Re: [Libguestfs] [PATCH nbdkit v5 FINAL 14/19] data, memory: Implement extents.

On 3/28/19 11:18 AM, Richard W.M. Jones wrote: > These plugins are both based on the same sparse array structure which > supports a simple implementation of extents. > --- > common/sparse/sparse.h | 7 +- > common/sparse/sparse.c | 37 ++++++++++- > plugins/data/data.c | 16 ++++- > plugins/memory/memory.c | 16 ++++- > README | 2 + > tests/Makefile.am | 2 + > tests/test-data-extents.sh | 131 +++++++++++++++++++++++++++++++++++++ > 7 files changed, 207 insertions(+), 4 deletions(-) > > +int > +sparse_array_extents (struct sparse_array *sa, > + uint32_t count, uint64_t offset, > + struct nbdkit_extents *extents) > +{ > + uint32_t n, type; > + void *p; > + > + while (count > 0) { > + p = lookup (sa, offset, false, &n, NULL); > + if (n > count) > + n = count; I know in earlier review I asked whether we can move the clamping... > + > + /* Work out the type of this extent. */ > + if (p == NULL) > + /* No backing page, so it's a hole. */ > + type = NBDKIT_EXTENT_HOLE | NBDKIT_EXTENT_ZERO; > + else { > + if (is_zero (p, n)) > + /* A backing page and it's all zero, it's a zero extent. */ > + type = NBDKIT_EXTENT_ZERO; > + else > + /* Normal allocated data. */ > + type = 0; > + } > + if (nbdkit_add_extent (extents, offset, n, type) == -1) > + return -1; > + ...to here, after the final nbdkit_add_extent, so that we can return a larger extent than the client's request. I remember when I originally asked, you declined due to odd interactions with REQ_ONE semantics, but since then, we changed how add_extent() works. Does it work now to defer the clamping?