error;
+ bool commit = false;
+
+ resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
+ XFS_TRANS_RESERVE, &tp);
+ if (error)
+ return error;
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, ip, 0);
+
+ error = xfs_reflink_end_cow_extent_locked(ip, offset_fsb,
+ end_fsb, tp, &commit);
+ if (commit)
+ error = xfs_trans_commit(tp);
+ else
+ xfs_trans_cancel(tp);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
return error;
}
--
2.31.1