ext2: disallow setting xip on remount

Yan Zheng pointed out that ext2_remount lacks checking if -o xip should be
enabled or not.  This patch checks for presence of direct_access on the
backing block device and if the blocksize meets the requirements.

Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 16337bff0272..c9fd8cf6eaa9 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1038,6 +1038,14 @@ static int ext2_remount (struct super_block * sb, int * flags, char * data)
         sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                 ((sbi->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ? MS_POSIXACL : 0);
 
+        ext2_xip_verify_sb(sb); /* see if bdev supports xip, unset
+                                    EXT2_MOUNT_XIP if not */
+
+        if ((ext2_use_xip(sb)) && (sb->s_blocksize != PAGE_SIZE)) {
+                printk("XIP: Unsupported blocksize\n");
+                goto restore_opts;
+        }
+
         es = sbi->s_es;
         if (((sbi->s_mount_opt & EXT2_MOUNT_XIP) !=
             (old_mount_opt & EXT2_MOUNT_XIP)) &&