Re: [PATCH] mkfs.xfs: introduce sunit/swidth validation helper

Gao Xiang
2020-08-03T15:45:46Z

Hi Darrick,

On Mon, Aug 03, 2020 at 08:26:09AM -0700, Darrick J. Wong wrote:
> On Mon, Aug 03, 2020 at 08:50:18PM +0800, Gao Xiang wrote:
> > Currently stripe unit/width checking logic is all over xfsprogs.
> > So, refactor the same code snippet into a single validation helper
> > xfs_validate_stripe_factors(), including:
> > - integer overflows of either value
> > - sunit and swidth alignment wrt sector size
> > - if either sunit or swidth are zero, both should be zero
> > - swidth must be a multiple of sunit
> >
> > Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> > ---
> >
> > This patch follows Darrick's original suggestion [1], yet I'm
> > not sure if I'm doing the right thing or if something is still
> > missing (e.g the meaning of six(ish) places)... So post it
> > right now...
> >
> > TBH, especially all these naming and the helper location (whether
> > in topology.c)...plus, click a dislike on calc_stripe_factors()
> > itself...
> >
> > (Hopefully hear some advice about this... Thanks!)
> >
> > [1] https://lore.kernel.org/r/20200515204802.GO6714@magnolia
> >
> > libfrog/topology.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++
> > libfrog/topology.h | 15 ++++++++++++++
> > mkfs/xfs_mkfs.c | 48 ++++++++++++++++++++++----------------------
> > 3 files changed, 89 insertions(+), 24 deletions(-)
> >
> > diff --git a/libfrog/topology.c b/libfrog/topology.c
> > index b1b470c9..cf56fb03 100644
> > --- a/libfrog/topology.c
> > +++ b/libfrog/topology.c
> > @@ -174,6 +174,41 @@ out:
> > return ret;
> > }
> >
> > +enum xfs_stripe_retcode
> > +xfs_validate_stripe_factors(
>
> libfrog functions (and enums) should be prefixed with libfrog, not xfs.
>
> LIBFROG_STRIPEVAL_{OK,SUNIT_MISALIGN, etc.}
>
> > + int sectorsize,
> > + int *sup,
>
> Errant space between "int" and "*sup".

Ack. Sorry about that.

>
> > + int *swp)
>
> Strange that a validator function has out parameters...
>
> Also, uh, .... full names, please.

see the reasons below...

>
> int *sunitp,
> int *swidthp)
>
> (I'm vaguely wondering why we use signed ints here vs. unsigned, but
> that isn't critical...)

That is because I saw many previous "sunit/swidth" usage in the codebase
by using "int" rather than "unsigned int". I don't have much tendency
of this. (either form is ok with me since signed int is also enough here.)

>
> > +{
> > + int sunit = *sup, swidth = *swp;
> > +
> > + if (sectorsize) {
> > + long long big_swidth;
> > +
> > + if (sunit % sectorsize)
> > + return XFS_STRIPE_RET_SUNIT_MISALIGN;
> > +
> > + sunit = (int)BTOBBT(sunit);
>
> Hmm. On input, *sup is in units of bytes, but on output it can be in
> units of 512b blocks? That is very surprising...

Yeah, It seems a bit weird at first. But I have no better idea
how to fulfill/wrap up "- sunit and swidth alignment wrt sector
size" check from the original thread in the validator helper.

So I finally implemented the helper in a form which accepts
either:
[1] (sectersize != 0) dsu (in bytes) / dsw (which is multiple of dsu)

Or
[2] (sectersize == 0) dunit / dwidth (in 512b sector size)

In [1], dsu and dsw would be turned into dunit / dwidth finally...

Yeah, that's my premature thought about this tho... hope for better
idea about this :)

>
> > + big_swidth = (long long)sunit * swidth;
> > +
> > + if (big_swidth > INT_MAX)
> > + return XFS_STRIPE_RET_SWIDTH_OVERFLOW;
> > + swidth = big_swidth;
> > + }
> > + if ((sunit && !swidth) || (!sunit && swidth))
> > + return XFS_STRIPE_RET_PARTIAL_VALID;
> > +
> > + if (sunit > swidth)
> > + return XFS_STRIPE_RET_SUNIT_TOO_LARGE;
> > +
> > + if (sunit && (swidth % sunit))
> > + return XFS_STRIPE_RET_SWIDTH_MISALIGN;
> > +
> > + *sup = sunit;
>
> ...especially since in the !sectorsize case we don't change it at all.

Yeah...

>
> > + *swp = swidth;
> > + return XFS_STRIPE_RET_OK;
> > +}
> > +
> > static void blkid_get_topology(
> > const char *device,
> > int *sunit,
> > @@ -229,6 +264,21 @@ static void blkid_get_topology(
> > */
> > *sunit = *sunit >> 9;
> > *swidth = *swidth >> 9;
> > + switch (xfs_validate_stripe_factors(0, sunit, swidth)) {
> > + case XFS_STRIPE_RET_OK:
> > + break;
> > + case XFS_STRIPE_RET_PARTIAL_VALID:
> > + fprintf(stderr,
> > +_("%s: Volume reports stripe unit of %d bytes and stripe width of %d bytes, ignoring.\n"),
> > + progname, BBTOB(*sunit), BBTOB(*swidth));
>
> Needs a "/* fallthrough */" comment here.

Ack.

>
> > + default:
>
> Why don't we warn about receiving garbage geometry that produces
> MISALIGN or OVERFLOW?

