Re: [Libguestfs] [nbdkit PATCH 2/2] blocksize: Default internal block size based on plugin

--- a/filters/blocksize/blocksize.c +++ b/filters/blocksize/blocksize.c @@ -171,17 +171,30 @@ blocksize_prepare (nbdkit_next *next, void *handle, int readonly) { struct blocksize_handle *h = handle; + uint32_t minimum, preferred, maximum; + + /* Here, minimum and maximum will clamp per-handle defaults not set + * by globals in .config; preferred has no impact until .block_size. + */ + if (next->block_size (next, &minimum, &preferred, &maximum) == -1) + return -1; + + h->minblock = MAX (MAX (h->minblock, 1), minimum); - if (h->minblock == 0) - h->minblock = 1; if (h->maxdata == 0) { if (h->maxlen) h->maxdata = MIN (h->maxlen, 64 * 1024 * 1024); else h->maxdata = 64 * 1024 * 1024; } + if (maximum) + h->maxdata = MIN (h->maxdata, maximum); + h->maxdata = ROUND_DOWN (h->maxdata, h->minblock); + if (h->maxlen == 0) h->maxlen = -h->minblock; + else + h->maxlen = ROUND_DOWN (h->maxlen, h->minblock); return 0;

} @@ -220,11 +233,11 @@ blocksize_block_size (nbdkit_next *next, void *handle, { struct blocksize_handle *h = handle; + /* Here we only need preferred; see also blocksize_prepare. */ if (next->block_size (next, minimum, preferred, maximum) == -1) return -1; - if (*preferred == 0) - *preferred = MAX (4096, h->minblock); + *preferred = MAX (MAX (*preferred, 4096), h->minblock);