Re: [PATCH 4/4] mm/memory-failure: Fall back to vma_address() when ->notify_failure() fails

From: Dan Williams <dan.j.williams@intel.com>
To: Miaohe Lin <linmiaohe@huawei.com>,
	Dan Williams <dan.j.williams@intel.com>
Cc: Shiyang Ruan <ruansy.fnst@fujitsu.com>,
	Christoph Hellwig <hch@lst.de>,
	Naoya Horiguchi <naoya.horiguchi@nec.com>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Dave Chinner <david@fromorbit.com>,
	Goldwyn Rodrigues <rgoldwyn@suse.de>,
	Jane Chu <jane.chu@oracle.com>,
	Matthew Wilcox <willy@infradead.org>,
	"Ritesh Harjani" <riteshh@linux.ibm.com>,
	<nvdimm@lists.linux.dev>, <linux-xfs@vger.kernel.org>,
	<linux-mm@kvack.org>, <linux-fsdevel@vger.kernel.org>,
	<akpm@linux-foundation.org>, <djwong@kernel.org>
Subject: Re: [PATCH 4/4] mm/memory-failure: Fall back to vma_address() when ->notify_failure() fails
Date: Mon, 29 Aug 2022 20:57:04 -0700	[thread overview]
Message-ID: <630d8a902231b_259e5b29490@dwillia2-xfh.jf.intel.com.notmuch> (raw)
In-Reply-To: <76fb4464-73eb-256c-60e0-a0c3dc152e78@huawei.com>

Miaohe Lin wrote:
> On 2022/8/27 1:18, Dan Williams wrote:
> > In the case where a filesystem is polled to take over the memory failure
> > and receives -EOPNOTSUPP it indicates that page->index and page->mapping
> > are valid for reverse mapping the failure address. Introduce
> > FSDAX_INVALID_PGOFF to distinguish when add_to_kill() is being called
> > from mf_dax_kill_procs() by a filesytem vs the typical memory_failure()
> > path.
> 
> Thanks for fixing.
> I'm sorry but I can't find the bug report email. 

Report is here:

https://lore.kernel.org/all/63069db388d43_1b3229426@dwillia2-xfh.jf.intel.com.notmuch/

> Do you mean mf_dax_kill_procs() can pass an invalid pgoff to the
> add_to_kill()? 

No, the problem is that ->notify_failure() returns -EOPNOTSUPP so
memory_failure_dev_pagemap() falls back to mf_generic_kill_procs().
However, mf_generic_kill_procs() end up passing '0' for fsdax_pgoff from
collect_procs_file() to add_to_kill(). A '0' for fsdax_pgoff results in
vma_pgoff_address() returning -EFAULT which causes the VM_BUG_ON() in
dev_pagemap_mapping_shift().