Re: [PATCH 4/4] fsx: move range generation logic into a common helper

[Filipe Manana <fdmanana@kernel.org>]

On Wed, Apr 8, 2020 at 4:48 PM Darrick J. Wong <darrick.wong@oracle.com> wrote:
>
> On Wed, Apr 08, 2020 at 11:36:27AM +0100, fdmanana@kernel.org wrote:
> > From: Filipe Manana <fdmanana@suse.com>
> >
> > We have very similar code that generates the destination range for clone,
> > dedupe and copy_file_range operations, so avoid duplicating the code three
> > times and move it into a helper function.
> >
> > Signed-off-by: Filipe Manana <fdmanana@suse.com>
> > ---
> >  ltp/fsx.c | 91 +++++++++++++++++++++++++--------------------------------------
> >  1 file changed, 36 insertions(+), 55 deletions(-)
> >
> > diff --git a/ltp/fsx.c b/ltp/fsx.c
> > index 89a5f60e..8873cd01 100644
> > --- a/ltp/fsx.c
> > +++ b/ltp/fsx.c
> > @@ -1930,6 +1930,36 @@ range_overlaps(
> >       return llabs((unsigned long long)off1 - off0) < size;
> >  }
> >
> > +static void generate_dest_range(unsigned long op,
> > +                             unsigned long max_range_end,
> > +                             unsigned long *src_offset,
> > +                             unsigned long *size,
> > +                             unsigned long *dst_offset)
> > +{
> > +     int tries = 0;
> > +
> > +     TRIM_OFF_LEN(*src_offset, *size, file_size);
> > +     if (op == OP_COPY_RANGE) {
>
> It feels funny that we pass in @op just to let COPY RANGE relax the
> block size alignment requirements.  How about passing a block_align
> parameter (instead of op) which would be the subject of the if test?
> This way we concentrate the alignment requirement knowlege of each type
> of call in the "case OP_FOO" part of the code instead of scattering it?

You mean something like the following:

https://pastebin.com/e2NZKbZV

?

>
> --D
>
> > +             *src_offset -= *src_offset % readbdy;
> > +             if (o_direct)
> > +                     *size -= *size % readbdy;
> > +     } else {
> > +             *src_offset = *src_offset & ~(block_size - 1);
> > +             *size = *size & ~(block_size - 1);
> > +     }
> > +
> > +     do {
> > +             if (tries++ >= 30) {
> > +                     *size = 0;
> > +                     break;
> > +             }
> > +             *dst_offset = random();
> > +             TRIM_OFF(*dst_offset, max_range_end);
> > +             *dst_offset = *dst_offset & ~(block_size - 1);
> > +     } while (range_overlaps(*src_offset, *dst_offset, *size) ||
> > +              *dst_offset + *size > max_range_end);
> > +}
> > +
> >  int
> >  test(void)
> >  {
> > @@ -2004,63 +2034,14 @@ test(void)
> >                       keep_size = random() % 2;
> >               break;
> >       case OP_CLONE_RANGE:
> > -             {
> > -                     int tries = 0;
> > -
> > -                     TRIM_OFF_LEN(offset, size, file_size);
> > -                     offset = offset & ~(block_size - 1);
> > -                     size = size & ~(block_size - 1);
> > -                     do {
> > -                             if (tries++ >= 30) {
> > -                                     size = 0;
> > -                                     break;
> > -                             }
> > -                             offset2 = random();
> > -                             TRIM_OFF(offset2, maxfilelen);
> > -                             offset2 = offset2 & ~(block_size - 1);
> > -                     } while (range_overlaps(offset, offset2, size) ||
> > -                              offset2 + size > maxfilelen);
> > -                     break;
> > -             }
> > +             generate_dest_range(op, maxfilelen, &offset, &size, &offset2);
> > +             break;
> >       case OP_DEDUPE_RANGE:
> > -             {
> > -                     int tries = 0;
> > -
> > -                     TRIM_OFF_LEN(offset, size, file_size);
> > -                     offset = offset & ~(block_size - 1);
> > -                     size = size & ~(block_size - 1);
> > -                     do {
> > -                             if (tries++ >= 30) {
> > -                                     size = 0;
> > -                                     break;
> > -                             }
> > -                             offset2 = random();
> > -                             TRIM_OFF(offset2, file_size);
> > -                             offset2 = offset2 & ~(block_size - 1);
> > -                     } while (range_overlaps(offset, offset2, size) ||
> > -                              offset2 + size > file_size);
> > -                     break;
> > -             }
> > +             generate_dest_range(op, file_size, &offset, &size, &offset2);
> > +             break;
> >       case OP_COPY_RANGE:
> > -             {
> > -                     int tries = 0;
> > -
> > -                     TRIM_OFF_LEN(offset, size, file_size);
> > -                     offset -= offset % readbdy;
> > -                     if (o_direct)
> > -                             size -= size % readbdy;
> > -                     do {
> > -                             if (tries++ >= 30) {
> > -                                     size = 0;
> > -                                     break;
> > -                             }
> > -                             offset2 = random();
> > -                             TRIM_OFF(offset2, maxfilelen);
> > -                             offset2 -= offset2 % writebdy;
> > -                     } while (range_overlaps(offset, offset2, size) ||
> > -                              offset2 + size > maxfilelen);
> > -                     break;
> > -             }
> > +             generate_dest_range(op, maxfilelen, &offset, &size, &offset2);
> > +             break;
> >       }
> >
> >  have_op:
> > --
> > 2.11.0
> >