reduce vfs_path_lookup() to do_path_lookup()
New lookup flag: LOOKUP_ROOT. nd->root is set (and held) by caller,
path_init() starts walking from that place and all pathname resolution
machinery never drops nd->root if that flag is set. That turns
vfs_path_lookup() into a special case of do_path_lookup() *and*
gets us down to 3 callers of link_path_walk(), making it finally
feasible to rip the handling of trailing symlink out of link_path_walk().
That will not only simply the living hell out of it, but make life
much simpler for unionfs merge. Trailing symlink handling will
become iterative, which is a good thing for stack footprint in
a lot of situations as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index 0bebd13..8ee7785 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -401,9 +401,11 @@
{
struct fs_struct *fs = current->fs;
struct dentry *dentry = nd->path.dentry;
+ int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
- if (nd->root.mnt) {
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ want_root = 1;
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
@@ -414,7 +416,7 @@
goto err;
BUG_ON(nd->inode != dentry->d_inode);
spin_unlock(&dentry->d_lock);
- if (nd->root.mnt) {
+ if (want_root) {
path_get(&nd->root);
spin_unlock(&fs->lock);
}
@@ -427,7 +429,7 @@
err:
spin_unlock(&dentry->d_lock);
err_root:
- if (nd->root.mnt)
+ if (want_root)
spin_unlock(&fs->lock);
return -ECHILD;
}
@@ -454,9 +456,11 @@
{
struct fs_struct *fs = current->fs;
struct dentry *parent = nd->path.dentry;
+ int want_root = 0;
BUG_ON(!(nd->flags & LOOKUP_RCU));
- if (nd->root.mnt) {
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+ want_root = 1;
spin_lock(&fs->lock);
if (nd->root.mnt != fs->root.mnt ||
nd->root.dentry != fs->root.dentry)
@@ -476,7 +480,7 @@
parent->d_count++;
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
- if (nd->root.mnt) {
+ if (want_root) {
path_get(&nd->root);
spin_unlock(&fs->lock);
}
@@ -490,7 +494,7 @@
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
err_root:
- if (nd->root.mnt)
+ if (want_root)
spin_unlock(&fs->lock);
return -ECHILD;
}
@@ -501,7 +505,8 @@
if (nd->flags & LOOKUP_RCU) {
if (unlikely(nameidata_dentry_drop_rcu(nd, dentry))) {
nd->flags &= ~LOOKUP_RCU;
- nd->root.mnt = NULL;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return -ECHILD;
@@ -525,7 +530,8 @@
BUG_ON(!(nd->flags & LOOKUP_RCU));
nd->flags &= ~LOOKUP_RCU;
- nd->root.mnt = NULL;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
spin_lock(&dentry->d_lock);
if (!__d_rcu_to_refcount(dentry, nd->seq))
goto err_unlock;
@@ -1053,7 +1059,8 @@
failed:
nd->flags &= ~LOOKUP_RCU;
- nd->root.mnt = NULL;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
return -ECHILD;
@@ -1310,7 +1317,8 @@
path_put(&nd->path);
} else {
nd->flags &= ~LOOKUP_RCU;
- nd->root.mnt = NULL;
+ if (!(nd->flags & LOOKUP_ROOT))
+ nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
}
@@ -1477,6 +1485,25 @@
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED;
nd->depth = 0;
+ if (flags & LOOKUP_ROOT) {
+ struct inode *inode = nd->root.dentry->d_inode;
+ if (!inode->i_op->lookup)
+ return -ENOTDIR;
+ retval = inode_permission(inode, MAY_EXEC);
+ if (retval)
+ return retval;
+ nd->path = nd->root;
+ nd->inode = inode;
+ if (flags & LOOKUP_RCU) {
+ br_read_lock(vfsmount_lock);
+ rcu_read_lock();
+ nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
+ } else {
+ path_get(&nd->path);
+ }
+ return 0;
+ }
+
nd->root.mnt = NULL;
if (*name=='/') {
@@ -1587,7 +1614,7 @@
if (base)
fput(base);
- if (nd->root.mnt) {
+ if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
@@ -1638,46 +1665,10 @@
const char *name, unsigned int flags,
struct nameidata *nd)
{
- int result;
-
- /* same as do_path_lookup */
- nd->last_type = LAST_ROOT;
- nd->flags = flags | LOOKUP_JUMPED;
- nd->depth = 0;
-
- nd->path.dentry = dentry;
- nd->path.mnt = mnt;
- path_get(&nd->path);
- nd->root = nd->path;
- path_get(&nd->root);
- nd->inode = nd->path.dentry->d_inode;
-
- current->total_link_count = 0;
-
- result = link_path_walk(name, nd);
- if (!result)
- result = handle_reval_path(nd);
- if (result == -ESTALE) {
- /* nd->path had been dropped */
- current->total_link_count = 0;
- nd->path.dentry = dentry;
- nd->path.mnt = mnt;
- nd->inode = dentry->d_inode;
- path_get(&nd->path);
- nd->flags = flags | LOOKUP_JUMPED | LOOKUP_REVAL;
-
- result = link_path_walk(name, nd);
- if (!result)
- result = handle_reval_path(nd);
- }
- if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&
- nd->inode))
- audit_inode(name, nd->path.dentry);
-
- path_put(&nd->root);
- nd->root.mnt = NULL;
-
- return result;
+ nd->root.dentry = dentry;
+ nd->root.mnt = mnt;
+ /* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
+ return do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, nd);
}
static struct dentry *__lookup_hash(struct qstr *name,
@@ -2320,7 +2311,7 @@
path_put(&link);
}
out:
- if (nd.root.mnt)
+ if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT))
path_put(&nd.root);
if (base)
fput(base);