This patch adds the support of preallocation (off/full) for the RBD
block driver.
If available, we use rbd_writesame() to quickly fill the image when
full preallocation is required.
Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
---
v2:
- Use 4 KiB buffer for rbd_writesame() [Jason]
- Use "rbd_concurrent_management_ops" and "stripe_unit" to limit
concurrent ops to the backing cluster [Jason]
---
block/rbd.c | 188 +++++++++++++++++++++++++++++++++++++++----
qapi/block-core.json | 4 +-
2 files changed, 175 insertions(+), 17 deletions(-)
diff --git a/block/rbd.c b/block/rbd.c
index 0c549c9935..bc54395e1c 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -13,6 +13,7 @@
#include "qemu/osdep.h"
+#include "qemu/units.h"
#include <rbd/librbd.h>
#include "qapi/error.h"
#include "qemu/error-report.h"
@@ -63,6 +64,7 @@
#define OBJ_MAX_SIZE (1UL << OBJ_DEFAULT_OBJ_ORDER)
#define RBD_MAX_SNAPS 100
+#define RBD_DEFAULT_CONCURRENT_OPS 10
/* The LIBRBD_SUPPORTS_IOVEC is defined in librbd.h */
#ifdef LIBRBD_SUPPORTS_IOVEC
@@ -331,6 +333,147 @@ static void qemu_rbd_memset(RADOSCB *rcb, int64_t offs)
}
}
+static int qemu_rbd_get_max_concurrent_ops(rados_t cluster)
+{
+ char buf[16];
+ int ret, max_concurrent_ops;
+
+ ret = rados_conf_get(cluster, "rbd_concurrent_management_ops", buf,
+ sizeof(buf));
+ if (ret < 0) {
+ return RBD_DEFAULT_CONCURRENT_OPS;
+ }
+
+ ret = qemu_strtoi(buf, NULL, 10, &max_concurrent_ops);
+ if (ret < 0) {
+ return RBD_DEFAULT_CONCURRENT_OPS;
+ }
+
+ return max_concurrent_ops;
+}
+
+static int qemu_rbd_do_truncate(rados_t cluster, rbd_image_t image,
+ int64_t offset, PreallocMode prealloc,
+ Error **errp)
+{
+ uint64_t current_length;
+ char *buf = NULL;
+ int ret;
+
+ ret = rbd_get_size(image, ¤t_length);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to get file length");
+ goto out;
+ }
+
+ if (current_length > offset && prealloc != PREALLOC_MODE_OFF) {
+ error_setg(errp, "Cannot use preallocation for shrinking files");
+ ret = -ENOTSUP;
+ goto out;
+ }
+
+ switch (prealloc) {
+ case PREALLOC_MODE_FULL: {
+ uint64_t current_offset = current_length;
+ int buf_size = 4 * KiB;
+ ssize_t bytes;
+
+#ifdef LIBRBD_SUPPORTS_WRITESAME
+ uint64_t stripe_unit, writesame_max_size;
+ int max_concurrent_ops;
+
+ max_concurrent_ops = qemu_rbd_get_max_concurrent_ops(cluster);
+ ret = rbd_get_stripe_unit(image, &stripe_unit);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to get stripe unit");
+ goto out;
+ }
+
+ /*
+ * We limit the rbd_writesame() size to avoid to spawn more then
+ * 'rbd_concurrent_management_ops' concurrent operations.
+ */
+ writesame_max_size = MIN(stripe_unit * max_concurrent_ops, INT_MAX);
+#endif /* LIBRBD_SUPPORTS_WRITESAME */
+
+ buf = g_malloc(buf_size);
+ /*
+ * Some versions of rbd_writesame() discards writes of buffers with
+ * all zeroes. In order to avoid this behaviour, we set the first byte
+ * to one.
+ */
+ buf[0] = 1;
+
+ ret = rbd_resize(image, offset);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to resize file");
+ goto out;
+ }
+
+#ifdef LIBRBD_SUPPORTS_WRITESAME
+ while (offset - current_offset > buf_size) {
+ bytes = MIN(offset - current_offset, writesame_max_size);
+ /*
+ * rbd_writesame() supports only request where the size of the
+ * operation is multiple of buffer size.
