linux-kernel - [PATCH 2.6.26-git] Fix oops on remounting nfsroot

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Message-Id: <20080724.185122.139681307.nemoto@toshiba-tops.co.jp>
Date:	Thu, 24 Jul 2008 18:51:22 +0900 (JST)
From:	Atsushi Nemoto <anemo@....ocn.ne.jp>
To:	linux-kernel@...r.kernel.org
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [PATCH 2.6.26-git] Fix oops on remounting nfsroot

I got this oops when remounting nfsroot using busybox's mount:

VFS: Mounted root (nfs filesystem) readonly.
Freeing unused kernel memory: 180k freed
CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 801c3160, ra == 801744d0
...
Call Trace:
[<801c3160>] nfs_remount+0x60/0x2e0
[<801744d0>] do_remount_sb+0x184/0x1fc
[<8018b7a8>] do_remount+0x140/0x194
[<8018d824>] do_mount+0x138/0x1f0
[<8018d970>] sys_mount+0x94/0x1b4
[<80108df0>] stack_done+0x20/0x3c

This is a quick workaround, but I'm not sure this is proper fix.

Signed-off-by: Atsushi Nemoto <anemo@....ocn.ne.jp>
---
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 1b94e36..adc96cd 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1718,7 +1718,8 @@ nfs_remount(struct super_block *sb, int *flags, char *raw_data)
 	 * ones were explicitly specified. Fall back to legacy behavior and
 	 * just return success.
 	 */
-	if ((nfsvers == 4 && options4->version == 1) ||
+	if (!options ||
+	    (nfsvers == 4 && options4->version == 1) ||
 	    (nfsvers <= 3 && options->version >= 1 &&
 	     options->version <= 6))
 		return 0;
--
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