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Date:   Wed, 20 Mar 2019 04:19:59 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
        pasha.tatashin@oracle.com, mhocko@suse.com,
        rppt@linux.vnet.ibm.com, richard.weiyang@gmail.com,
        linux-mm@kvack.org
Subject: Re: [PATCH 1/3] mm/sparse: Clean up the obsolete code comment
Message-ID: <20190320111959.GV19508@bombadil.infradead.org>
References: <20190320073540.12866-1-bhe@redhat.com>
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On Wed, Mar 20, 2019 at 03:35:38PM +0800, Baoquan He wrote:
>  /*
> - * returns the number of sections whose mem_maps were properly
> - * set.  If this is <=0, then that means that the passed-in
> - * map was not consumed and must be freed.
> + * sparse_add_one_section - add a memory section
> + * @nid:	The node to add section on
> + * @start_pfn:	start pfn of the memory range
> + * @altmap:	device page map
> + *
> + * Return 0 on success and an appropriate error code otherwise.
>   */

I think it's worth documenting what those error codes are.  Seems to be
just -ENOMEM and -EEXIST, but it'd be nice for users to know what they
can expect under which circumstances.

Also, -EEXIST is a bad errno to return here:

$ errno EEXIST
EEXIST 17 File exists

What file?  I think we should be using -EBUSY instead in case this errno
makes it back to userspace:

$ errno EBUSY
EBUSY 16 Device or resource busy