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[PATCH v5 27/31] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes
From: |
Alberto Garcia |
Subject: |
[PATCH v5 27/31] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes() |
Date: |
Tue, 5 May 2020 19:38:27 +0200 |
This works now at the subcluster level and pwrite_zeroes_alignment is
updated accordingly.
qcow2_cluster_zeroize() is turned into qcow2_subcluster_zeroize() with
the following changes:
- The request can now be subcluster-aligned.
- The cluster-aligned body of the request is still zeroized using
zero_in_l2_slice() as before.
- The subcluster-aligned head and tail of the request are zeroized
with the new zero_l2_subclusters() function.
There is just one thing to take into account for a possible future
improvement: compressed clusters cannot be partially zeroized so
zero_l2_subclusters() on the head or the tail can return -ENOTSUP.
This makes the caller repeat the *complete* request and write actual
zeroes to disk. This is sub-optimal because
1) if the head area was compressed we would still be able to use
the fast path for the body and possibly the tail.
2) if the tail area was compressed we are writing zeroes to the
head and the body areas, which are already zeroized.
Signed-off-by: Alberto Garcia <address@hidden>
---
block/qcow2.h | 4 +--
block/qcow2-cluster.c | 80 +++++++++++++++++++++++++++++++++++++++----
block/qcow2.c | 27 ++++++++-------
3 files changed, 90 insertions(+), 21 deletions(-)
diff --git a/block/qcow2.h b/block/qcow2.h
index 05e3ef0ece..7349c6ce40 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -881,8 +881,8 @@ void qcow2_alloc_cluster_abort(BlockDriverState *bs,
QCowL2Meta *m);
int qcow2_cluster_discard(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, enum qcow2_discard_type type,
bool full_discard);
-int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset,
- uint64_t bytes, int flags);
+int qcow2_subcluster_zeroize(BlockDriverState *bs, uint64_t offset,
+ uint64_t bytes, int flags);
int qcow2_expand_zero_clusters(BlockDriverState *bs,
BlockDriverAmendStatusCB *status_cb,
diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 0a295076a3..d0cf9d52e6 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1971,12 +1971,58 @@ static int zero_in_l2_slice(BlockDriverState *bs,
uint64_t offset,
return nb_clusters;
}
-int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t offset,
- uint64_t bytes, int flags)
+static int zero_l2_subclusters(BlockDriverState *bs, uint64_t offset,
+ unsigned nb_subclusters)
+{
+ BDRVQcow2State *s = bs->opaque;
+ uint64_t *l2_slice;
+ uint64_t old_l2_bitmap, l2_bitmap;
+ int l2_index, ret, sc = offset_to_sc_index(s, offset);
+
+ /* For full clusters use zero_in_l2_slice() instead */
+ assert(nb_subclusters > 0 && nb_subclusters < s->subclusters_per_cluster);
+ assert(sc + nb_subclusters <= s->subclusters_per_cluster);
+
+ ret = get_cluster_table(bs, offset, &l2_slice, &l2_index);
+ if (ret < 0) {
+ return ret;
+ }
+
+ switch (qcow2_get_cluster_type(bs, get_l2_entry(s, l2_slice, l2_index))) {
+ case QCOW2_CLUSTER_COMPRESSED:
+ ret = -ENOTSUP; /* We cannot partially zeroize compressed clusters */
+ goto out;
+ case QCOW2_CLUSTER_NORMAL:
+ case QCOW2_CLUSTER_UNALLOCATED:
+ break;
+ default:
+ g_assert_not_reached();
+ }
+
