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[Qemu-block] [PULL 31/55] qcow2: Update l2_load() to support L2 slices
From: |
Kevin Wolf |
Subject: |
[Qemu-block] [PULL 31/55] qcow2: Update l2_load() to support L2 slices |
Date: |
Tue, 13 Feb 2018 18:05:05 +0100 |
From: Alberto Garcia <address@hidden>
Each entry in the qcow2 L2 cache stores a full L2 table (which uses a
complete cluster in the qcow2 image). A cluster is usually too large
to be used efficiently as the size for a cache entry, so we want to
decouple both values by allowing smaller cache entries. Therefore the
qcow2 L2 cache will no longer return full L2 tables but slices
instead.
This patch updates l2_load() so it can handle L2 slices correctly.
Apart from the offset of the L2 table (which we already had) we also
need the guest offset in order to calculate which one of the slices
we need.
An L2 slice has currently the same size as an L2 table (one cluster),
so for now this function will load exactly the same data as before.
This patch also removes a stale comment about the return value being
a pointer to the L2 table. This function returns an error code since
55c17e9821c474d5fcdebdc82ed2fc096777d611.
Signed-off-by: Alberto Garcia <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
Signed-off-by: Max Reitz <address@hidden>
---
block/qcow2-cluster.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index ce7591dc3d..542080aed0 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -195,20 +195,26 @@ int qcow2_grow_l1_table(BlockDriverState *bs, uint64_t
min_size,
/*
* l2_load
*
- * Loads a L2 table into memory. If the table is in the cache, the cache
- * is used; otherwise the L2 table is loaded from the image file.
+ * @bs: The BlockDriverState
+ * @offset: A guest offset, used to calculate what slice of the L2
+ * table to load.
+ * @l2_offset: Offset to the L2 table in the image file.
+ * @l2_slice: Location to store the pointer to the L2 slice.
*
- * Returns a pointer to the L2 table on success, or NULL if the read from
- * the image file failed.
+ * Loads a L2 slice into memory (L2 slices are the parts of L2 tables
+ * that are loaded by the qcow2 cache). If the slice is in the cache,
+ * the cache is used; otherwise the L2 slice is loaded from the image
+ * file.
*/
-
-static int l2_load(BlockDriverState *bs, uint64_t l2_offset,
- uint64_t **l2_table)
+static int l2_load(BlockDriverState *bs, uint64_t offset,
+ uint64_t l2_offset, uint64_t **l2_slice)
{
BDRVQcow2State *s = bs->opaque;
+ int start_of_slice = sizeof(uint64_t) *
+ (offset_to_l2_index(s, offset) - offset_to_l2_slice_index(s, offset));
- return qcow2_cache_get(bs, s->l2_table_cache, l2_offset,
- (void **)l2_table);
+ return qcow2_cache_get(bs, s->l2_table_cache, l2_offset + start_of_slice,
+ (void **)l2_slice);
}
/*
@@ -561,7 +567,7 @@ int qcow2_get_cluster_offset(BlockDriverState *bs, uint64_t
offset,
/* load the l2 table in memory */
- ret = l2_load(bs, l2_offset, &l2_table);
+ ret = l2_load(bs, offset, l2_offset, &l2_table);
if (ret < 0) {
return ret;
}
@@ -684,7 +690,7 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t
offset,
if (s->l1_table[l1_index] & QCOW_OFLAG_COPIED) {
/* load the l2 table in memory */
- ret = l2_load(bs, l2_offset, &l2_table);
+ ret = l2_load(bs, offset, l2_offset, &l2_table);
if (ret < 0) {
return ret;
}
--
2.13.6
- [Qemu-block] [PULL 29/55] qcow2: Add l2_slice_size field to BDRVQcow2State, (continued)
- [Qemu-block] [PULL 29/55] qcow2: Add l2_slice_size field to BDRVQcow2State, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 24/55] qcow2: Remove BDS parameter from qcow2_cache_destroy(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 28/55] qcow2: Add offset_to_l1_index(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 37/55] qcow2: Update qcow2_alloc_cluster_link_l2() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 35/55] qcow2: Update get_cluster_table() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 33/55] qcow2: Update l2_allocate() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 25/55] qcow2: Remove BDS parameter from qcow2_cache_clean_unused(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 38/55] qcow2: Update handle_copied() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 30/55] qcow2: Add offset_to_l2_slice_index(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 27/55] qcow2: Remove BDS parameter from qcow2_cache_is_table_offset(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 31/55] qcow2: Update l2_load() to support L2 slices,
Kevin Wolf <=
- [Qemu-block] [PULL 32/55] qcow2: Prepare l2_allocate() for adding L2 slice support, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 34/55] qcow2: Refactor get_cluster_table(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 44/55] qcow2: Read refcount before L2 table in expand_zero_clusters_in_l1(), Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 41/55] qcow2: Update zero_single_l2() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 39/55] qcow2: Update handle_alloc() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 42/55] qcow2: Prepare qcow2_update_snapshot_refcount() for adding L2 slice support, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 36/55] qcow2: Update qcow2_get_cluster_offset() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 40/55] qcow2: Update discard_single_l2() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 43/55] qcow2: Update qcow2_update_snapshot_refcount() to support L2 slices, Kevin Wolf, 2018/02/13
- [Qemu-block] [PULL 45/55] qcow2: Prepare expand_zero_clusters_in_l1() for adding L2 slice support, Kevin Wolf, 2018/02/13