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get rid of CL_SHARE_TO_SLAVE

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the only difference between it and CL_SLAVE is in this predicate
in clone_mnt():
	if ((flag & CL_SLAVE) ||
	    ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
However, in case of CL_SHARED_TO_SLAVE we have not allocated any
mount group ids since the time we'd grabbed namespace_sem, so
IS_MNT_SHARED() is equivalent to non-zero ->mnt_group_id.  And
in case of CL_SLAVE old has come either from the original tree,
which had ->mnt_group_id allocated for all nodes or from result
of sequence of CL_MAKE_SHARED or CL_MAKE_SHARED|CL_SLAVE copies,
ultimately going back to the original tree.  In both cases we are
guaranteed that old->mnt_group_id will be non-zero.

In other words, the predicate is always equal to
	(flags & (CL_SLAVE | CL_SHARED_TO_SLAVE)) && old->mnt_group_id
and with that replacement CL_SLAVE and CL_SHARED_TO_SLAVE have exact
same behaviour.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-06-25 14:48:50 -04:00
parent aab771f34e
commit 725ab435ff
2 changed files with 3 additions and 5 deletions
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7
fs/namespace.c
View file

@ -1309,7 +1309,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
mnt->mnt.mnt_flags = READ_ONCE(old->mnt.mnt_flags) &
~MNT_INTERNAL_FLAGS;
if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
if (flag & (CL_SLAVE | CL_PRIVATE))
mnt->mnt_group_id = 0; /* not a peer of original */
else
mnt->mnt_group_id = old->mnt_group_id;
@ -1340,8 +1340,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
if (peers(mnt, old))
list_add(&mnt->mnt_share, &old->mnt_share);
if ((flag & CL_SLAVE) ||
((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
if ((flag & CL_SLAVE) && old->mnt_group_id) {
hlist_add_head(&mnt->mnt_slave, &old->mnt_slave_list);
mnt->mnt_master = old;
} else if (IS_MNT_SLAVE(old)) {
@ -4228,7 +4227,7 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
/* First pass: copy the tree topology */
copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
if (user_ns != ns->user_ns)
copy_flags |= CL_SHARED_TO_SLAVE;
copy_flags |= CL_SLAVE;
new = copy_tree(old, old->mnt.mnt_root, copy_flags);
if (IS_ERR(new)) {
namespace_unlock();

1
fs/pnode.h
View file

@ -25,7 +25,6 @@
#define CL_COPY_UNBINDABLE 0x04
#define CL_MAKE_SHARED 0x08
#define CL_PRIVATE 0x10
#define CL_SHARED_TO_SLAVE 0x20
#define CL_COPY_MNT_NS_FILE 0x40
/*