[PATCH v2 5/5] xfs: toggle XFS_DIFLAG2_IOMAP_IMMUTABLE in response to fallocate

[Dan Williams <dan.j.williams@xxxxxxxxx>]

After validating the state of the file as not having holes, shared
extents, or active mappings try to commit the
XFS_DIFLAG2_IOMAP_IMMUTABLE flag to the on-disk inode metadata. If that
succeeds then allow the S_IOMAP_IMMUTABLE to be set on the vfs inode.

Cc: Jan Kara <jack@xxxxxxx>
Cc: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Suggested-by: Dave Chinner <david@xxxxxxxxxxxxx>
Suggested-by: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 fs/xfs/xfs_bmap_util.c |   32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 70ac2d33ab27..8464c25a2403 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1436,9 +1436,11 @@ xfs_seal_file_space(
 	xfs_off_t		offset,
 	xfs_off_t		len)
 {
+	struct xfs_mount	*mp = ip->i_mount;
 	struct inode		*inode = VFS_I(ip);
 	struct address_space	*mapping = inode->i_mapping;
 	int			error;
+	struct xfs_trans	*tp;
 
 	ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
 
@@ -1454,6 +1456,10 @@ xfs_seal_file_space(
 	if (error)
 		return error;
 
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
+	if (error)
+		return error;
+
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	/*
 	 * Either the size changed after we performed allocation /
@@ -1486,10 +1492,20 @@ xfs_seal_file_space(
 	if (error < 0)
 		goto out_unlock;
 
+	xfs_trans_ijoin(tp, ip, 0);
+	ip->i_d.di_flags2 |= XFS_DIFLAG2_IOMAP_IMMUTABLE;
+	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+	error = xfs_trans_commit(tp);
+	tp = NULL; /* nothing to cancel */
+	if (error)
+		goto out_unlock;
+
 	inode->i_flags |= S_IOMAP_IMMUTABLE;
 
 out_unlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	if (tp)
+		xfs_trans_cancel(tp);
 
 	return error;
 }
@@ -1500,15 +1516,21 @@ xfs_unseal_file_space(
 	xfs_off_t		offset,
 	xfs_off_t		len)
 {
+	struct xfs_mount	*mp = ip->i_mount;
 	struct inode		*inode = VFS_I(ip);
 	struct address_space	*mapping = inode->i_mapping;
 	int			error;
+	struct xfs_trans	*tp;
 
 	ASSERT(xfs_isilocked(ip, XFS_MMAPLOCK_EXCL));
 
 	if (offset)
 		return -EINVAL;
 
+	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
+	if (error)
+		return error;
+
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	/*
 	 * It does not make sense to unseal less than the full range of
@@ -1527,11 +1549,21 @@ xfs_unseal_file_space(
 	if (mapping_mapped(mapping))
 		goto out_unlock;
 
+	xfs_trans_ijoin(tp, ip, 0);
+	ip->i_d.di_flags2 &= ~XFS_DIFLAG2_IOMAP_IMMUTABLE;
+	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+	error = xfs_trans_commit(tp);
+	tp = NULL; /* nothing to cancel */
+	if (error)
+		goto out_unlock;
+
 	inode->i_flags &= ~S_IOMAP_IMMUTABLE;
 	error = 0;
 
 out_unlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	if (tp)
+		xfs_trans_cancel(tp);
 
 	return error;
 }