From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34587) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cv4Yw-0001Pi-QP for qemu-devel@nongnu.org; Mon, 03 Apr 2017 12:10:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cv4Yv-0000Y2-7K for qemu-devel@nongnu.org; Mon, 03 Apr 2017 12:10:38 -0400 From: Max Reitz Date: Mon, 3 Apr 2017 18:09:32 +0200 Message-Id: <20170403160936.28293-13-mreitz@redhat.com> In-Reply-To: <20170403160936.28293-1-mreitz@redhat.com> References: <20170403160936.28293-1-mreitz@redhat.com> Subject: [Qemu-devel] [PATCH v2 for-2.10 12/16] block/qcow2: Extract qcow2_calc_size_usage() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Max Reitz , Stefan Hajnoczi , Kevin Wolf We will need very similar functionality for full/falloc preallocation in qcow2_truncate(). Although we will not be able to reuse much of the actual code, it still makes sense to keep all of this in one place. Signed-off-by: Max Reitz Reviewed-by: Stefan Hajnoczi --- block/qcow2.c | 126 +++++++++++++++++++++++++++++++--------------------------- 1 file changed, 68 insertions(+), 58 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index bb0bd5561c..aafbc8dbed 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2108,6 +2108,70 @@ done: return ret; } +static uint64_t qcow2_calc_size_usage(uint64_t new_size, + int cluster_bits, int refcount_order) +{ + size_t cluster_size = 1u << cluster_bits; + + /* Note: The following calculation does not need to be exact; if it is a + * bit off, either some bytes will be "leaked" (which is fine) or we + * will need to increase the file size by some bytes (which is fine, + * too, as long as the bulk is allocated here). Therefore, using + * floating point arithmetic is fine. */ + int64_t meta_size = 0; + uint64_t nreftablee, nrefblocke, nl1e, nl2e; + uint64_t aligned_total_size = align_offset(new_size, cluster_size); + int refblock_bits, refblock_size; + /* refcount entry size in bytes */ + double rces = (1 << refcount_order) / 8.; + + /* see qcow2_open() */ + refblock_bits = cluster_bits - (refcount_order - 3); + refblock_size = 1 << refblock_bits; + + /* header: 1 cluster */ + meta_size += cluster_size; + + /* total size of L2 tables */ + nl2e = aligned_total_size / cluster_size; + nl2e = align_offset(nl2e, cluster_size / sizeof(uint64_t)); + meta_size += nl2e * sizeof(uint64_t); + + /* total size of L1 tables */ + nl1e = nl2e * sizeof(uint64_t) / cluster_size; + nl1e = align_offset(nl1e, cluster_size / sizeof(uint64_t)); + meta_size += nl1e * sizeof(uint64_t); + + /* total size of refcount blocks + * + * note: every host cluster is reference-counted, including metadata + * (even refcount blocks are recursively included). + * Let: + * a = total_size (this is the guest disk size) + * m = meta size not including refcount blocks and refcount tables + * c = cluster size + * y1 = number of refcount blocks entries + * y2 = meta size including everything + * rces = refcount entry size in bytes + * then, + * y1 = (y2 + a)/c + * y2 = y1 * rces + y1 * rces * sizeof(u64) / c + m + * we can get y1: + * y1 = (a + m) / (c - rces - rces * sizeof(u64) / c) + */ + nrefblocke = (aligned_total_size + meta_size + cluster_size) + / (cluster_size - rces - rces * sizeof(uint64_t) + / cluster_size); + meta_size += DIV_ROUND_UP(nrefblocke, refblock_size) * cluster_size; + + /* total size of refcount tables */ + nreftablee = nrefblocke / refblock_size; + nreftablee = align_offset(nreftablee, cluster_size / sizeof(uint64_t)); + meta_size += nreftablee * sizeof(uint64_t); + + return aligned_total_size + meta_size; +} + static int qcow2_create2(const char *filename, int64_t total_size, const char *backing_file, const char *backing_format, int flags, size_t cluster_size, PreallocMode prealloc, @@ -2146,64 +2210,10 @@ static int qcow2_create2(const char *filename, int64_t total_size, int ret; if (prealloc == PREALLOC_MODE_FULL || prealloc == PREALLOC_MODE_FALLOC) { - /* Note: The following calculation does not need to be exact; if it is a - * bit off, either some bytes will be "leaked" (which is fine) or we - * will need to increase the file size by some bytes (which is fine, - * too, as long as the bulk is allocated here). Therefore, using - * floating point arithmetic is fine. */ - int64_t meta_size = 0; - uint64_t nreftablee, nrefblocke, nl1e, nl2e; - int64_t aligned_total_size = align_offset(total_size, cluster_size); - int refblock_bits, refblock_size; - /* refcount entry size in bytes */ - double rces = (1 << refcount_order) / 8.; - - /* see qcow2_open() */ - refblock_bits = cluster_bits - (refcount_order - 3); - refblock_size = 1 << refblock_bits; - - /* header: 1 cluster */ - meta_size += cluster_size; - - /* total size of L2 tables */ - nl2e = aligned_total_size / cluster_size; - nl2e = align_offset(nl2e, cluster_size / sizeof(uint64_t)); - meta_size += nl2e * sizeof(uint64_t); - - /* total size of L1 tables */ - nl1e = nl2e * sizeof(uint64_t) / cluster_size; - nl1e = align_offset(nl1e, cluster_size / sizeof(uint64_t)); - meta_size += nl1e * sizeof(uint64_t); - - /* total size of refcount blocks - * - * note: every host cluster is reference-counted, including metadata - * (even refcount blocks are recursively included). - * Let: - * a = total_size (this is the guest disk size) - * m = meta size not including refcount blocks and refcount tables - * c = cluster size - * y1 = number of refcount blocks entries - * y2 = meta size including everything - * rces = refcount entry size in bytes - * then, - * y1 = (y2 + a)/c - * y2 = y1 * rces + y1 * rces * sizeof(u64) / c + m - * we can get y1: - * y1 = (a + m) / (c - rces - rces * sizeof(u64) / c) - */ - nrefblocke = (aligned_total_size + meta_size + cluster_size) - / (cluster_size - rces - rces * sizeof(uint64_t) - / cluster_size); - meta_size += DIV_ROUND_UP(nrefblocke, refblock_size) * cluster_size; - - /* total size of refcount tables */ - nreftablee = nrefblocke / refblock_size; - nreftablee = align_offset(nreftablee, cluster_size / sizeof(uint64_t)); - meta_size += nreftablee * sizeof(uint64_t); - - qemu_opt_set_number(opts, BLOCK_OPT_SIZE, - aligned_total_size + meta_size, &error_abort); + uint64_t file_size = qcow2_calc_size_usage(total_size, cluster_bits, + refcount_order); + + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, file_size, &error_abort); qemu_opt_set(opts, BLOCK_OPT_PREALLOC, PreallocMode_lookup[prealloc], &error_abort); } -- 2.12.1