[PATCH v4 1/2] xfs: avoid double restore PF_MEMALLOC_NOFS if transaction reservation fails

[Yafang Shao <laoar.shao@xxxxxxxxx>]

From: Yafang Shao <shaoyafang@xxxxxxxxxxxxxx>

In xfs_trans_alloc(), if xfs_trans_reserve() fails, it will call
xfs_trans_cancel(), in which it will restore the flag PF_MEMALLOC_NOFS.
However this flags has been restored in xfs_trans_reserve(). Although
this behavior doesn't introduce any obvious issue, we'd better improve it.

Signed-off-by: Yafang Shao <shaoyafang@xxxxxxxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_trans.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 3c94e5ff4316..9ff41970d0c7 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -162,10 +162,9 @@ xfs_trans_reserve(
 	 */
 	if (blocks > 0) {
 		error = xfs_mod_fdblocks(mp, -((int64_t)blocks), rsvd);
-		if (error != 0) {
-			current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
+		if (error != 0)
 			return -ENOSPC;
-		}
+
 		tp->t_blk_res += blocks;
 	}
 
@@ -240,8 +239,6 @@ xfs_trans_reserve(
 		tp->t_blk_res = 0;
 	}
 
-	current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
-
 	return error;
 }
 
@@ -972,6 +969,7 @@ xfs_trans_roll(
 	struct xfs_trans	**tpp)
 {
 	struct xfs_trans	*trans = *tpp;
+	struct xfs_trans        *tp;
 	struct xfs_trans_res	tres;
 	int			error;
 
@@ -1005,5 +1003,10 @@ xfs_trans_roll(
 	 * the prior and the next transactions.
 	 */
 	tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;
-	return xfs_trans_reserve(*tpp, &tres, 0, 0);
+	tp = *tpp;
+	error = xfs_trans_reserve(tp, &tres, 0, 0);
+	if (error)
+		current_restore_flags_nested(&tp->t_pflags, PF_MEMALLOC_NOFS);
+
+	return error;
 }
-- 
2.18.1