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mount: separate the flags accessed only under namespace_sem

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Several flags are updated and checked only under namespace_sem; we are
already making use of that when we are checking them without mount_lock,
but we have to hold mount_lock for all updates, which makes things
clumsier than they have to be.

Take MNT_SHARED, MNT_UNBINDABLE, MNT_MARKED and MNT_UMOUNT_CANDIDATE
into a separate field (->mnt_t_flags), renaming them to T_SHARED,
etc. to avoid confusion.  All accesses must be under namespace_sem.

That changes locking requirements for mnt_change_propagation() and
set_mnt_shared() - only namespace_sem is needed now.  The same goes
for SET_MNT_MARKED et.al.

There might be more flags moved from ->mnt_flags to that field;
this is just the initial set.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2025-06-21 18:06:19 -04:00
parent 493a4bebf5
commit 406fea7999
6 changed files with 46 additions and 46 deletions
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22
fs/pnode.c
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@@ -112,7 +112,7 @@ static int do_make_slave(struct mount *mnt)
}
/*
* vfsmount lock must be held for write
* EXCL[namespace_sem]
*/
void change_mnt_propagation(struct mount *mnt, int type)
{
@@ -125,9 +125,9 @@ void change_mnt_propagation(struct mount *mnt, int type)
list_del_init(&mnt->mnt_slave);
mnt->mnt_master = NULL;
if (type == MS_UNBINDABLE)
mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
mnt->mnt_t_flags |= T_UNBINDABLE;
else
mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
mnt->mnt_t_flags &= ~T_UNBINDABLE;
}
}
@@ -263,9 +263,9 @@ static int propagate_one(struct mount *m, struct mountpoint *dest_mp)
return PTR_ERR(child);
read_seqlock_excl(&mount_lock);
mnt_set_mountpoint(m, dest_mp, child);
read_sequnlock_excl(&mount_lock);
if (m->mnt_master != dest_master)
SET_MNT_MARK(m->mnt_master);
read_sequnlock_excl(&mount_lock);
last_dest = m;
last_source = child;
hlist_add_head(&child->mnt_hash, list);
@@ -322,13 +322,11 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
} while (n != m);
}
out:
read_seqlock_excl(&mount_lock);
hlist_for_each_entry(n, tree_list, mnt_hash) {
m = n->mnt_parent;
if (m->mnt_master != dest_mnt->mnt_master)
CLEAR_MNT_MARK(m->mnt_master);
}
read_sequnlock_excl(&mount_lock);
return ret;
}
@@ -447,7 +445,7 @@ void propagate_mount_unlock(struct mount *mnt)
static inline bool is_candidate(struct mount *m)
{
return m->mnt.mnt_flags & MNT_UMOUNT_CANDIDATE;
return m->mnt_t_flags & T_UMOUNT_CANDIDATE;
}
static inline bool will_be_unmounted(struct mount *m)
@@ -464,7 +462,7 @@ static void umount_one(struct mount *m, struct list_head *to_umount)
static void remove_from_candidate_list(struct mount *m)
{
m->mnt.mnt_flags &= ~(MNT_MARKED | MNT_UMOUNT_CANDIDATE);
m->mnt_t_flags &= ~(T_MARKED | T_UMOUNT_CANDIDATE);
list_del_init(&m->mnt_list);
}
@@ -476,7 +474,7 @@ static void gather_candidates(struct list_head *set,
list_for_each_entry(m, set, mnt_list) {
if (is_candidate(m))
continue;
m->mnt.mnt_flags |= MNT_UMOUNT_CANDIDATE;
m->mnt_t_flags |= T_UMOUNT_CANDIDATE;
p = m->mnt_parent;
q = propagation_next(p, p);
while (q) {
@@ -494,7 +492,7 @@ static void gather_candidates(struct list_head *set,
q = skip_propagation_subtree(q, p);
continue;
}
child->mnt.mnt_flags |= MNT_UMOUNT_CANDIDATE;
child->mnt_t_flags |= T_UMOUNT_CANDIDATE;
if (!will_be_unmounted(child))
list_add(&child->mnt_list, candidates);
}
@@ -502,7 +500,7 @@ static void gather_candidates(struct list_head *set,
}
}
list_for_each_entry(m, set, mnt_list)
m->mnt.mnt_flags &= ~MNT_UMOUNT_CANDIDATE;
m->mnt_t_flags &= ~T_UMOUNT_CANDIDATE;
}
/*
@@ -519,7 +517,7 @@ static void trim_ancestors(struct mount *m)
return;
SET_MNT_MARK(m);
if (m != p->overmount)
p->mnt.mnt_flags &= ~MNT_UMOUNT_CANDIDATE;
p->mnt_t_flags &= ~T_UMOUNT_CANDIDATE;
}
}