[PATCH] xfs: use GFP_NOFS in __xfs_trans_alloc

[Morduan Zang]

__xfs_trans_alloc() allocates the transaction structure before
xfs_trans_set_context() establishes the nofs context. If memory reclaim
enters XFS through xfs_vn_sync_lazytime(), this GFP_KERNEL allocation can
trigger a warning from the reclaim path.

Use GFP_NOFS for the transaction allocation to avoid filesystem reclaim
recursion before the nofs context is set.

Link: https://syzkaller.appspot.com/bug?extid=d78ace33ad4ee69329d5
Fixes: 83a80e95e797 ("xfs: decouple xfs_trans_alloc_empty from xfs_trans_alloc")
Reported-by: syzbot+d78ace33ad4ee69329d5@xxxxxxxxxxxxxxxxxxxxxxxxx

Signed-off-by: Zhan Jun <zhanjun@xxxxxxxxxxxxx>
Signed-off-by: Morduan Zang <zhangdandan@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_trans.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index bcc470f56e46..0d347cff7317 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -217,7 +217,7 @@ __xfs_trans_alloc(
 
 	ASSERT(!(flags & XFS_TRANS_RES_FDBLKS) || xfs_has_lazysbcount(mp));
 
-	tp = kmem_cache_zalloc(xfs_trans_cache, GFP_KERNEL | __GFP_NOFAIL);
+	tp = kmem_cache_zalloc(xfs_trans_cache, GFP_NOFS | __GFP_NOFAIL);
 	if (!(flags & XFS_TRANS_NO_WRITECOUNT))
 		sb_start_intwrite(mp->m_super);
 	xfs_trans_set_context(tp);
-- 
2.50.1