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[Qemu-devel] [PATCH 1/5] qcow2: Work with bytes in qcow2_get_cluster_off
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 1/5] qcow2: Work with bytes in qcow2_get_cluster_offset() |
Date: |
Fri, 3 Jun 2016 19:21:14 +0200 |
This patch changes the units that qcow2_get_cluster_offset() uses
internally, without touching the interface just yet. This will be done
in another patch.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/qcow2-cluster.c | 43 ++++++++++++++++++++++---------------------
1 file changed, 22 insertions(+), 21 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d901d89..b2405b1 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -482,29 +482,27 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
uint64_t offset,
unsigned int l2_index;
uint64_t l1_index, l2_offset, *l2_table;
int l1_bits, c;
- unsigned int index_in_cluster, nb_clusters;
- uint64_t nb_available, nb_needed;
+ unsigned int offset_in_cluster, nb_clusters;
+ uint64_t bytes_available, bytes_needed;
int ret;
+ unsigned int bytes;
- index_in_cluster = (offset >> 9) & (s->cluster_sectors - 1);
- nb_needed = *num + index_in_cluster;
+ bytes = *num * BDRV_SECTOR_SIZE;
- l1_bits = s->l2_bits + s->cluster_bits;
-
- /* compute how many bytes there are between the offset and
- * the end of the l1 entry
- */
+ offset_in_cluster = offset_into_cluster(s, offset);
+ bytes_needed = bytes + offset_in_cluster;
- nb_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1));
-
- /* compute the number of available sectors */
+ l1_bits = s->l2_bits + s->cluster_bits;
- nb_available = (nb_available >> 9) + index_in_cluster;
+ /* compute how many bytes there are between the start of the cluster
+ * containing offset and the end of the l1 entry */
+ bytes_available = (1ULL << l1_bits) - (offset & ((1ULL << l1_bits) - 1))
+ + offset_in_cluster;
- if (nb_needed > nb_available) {
- nb_needed = nb_available;
+ if (bytes_needed > bytes_available) {
+ bytes_needed = bytes_available;
}
- assert(nb_needed <= INT_MAX);
+ assert(bytes_needed <= INT_MAX);
*cluster_offset = 0;
@@ -542,7 +540,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t
offset,
*cluster_offset = be64_to_cpu(l2_table[l2_index]);
/* nb_needed <= INT_MAX, thus nb_clusters <= INT_MAX, too */
- nb_clusters = size_to_clusters(s, nb_needed << 9);
+ nb_clusters = size_to_clusters(s, bytes_needed);
ret = qcow2_get_cluster_type(*cluster_offset);
switch (ret) {
@@ -589,13 +587,16 @@ int qcow2_get_cluster_offset(BlockDriverState *bs,
uint64_t offset,
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
- nb_available = (c * s->cluster_sectors);
+ bytes_available = (c * s->cluster_size);
out:
- if (nb_available > nb_needed)
- nb_available = nb_needed;
+ if (bytes_available > bytes_needed) {
+ bytes_available = bytes_needed;
+ }
- *num = nb_available - index_in_cluster;
+ bytes = bytes_available - offset_in_cluster;
+ assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
+ *num = bytes >> BDRV_SECTOR_BITS;
return ret;
--
1.8.3.1