+ old_l2_bitmap = l2_bitmap = get_l2_bitmap(s, l2_slice, l2_index);
+
+ l2_bitmap |= QCOW_OFLAG_SUB_ZERO_RANGE(sc, sc + nb_subclusters - 1);
+ l2_bitmap &= ~QCOW_OFLAG_SUB_ALLOC_RANGE(sc, sc + nb_subclusters - 1);
+
+ if (old_l2_bitmap != l2_bitmap) {
+ set_l2_bitmap(s, l2_slice, l2_index, l2_bitmap);
+ qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_slice);
+ }
+
+ ret = 0;
+out:
+ qcow2_cache_put(s->l2_table_cache, (void **) &l2_slice);
+
+ return ret;
+}
+
+int qcow2_subcluster_zeroize(BlockDriverState *bs, uint64_t offset,
+ uint64_t bytes, int flags)
{
BDRVQcow2State *s = bs->opaque;
uint64_t end_offset = offset + bytes;
uint64_t nb_clusters;
+ unsigned head, tail;
int64_t cleared;
int ret;
@@ -1991,8 +2037,8 @@ int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t
offset,
}
/* Caller must pass aligned values, except at image end */
- assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
- assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
+ assert(offset_into_subcluster(s, offset) == 0);
+ assert(offset_into_subcluster(s, end_offset) == 0 ||
end_offset >= bs->total_sectors << BDRV_SECTOR_BITS);
/* The zero flag is only supported by version 3 and newer */
@@ -2000,11 +2046,26 @@ int qcow2_cluster_zeroize(BlockDriverState *bs,
uint64_t offset,
return -ENOTSUP;
}
- /* Each L2 slice is handled by its own loop iteration */
- nb_clusters = size_to_clusters(s, bytes);
+ head = MIN(end_offset, ROUND_UP(offset, s->cluster_size)) - offset;
+ offset += head;
+
+ tail = (end_offset >= bs->total_sectors << BDRV_SECTOR_BITS) ? 0 :
+ end_offset - MAX(offset, start_of_cluster(s, end_offset));
+ end_offset -= tail;
s->cache_discards = true;
+ if (head) {
+ ret = zero_l2_subclusters(bs, offset - head,
+ size_to_subclusters(s, head));
+ if (ret < 0) {
+ goto fail;
+ }
+ }
+
+ /* Each L2 slice is handled by its own loop iteration */
+ nb_clusters = size_to_clusters(s, end_offset - offset);
+
while (nb_clusters > 0) {
cleared = zero_in_l2_slice(bs, offset, nb_clusters, flags);
if (cleared < 0) {
@@ -2016,6 +2077,13 @@ int qcow2_cluster_zeroize(BlockDriverState *bs, uint64_t
offset,
offset += (cleared * s->cluster_size);
}
+ if (tail) {
+ ret = zero_l2_subclusters(bs, end_offset, size_to_subclusters(s,
tail));
+ if (ret < 0) {
+ goto fail;
+ }
+ }
+
ret = 0;
fail:
s->cache_discards = false;
diff --git a/block/qcow2.c b/block/qcow2.c
index cc5591fe8f..ec4d1405f0 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1843,7 +1843,7 @@ static void qcow2_refresh_limits(BlockDriverState *bs,
Error **errp)
/* Encryption works on a sector granularity */
bs->bl.request_alignment = qcrypto_block_get_sector_size(s->crypto);
}
- bs->bl.pwrite_zeroes_alignment = s->cluster_size;
+ bs->bl.pwrite_zeroes_alignment = s->subcluster_size;
bs->bl.pdiscard_alignment = s->cluster_size;
}
@@ -3736,8 +3736,9 @@ static coroutine_fn int
qcow2_co_pwrite_zeroes(BlockDriverState *bs,
int ret;
BDRVQcow2State *s = bs->opaque;
- uint32_t head = offset % s->cluster_size;
- uint32_t tail = (offset + bytes) % s->cluster_size;
+ uint32_t head = offset_into_subcluster(s, offset);
+ uint32_t tail = ROUND_UP(offset + bytes, s->subcluster_size) -
+ (offset + bytes);
trace_qcow2_pwrite_zeroes_start_req(qemu_coroutine_self(), offset, bytes);
if (offset + bytes == bs->total_sectors * BDRV_SECTOR_SIZE) {
@@ -3749,20 +3750,19 @@ static coroutine_fn int
