Re: [Libguestfs] [PATCH nbdkit] server: Implement extents/can_extents calls for plugins and filters.

This pair of calls allows plugins to describe which extents in the virtual disk are allocated, holes or zeroes. --- docs/nbdkit-filter.pod | 22 +++++++++++ docs/nbdkit-plugin.pod | 86 +++++++++++++++++++++++++++++++++++++++++ include/nbdkit-common.h | 14 ++++++- include/nbdkit-filter.h | 12 +++++- include/nbdkit-plugin.h | 6 ++- server/internal.h | 7 +++- server/filters.c | 61 +++++++++++++++++++++++++++++ server/plugins.c | 72 +++++++++++++++++++++++++++++++++- 8 files changed, 275 insertions(+), 5 deletions(-)

diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index 47545f3..9cc62b6 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod

@@ -717,6 +731,78 @@ If there is an error, C<.zero> should call C<nbdkit_error> with an error message, and C<nbdkit_set_error> to record an appropriate error (unless C<errno> is sufficient), then return C<-1>. +=head2 C<.extents> + + int zero (void *handle, uint32_t count, uint64_t offset, uint32_t flags,

diff --git a/server/filters.c b/server/filters.c index 5b7abc4..d6cc00f 100644 --- a/server/filters.c +++ b/server/filters.c

@@ -646,6 +680,31 @@ filter_zero (struct backend *b, struct connection *conn, count, offset, flags, err); } +static int +filter_extents (struct backend *b, struct connection *conn, + uint32_t count, uint64_t offset, uint32_t flags, + size_t *nr_extents, struct nbdkit_extent **extents, + int *err) +{ + struct backend_filter *f = container_of (b, struct backend_filter, backend); + void *handle = connection_get_handle (conn, f->backend.i); + struct b_conn nxdata = { .b = f->backend.next, .conn = conn }; + + assert (!(flags & ~NBDKIT_FLAG_REQ_ONE)); + + debug ("%s: extents count=%" PRIu32 " offset=%" PRIu64 " flags=0x%" PRIx32, + f->name, count, offset, flags); + + if (f->filter.extents) + return f->filter.extents (&next_ops, &nxdata, handle, + count, offset, flags, + nr_extents, extents, err); + else + return f->backend.next->extents (f->backend.next, conn, + count, offset, flags, + nr_extents, extents, err);