xfs: pull up dfops from xfs_itruncate_extents()

xfs_itruncate_extents[_flags]() uses a local dfops with a
transaction provided by the caller. It uses hacky ->t_dfops
replacement logic to avoid stomping over an already populated
->t_dfops.

The latter never occurs for current callers and the logic itself is
not really appropriate. Clean this up by updating all callers to
initialize a dfops and to use that down in xfs_itruncate_extents().
This more closely resembles the upcoming logic where dfops will be
embedded within the transaction. We can also replace the
xfs_defer_init() in the xfs_itruncate_extents_flags() loop with an
assert. Both dfops and firstblock should be in a valid state
after xfs_defer_finish() and the inode joined to the dfops is fixed
throughout the loop.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bill O'Donnell <billodo@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_attr_inactive.c

@@ -26,6 +26,7 @@
 #include "xfs_quota.h"
 #include "xfs_trace.h"
 #include "xfs_dir2.h"
+#include "xfs_defer.h"
 
 /*
  * Look at all the extents for this logical region,
@@ -381,6 +382,7 @@ xfs_attr_inactive(
 {
 	struct xfs_trans	*trans;
 	struct xfs_mount	*mp;
+	struct xfs_defer_ops	dfops;
 	int			lock_mode = XFS_ILOCK_SHARED;
 	int			error = 0;
 
@@ -397,6 +399,7 @@ xfs_attr_inactive(
 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_attrinval, 0, 0, 0, &trans);
 	if (error)
 		goto out_destroy_fork;
+	xfs_defer_init(trans, &dfops);
 
 	lock_mode = XFS_ILOCK_EXCL;
 	xfs_ilock(dp, lock_mode);

fs/xfs/xfs_bmap_util.c

@@ -792,6 +792,7 @@ xfs_free_eofblocks(
 	int			nimaps;
 	struct xfs_bmbt_irec	imap;
 	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_defer_ops	dfops;
 
 	/*
 	 * Figure out if there are any blocks beyond the end
@@ -831,6 +832,7 @@ xfs_free_eofblocks(
 			ASSERT(XFS_FORCED_SHUTDOWN(mp));
 			return error;
 		}
+		xfs_defer_init(tp, &dfops);
 
 		xfs_ilock(ip, XFS_ILOCK_EXCL);
 		xfs_trans_ijoin(tp, ip, 0);

fs/xfs/xfs_inode.c

@@ -1541,8 +1541,6 @@ xfs_itruncate_extents_flags(
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_trans	*tp = *tpp;
-	struct xfs_defer_ops	*odfops = tp->t_dfops;
-	struct xfs_defer_ops	dfops;
 	xfs_fileoff_t		first_unmap_block;
 	xfs_fileoff_t		last_block;
 	xfs_filblks_t		unmap_len;
@@ -1579,7 +1577,7 @@ xfs_itruncate_extents_flags(
 	ASSERT(first_unmap_block < last_block);
 	unmap_len = last_block - first_unmap_block + 1;
 	while (!done) {
-		xfs_defer_init(tp, &dfops);
+		ASSERT(tp->t_firstblock == NULLFSBLOCK);
 		error = xfs_bunmapi(tp, ip, first_unmap_block, unmap_len, flags,
 				    XFS_ITRUNC_MAX_EXTENTS, &done);
 		if (error)
@@ -1618,8 +1616,6 @@ xfs_itruncate_extents_flags(
 	trace_xfs_itruncate_extents_end(ip, new_size);
 
 out:
-	/* ->t_dfops points to local stack, don't leak it! */
-	tp->t_dfops = odfops;
 	*tpp = tp;
 	return error;
 out_bmap_cancel:
@@ -1723,6 +1719,7 @@ xfs_inactive_truncate(
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct xfs_trans	*tp;
+	struct xfs_defer_ops	dfops;
 	int			error;
 
 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
@@ -1730,6 +1727,7 @@ xfs_inactive_truncate(
 		ASSERT(XFS_FORCED_SHUTDOWN(mp));
 		return error;
 	}
+	xfs_defer_init(tp, &dfops);
 
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(tp, ip, 0);

fs/xfs/xfs_iops.c

@@ -26,6 +26,7 @@
 #include "xfs_dir2.h"
 #include "xfs_trans_space.h"
 #include "xfs_iomap.h"
+#include "xfs_defer.h"
 
 #include <linux/capability.h>
 #include <linux/xattr.h>
@@ -812,6 +813,7 @@ xfs_setattr_size(
 	struct inode		*inode = VFS_I(ip);
 	xfs_off_t		oldsize, newsize;
 	struct xfs_trans	*tp;
+	struct xfs_defer_ops	dfops;
 	int			error;
 	uint			lock_flags = 0;
 	bool			did_zeroing = false;
@@ -915,6 +917,7 @@ xfs_setattr_size(
 	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
 	if (error)
 		return error;
+	xfs_defer_init(tp, &dfops);
 
 	lock_flags |= XFS_ILOCK_EXCL;
 	xfs_ilock(ip, XFS_ILOCK_EXCL);

fs/xfs/xfs_qm_syscalls.c

@@ -22,6 +22,7 @@
 #include "xfs_qm.h"
 #include "xfs_trace.h"
 #include "xfs_icache.h"
+#include "xfs_defer.h"
 
 STATIC int	xfs_qm_log_quotaoff(xfs_mount_t *, xfs_qoff_logitem_t **, uint);
 STATIC int	xfs_qm_log_quotaoff_end(xfs_mount_t *, xfs_qoff_logitem_t *,
@@ -213,6 +214,7 @@ xfs_qm_scall_trunc_qfile(
 {
 	struct xfs_inode	*ip;
 	struct xfs_trans	*tp;
+	struct xfs_defer_ops	dfops;
 	int			error;
 
 	if (ino == NULLFSINO)
@@ -229,6 +231,7 @@ xfs_qm_scall_trunc_qfile(
 		xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 		goto out_put;
 	}
+	xfs_defer_init(tp, &dfops);
 
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	xfs_trans_ijoin(tp, ip, 0);