[LTP] [linux-next:master] [block/bdev] 3c20917120: BUG:sleeping_function_called_from_invalid_context_at_mm/util.c

[Luis Chamberlain]

On Tue, Apr 08, 2025 at 10:48:55AM -0700, Darrick J. Wong wrote:
> On Tue, Apr 08, 2025 at 10:24:40AM -0700, Luis Chamberlain wrote:
> > On Tue, Apr 8, 2025 at 10:06 AM Luis Chamberlain <mcgrof@kernel.org> wrote:
> > > Fun
> > > puzzle for the community is figuring out *why* oh why did a large folio
> > > end up being used on buffer-heads for your use case *without* an LBS
> > > device (logical block size) being present, as I assume you didn't have
> > > one, ie say a nvme or virtio block device with logical block size  >
> > > PAGE_SIZE. The area in question would trigger on folio migration *only*
> > > if you are migrating large buffer-head folios. We only create those
> > 
> > To be clear, large folios for buffer-heads.
> > > if
> > > you have an LBS device and are leveraging the block device cache or a
> > > filesystem with buffer-heads with LBS (they don't exist yet other than
> > > the block device cache).
> 
> My guess is that udev or something tries to read the disk label in
> response to some uevent (mkfs, mount, unmount, etc), which creates a
> large folio because min_order > 0, and attaches a buffer head.  There's
> a separate crash report that I'll cc you on.

OK so as willy pointed out I buy that for x86_64 *iff* we do already
have opportunistic large folio support for the buffer-head read/write
path. But also, I don't think we enable large folios yet on the block
device cache aops unless we have a min order block device... so what
gives?

  Luis