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Date: Thu, 6 Sep 2018 06:05:36 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: linux-next test error
Message-ID: <20180906130536.GA29639@bombadil.infradead.org>
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To: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Jan Kara <jack@suse.cz>, Theodore Ts'o <tytso@mit.edu>, syzbot+87a05ae4accd500f5242@syzkaller.appspotmail.com, ak@linux.intel.com, Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, Linux-MM <linux-mm@kvack.org>, mgorman@techsingularity.net, syzkaller-bugs@googlegroups.com, tim.c.chen@linux.intel.com, zwisler@kernel.org

On Thu, Sep 06, 2018 at 05:56:31PM +0530, Souptick Joarder wrote:
> On Thu, Sep 6, 2018 at 2:08 PM Jan Kara <jack@suse.cz> wrote:
> > Yes, I'd start with converting ext4_page_mkwrite() - that should be pretty
> > straightforward - and we can leave block_page_mkwrite() as is for now. I
> > don't think allocating other VM_FAULT_ codes is going to cut it as
> > generally the filesystem may need to communicate different error codes back
> > and you don't know in advance which are interesting.
> 
> Then I need to take care of ext4_page_mkwrite() and ext4_filemap_fault()
> to migrate to use vm_fault_t return type. Everything else can be removed
> from this patch and it will go as a separate patch.
> 
> As block_page_mkwrite() is getting called from 2 places in ext4 and nilfs and
> both places fault handler code convert errno to VM_FAULT_CODE using
> block_page_mkwrite_return(), is it required to migrate block_page_mkwrite()
> to use vm_fault_t return type and further complicate the API or better to
> leave this API in current state ??

Leave block_page_mkwrite() alone.  Somebody who understands it better
than you do can take care of converting it, if that's even the right
thing to do.  Let's get the typedef conversion _finished_ so we get the
benefit of typechecking for driver writers.