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authorEric Blake <eblake@redhat.com>2020-04-28 15:29:03 -0500
committerKevin Wolf <kwolf@redhat.com>2020-05-08 13:26:35 +0200
commitbda4cdcbb997d34762e2af27e1f475357a9b4453 (patch)
treeb594654388c54a5d67dd58686702cbd5e8be6246 /block
parentbe9c9404db7e6992946fa55c75ca61dfb20926eb (diff)
parallels: Rework truncation logic
The parallels driver tries to use truncation for image growth, but can only do so when reads are guaranteed as zero. Now that we have a way to request zero contents from truncation, we can defer the decision to actual allocation attempts rather than up front, reducing the number of places that still use bdrv_has_zero_init_truncate. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <20200428202905.770727-8-eblake@redhat.com> Reviewed-by: Denis V. Lunev <den@openvz.org> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block')
-rw-r--r--block/parallels.c25
1 files changed, 16 insertions, 9 deletions
diff --git a/block/parallels.c b/block/parallels.c
index 8db64a55e3..e7717c508e 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -166,7 +166,7 @@ static int64_t block_status(BDRVParallelsState *s, int64_t sector_num,
static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, int *pnum)
{
- int ret;
+ int ret = 0;
BDRVParallelsState *s = bs->opaque;
int64_t pos, space, idx, to_allocate, i, len;
@@ -196,14 +196,24 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
}
if (s->data_end + space > (len >> BDRV_SECTOR_BITS)) {
space += s->prealloc_size;
+ /*
+ * We require the expanded size to read back as zero. If the
+ * user permitted truncation, we try that; but if it fails, we
+ * force the safer-but-slower fallocate.
+ */
+ if (s->prealloc_mode == PRL_PREALLOC_MODE_TRUNCATE) {
+ ret = bdrv_truncate(bs->file,
+ (s->data_end + space) << BDRV_SECTOR_BITS,
+ false, PREALLOC_MODE_OFF, BDRV_REQ_ZERO_WRITE,
+ NULL);
+ if (ret == -ENOTSUP) {
+ s->prealloc_mode = PRL_PREALLOC_MODE_FALLOCATE;
+ }
+ }
if (s->prealloc_mode == PRL_PREALLOC_MODE_FALLOCATE) {
ret = bdrv_pwrite_zeroes(bs->file,
s->data_end << BDRV_SECTOR_BITS,
space << BDRV_SECTOR_BITS, 0);
- } else {
- ret = bdrv_truncate(bs->file,
- (s->data_end + space) << BDRV_SECTOR_BITS,
- false, PREALLOC_MODE_OFF, 0, NULL);
}
if (ret < 0) {
return ret;
@@ -828,6 +838,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
qemu_opt_get_size_del(opts, PARALLELS_OPT_PREALLOC_SIZE, 0);
s->prealloc_size = MAX(s->tracks, s->prealloc_size >> BDRV_SECTOR_BITS);
buf = qemu_opt_get_del(opts, PARALLELS_OPT_PREALLOC_MODE);
+ /* prealloc_mode can be downgraded later during allocate_clusters */
s->prealloc_mode = qapi_enum_parse(&prealloc_mode_lookup, buf,
PRL_PREALLOC_MODE_FALLOCATE,
&local_err);
@@ -836,10 +847,6 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
goto fail_options;
}
- if (!bdrv_has_zero_init_truncate(bs->file->bs)) {
- s->prealloc_mode = PRL_PREALLOC_MODE_FALLOCATE;
- }
-
if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_INACTIVE)) {
s->header->inuse = cpu_to_le32(HEADER_INUSE_MAGIC);
ret = parallels_update_header(bs);