Re: [BUG] mmap and file init with 0 length

On Wed, Mar 26 2008, Zhang, Yanmin wrote:
> On Wed, 2008-03-26 at 09:20 +0100, Jens Axboe wrote:
> > On Wed, Mar 26 2008, Zhang, Yanmin wrote:
> > > fio is killed with a SIGBUS. Pls. see below job file.
> > >
> > > Actually, if the ioengine=mmap and rw=write/randwrite, fio just
> > > unlinks the file and creates a new file whose length is 0. sys_mmap
> > > could succeed, but later on when fio accesses the mmapped area, kernel
> > > will send fio a SIGBUS and kill it.
> > >
> > >
> > > Could fio create a real file when ioengine=mmap and
> > > rw=write/randwrite? For exmaple, below job_file could ask fi oto
> > > create file data0/f1 whose length is 4G.
> > >
> >
> > I've committed a fix for this, the below one-liner should fix it for
> > you.
> >
> > diff --git a/filesetup.c b/filesetup.c
> > index e847276..bb43ee5 100644
> > --- a/filesetup.c
> > +++ b/filesetup.c
> > @@ -30,7 +30,8 @@ static int extend_file(struct thread_data *td, struct fio_file *f)
> > * does that for operations involving reads, or for writes
> > * where overwrite is set
> > */
> > - if (td_read(td) || (td_write(td) && td->o.overwrite))
> > + if (td_read(td) || (td_write(td) && td->o.overwrite) ||
> > + (td_write(td) && td->io_ops->flags & FIO_NOEXTEND))
> > new_layout = 1;
> > if (td_write(td) && !td->o.overwrite)
> > unlink_file = 1;
> This patch does fix it. I downloaded the latest git tarball of fio and got below error.
>
>
> [ymzhang_at_lkp-tt02-x8664 fio]$ fio /tmp/job_file
> job_group0_sub0: (g=0): rw=randrw, bs=1K-1K/4K-4K, ioengine=vsync, iodepth=256
> job_group0_sub0: (g=0): rw=randrw, bs=1K-1K/4K-4K, ioengine=vsync, iodepth=256
> job_group0_sub1: (g=1): rw=randrw, bs=1K-1K/4K-4K, ioengine=vsync, iodepth=256
> job_group0_sub1: (g=1): rw=randrw, bs=1K-1K/4K-4K, ioengine=vsync, iodepth=256
> Starting 4 processes
> fio: failed allocating random map. If running a large number of jobs, try the 'norandommap' option
> fio: failed allocating random map. If running a large number of jobs, try the 'norandommap' option
> fio: failed allocating random map. If running a large number of jobs, try the 'norandommap' option
> fio: failed allocating random map. If running a large number of jobs, try the 'norandommap' option
>
>
> I checked HOWTO that norandommap couldn't guarantee every block is
> written/read. Is there any other method to solve above error?

It's a bit quirky, fio should probably just fallback to norandommap when
that happens, it's not a huge deal.

-- 
Jens Axboe