Re: [PATCH] fio: make sure io_u->file isn't NULL before using it

["Luís Henriques" <lhenriques@suse.de>]

On Mon, Oct 11, 2021 at 06:58:52AM -0600, Jens Axboe wrote:
> On 10/11/21 4:27 AM, Luís Henriques wrote:
> > While running fstests generic/095 against ext4 on a zram device I started
> > seeing fio crashing.  Fix it by making sure io_u->file isn't NULL before
> > accessing it.
> > 
> > Signed-off-by: Luís Henriques <lhenriques@suse.de>
> > ---
> >  io_u.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/io_u.c b/io_u.c
> > index 5289b5d1d9c6..b8e715d4118c 100644
> > --- a/io_u.c
> > +++ b/io_u.c
> > @@ -2009,7 +2009,8 @@ static void io_completed(struct thread_data *td, struct io_u **io_u_ptr,
> >  			io_u->xfer_buf += bytes;
> >  			io_u->offset += bytes;
> >  			td->ts.short_io_u[io_u->ddir]++;
> > -			if (io_u->offset < io_u->file->real_file_size) {
> > +			if (io_u->file &&
> > +			    (io_u->offset < io_u->file->real_file_size)) {
> >  				requeue_io_u(td, io_u_ptr);
> >  				return;
> >  			}
> 
> This will prevent the crash, but I'm wondering why io_u-> == NULL for this case.
> It really should be a valid file.
> 
> Can you let me know exactly how you're reproducing this? Then I'll give it
> a whirl too.

Sure, here's my recipe for reproducing this bug:

 # modprobe zram num_devices=2
 # echo 1G > /sys/block/zram0/disksize 
 # echo 1G > /sys/block/zram1/disksize 
 # mkfs.ext4 /dev/zram0
 # mkfs.ext4 /dev/zram1

 # ./check generic/095

Cheers,
--
Luís