sysfs: Remove usage of S_BIAS to avoid merge conflict with the vfs tree

In Al's latest vfs tree the code is reworked and S_BIAS has been removed.

It turns out that checking to see if a super block is in the
middle of an unmount in sysfs_exit_ns is unnecessary because we
remove the super_block from the s_supers/s_instances list before
struct sysfs_super_info pointed to by sb->s_fs_info is freed.

For now just delete the unnecessary check to see if a superblock is in the
middle of an unmount, it isn't necessary with or without Al's changes
and it just causes a needless conflict.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 1afa32ba242..281c0c9bc39 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -138,6 +138,9 @@ static void sysfs_kill_sb(struct super_block *sb)
 {
         struct sysfs_super_info *info = sysfs_info(sb);
 
+        /* Remove the superblock from fs_supers/s_instances
+         * so we can't find it, before freeing sysfs_super_info.
+         */
         kill_anon_super(sb);
         kfree(info);
 }
@@ -156,9 +159,11 @@ void sysfs_exit_ns(enum kobj_ns_type type, const void *ns)
         spin_lock(&sb_lock);
         list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
                 struct sysfs_super_info *info = sysfs_info(sb);
-                /* Ignore superblocks that are in the process of unmounting */
-                if (sb->s_count <= S_BIAS)
-                        continue;
+                /*
+                 * If we see a superblock on the fs_supers/s_instances
+                 * list the unmount has not completed and sb->s_fs_info
+                 * points to a valid struct sysfs_super_info.
+                 */
                 /* Ignore superblocks with the wrong ns */
                 if (info->ns[type] != ns)
                         continue;