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namei: move clearing LOOKUP_RCU towards rcu_read_unlock()

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try_to_unlazy()/try_to_unlazy_next() drop LOOKUP_RCU in the
very beginning and do rcu_read_unlock() only at the very end.
However, nothing done in between even looks at the flag in
question; might as well clear it at the same time we unlock.

Note that try_to_unlazy_next() used to call legitimize_mnt(),
which might drop/regain rcu_read_lock() in some cases.  This
is no longer true, so we really have rcu_read_lock() held
all along until the end.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-07-06 12:40:31 -04:00
parent 7e4745a094
commit 6e18032715
1 changed files with 12 additions and 9 deletions
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21
fs/namei.c
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@ -665,6 +665,12 @@ static void drop_links(struct nameidata *nd)
}
}
static void leave_rcu(struct nameidata *nd)
{
nd->flags &= ~LOOKUP_RCU;
rcu_read_unlock();
}
static void terminate_walk(struct nameidata *nd)
{
drop_links(nd);
@ -678,8 +684,7 @@ static void terminate_walk(struct nameidata *nd)
nd->state &= ~ND_ROOT_GRABBED;
}
} else {
nd->flags &= ~LOOKUP_RCU;
rcu_read_unlock();
leave_rcu(nd);
}
nd->depth = 0;
nd->path.mnt = NULL;
@ -765,14 +770,13 @@ static bool try_to_unlazy(struct nameidata *nd)
BUG_ON(!(nd->flags & LOOKUP_RCU));
nd->flags &= ~LOOKUP_RCU;
if (unlikely(!legitimize_links(nd)))
goto out1;
if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
goto out;
if (unlikely(!legitimize_root(nd)))
goto out;
rcu_read_unlock();
leave_rcu(nd);
BUG_ON(nd->inode != parent->d_inode);
return true;
@ -780,7 +784,7 @@ out1:
nd->path.mnt = NULL;
nd->path.dentry = NULL;
out:
rcu_read_unlock();
leave_rcu(nd);
return false;
}
@ -802,7 +806,6 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi
int res;
BUG_ON(!(nd->flags & LOOKUP_RCU));
nd->flags &= ~LOOKUP_RCU;
if (unlikely(!legitimize_links(nd)))
goto out2;
res = __legitimize_mnt(nd->path.mnt, nd->m_seq);
@ -831,7 +834,7 @@ static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsi
*/
if (unlikely(!legitimize_root(nd)))
goto out_dput;
rcu_read_unlock();
leave_rcu(nd);
return true;
out2:
@ -839,10 +842,10 @@ out2:
out1:
nd->path.dentry = NULL;
out:
rcu_read_unlock();
leave_rcu(nd);
return false;
out_dput:
rcu_read_unlock();
leave_rcu(nd);
dput(dentry);
return false;
}