On Thu, Feb 22, 2018 at 10:34:45AM -0800, Darrick J. Wong wrote:
> On Thu, Feb 22, 2018 at 06:17:31PM +0000, Luis Henriques wrote:
> > On Thu, Feb 22, 2018 at 09:27:41AM -0800, Darrick J. Wong wrote:
> > > On Thu, Feb 22, 2018 at 04:06:14PM +0000, Luis Henriques wrote:
> > > > On Thu, Dec 14, 2017 at 06:07:31PM -0800, Darrick J. Wong wrote:
> > > >
> > > > <snip>
> > > >
> > > > > +void
> > > > > +clonerange_f(
> > > > > + int opno,
> > > > > + long r)
> > > > > +{
> > > >
> > > > <snip>
> > > >
> > > > > + /* Calculate offsets */
> > > > > + len = (random() % FILELEN_MAX) + 1;
> > > > > + len &= ~(stat1.st_blksize - 1);
> > > > > + if (len == 0)
> > > > > + len = stat1.st_blksize;
> > > > > + if (len > stat1.st_size)
> > > > > + len = stat1.st_size;
> > > > > +
> > > > > + lr = ((__int64_t)random() << 32) + random();
> > > > > + if (stat1.st_size == len)
> > > > > + off1 = 0;
> > > > > + else
> > > > > + off1 = (off64_t)(lr % MIN(stat1.st_size - len, MAXFSIZE));
> > > > > + off1 %= maxfsize;
> > > > > + off1 &= ~(stat1.st_blksize - 1);
> > > > > +
> > > > > + /*
> > > > > + * If srcfile == destfile, randomly generate destination ranges
> > > > > + * until we find one that doesn't overlap the source range.
> > > > > + */
> > > > > + do {
> > > > > + lr = ((__int64_t)random() << 32) + random();
> > > > > + off2 = (off64_t)(lr % MIN(stat2.st_size + (1024 * 1024), MAXFSIZE));
> > > > > + off2 %= maxfsize;
> > > > > + off2 &= ~(stat2.st_blksize - 1);
> > > > > + } while (stat1.st_ino == stat2.st_ino && llabs(off2 - off1) < len);
> > > >
> > > > I started seeing hangs in generic/013 on cephfs. After spending some
> > > > time looking, I found that this loops forever. And the reason seems to
> > > > be that stat1.st_blksize is too big for this filesystem (4M) -- when
> > > > doing:
> > >
> > > "Too big for this filesystem"?
> > >
> > > Uh... maybe you'd better start by giving me more stat buffer info --
> > > what's st_size?
> > >
> > > > off1 &= ~(stat1.st_blksize - 1);
> > >
> > > These bits round the start offset down to block granularity, since clone
> > > range implementations generally require that the ranges align to block
> > > boundaries.
> > >
> > > (Though AFAICT ceph doesn't support clone range anyway...)
> > >
> > > So reading between the lines, is the problem here that ceph advertises a
> > > blocksize of 4M and fsstress calls clonerange_f with files that are
> > > smaller than 4M in size, so the only possible offsets with a 4M
> > > blocksize are zero and that's why we end up looping forever?
> >
> > Brilliantly described! That is *exactly* what I'm seeing and failed to
> > describe. I guess I could use FSSTRESS_AVOID to work around this issue,
> > but there are probably better options.
>
> Better to patch fsstress.c against this bug. :)
>
> Does the following patch help?
Yes, it does. Thanks! Feel free to add my
Tested-by: Luis Henriques <lhenriques@xxxxxxxx>
Cheers,
--
Luís
>
> --D
>
> diff --git a/ltp/fsstress.c b/ltp/fsstress.c
> index 935f5de..e107099 100644
> --- a/ltp/fsstress.c
> +++ b/ltp/fsstress.c
> @@ -2222,6 +2222,7 @@ clonerange_f(
> off64_t lr;
> off64_t off1;
> off64_t off2;
> + off64_t max_off2;
> size_t len;
> int v1;
> int v2;
> @@ -2305,9 +2306,10 @@ clonerange_f(
> * If srcfile == destfile, randomly generate destination ranges
> * until we find one that doesn't overlap the source range.
> */
> + max_off2 = MIN(stat2.st_size + (1024ULL * stat2.st_blksize), MAXFSIZE);
> do {
> lr = ((int64_t)random() << 32) + random();
> - off2 = (off64_t)(lr % MIN(stat2.st_size + (1024 * 1024), MAXFSIZE));
> + off2 = (off64_t)(lr % max_off2);
> off2 %= maxfsize;
> off2 &= ~(stat2.st_blksize - 1);
> } while (stat1.st_ino == stat2.st_ino && llabs(off2 - off1) < len);
>
--
To unsubscribe from this list: send the line "unsubscribe linux-xfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
