From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51431) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cqfMz-0000mF-0B for qemu-devel@nongnu.org; Wed, 22 Mar 2017 08:28:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cqfMu-0003ws-PG for qemu-devel@nongnu.org; Wed, 22 Mar 2017 08:28:02 -0400 Received: from mx1.redhat.com ([209.132.183.28]:41392) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cqfMu-0003wh-GT for qemu-devel@nongnu.org; Wed, 22 Mar 2017 08:28:00 -0400 From: Stefan Hajnoczi Date: Wed, 22 Mar 2017 11:16:03 +0000 Message-Id: <20170322111608.31230-4-stefanha@redhat.com> In-Reply-To: <20170322111608.31230-1-stefanha@redhat.com> References: <20170322111608.31230-1-stefanha@redhat.com> Subject: [Qemu-devel] [PATCH v3 3/8] qcow2: extract preallocation calculation function List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Eric Blake , Kevin Wolf , Maor Lipchuk , "Daniel P. Berrange" , Nir Soffer , Alberto Garcia , John Snow , Stefan Hajnoczi Calculating the preallocated image size will be needed to implement .bdrv_measure(). Extract the code out into a separate function. Signed-off-by: Stefan Hajnoczi --- block/qcow2.c | 134 +++++++++++++++++++++++++++++++++------------------------- 1 file changed, 76 insertions(+), 58 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index 6a92d2e..7c702f4 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -2095,6 +2095,79 @@ static int preallocate(BlockDriverState *bs) return 0; } +/** + * qcow2_calc_prealloc_size: + * @total_size: virtual disk size in bytes + * @cluster_size: cluster size in bytes + * @refcount_order: refcount bits power-of-2 exponent + * + * Returns: Total number of bytes required for the fully allocated image + * (including metadata). + */ +static int64_t qcow2_calc_prealloc_size(int64_t total_size, + size_t cluster_size, + int refcount_order) +{ + /* 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 cluster_bits = ctz32(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 meta_size + aligned_total_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, @@ -2133,64 +2206,9 @@ 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); + int64_t prealloc_size = + qcow2_calc_prealloc_size(total_size, cluster_size, refcount_order); + qemu_opt_set_number(opts, BLOCK_OPT_SIZE, prealloc_size, &error_abort); qemu_opt_set(opts, BLOCK_OPT_PREALLOC, PreallocMode_lookup[prealloc], &error_abort); } -- 2.9.3