[Libguestfs] [PATCH nbdkit v5 FINAL 12/19] truncate: Implement extents for beyond end of truncated region.

--- filters/truncate/truncate.c | 55 +++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/filters/truncate/truncate.c b/filters/truncate/truncate.c index b95432a..e8e56f7 100644 --- a/filters/truncate/truncate.c +++ b/filters/truncate/truncate.c @@ -285,6 +285,60 @@ truncate_zero (struct nbdkit_next_ops *next_ops, void *nxdata, return 0; } +/* Extents. */ +static int +truncate_extents (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle, uint32_t count, uint64_t offset, + uint32_t flags, struct nbdkit_extents *extents, int *err) +{ + uint32_t n; + uint64_t real_size_copy; + struct nbdkit_extents *extents2; + size_t i; + + pthread_mutex_lock (&lock); + real_size_copy = real_size; + pthread_mutex_unlock (&lock); + + /* If the entire request is beyond the end of the underlying plugin + * then this is the easy case: return a hole. + */ + if (offset >= real_size_copy) + return nbdkit_add_extent (extents, offset, (uint64_t) count, + NBDKIT_EXTENT_ZERO|NBDKIT_EXTENT_HOLE); + + /* We're asked first for extents information about the plugin, then + * possibly (if truncating larger) for the hole after the plugin. + * Since we're not required to provide all of this information, the + * easiest thing is to only return data from the plugin. We will be + * called later about the hole. However we do need to make sure + * that the extents array is truncated to the real size, hence we + * have to create a new extents array, ask the plugin, then copy the + * returned data to the original array. + */ + extents2 = nbdkit_extents_new (0, real_size_copy); + if (offset + count <= real_size_copy) + n = count; + else + n = real_size_copy - offset; + if (next_ops->extents (nxdata, n, offset, flags, extents2, err) == -1) { + nbdkit_extents_free (extents2); + return -1; + } + + for (i = 0; i < nbdkit_extents_count (extents2); ++i) { + struct nbdkit_extent e = nbdkit_get_extent (extents2, i); + + if (nbdkit_add_extent (extents, e.offset, e.length, e.type) == -1) { + nbdkit_extents_free (extents2); + return -1; + } + } + nbdkit_extents_free (extents2); + + return 0; +} + static struct nbdkit_filter filter = { .name = "truncate", .longname = "nbdkit truncate filter", @@ -297,6 +351,7 @@ static struct nbdkit_filter filter = { .pwrite = truncate_pwrite, .trim = truncate_trim, .zero = truncate_zero, + .extents = truncate_extents, }; NBDKIT_REGISTER_FILTER(filter) -- 2.20.1