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[PATCH 7/9] parallels: Rework truncation logic
From: |
Eric Blake |
Subject: |
[PATCH 7/9] parallels: Rework truncation logic |
Date: |
Tue, 28 Apr 2020 15:29:03 -0500 |
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 <address@hidden>
---
block/parallels.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/block/parallels.c b/block/parallels.c
index 2be92cf41708..9dadaa3217b9 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -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);
--
2.26.2
- [PATCH 0/9] More truncate improvements, Eric Blake, 2020/04/28
- [PATCH 2/9] file-win32: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 3/9] nfs: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 1/9] gluster: Drop useless has_zero_init callback, Eric Blake, 2020/04/28
- [PATCH 4/9] rbd: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 6/9] ssh: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 5/9] sheepdog: Support BDRV_REQ_ZERO_WRITE for truncate, Eric Blake, 2020/04/28
- [PATCH 7/9] parallels: Rework truncation logic,
Eric Blake <=
- [PATCH 8/9] vhdx: Rework truncation logic, Eric Blake, 2020/04/28
- [PATCH 9/9] block: Drop unused .bdrv_has_zero_init_truncate, Eric Blake, 2020/04/28
- Re: [PATCH 0/9] More truncate improvements, no-reply, 2020/04/28
- Re: [PATCH 0/9] More truncate improvements, no-reply, 2020/04/28