From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Sun, 10 Jan 2021 15:58:08 -0500
Subject: [PATCH] NFS: nfs_igrab_and_active must first reference the superblock
Git-commit: 896567ee7f17a8a736cda8a28cc987228410a2ac
Patch-mainline: v5.11
References: git-fixes

Before referencing the inode, we must ensure that the superblock can be
referenced. Otherwise, we can end up with iput() calling superblock
operations that are no longer valid or accessible.

Fixes: ea7c38fef0b7 ("NFSv4: Ensure we reference the inode for return-on-close in delegreturn")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/internal.h |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -574,12 +574,14 @@ extern int nfs4_test_session_trunk(struc
 
 static inline struct inode *nfs_igrab_and_active(struct inode *inode)
 {
-	inode = igrab(inode);
-	if (inode != NULL && !nfs_sb_active(inode->i_sb)) {
-		iput(inode);
-		inode = NULL;
+	struct super_block *sb = inode->i_sb;
+
+	if (sb && nfs_sb_active(sb)) {
+		if (igrab(inode))
+			return inode;
+		nfs_sb_deactive(sb);
 	}
-	return inode;
+	return NULL;
 }
 
 static inline void nfs_iput_and_deactive(struct inode *inode)