+ */
+ bytes -= bytes % buf_size;
+
+ bytes = rbd_writesame(image, current_offset, bytes, buf, buf_size,
+ 0);
+ if (bytes < 0) {
+ ret = bytes;
+ error_setg_errno(errp, -ret,
+ "Failed to write for preallocation");
+ goto out;
+ }
+
+ current_offset += bytes;
+ }
+#endif /* LIBRBD_SUPPORTS_WRITESAME */
+
+ while (current_offset < offset) {
+ bytes = rbd_write(image, current_offset,
+ MIN(offset - current_offset, buf_size), buf);
+ if (bytes < 0) {
+ ret = bytes;
+ error_setg_errno(errp, -ret,
+ "Failed to write for preallocation");
+ goto out;
+ }
+
+ current_offset += bytes;
+ }
+
+ ret = rbd_flush(image);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to flush the file");
+ goto out;
+ }
+
+ break;
+ }
+ case PREALLOC_MODE_OFF:
+ ret = rbd_resize(image, offset);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "Failed to resize file");
+ goto out;
+ }
+ break;
+ default:
+ error_setg(errp, "Unsupported preallocation mode: %s",
+ PreallocMode_str(prealloc));
+ ret = -ENOTSUP;
+ goto out;
+ }
+
+ ret = 0;
+
+out:
+ g_free(buf);
+ return ret;
+}
+
static QemuOptsList runtime_opts = {
.name = "rbd",
.head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
@@ -376,6 +519,7 @@ static int qemu_rbd_do_create(BlockdevCreateOptions
*options,
BlockdevCreateOptionsRbd *opts = &options->u.rbd;
rados_t cluster;
rados_ioctx_t io_ctx;
+ rbd_image_t image;
int obj_order = 0;
int ret;
@@ -404,13 +548,22 @@ static int qemu_rbd_do_create(BlockdevCreateOptions
*options,
return ret;
}
- ret = rbd_create(io_ctx, opts->location->image, opts->size, &obj_order);
+ ret = rbd_create(io_ctx, opts->location->image, 0, &obj_order);
if (ret < 0) {
error_setg_errno(errp, -ret, "error rbd create");
goto out;
}
- ret = 0;
+ ret = rbd_open(io_ctx, opts->location->image, &image, NULL);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "error rbd open");
+ goto out;
+ }
+
+ ret = qemu_rbd_do_truncate(cluster, image, opts->size, opts->preallocation,
+ errp);
+
+ rbd_close(image);
out:
rados_ioctx_destroy(io_ctx);
rados_shutdown(cluster);
@@ -431,6 +584,7 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char
*filename,
BlockdevOptionsRbd *loc;
Error *local_err = NULL;
const char *keypairs, *password_secret;
+ char *prealloc;
QDict *options = NULL;
int ret = 0;
@@ -449,6 +603,16 @@ static int coroutine_fn qemu_rbd_co_create_opts(const char
*filename,
BLOCK_OPT_CLUSTER_SIZE, 0);
rbd_opts->has_cluster_size = (rbd_opts->cluster_size != 0);
+ prealloc = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
+ rbd_opts->preallocation = qapi_enum_parse(&PreallocMode_lookup, prealloc,
+ PREALLOC_MODE_OFF, &local_err);
+ g_free(prealloc);
+ if (local_err) {
+ ret = -EINVAL;
+ error_propagate(errp, local_err);
+ goto exit;
+ }
+
options = qdict_new();
qemu_rbd_parse_filename(filename, options, &local_err);
if (local_err) {
@@ -1052,21 +1216,8 @@ static int coroutine_fn
qemu_rbd_co_truncate(BlockDriverState *bs,
Error **errp)
{
BDRVRBDState *s = bs->opaque;
- int r;
- if (prealloc != PREALLOC_MODE_OFF) {
- error_setg(errp, "Unsupported preallocation mode '%s'",
- PreallocMode_str(prealloc));
- return -ENOTSUP;
- }
-
- r = rbd_resize(s->image, offset);
- if (r < 0) {
- error_setg_errno(errp, -r, "Failed to resize file");
- return r;
- }
-
- return 0;
+ return qemu_rbd_do_truncate(s->cluster, s->image, offset, prealloc, errp);
}
static int qemu_rbd_snap_create(BlockDriverState *bs,
@@ -1219,6 +1370,11 @@ static QemuOptsList qemu_rbd_create_opts = {
.type = QEMU_OPT_SIZE,
.help = "RBD object size"
},
+ {
+ .name = BLOCK_OPT_PREALLOC,
+ .type = QEMU_OPT_STRING,
+ .help = "Preallocation mode (allowed values: off, full)"
+ },
{
.name = "password-secret",
.type = QEMU_OPT_STRING,
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 7ccbfff9d0..db25a4065b 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -4277,13 +4277,15 @@
# point to a snapshot.
# @size Size of the virtual disk in bytes
# @cluster-size RBD object size
+# @preallocation Preallocation mode (allowed values: off, full)
#
# Since: 2.12
##
{ 'struct': 'BlockdevCreateOptionsRbd',
'data': { 'location': 'BlockdevOptionsRbd',
'size': 'size',
- '*cluster-size' : 'size' } }
+ '*cluster-size' : 'size',
+ '*preallocation': 'PreallocMode' } }
##
# @BlockdevVmdkSubformat:
--
2.20.1