qcow2_co_pwrite_zeroes(BlockDriverState *bs,
unsigned int nr;
QCow2SubclusterType type;
- assert(head + bytes <= s->cluster_size);
+ assert(head + bytes + tail <= s->subcluster_size);
/* check whether remainder of cluster already reads as zero */
if (!(is_zero(bs, offset - head, head) &&
- is_zero(bs, offset + bytes,
- tail ? s->cluster_size - tail : 0))) {
+ is_zero(bs, offset + bytes, tail))) {
return -ENOTSUP;
}
qemu_co_mutex_lock(&s->lock);
/* We can have new write after previous check */
- offset = QEMU_ALIGN_DOWN(offset, s->cluster_size);
- bytes = s->cluster_size;
- nr = s->cluster_size;
+ offset -= head;
+ bytes = s->subcluster_size;
+ nr = s->subcluster_size;
ret = qcow2_get_host_offset(bs, offset, &nr, &off, &type);
if (ret < 0 ||
(type != QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN &&
@@ -3778,8 +3778,8 @@ static coroutine_fn int
qcow2_co_pwrite_zeroes(BlockDriverState *bs,
trace_qcow2_pwrite_zeroes(qemu_coroutine_self(), offset, bytes);
- /* Whatever is left can use real zero clusters */
- ret = qcow2_cluster_zeroize(bs, offset, bytes, flags);
+ /* Whatever is left can use real zero subclusters */
+ ret = qcow2_subcluster_zeroize(bs, offset, bytes, flags);
qemu_co_mutex_unlock(&s->lock);
return ret;
@@ -4243,12 +4243,13 @@ static int coroutine_fn
qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
/*
- * Use zero clusters as much as we can. qcow2_cluster_zeroize()
+ * Use zero clusters as much as we can. qcow2_subcluster_zeroize()
* requires a cluster-aligned start. The end may be unaligned if it is
* at the end of the image (which it is here).
*/
if (offset > zero_start) {
- ret = qcow2_cluster_zeroize(bs, zero_start, offset - zero_start,
0);
+ ret = qcow2_subcluster_zeroize(bs, zero_start, offset - zero_start,
+ 0);
if (ret < 0) {
error_setg_errno(errp, -ret, "Failed to zero out new
clusters");
goto fail;
--
2.20.1
- [PATCH v5 03/31] qcow2: Add calculate_l2_meta(), (continued)
- [PATCH v5 03/31] qcow2: Add calculate_l2_meta(), Alberto Garcia, 2020/05/05
- [PATCH v5 22/31] qcow2: Add subcluster support to discard_in_l2_slice(), Alberto Garcia, 2020/05/05
- [PATCH v5 18/31] qcow2: Handle QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC, Alberto Garcia, 2020/05/05
- [PATCH v5 01/31] qcow2: Make Qcow2AioTask store the full host offset, Alberto Garcia, 2020/05/05
- [PATCH v5 02/31] qcow2: Convert qcow2_get_cluster_offset() into qcow2_get_host_offset(), Alberto Garcia, 2020/05/05
- [PATCH v5 09/31] qcow2: Add subcluster-related fields to BDRVQcow2State, Alberto Garcia, 2020/05/05
- [PATCH v5 12/31] qcow2: Add l2_entry_size(), Alberto Garcia, 2020/05/05
- [PATCH v5 24/31] qcow2: Update L2 bitmap in qcow2_alloc_cluster_link_l2(), Alberto Garcia, 2020/05/05
- [PATCH v5 06/31] qcow2: Add get_l2_entry() and set_l2_entry(), Alberto Garcia, 2020/05/05
- [PATCH v5 21/31] qcow2: Add subcluster support to zero_in_l2_slice(), Alberto Garcia, 2020/05/05
- [PATCH v5 27/31] qcow2: Add subcluster support to qcow2_co_pwrite_zeroes(),
Alberto Garcia <=
- [PATCH v5 30/31] qcow2: Add subcluster support to qcow2_measure(), Alberto Garcia, 2020/05/05
- [PATCH v5 29/31] qcow2: Assert that expand_zero_clusters_in_l1() does not support subclusters, Alberto Garcia, 2020/05/05
- [PATCH v5 19/31] qcow2: Add subcluster support to calculate_l2_meta(), Alberto Garcia, 2020/05/05