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Define get_init_pts_sb()

Browse source 
See comments in the function header for details. The new interface will
be used in a follow-on patch.

Changelog [v2]:
	[Dave Hansen] Replace get_sb_ref() in fs/super.c with get_init_pts_sb()
	and make the new interface private to devpts

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Sukadev Bhattiprolu 2009-01-02 13:42:19 +00:00 committed by Linus Torvalds
parent 1f8f1e2965
commit d4076ac55b
1 changed files with 54 additions and 1 deletions
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55
fs/devpts/inode.c
View file

@ -305,10 +305,63 @@ fail:
return -ENOMEM;
}
static int compare_init_pts_sb(struct super_block *s, void *p)
{
if (devpts_mnt)
return devpts_mnt->mnt_sb == s;
return 0;
}
/*
* get_init_pts_sb()
*
* This interface is needed to support multiple namespace semantics in
* devpts while preserving backward compatibility of the current 'single-
* namespace' semantics. i.e all mounts of devpts without the 'newinstance'
* mount option should bind to the initial kernel mount, like
* get_sb_single().
*
* Mounts with 'newinstance' option create a new private namespace.
*
* But for single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_single()/sget() find and use the super-block from
* the most recent mount of devpts. But that recent mount may be a
* 'newinstance' mount and get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
*
* This interface is identical to get_sb_single() except that it
* consistently selects the 'single-namespace' superblock even in the
* presence of the private namespace (i.e 'newinstance') super-blocks.
*/
static int get_init_pts_sb(struct file_system_type *fs_type, int flags,
void *data, struct vfsmount *mnt)
{
struct super_block *s;
int error;
s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
if (IS_ERR(s))
return PTR_ERR(s);
if (!s->s_root) {
s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error) {
up_write(&s->s_umount);
deactivate_super(s);
return error;
}
s->s_flags |= MS_ACTIVE;
}
do_remount_sb(s, flags, data, 0);
return simple_set_mnt(mnt, s);
}
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
return get_init_pts_sb(fs_type, flags, data, mnt);
}
static void devpts_kill_sb(struct super_block *sb)