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

[Richard W.M. Jones]

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’)

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 '(' ...

>  {
>  #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?

> 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?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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