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

[Darrick J. Wong]

On Tue, Apr 08, 2025 at 06:51:14PM +0100, Matthew Wilcox wrote:
> 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.
> 
> But you said:
> 
> > the machine is arm64 with 64k basepages and 4k fsblock size:
> 
> so that shouldn't be using large folios because you should have set the
> order to 0.  Right?  Or did you mis-speak and use a 4K PAGE_SIZE kernel
> with a 64k fsblocksize?

This particular kernel warning is arm64 with 64k base pages and a 4k
fsblock size, and my suspicion is that udev/libblkid are creating the
buffer heads or something weird like that.

On x64 with 4k base pages, xfs/032 creates a filesystem with 64k sector
size and there's an actual kernel crash resulting from a udev worker:
https://lore.kernel.org/linux-fsdevel/20250408175125.GL6266@frogsfrogsfrogs/T/#u

So I didn't misspeak, I just have two problems.  I actually have four
problems, but the others are loop device behavior changes.

--D