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From: Greg Kroah-Hartman on 21 May 2010 13:00
From: Eric W. Biederman <ebiederm(a)aristanetworks.com>

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(a)canb.auug.org.au>
Cc: Al Viro <viro(a)zeniv.linux.org.uk>
Signed-off-by: Eric W. Biederman <ebiederm(a)aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de>
---
fs/sysfs/mount.c | 11 ++++++++---
1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 1afa32b..281c0c9 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;
--
1.7.0.3

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