Re: [btrfs] 0f80799866: WARNING:at_fs/sysfs/file.c:#sysfs_emit

[Anand Jain]

On 22/10/2021 00:06, David Sterba wrote:
> On Thu, Oct 21, 2021 at 09:35:38PM +0800, kernel test robot wrote:
> > Greeting,
> >
> > FYI, we noticed the following commit (built with gcc-9):
> >
> > commit: 0f807998661ecadb74638c18cbaff8785bb46f8d ("[PATCH 1/2] btrfs: sysfs convert scnprintf and snprintf to use sysfs_emit")
> > url: https://github.com/0day-ci/linux/commits/Anand-Jain/provide-fsid-in-sysfs-devinfo/20211019-082356
> > base: https://git.kernel.org/cgit/linux/kernel/git/kdave/linux.git for-next
> >
> > in testcase: boot
> >
> > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
>
> I wonder if it's related to the 32bit host, I don't see any crash.


We are hitting this warning:

int sysfs_emit(char *buf, const char *fmt, ...)
{
        va_list args;
        int len;

        if (WARN(!buf || offset_in_page(buf),   <====
                 "invalid sysfs_emit: buf:%p\n", buf))
                return 0;
<snip>


The input buf wasn't page-aligned because it wasn't part of the show().