diff options
Diffstat (limited to 'emulators/qemu/files/patch-0001-qcow2-Bring-synchronous-read-write-back-to-life')
| -rw-r--r-- | emulators/qemu/files/patch-0001-qcow2-Bring-synchronous-read-write-back-to-life | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/emulators/qemu/files/patch-0001-qcow2-Bring-synchronous-read-write-back-to-life b/emulators/qemu/files/patch-0001-qcow2-Bring-synchronous-read-write-back-to-life new file mode 100644 index 000000000000..b4ef8ae45b8f --- /dev/null +++ b/emulators/qemu/files/patch-0001-qcow2-Bring-synchronous-read-write-back-to-life @@ -0,0 +1,144 @@ +From 08fd2f30bd3ee5d04596da8293689af4d4f7eb6c Mon Sep 17 00:00:00 2001 +From: Kevin Wolf <kwolf@redhat.com> +Date: Thu, 3 Dec 2009 10:28:44 +0100 +Subject: [PATCH] qcow2: Bring synchronous read/write back to life + +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> +--- + block/qcow2-cluster.c | 6 ++-- + block/qcow2.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++- + block/qcow2.h | 3 ++ + 3 files changed, 55 insertions(+), 5 deletions(-) + +diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c +index d4631c3..4d0ce16 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 dd32ea2..ced257e 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 965a2f4..b41aa63 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); +-- +1.6.5.2 + |