[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 868901b1e779301c5bae15911ae89dcc49aa2fe8..2e4e2a57708cf95dcdf348235376ef901f4dc295 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 c5be889de449555dc31b5c5d50a061f34187fdb6..6415d053e2bfa838e3a95313137d07a944261fd8 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