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[Qemu-devel] [PATCH 14/28] qcow2: Add bdrv_discard support
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 14/28] qcow2: Add bdrv_discard support |
Date: |
Mon, 31 Jan 2011 16:29:02 +0100 |
This adds a bdrv_discard function to qcow2 that frees the discarded clusters.
It does not yet pass the discard on to the underlying file system driver, but
the space can be reused by future writes to the image.
Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
block/qcow2-cluster.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++
block/qcow2.c | 8 +++++
block/qcow2.h | 2 +
3 files changed, 92 insertions(+), 0 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 1c2003a..5fb8c66 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -888,3 +888,85 @@ int qcow2_decompress_cluster(BlockDriverState *bs,
uint64_t cluster_offset)
}
return 0;
}
+
+/*
+ * This discards as many clusters of nb_clusters as possible at once (i.e.
+ * all clusters in the same L2 table) and returns the number of discarded
+ * clusters.
+ */
+static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
+ unsigned int nb_clusters)
+{
+ BDRVQcowState *s = bs->opaque;
+ uint64_t l2_offset, *l2_table;
+ int l2_index;
+ int ret;
+ int i;
+
+ ret = get_cluster_table(bs, offset, &l2_table, &l2_offset, &l2_index);
+ if (ret < 0) {
+ return ret;
+ }
+
+ /* Limit nb_clusters to one L2 table */
+ nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);
+
+ for (i = 0; i < nb_clusters; i++) {
+ uint64_t old_offset;
+
+ old_offset = be64_to_cpu(l2_table[l2_index + i]);
+ old_offset &= ~QCOW_OFLAG_COPIED;
+
+ if (old_offset == 0) {
+ continue;
+ }
+
+ /* First remove L2 entries */
+ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
+ l2_table[l2_index + i] = cpu_to_be64(0);
+
+ /* Then decrease the refcount */
+ qcow2_free_any_clusters(bs, old_offset, 1);
+ }
+
+ ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
+ if (ret < 0) {
+ return ret;
+ }
+
+ return nb_clusters;
+}
+
+int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
+ int nb_sectors)
+{
+ BDRVQcowState *s = bs->opaque;
+ uint64_t end_offset;
+ unsigned int nb_clusters;
+ int ret;
+
+ end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
+
+ /* Round start up and end down */
+ offset = align_offset(offset, s->cluster_size);
+ end_offset &= ~(s->cluster_size - 1);
+
+ if (offset > end_offset) {
+ return 0;
+ }
+
+ nb_clusters = size_to_clusters(s, end_offset - offset);
+
+ /* Each L2 table is handled by its own loop iteration */
+ while (nb_clusters > 0) {
+ ret = discard_single_l2(bs, offset, nb_clusters);
+ if (ret < 0) {
+ return ret;
+ }
+
+ nb_clusters -= ret;
+ offset += (ret * s->cluster_size);
+ }
+
+ return 0;
+}
diff --git a/block/qcow2.c b/block/qcow2.c
index 49bf7b9..dbe4fdd 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1084,6 +1084,13 @@ static int qcow2_make_empty(BlockDriverState *bs)
return 0;
}
+static int qcow2_discard(BlockDriverState *bs, int64_t sector_num,
+ int nb_sectors)
+{
+ return qcow2_discard_clusters(bs, sector_num << BDRV_SECTOR_BITS,
+ nb_sectors);
+}
+
static int qcow2_truncate(BlockDriverState *bs, int64_t offset)
{
BDRVQcowState *s = bs->opaque;
@@ -1349,6 +1356,7 @@ static BlockDriver bdrv_qcow2 = {
.bdrv_aio_writev = qcow2_aio_writev,
.bdrv_aio_flush = qcow2_aio_flush,
+ .bdrv_discard = qcow2_discard,
.bdrv_truncate = qcow2_truncate,
.bdrv_write_compressed = qcow2_write_compressed,
diff --git a/block/qcow2.h b/block/qcow2.h
index 6d80120..a019831 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -209,6 +209,8 @@ uint64_t
qcow2_alloc_compressed_cluster_offset(BlockDriverState *bs,
int compressed_size);
int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m);
+int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
+ int nb_sectors);
/* qcow2-snapshot.c functions */
int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
--
1.7.2.3
- [Qemu-devel] [PATCH 02/28] strtosz() use qemu_toupper() to simplify switch statement, (continued)
- [Qemu-devel] [PATCH 02/28] strtosz() use qemu_toupper() to simplify switch statement, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 07/28] virtio-blk: tell the guest about size changes, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 03/28] strtosz(): Fix name confusion in use of modf(), Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 12/28] sheepdog: support creating images on remote hosts, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 05/28] block: add block_resize monitor command, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 08/28] virtio-pci: Disable virtio-ioeventfd when !CONFIG_IOTHREAD, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 10/28] ahci: Fix cpu_physical_memory_unmap() argument ordering, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 18/28] qcow2-refcount: remove write-only variables, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 15/28] qed: Images with backing file do not require QED_F_NEED_CHECK, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 11/28] Reorganize struct Qcow2Cache for better struct packing, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 14/28] qcow2: Add bdrv_discard support,
Kevin Wolf <=
- [Qemu-devel] [PATCH 17/28] scsi hotplug: Set DriveInfo member bus correctly, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 16/28] raw-win32: Fix bdrv_flush return value, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 24/28] blockdev: Factor drive_index_to_{bus, unit}_id out of drive_init(), Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 27/28] blockdev: Replace drive_add()'s fmt, ... by optstr parameter, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 25/28] blockdev: New drive_get_by_index(), Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 28/28] blockdev: Fix drive_add for drives without media, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 19/28] blockdev: New drive_get_next(), replacing qdev_init_bdrv(), Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 06/28] block: tell drivers about an image resize, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 21/28] blockdev: Put BlockInterfaceType names and max_devs in tables, Kevin Wolf, 2011/01/31
- [Qemu-devel] [PATCH 13/28] qemu-io: Fix discard command, Kevin Wolf, 2011/01/31