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

[Matthew Wilcox]

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.