[PATCH] Document idr_get_new_above() semantics, update inotify

There is an off by one problem with idr_get_new_above.

The comment and function name suggest that it will return an id >
starting_id, but it actually returned an id >= starting_id, and kernel
callers other than inotify treated it as such.

The patch below fixes the comment, and fixes inotifys usage.  The
function name still doesn't match the behaviour, but it never did.

Signed-off-by: John McCutchan <ttb@tentacle.dhs.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/fs/inotify.c b/fs/inotify.c
index 868901b..2e4e2a5 100644 (file)
--- a/fs/inotify.c
+++ b/fs/inotify.c
@@ -353,7 +353,7 @@ static int inotify_dev_get_wd(struct inotify_device *dev,
        do {
                if (unlikely(!idr_pre_get(&dev->idr, GFP_KERNEL)))
                        return -ENOSPC;
-               ret = idr_get_new_above(&dev->idr, watch, dev->last_wd, &watch->wd);
+               ret = idr_get_new_above(&dev->idr, watch, dev->last_wd+1, &watch->wd);
        } while (ret == -EAGAIN);
 
        return ret;

diff --git a/lib/idr.c b/lib/idr.c
index c5be889..6415d05 100644 (file)
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -207,7 +207,7 @@ build_up:
 }
 
 /**
- * idr_get_new_above - allocate new idr entry above a start id
+ * idr_get_new_above - allocate new idr entry above or equal to a start id
  * @idp: idr handle
  * @ptr: pointer you want associated with the ide
  * @start_id: id to start search at