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[Qemu-devel] [PATCH 19/23] qcow2: Use byte granularity in qcow2_alloc_cl
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 19/23] qcow2: Use byte granularity in qcow2_alloc_cluster_offset() |
Date: |
Thu, 28 Mar 2013 17:40:33 +0100 |
From: Kevin Wolf <address@hidden>
This gets rid of the nb_clusters and keep_clusters and the associated
complicated calculations. Just advance the number of bytes that have
been processed and everything is fine.
This patch advances the variables even after the last operation even
though they aren't used any more afterwards to make things look more
uniform. A later patch will turn the whole thing into a loop and then
it actually starts making sense.
Signed-off-by: Kevin Wolf <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
block/qcow2-cluster.c | 84 +++++++++++++++++----------------------------------
1 file changed, 28 insertions(+), 56 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 4f43d41..78e7db9 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1127,28 +1127,24 @@ int qcow2_alloc_cluster_offset(BlockDriverState *bs,
uint64_t offset,
int n_start, int n_end, int *num, uint64_t *host_offset, QCowL2Meta **m)
{
BDRVQcowState *s = bs->opaque;
- int l2_index, ret, sectors;
- unsigned int nb_clusters, keep_clusters;
+ uint64_t start, remaining;
uint64_t cluster_offset;
uint64_t cur_bytes;
+ int ret;
trace_qcow2_alloc_clusters_offset(qemu_coroutine_self(), offset,
n_start, n_end);
+ assert(n_start * BDRV_SECTOR_SIZE == offset_into_cluster(s, offset));
+ offset = start_of_cluster(s, offset);
+
again:
+ start = offset + (n_start << BDRV_SECTOR_BITS);
+ remaining = (n_end - n_start) << BDRV_SECTOR_BITS;
cluster_offset = 0;
*host_offset = 0;
/*
- * Calculate the number of clusters to look for. We stop at L2 table
- * boundaries to keep things simple.
- */
- l2_index = offset_to_l2_index(s, offset);
- nb_clusters = MIN(size_to_clusters(s, n_end << BDRV_SECTOR_BITS),
- s->l2_size - l2_index);
- n_end = MIN(n_end, nb_clusters * s->cluster_sectors);
-
- /*
* Now start gathering as many contiguous clusters as possible:
*
* 1. Check for overlaps with in-flight allocations
@@ -1165,8 +1161,8 @@ again:
* cluster_offset to write to the same cluster and set up the right
* synchronisation between the in-flight request and the new one.
*/
- cur_bytes = (n_end - n_start) * BDRV_SECTOR_SIZE;
- ret = handle_dependencies(bs, offset, &cur_bytes);
+ cur_bytes = remaining;
+ ret = handle_dependencies(bs, start, &cur_bytes);
if (ret == -EAGAIN) {
goto again;
} else if (ret < 0) {
@@ -1177,33 +1173,28 @@ again:
* correctly during the next loop iteration. */
}
- nb_clusters = size_to_clusters(s, offset + cur_bytes)
- - (offset >> s->cluster_bits);
-
/*
* 2. Count contiguous COPIED clusters.
*/
- uint64_t tmp_bytes = cur_bytes;
- ret = handle_copied(bs, offset, &cluster_offset, &tmp_bytes, m);
+ ret = handle_copied(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
} else if (ret) {
- keep_clusters =
- size_to_clusters(s, tmp_bytes + offset_into_cluster(s, offset));
- nb_clusters -= keep_clusters;
-
if (!*host_offset) {
*host_offset = start_of_cluster(s, cluster_offset);
}
+
+ start += cur_bytes;
+ remaining -= cur_bytes;
+ cluster_offset += cur_bytes;
+
+ cur_bytes = remaining;
} else if (cur_bytes == 0) {
- keep_clusters = 0;
goto done;
- } else {
- keep_clusters = 0;
}
/* If there is something left to allocate, do that now */
- if (nb_clusters == 0) {
+ if (remaining == 0) {
goto done;
}
@@ -1211,43 +1202,24 @@ again:
* 3. If the request still hasn't completed, allocate new clusters,
* considering any cluster_offset of steps 1c or 2.
*/
- int alloc_n_start;
- int alloc_n_end;
-
- if (keep_clusters != 0) {
- offset = start_of_cluster(s, offset
- + keep_clusters *
s->cluster_size);
- cluster_offset = start_of_cluster(s, cluster_offset
- + keep_clusters *
s->cluster_size);
-
- alloc_n_start = 0;
- alloc_n_end = n_end - keep_clusters * s->cluster_sectors;
- } else {
- alloc_n_start = n_start;
- alloc_n_end = n_end;
- }
-
- cur_bytes = MIN(cur_bytes, ((alloc_n_end - alloc_n_start) <<
BDRV_SECTOR_BITS));
-
- ret = handle_alloc(bs, offset, &cluster_offset, &cur_bytes, m);
+ ret = handle_alloc(bs, start, &cluster_offset, &cur_bytes, m);
if (ret < 0) {
return ret;
- }
+ } else if (ret) {
+ if (!*host_offset) {
+ *host_offset = start_of_cluster(s, cluster_offset);
+ }
- if (!*host_offset) {
- *host_offset = start_of_cluster(s, cluster_offset);
+ start += cur_bytes;
+ remaining -= cur_bytes;
+ cluster_offset += cur_bytes;
}
- nb_clusters = size_to_clusters(s, cur_bytes + offset_into_cluster(s,
offset));
/* Some cleanup work */
done:
- sectors = (keep_clusters + nb_clusters) << (s->cluster_bits - 9);
- if (sectors > n_end) {
- sectors = n_end;
- }
-
- assert(sectors > n_start);
- *num = sectors - n_start;
+ *num = (n_end - n_start) - (remaining >> BDRV_SECTOR_BITS);
+ assert(*num > 0);
+ assert(*host_offset != 0);
return 0;
}
--
1.8.1.4
- [Qemu-devel] [PATCH 09/23] qcow2: Factor out handle_alloc(), (continued)
- [Qemu-devel] [PATCH 09/23] qcow2: Factor out handle_alloc(), Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 11/23] qcow2: handle_alloc(): Get rid of keep_clusters parameter, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 10/23] qcow2: handle_alloc(): Get rid of nb_clusters parameter, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 12/23] qcow2: Finalise interface of handle_alloc(), Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 13/23] qcow2: Clean up handle_alloc(), Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 14/23] qcow2: Factor out handle_copied(), Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 15/23] qcow2: handle_copied(): Get rid of nb_clusters parameter, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 16/23] qcow2: handle_copied(): Get rid of keep_clusters parameter, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 18/23] qcow2: Prepare handle_alloc/copied() for byte granularity, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 17/23] qcow2: handle_copied(): Implement non-zero host_offset, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 19/23] qcow2: Use byte granularity in qcow2_alloc_cluster_offset(),
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH 20/23] qcow2: Allow requests with multiple l2metas, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 21/23] qcow2: Move cluster gathering to a non-looping loop, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 22/23] qcow2: Gather clusters in a looping loop, Stefan Hajnoczi, 2013/03/28
- [Qemu-devel] [PATCH 23/23] block: Fix direct use of protocols as driver for bdrv_open(), Stefan Hajnoczi, 2013/03/28