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Date: Fri, 22 Jun 2018 14:12:59 -0700
From: Matthew Wilcox <willy@infradead.org>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: linux-kernel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 05/26] fs: Convert unnamed_dev_ida to new API
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On Fri, Jun 22, 2018 at 12:45:10PM -0700, Randy Dunlap wrote:
> > + * Context: Any context.  Frequently called while holding sb_lock.
> > + * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
> > + * or -EAGAIN if memory allocation failed.
> 
> Looks to me like the code used to return -ENOMEM and used -EAGAIN as an
> internal retry code.
> 
> confused?  (/me)

Quite right.

+++ b/fs/super.c
@@ -989,7 +989,7 @@ static DEFINE_IDA(unnamed_dev_ida);
  *
  * Context: Any context.  Frequently called while holding sb_lock.
  * Return: 0 on success, -EMFILE if there are no anonymous bdevs left
- * or -EAGAIN if memory allocation failed.
+ * or -ENOMEM if memory allocation failed.
  */
 int get_anon_bdev(dev_t *p)
 {
@@ -1002,9 +1002,9 @@ int get_anon_bdev(dev_t *p)
        dev = ida_alloc_range(&unnamed_dev_ida, 1, (1 << MINORBITS) - 1,
                        GFP_ATOMIC);
        if (dev == -ENOSPC)
-               return -EMFILE;
+               dev = -EMFILE;
        if (dev < 0)
-               return -EAGAIN;
+               return dev;
 
        *p = MKDEV(0, dev);
        return 0;