From: Eric Blake <eblake@redhat.com>
To: qemu-devel@nongnu.org
Cc: kwolf@redhat.com, "Denis V. Lunev" <den@openvz.org>,
Stefan Hajnoczi <stefanha@redhat.com>,
qemu-block@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PATCH 7/9] parallels: Rework truncation logic
Date: Tue, 28 Apr 2020 15:29:03 -0500 [thread overview]
Message-ID: <20200428202905.770727-8-eblake@redhat.com> (raw)
In-Reply-To: <20200428202905.770727-1-eblake@redhat.com>
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>
---
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
next prev parent reply other threads:[~2020-04-28 20:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 20:28 [PATCH 0/9] More truncate improvements Eric Blake
2020-04-28 20:28 ` [PATCH 1/9] gluster: Drop useless has_zero_init callback Eric Blake
2020-04-28 20:28 ` [PATCH 2/9] file-win32: Support BDRV_REQ_ZERO_WRITE for truncate Eric Blake
2020-04-28 20:28 ` [PATCH 3/9] nfs: " Eric Blake
2020-04-28 20:29 ` [PATCH 4/9] rbd: " Eric Blake
2020-04-28 20:29 ` [PATCH 5/9] sheepdog: " Eric Blake
2020-04-28 20:29 ` [PATCH 6/9] ssh: " Eric Blake
2020-04-29 9:01 ` Richard W.M. Jones
2020-04-28 20:29 ` Eric Blake [this message]
2020-05-07 11:14 ` [PATCH 7/9] parallels: Rework truncation logic Denis V. Lunev
2020-04-28 20:29 ` [PATCH 8/9] vhdx: " Eric Blake
2020-04-28 20:29 ` [PATCH 9/9] block: Drop unused .bdrv_has_zero_init_truncate Eric Blake
2020-04-29 9:02 ` Richard W.M. Jones
2020-04-29 2:24 ` [PATCH 0/9] More truncate improvements no-reply
2020-04-29 13:14 ` Eric Blake
2020-04-29 2:24 ` no-reply
2020-05-06 13:03 ` Eric Blake
2020-05-07 10:15 ` Kevin Wolf
2020-05-07 14:29 ` Eric Blake
2020-05-07 14:32 ` Kevin Wolf
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