forked from Minki/linux
namei.c: split unlazy_walk()
In all but one case, the last two arguments are NULL and 0 resp.; almost everyone just wants to switch nameidata to non-RCU mode. The only exception is lookup_fast(), where we have a child dentry we want to legitimize as well. Split these two cases. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
parent
a89f833737
commit
4675ac39b5
105
fs/namei.c
105
fs/namei.c
@ -672,52 +672,83 @@ static bool legitimize_links(struct nameidata *nd)
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/**
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* unlazy_walk - try to switch to ref-walk mode.
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* @nd: nameidata pathwalk data
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* @dentry: child of nd->path.dentry or NULL
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* @seq: seq number to check dentry against
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* Returns: 0 on success, -ECHILD on failure
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*
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* unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
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* for ref-walk mode. @dentry must be a path found by a do_lookup call on
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* @nd or NULL. Must be called from rcu-walk context.
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* unlazy_walk attempts to legitimize the current nd->path and nd->root
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* for ref-walk mode.
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* Must be called from rcu-walk context.
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* Nothing should touch nameidata between unlazy_walk() failure and
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* terminate_walk().
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*/
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static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq)
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static int unlazy_walk(struct nameidata *nd)
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{
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struct dentry *parent = nd->path.dentry;
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BUG_ON(!(nd->flags & LOOKUP_RCU));
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nd->flags &= ~LOOKUP_RCU;
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if (unlikely(!legitimize_links(nd)))
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goto out2;
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if (unlikely(!legitimize_path(nd, &nd->path, nd->seq)))
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goto out1;
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if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
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if (unlikely(!legitimize_path(nd, &nd->root, nd->root_seq)))
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goto out;
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}
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rcu_read_unlock();
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BUG_ON(nd->inode != parent->d_inode);
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return 0;
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out2:
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nd->path.mnt = NULL;
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nd->path.dentry = NULL;
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out1:
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if (!(nd->flags & LOOKUP_ROOT))
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nd->root.mnt = NULL;
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out:
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rcu_read_unlock();
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return -ECHILD;
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}
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/**
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* unlazy_child - try to switch to ref-walk mode.
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* @nd: nameidata pathwalk data
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* @dentry: child of nd->path.dentry
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* @seq: seq number to check dentry against
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* Returns: 0 on success, -ECHILD on failure
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*
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* unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
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* for ref-walk mode. @dentry must be a path found by a do_lookup call on
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* @nd. Must be called from rcu-walk context.
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* Nothing should touch nameidata between unlazy_child() failure and
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* terminate_walk().
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*/
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static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq)
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{
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BUG_ON(!(nd->flags & LOOKUP_RCU));
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nd->flags &= ~LOOKUP_RCU;
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if (unlikely(!legitimize_links(nd)))
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goto out2;
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if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq)))
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goto out2;
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if (unlikely(!lockref_get_not_dead(&parent->d_lockref)))
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if (unlikely(!lockref_get_not_dead(&nd->path.dentry->d_lockref)))
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goto out1;
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/*
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* For a negative lookup, the lookup sequence point is the parents
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* sequence point, and it only needs to revalidate the parent dentry.
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*
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* For a positive lookup, we need to move both the parent and the
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* dentry from the RCU domain to be properly refcounted. And the
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* sequence number in the dentry validates *both* dentry counters,
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* since we checked the sequence number of the parent after we got
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* the child sequence number. So we know the parent must still
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* be valid if the child sequence number is still valid.
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* We need to move both the parent and the dentry from the RCU domain
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* to be properly refcounted. And the sequence number in the dentry
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* validates *both* dentry counters, since we checked the sequence
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* number of the parent after we got the child sequence number. So we
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* know the parent must still be valid if the child sequence number is
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*/
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if (!dentry) {
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if (read_seqcount_retry(&parent->d_seq, nd->seq))
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goto out;
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BUG_ON(nd->inode != parent->d_inode);
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} else {
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if (!lockref_get_not_dead(&dentry->d_lockref))
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goto out;
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if (read_seqcount_retry(&dentry->d_seq, seq))
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goto drop_dentry;
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if (unlikely(!lockref_get_not_dead(&dentry->d_lockref)))
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goto out;
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if (unlikely(read_seqcount_retry(&dentry->d_seq, seq))) {
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rcu_read_unlock();
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dput(dentry);
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goto drop_root_mnt;
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}
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/*
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* Sequence counts matched. Now make sure that the root is
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* still valid and get it if required.
