Re: [dm-devel] [PATCH] use uptodate bit to test status of bios (take2)

[Mike Christie <michaelc cs wisc edu>]

Mike Christie wrote:
> Mike Christie wrote:
>
> > Kevin Corry wrote:
> >
> > > On Friday 05 March 2004 3:32 pm, Mike Christie wrote:
> > >
> > > > If there is an error on a partially completed bio it's uptodate
> > > > bit is cleared and an error value is retured, but DM will see
> > > > that bi_size is not yet zero and ignore it. SCSI will fail the rest
> > > > of the IO if the fail fast bit is set, so DM multipath will
> > > > eventually see the error from them. However, if that behavior is not
> > > > a requirement the patch below would be needed to detect errors in
> > > > bios where the begining is not uptodate but the end completed without
> > > > errors.
> > > >
> > > > SCSI will not always fail the rest of the IO when the fail fast bit
> > > > is not set, so this may be a bug in dm-crypt and dm-raid1.
> > > >
> > > > Mike Christie
> > > >
> > > >
> > > > --- linux-2.6.4-rc1-udm1.orig/drivers/md/dm-mpath.c    2004-03-03
> > > > 19:56:43.000000000 -0800 +++
> > > > linux-2.6.4-rc1-udm1/drivers/md/dm-mpath.c    2004-03-03 
> > > > 19:52:55.000000000
> > > > -0800 @@ -551,8 +551,9 @@ static int do_end_io(struct multipath *m
> > > >               int error, struct mpath_io *io)
> > > >  {
> > > >      int r;
> > > > +    int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
> > > >
> > > > -    if (error) {
> > > > +    if (uptodate) {
> > > >          spin_lock(&m->lock);
> > > >          if (!m->nr_valid_paths) {
> > > >              spin_unlock(&m->lock);
> > >
> > >
> > >
> > >
> > > It looks like this test should be "if (!uptodate) {".
> >
> > darn.
> >
> > > Also, couldn't we do this in clone_endio() in dm.c and not have to 
> > > change all the targets? Something like this.
> >
> >
> > We also want to preserve the error value. Hopefully soon they will
> > be meaningful ;) This means we have the normal error case, and the 
> > funky one
> > where uptodate is cleared and error is 0.
> >
> >
> >
> > --- linux-2.6.4-rc1-udm1.orig/drivers/md/dm.c    2004-03-03 
> > 19:56:43.000000000 -0800
> > +++ linux-2.6.4-rc1-udm1/drivers/md/dm.c    2004-03-05 
> > 14:08:11.801747069 -0800
> > @@ -278,6 +278,9 @@ static int clone_endio(struct bio *bio,
> >      if (bio->bi_size)
> >          return 1;
> >
> > +    if (!bio_flagged(bio, BIO_UPTODATE) && !error)
> > +        error = -EIO;
> > +
> >      if (endio) {
> >          r = endio(tio->ti, bio, error, &tio->info);
> >          if (r < 0)
>
>
> oops that's wrong too.

I am resending it as an attached patch this time.
In my mailer it shows I was squashing tabs.

--- linux-2.6.4-rc1-udm1.orig/drivers/md/dm.c	2004-03-03 19:56:43.000000000 -0800
+++ linux-2.6.4-rc1-udm1/drivers/md/dm.c	2004-03-05 14:08:11.801747069 -0800
@@ -278,6 +278,9 @@ static int clone_endio(struct bio *bio, 
 	if (bio->bi_size)
 		return 1;
 
+	if (!bio_flagged(bio, BIO_UPTODATE) && !error)
+		error = -EIO;
+
 	if (endio) {
 		r = endio(tio->ti, bio, error, &tio->info);
 		if (r < 0)