fs: make unlazy_walk() error handling consistent

Most callers check for non-zero return, and assume it's -ECHILD (which
it always will be). One caller uses the actual error return. Clean this
up and make it fully consistent, by having unlazy_walk() return a bool
instead. Rename it to try_to_unlazy() and return true on success, and
failure on error. That's easier to read.

No functional changes in this patch.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namei.c b/fs/namei.c
index 3345a9f38ccb4bb21c50c0c10dbccc50629c4db2..21fd06753504e1610a04c1e83972ff758f3d1863 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -669,17 +669,17 @@ static bool legitimize_root(struct nameidata *nd)
  */
 
 /**
- * unlazy_walk - try to switch to ref-walk mode.
+ * try_to_unlazy - try to switch to ref-walk mode.
  * @nd: nameidata pathwalk data
- * Returns: 0 on success, -ECHILD on failure
+ * Returns: true on success, false on failure
  *
- * unlazy_walk attempts to legitimize the current nd->path and nd->root
+ * try_to_unlazy attempts to legitimize the current nd->path and nd->root
  * for ref-walk mode.
  * Must be called from rcu-walk context.
- * Nothing should touch nameidata between unlazy_walk() failure and
+ * Nothing should touch nameidata between try_to_unlazy() failure and
  * terminate_walk().
  */
-static int unlazy_walk(struct nameidata *nd)
+static bool try_to_unlazy(struct nameidata *nd)
 {
        struct dentry *parent = nd->path.dentry;
 
@@ -694,14 +694,14 @@ static int unlazy_walk(struct nameidata *nd)
                goto out;
        rcu_read_unlock();
        BUG_ON(nd->inode != parent->d_inode);
-       return 0;
+       return true;
 
 out1:
        nd->path.mnt = NULL;
        nd->path.dentry = NULL;
 out:
        rcu_read_unlock();
-       return -ECHILD;
+       return false;
 }
 
 /**
@@ -792,7 +792,7 @@ static int complete_walk(struct nameidata *nd)
                 */
                if (!(nd->flags & (LOOKUP_ROOT | LOOKUP_IS_SCOPED)))
                        nd->root.mnt = NULL;
-               if (unlikely(unlazy_walk(nd)))
+               if (!try_to_unlazy(nd))
                        return -ECHILD;
        }
 
@@ -1466,7 +1466,7 @@ static struct dentry *lookup_fast(struct nameidata *nd,
                unsigned seq;
                dentry = __d_lookup_rcu(parent, &nd->last, &seq);
                if (unlikely(!dentry)) {
-                       if (unlazy_walk(nd))
+                       if (!try_to_unlazy(nd))
                                return ERR_PTR(-ECHILD);
                        return NULL;
                }
@@ -1567,10 +1567,8 @@ static inline int may_lookup(struct nameidata *nd)
 {
        if (nd->flags & LOOKUP_RCU) {
                int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
-               if (err != -ECHILD)
+               if (err != -ECHILD || !try_to_unlazy(nd))
                        return err;
-               if (unlazy_walk(nd))
-                       return -ECHILD;
        }
        return inode_permission(nd->inode, MAY_EXEC);
 }
@@ -1592,7 +1590,7 @@ static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq)
                // unlazy even if we fail to grab the link - cleanup needs it
                bool grabbed_link = legitimize_path(nd, link, seq);
 
-               if (unlazy_walk(nd) != 0 || !grabbed_link)
+               if (!try_to_unlazy(nd) != 0 || !grabbed_link)
                        return -ECHILD;
 
                if (nd_alloc_stack(nd))
@@ -1634,7 +1632,7 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
                touch_atime(&last->link);
                cond_resched();
        } else if (atime_needs_update(&last->link, inode)) {
-               if (unlikely(unlazy_walk(nd)))
+               if (!try_to_unlazy(nd))
                        return ERR_PTR(-ECHILD);
                touch_atime(&last->link);
        }
@@ -1651,11 +1649,8 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
                get = inode->i_op->get_link;
                if (nd->flags & LOOKUP_RCU) {
                        res = get(NULL, inode, &last->done);
-                       if (res == ERR_PTR(-ECHILD)) {
-                               if (unlikely(unlazy_walk(nd)))
-                                       return ERR_PTR(-ECHILD);
+                       if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
                                res = get(link->dentry, inode, &last->done);
-                       }
                } else {
                        res = get(link->dentry, inode, &last->done);
                }
@@ -2195,7 +2190,7 @@ OK:
                }
                if (unlikely(!d_can_lookup(nd->path.dentry))) {
                        if (nd->flags & LOOKUP_RCU) {
-                               if (unlazy_walk(nd))
+                               if (!try_to_unlazy(nd))
                                        return -ECHILD;
                        }
                        return -ENOTDIR;
@@ -3129,7 +3124,6 @@ static const char *open_last_lookups(struct nameidata *nd,
        struct inode *inode;
        struct dentry *dentry;
        const char *res;
-       int error;
 
        nd->flags |= op->intent;
 
@@ -3153,9 +3147,8 @@ static const char *open_last_lookups(struct nameidata *nd,
        } else {
                /* create side of things */
                if (nd->flags & LOOKUP_RCU) {
-                       error = unlazy_walk(nd);
-                       if (unlikely(error))
-                               return ERR_PTR(error);
+                       if (!try_to_unlazy(nd))
+                               return ERR_PTR(-ECHILD);
                }
                audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
                /* trailing slashes? */
@@ -3164,9 +3157,7 @@ static const char *open_last_lookups(struct nameidata *nd,
        }
 
        if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
-               error = mnt_want_write(nd->path.mnt);
-               if (!error)
-                       got_write = true;
+               got_write = !mnt_want_write(nd->path.mnt);
                /*
                 * do _not_ fail yet - we might not need that or fail with
                 * a different error; let lookup_open() decide; we'll be