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@ -733,10 +764,6 @@ static int unlazy_walk(struct nameidata *nd, struct dentry *dentry, unsigned seq
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rcu_read_unlock();
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return 0;
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drop_dentry:
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rcu_read_unlock();
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dput(dentry);
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goto drop_root_mnt;
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out2:
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nd->path.mnt = NULL;
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out1:
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@ -775,7 +802,7 @@ static int complete_walk(struct nameidata *nd)
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if (nd->flags & LOOKUP_RCU) {
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if (!(nd->flags & LOOKUP_ROOT))
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nd->root.mnt = NULL;
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if (unlikely(unlazy_walk(nd, NULL, 0)))
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if (unlikely(unlazy_walk(nd)))
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return -ECHILD;
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}
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@ -1001,7 +1028,7 @@ const char *get_link(struct nameidata *nd)
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touch_atime(&last->link);
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cond_resched();
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} else if (atime_needs_update_rcu(&last->link, inode)) {
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if (unlikely(unlazy_walk(nd, NULL, 0)))
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if (unlikely(unlazy_walk(nd)))
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return ERR_PTR(-ECHILD);
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touch_atime(&last->link);
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}
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@ -1020,7 +1047,7 @@ const char *get_link(struct nameidata *nd)
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if (nd->flags & LOOKUP_RCU) {
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res = get(NULL, inode, &last->done);
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if (res == ERR_PTR(-ECHILD)) {
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if (unlikely(unlazy_walk(nd, NULL, 0)))
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if (unlikely(unlazy_walk(nd)))
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return ERR_PTR(-ECHILD);
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res = get(dentry, inode, &last->done);
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}
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@ -1529,7 +1556,7 @@ static int lookup_fast(struct nameidata *nd,
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bool negative;
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dentry = __d_lookup_rcu(parent, &nd->last, &seq);
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if (unlikely(!dentry)) {
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if (unlazy_walk(nd, NULL, 0))
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if (unlazy_walk(nd))
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return -ECHILD;
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return 0;
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}
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@ -1567,7 +1594,7 @@ static int lookup_fast(struct nameidata *nd,
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if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
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return 1;
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}
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if (unlazy_walk(nd, dentry, seq))
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if (unlazy_child(nd, dentry, seq))
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return -ECHILD;
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if (unlikely(status == -ECHILD))
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/* we'd been told to redo it in non-rcu mode */
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@ -1646,7 +1673,7 @@ static inline int may_lookup(struct nameidata *nd)
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int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
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if (err != -ECHILD)
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return err;
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if (unlazy_walk(nd, NULL, 0))
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if (unlazy_walk(nd))
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return -ECHILD;
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}
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return inode_permission(nd->inode, MAY_EXEC);
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@ -1690,7 +1717,7 @@ static int pick_link(struct nameidata *nd, struct path *link,
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if (!(nd->flags & LOOKUP_ROOT))
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nd->root.mnt = NULL;
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rcu_read_unlock();
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} else if (likely(unlazy_walk(nd, NULL, 0)) == 0)
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} else if (likely(unlazy_walk(nd)) == 0)
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error = nd_alloc_stack(nd);
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}
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if (error) {
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@ -2108,7 +2135,7 @@ OK:
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}
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if (unlikely(!d_can_lookup(nd->path.dentry))) {
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if (nd->flags & LOOKUP_RCU) {
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if (unlazy_walk(nd, NULL, 0))
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if (unlazy_walk(nd))
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return -ECHILD;
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}
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return -ENOTDIR;
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@ -2565,7 +2592,7 @@ mountpoint_last(struct nameidata *nd)
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/* If we're in rcuwalk, drop out of it to handle last component */
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if (nd->flags & LOOKUP_RCU) {
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if (unlazy_walk(nd, NULL, 0))
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if (unlazy_walk(nd))
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return -ECHILD;
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}
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