linux-kernel - Re: [PATCH v14 00/74] Convert page cache to XArray

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Date:   Tue, 19 Jun 2018 10:40:37 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jan Kara <jack@...e.cz>, Jeff Layton <jlayton@...hat.com>,
        Lukas Czerner <lczerner@...hat.com>,
        Christoph Hellwig <hch@....de>,
        Goldwyn Rodrigues <rgoldwyn@...e.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
        linux-nilfs@...r.kernel.org, Jaegeuk Kim <jaegeuk@...nel.org>,
        Chao Yu <yuchao0@...wei.com>,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [PATCH v14 00/74] Convert page cache to XArray

On Tue, Jun 19, 2018 at 02:22:30AM -0700, Matthew Wilcox wrote:
> On Mon, Jun 18, 2018 at 09:12:57PM -0600, Ross Zwisler wrote:
> > Hit another deadlock.  This one reproduces 100% of the time in my setup with
> > XFS + DAX + generic/340.  It doesn't reproduce for me at all with
> > next-20180615.  Here's the output from "echo w > /proc/sysrq-trigger":
> 
> *sigh*.  I wonder what the differences are between our setups ...
> 
> > [   92.849119] sysrq: SysRq : Show Blocked State
> > [   92.850506]   task                        PC stack   pid father
> > [   92.852299] holetest        D    0  1651   1466 0x00000000
> > [   92.853912] Call Trace:
> > [   92.854610]  __schedule+0x2c5/0xad0
> > [   92.855612]  schedule+0x36/0x90
> > [   92.856602]  get_unlocked_entry+0xce/0x120
> > [   92.857756]  ? dax_insert_entry+0x2b0/0x2b0
> > [   92.858931]  grab_mapping_entry+0x19e/0x250
> > [   92.860119]  dax_iomap_pte_fault+0x115/0x1140
> > [   92.860836]  dax_iomap_fault+0x37/0x40
> ...
> > This looks very similar to the one I reported last week with generic/269.
> 
> Yeah, another missing wakeup, no doubt.  Can you bisect this?  That was
> how I found the last one; bisected it to a single patch and stared very
> hard at the patch until I saw it.  I'm not going to be in a position to
> tinker with my DAX setup until the first week of July.

It bisected to this commit:

b4b4daa7e8fb0ad0fee35d3e28d00e97c849a6cb is the first bad commit
commit b4b4daa7e8fb0ad0fee35d3e28d00e97c849a6cb
Author: Matthew Wilcox <willy@...radead.org>
Date:   Thu Mar 29 22:58:27 2018 -0400

    dax: Convert page fault handlers to XArray

    This is the last part of DAX to be converted to the XArray so
    remove all the old helper functions.

    Signed-off-by: Matthew Wilcox <willy@...radead.org>