[Libguestfs] [PATCH libnbd 1/2] nbdcopy: Do not use trim for zeroing

[Nir Soffer]

On Mon, Feb 22, 2021, 13:39 Richard W.M. Jones <rjones at redhat.com> wrote:

> The patch doesn't compile for me:
>
> pipe-ops.c:121:17: error: initialization of ‘_Bool (*)(struct rw *,
> uint64_t,  uint64_t,  _Bool)’ {aka ‘_Bool (*)(struct rw *, long unsigned
> int,  long unsigned int,  _Bool)’} from incompatible pointer type ‘_Bool
> (*)(struct rw *, uint64_t,  uint64_t)’ {aka ‘_Bool (*)(struct rw *, long
> unsigned int,  long unsigned int)’} [-Werror=incompatible-pointer-types]
>   121 |   .synch_zero = pipe_synch_trim_zero,
>       |                 ^~~~~~~~~~~~~~~~~~~~
> pipe-ops.c:121:17: note: (near initialization for ‘pipe_ops.synch_zero’)
> pipe-ops.c:133:18: error: initialization of ‘_Bool (*)(struct rw *, struct
> command *, nbd_completion_callback,  _Bool)’ from incompatible pointer type
> ‘_Bool (*)(struct rw *, struct command *, nbd_completion_callback)’
> [-Werror=incompatible-pointer-types]
>   133 |   .asynch_zero = pipe_asynch_trim_zero,
>       |                  ^~~~~~~~~~~~~~~~~~~~~
> pipe-ops.c:133:18: note: (near initialization for ‘pipe_ops.asynch_zero’)
>

It compiled here on top of master, will check again.


> More comments below.
>
> On Sun, Feb 21, 2021 at 03:09:05AM +0200, Nir Soffer wrote:
> > diff --git a/copy/file-ops.c b/copy/file-ops.c
> > index 2a239d0..d0b9447 100644
> > --- a/copy/file-ops.c
> > +++ b/copy/file-ops.c
> > @@ -100,10 +100,9 @@ file_synch_write (struct rw *rw,
> >  }
> >
> >  static bool
> > -file_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
> > +file_punch_hole(int fd, uint64_t offset, uint64_t count)
>
> (Style) missing space before '(' ...
>

Sorry, will fix in next version.


> >  {
> >  #ifdef FALLOC_FL_PUNCH_HOLE
> > -  int fd = rw->u.local.fd;
> >    int r;
> >
> >    r = fallocate (fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
> > @@ -113,17 +112,14 @@ file_synch_trim (struct rw *rw, uint64_t offset,
> uint64_t count)
> >      exit (EXIT_FAILURE);
> >    }
> >    return true;
> > -#else /* !FALLOC_FL_PUNCH_HOLE */
> > -  return false;
> >  #endif
> > +  return false;
> >  }
> >
> >  static bool
> > -file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count)
> > +file_zero_range(int fd, uint64_t offset, uint64_t count)
>
> ... and here
>
> >  {
> > -  if (S_ISREG (rw->u.local.stat.st_mode)) {
> >  #ifdef FALLOC_FL_ZERO_RANGE
> > -    int fd = rw->u.local.fd;
> >      int r;
> >
> >      r = fallocate (fd, FALLOC_FL_ZERO_RANGE, offset, count);
> > @@ -133,11 +129,13 @@ file_synch_zero (struct rw *rw, uint64_t offset,
> uint64_t count)
> >      }
> >      return true;
> >  #endif
> > -  }
> > -  else if (S_ISBLK (rw->u.local.stat.st_mode) &&
> > -           IS_ALIGNED (offset | count, rw->u.local.sector_size)) {
> > +  return false;
> > +}
> > +
> > +static bool
> > +file_zeroout(int fd, uint64_t offset, uint64_t count)
>
> ... and here
>
> > +{
> >  #ifdef BLKZEROOUT
> > -    int fd = rw->u.local.fd;
> >      int r;
> >      uint64_t range[2] = {offset, count};
> >
> > @@ -148,6 +146,31 @@ file_synch_zero (struct rw *rw, uint64_t offset,
> uint64_t count)
> >      }
> >      return true;
> >  #endif
> > +    return false;
> > +}
> > +
> > +static bool
> > +file_synch_trim (struct rw *rw, uint64_t offset, uint64_t count)
> > +{
> > +  return file_punch_hole(rw->u.local.fd, offset, count);
> > +}
> > +
> > +static bool
> > +file_synch_zero (struct rw *rw, uint64_t offset, uint64_t count, bool
> allocate)
>
> ... and overlong line.
>
> > +{
> > +  int fd = rw->u.local.fd;
> > +
> > +  if (S_ISREG (rw->u.local.stat.st_mode)) {
> > +    if (allocate) {
> > +        return file_zero_range (fd, offset, count);
> > +    } else {
> > +        return file_punch_hole (fd, offset, count);
> > +    }
> > +  }
> > +  else if (S_ISBLK (rw->u.local.stat.st_mode) &&
> > +           IS_ALIGNED (offset | count, rw->u.local.sector_size)) {
> > +    /* Always allocate, discard and gurantee zeroing. */
> > +    return file_zeroout (fd, offset, count);
> >    }
> >    return false;
>
> In the S_ISBLK && not aligned case, is giving up OK?
>

Not sure what do you mean by this, but it returns false love ke the
previous version, right?


> > diff --git a/copy/nbdcopy.h b/copy/nbdcopy.h
> > index 69fac2a..21d09bf 100644
> > --- a/copy/nbdcopy.h
> > +++ b/copy/nbdcopy.h
> > @@ -134,7 +134,8 @@ struct rw_ops {
> >    bool (*synch_trim) (struct rw *rw, uint64_t offset, uint64_t count);
> >
> >    /* Synchronously zero.  If not possible, returns false. */
> > -  bool (*synch_zero) (struct rw *rw, uint64_t offset, uint64_t count);
> > +  bool (*synch_zero) (struct rw *rw, uint64_t offset, uint64_t count,
> > +                      bool allocate);
>
> After this change ops->synch_trim and ops->asynch_trim are no longer
> used, so I guess they should be removed completely from the code?
>

Yes, unless we have a reason to keep the trim option.


> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
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>
>
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