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follow_dotdot(): be lazy about changing nd->path

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Change nd->path only after the loop is done and only in case we hadn't
ended up finding ourselves in root.  Same for NO_XDEV check.

That separates the "check how far back do we need to go through the
mount stack" logics from the rest of .. traversal.

NOTE: path_get/path_put introduced here are temporary.  They will
go away later in the series.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-02-28 10:17:52 -05:00
parent efe772d628
commit 165200d6cb
1 changed files with 13 additions and 5 deletions
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18
fs/namei.c
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@ -1748,16 +1748,24 @@ static struct dentry *follow_dotdot(struct nameidata *nd,
if (path_equal(&nd->path, &nd->root))
goto in_root;
if (unlikely(nd->path.dentry == nd->path.mnt->mnt_root)) {
struct path path = nd->path;
path_get(&path);
while (1) {
if (!follow_up(&nd->path))
if (!follow_up(&path)) {
path_put(&path);
goto in_root;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return ERR_PTR(-EXDEV);
if (path_equal(&nd->path, &nd->root))
}
if (path_equal(&path, &nd->root)) {
path_put(&path);
goto in_root;
if (nd->path.dentry != nd->path.mnt->mnt_root)
}
if (path.dentry != nd->path.mnt->mnt_root)
break;
}
path_put(&nd->path);
nd->path = path;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return ERR_PTR(-EXDEV);
}
/* rare case of legitimate dget_parent()... */
parent = dget_parent(nd->path.dentry);