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authorKevin Wolf <kwolf@redhat.com>2009-12-03 10:28:44 +0100
committerAurelien Jarno <aurelien@aurel32.net>2009-12-03 11:29:25 +0100
commit08fd2f30bd3ee5d04596da8293689af4d4f7eb6c (patch)
treeeb72c9f023390352184a981fb23df34234e2a6e5
parent35bfc7324e2e6946c4113ada5db30553a1a7c40b (diff)
downloadqemu-arm-stable-0.11.tar.gz
qcow2: Bring synchronous read/write back to lifestable-0.11
When the synchronous read and write functions were dropped, they were replaced by generic emulation functions. Unfortunately, these emulation functions don't provide the same semantics as the original functions did. The original bdrv_read would mean that we read some data synchronously and that we won't be interrupted during this read. The latter assumption is no longer true with the emulation function which needs to use qemu_aio_poll and therefore allows the callback of any other concurrent AIO request to be run during the read. Which in turn means that (meta)data read earlier could have changed and be invalid now. qcow2 is not prepared to work in this way and it's just scary how many places there are where other requests could run. I'm not sure yet where exactly it breaks, but you'll see breakage with virtio on qcow2 with a backing file. Providing synchronous functions again fixes the problem for me. Patchworks-ID: 35437 Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> (cherry picked from commit ef845c3bf421290153154635dc18eaa677cecb43) Signed-off-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
-rw-r--r--block/qcow2-cluster.c6
-rw-r--r--block/qcow2.c51
-rw-r--r--block/qcow2.h3
3 files changed, 55 insertions, 5 deletions
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index d4631c3974..4d0ce161ae 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -306,8 +306,8 @@ void qcow2_encrypt_sectors(BDRVQcowState *s, int64_t sector_num,
}
-static int qcow_read(BlockDriverState *bs, int64_t sector_num,
- uint8_t *buf, int nb_sectors)
+int qcow2_read(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
+ int nb_sectors)
{
BDRVQcowState *s = bs->opaque;
int ret, index_in_cluster, n, n1;
@@ -358,7 +358,7 @@ static int copy_sectors(BlockDriverState *bs, uint64_t start_sect,
n = n_end - n_start;
if (n <= 0)
return 0;
- ret = qcow_read(bs, start_sect + n_start, s->cluster_data, n);
+ ret = qcow2_read(bs, start_sect + n_start, s->cluster_data, n);
if (ret < 0)
return ret;
if (s->crypt_method) {
diff --git a/block/qcow2.c b/block/qcow2.c
index dd32ea2078..ced257e9f5 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -855,6 +855,51 @@ static int qcow_make_empty(BlockDriverState *bs)
return 0;
}
+static int qcow2_write(BlockDriverState *bs, int64_t sector_num,
+ const uint8_t *buf, int nb_sectors)
+{
+ BDRVQcowState *s = bs->opaque;
+ int ret, index_in_cluster, n;
+ uint64_t cluster_offset;
+ int n_end;
+ QCowL2Meta l2meta;
+
+ while (nb_sectors > 0) {
+ memset(&l2meta, 0, sizeof(l2meta));
+
+ index_in_cluster = sector_num & (s->cluster_sectors - 1);
+ n_end = index_in_cluster + nb_sectors;
+ if (s->crypt_method &&
+ n_end > QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors)
+ n_end = QCOW_MAX_CRYPT_CLUSTERS * s->cluster_sectors;
+ cluster_offset = qcow2_alloc_cluster_offset(bs, sector_num << 9,
+ index_in_cluster,
+ n_end, &n, &l2meta);
+ if (!cluster_offset)
+ return -1;
+ if (s->crypt_method) {
+ qcow2_encrypt_sectors(s, sector_num, s->cluster_data, buf, n, 1,
+ &s->aes_encrypt_key);
+ ret = bdrv_pwrite(s->hd, cluster_offset + index_in_cluster * 512,
+ s->cluster_data, n * 512);
+ } else {
+ ret = bdrv_pwrite(s->hd, cluster_offset + index_in_cluster * 512, buf, n * 512);
+ }
+ if (ret != n * 512 || qcow2_alloc_cluster_link_l2(bs, cluster_offset, &l2meta) < 0) {
+ qcow2_free_any_clusters(bs, cluster_offset, l2meta.nb_clusters);
+ return -1;
+ }
+ nb_sectors -= n;
+ sector_num += n;
+ buf += n * 512;
+ if (l2meta.nb_clusters != 0) {
+ LIST_REMOVE(&l2meta, next_in_flight);
+ }
+ }
+ s->cluster_cache_offset = -1; /* disable compressed cache */
+ return 0;
+}
+
/* XXX: put compressed sectors first, then all the cluster aligned
tables to avoid losing bytes in alignment */
static int qcow_write_compressed(BlockDriverState *bs, int64_t sector_num,
@@ -1037,8 +1082,10 @@ static BlockDriver bdrv_qcow2 = {
.bdrv_set_key = qcow_set_key,
.bdrv_make_empty = qcow_make_empty,
- .bdrv_aio_readv = qcow_aio_readv,
- .bdrv_aio_writev = qcow_aio_writev,
+ .bdrv_read = qcow2_read,
+ .bdrv_write = qcow2_write,
+ .bdrv_aio_readv = qcow_aio_readv,
+ .bdrv_aio_writev = qcow_aio_writev,
.bdrv_write_compressed = qcow_write_compressed,
.bdrv_snapshot_create = qcow2_snapshot_create,
diff --git a/block/qcow2.h b/block/qcow2.h
index 965a2f45c1..b41aa63409 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -202,6 +202,9 @@ uint64_t qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, uint64_t cluster_offset,
QCowL2Meta *m);
+int qcow2_read(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
+ int nb_sectors);
+
/* qcow2-snapshot.c functions */
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);