[PATCH] Document idr_get_new_above() semantics, update inotify

John McCutchan · Linus Torvalds · commit 7c657f2f25d5 · 2005-08-26T11:32:57.000-07:00
There is an off by one problem with idr_get_new_above.

The comment and function name suggest that it will return an id &gt;
starting_id, but it actually returned an id &gt;= 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 &lt;ttb@tentacle.dhs.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@osdl.org&gt;
diff --git 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
@@ -207,7 +207,7 @@ static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
 }
 
 /**
- * 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

Original file line number	Diff line number	Diff line change
`@@ -207,7 +207,7 @@ static int idr_get_new_above_int(struct idr idp, void ptr, int starting_id)`
`207`	`207`	`}`
`208`	`208`
`209`	`209`	`/**`
`210`		`- * idr_get_new_above - allocate new idr entry above a start id`
	`210`	`+ * idr_get_new_above - allocate new idr entry above or equal to a start id`
`211`	`211`	`* @idp: idr handle`
`212`	`212`	`* @ptr: pointer you want associated with the ide`
`213`	`213`	`* @start_id: id to start search at`