Okay, I could add them in the next version...
Yet I still suspect my broken English works... :)

>
> > + /*
> > + * if firmware is broken, just give up and set both to zero,
> > + * we can't trust information from this device.
> > + */
> > + *sunit = 0;
> > + *swidth = 0;
> > + }
> >
> > if (blkid_topology_get_alignment_offset(tp) != 0) {
> > fprintf(stderr,
> > diff --git a/libfrog/topology.h b/libfrog/topology.h
> > index 6fde868a..e8be26b2 100644
> > --- a/libfrog/topology.h
> > +++ b/libfrog/topology.h
> > @@ -36,4 +36,19 @@ extern int
> > check_overwrite(
> > const char *device);
> >
> > +enum xfs_stripe_retcode {
> > + XFS_STRIPE_RET_OK = 0,
> > + XFS_STRIPE_RET_SUNIT_MISALIGN,
> > + XFS_STRIPE_RET_SWIDTH_OVERFLOW,
> > + XFS_STRIPE_RET_PARTIAL_VALID,
> > + XFS_STRIPE_RET_SUNIT_TOO_LARGE,
> > + XFS_STRIPE_RET_SWIDTH_MISALIGN,
> > +};
> > +
> > +enum xfs_stripe_retcode
> > +xfs_validate_stripe_factors(
> > + int sectorsize,
> > + int *sup,
>
> Errant space between "int" and "*sup".

Sorry, copy again.

>
> > + int *swp);
> > +
> > #endif /* __LIBFROG_TOPOLOGY_H__ */
> > diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> > index 2e6cd280..a3d6032c 100644
> > --- a/mkfs/xfs_mkfs.c
> > +++ b/mkfs/xfs_mkfs.c
> > @@ -2255,7 +2255,6 @@ calc_stripe_factors(
> > struct cli_params *cli,
> > struct fs_topology *ft)
> > {
> > - long long int big_dswidth;
> > int dsunit = 0;
> > int dswidth = 0;
> > int lsunit = 0;
> > @@ -2263,6 +2262,7 @@ calc_stripe_factors(
> > int dsw = 0;
> > int lsu = 0;
> > bool use_dev = false;
> > + int error;
> >
> > if (cli_opt_set(&dopts, D_SUNIT))
> > dsunit = cli->dsunit;
> > @@ -2289,31 +2289,40 @@ _("both data su and data sw options must be specified\n"));
> > usage();
> > }
> >
> > - if (dsu % cfg->sectorsize) {
> > + dsunit = dsu;
> > + dswidth = dsw;
> > + error = xfs_validate_stripe_factors(cfg->sectorsize, &dsunit, &dswidth);
>
> I thought this function returned an enum?

okay, will update in the next version.

>
> > + switch(error) {
> > + case XFS_STRIPE_RET_SUNIT_MISALIGN:
> > fprintf(stderr,
> > _("data su must be a multiple of the sector size (%d)\n"), cfg->sectorsize);
> > usage();
> > - }
> > -
> > - dsunit = (int)BTOBBT(dsu);
> > - big_dswidth = (long long int)dsunit * dsw;
> > - if (big_dswidth > INT_MAX) {
> > + break;
> > + case XFS_STRIPE_RET_SWIDTH_OVERFLOW:
> > fprintf(stderr,
> > -_("data stripe width (%lld) is too large of a multiple of the data stripe unit (%d)\n"),
> > - big_dswidth, dsunit);
> > +_("data stripe width (dsw %d) is too large of a multiple of the data stripe unit (%d)\n"),
>
> Why change this message?

big_dswidth isn't defined here.
So I'm not sure if the original message can still be properly used here.
(I could leave it alone...)

>
> > + dsw, dsunit);
> > usage();
> > + break;
> > }
> > - dswidth = big_dswidth;
> > + } else {
> > + error = xfs_validate_stripe_factors(0, &dsunit, &dswidth);
> > }
> >
> > - if ((dsunit && !dswidth) || (!dsunit && dswidth) ||
> > - (dsunit && (dswidth % dsunit != 0))) {
> > + if (error == XFS_STRIPE_RET_PARTIAL_VALID ||
> > + error == XFS_STRIPE_RET_SWIDTH_MISALIGN) {
> > fprintf(stderr,
> > _("data stripe width (%d) must be a multiple of the data stripe unit (%d)\n"),
> > dswidth, dsunit);
> > usage();
> > }
> >
> > + if (error) {
> > + fprintf(stderr,
> > +_("invalid data stripe unit (%d), width (%d)\n"), dsunit, dswidth);
>
> Invalid how? We know the exact reason, so we should say so.

Okay, let me think more about some cleaner way for these message.
I feel it could be a bit messy here.

Thanks，
Gao Xiang

>
> --D
>
> > + usage();
> > + }
> > +
> > /* If sunit & swidth were manually specified as 0, same as noalign */
> > if ((cli_opt_set(&dopts, D_SUNIT) || cli_opt_set(&dopts, D_SU)) &&
> > !dsunit && !dswidth)
> > @@ -2328,18 +2337,9 @@ _("data stripe width (%d) must be a multiple of the data stripe unit (%d)\n"),
> >
> > /* if no stripe config set, use the device default */
> > if (!dsunit) {
> > - /* Ignore nonsense from device. XXX add more validation */
> > - if (ft->dsunit && ft->dswidth == 0) {
> > - fprintf(stderr,
> > -_("%s: Volume reports stripe unit of %d bytes and stripe width of 0, ignoring.\n"),
> > - progname, BBTOB(ft->dsunit));
> > - ft->dsunit = 0;
> > - ft->dswidth = 0;
> > - } else {
> > - dsunit = ft->dsunit;
> > - dswidth = ft->dswidth;
> > - use_dev = true;
> > - }
> > + dsunit = ft->dsunit;
> > + dswidth = ft->dswidth;
> > + use_dev = true;
> > } else {
> > /* check and warn if user-specified alignment is sub-optimal */
> > if (ft->dsunit && ft->dsunit != dsunit) {
> > --
> > 2.18.1
> >
>