[Libguestfs] [nbdkit PATCH v2 22/24] truncate: Implement .cache

In the truncate filter, all we need to do is copy-and-paste existing per-command count rewriting (well, technically, this isn't enabled until a later patch flips the default for .can_cache to pass-through). Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- filters/truncate/truncate.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/filters/truncate/truncate.c b/filters/truncate/truncate.c index 6408c35..38b1cd9 100644 --- a/filters/truncate/truncate.c +++ b/filters/truncate/truncate.c @@ -354,6 +354,29 @@ truncate_extents (struct nbdkit_next_ops *next_ops, void *nxdata, return 0; } +/* Cache. */ +static int +truncate_cache (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, + uint32_t flags, int *err) +{ + int r; + uint32_t n; + struct handle *h = handle; + + if (offset < h->real_size) { + if (offset + count <= h->real_size) + n = count; + else + n = h->real_size - offset; + r = next_ops->cache (nxdata, n, offset, flags, err); + if (r == -1) + return -1; + } + + return 0; +} + static struct nbdkit_filter filter = { .name = "truncate", .longname = "nbdkit truncate filter", @@ -369,6 +392,7 @@ static struct nbdkit_filter filter = { .trim = truncate_trim, .zero = truncate_zero, .extents = truncate_extents, + .cache = truncate_cache, }; NBDKIT_REGISTER_FILTER(filter) -- 2.20.1