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nbd: Merge nbd_export_bitmap into nbd_export_new

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We only have one caller that wants to export a bitmap name,
which it does right after creation of the export. But there is
still a brief window of time where an NBD client could see the
export but not the dirty bitmap, which a robust client would
have to interpret as meaning the entire image should be treated
as dirty.  Better is to eliminate the window entirely, by
inlining nbd_export_bitmap() into nbd_export_new(), and refusing
to create the bitmap in the first place if the requested bitmap
can't be located.

We also no longer need logic for setting a different bitmap
name compared to the bitmap being exported.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20190111194720.15671-8-eblake@redhat.com>
This commit is contained in:
Eric Blake 2019-01-11 13:47:19 -06:00
parent 7dc570b380
commit 678ba275c7
4 changed files with 47 additions and 65 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
blockdev-nbd.c
View File

@ -175,7 +175,7 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
writable = false;
}
exp = nbd_export_new(bs, 0, -1, name, NULL,
exp = nbd_export_new(bs, 0, -1, name, NULL, bitmap,
writable ? 0 : NBD_FLAG_READ_ONLY,
NULL, false, on_eject_blk, errp);
if (!exp) {
@ -186,15 +186,6 @@ void qmp_nbd_server_add(const char *device, bool has_name, const char *name,
* our only way of accessing it is through nbd_export_find(), so we can drop
* the strong reference that is @exp. */
nbd_export_put(exp);
if (has_bitmap) {
Error *err = NULL;
nbd_export_bitmap(exp, bitmap, bitmap, &err);
if (err) {
error_propagate(errp, err);
nbd_export_remove(exp, NBD_SERVER_REMOVE_MODE_HARD, NULL);
}
}
}
void qmp_nbd_server_remove(const char *name,

9
include/block/nbd.h
View File

@ -296,9 +296,9 @@ typedef struct NBDClient NBDClient;
NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
const char *name, const char *description,
uint16_t nbdflags, void (*close)(NBDExport *),
bool writethrough, BlockBackend *on_eject_blk,
Error **errp);
const char *bitmap, uint16_t nbdflags,
void (*close)(NBDExport *), bool writethrough,
BlockBackend *on_eject_blk, Error **errp);
void nbd_export_close(NBDExport *exp);
void nbd_export_remove(NBDExport *exp, NbdServerRemoveMode mode, Error **errp);
void nbd_export_get(NBDExport *exp);
@ -319,9 +319,6 @@ void nbd_client_put(NBDClient *client);
void nbd_server_start(SocketAddress *addr, const char *tls_creds,
Error **errp);
void nbd_export_bitmap(NBDExport *exp, const char *bitmap,
const char *bitmap_export_name, Error **errp);
/* nbd_read
* Reads @size bytes from @ioc. Returns 0 on success.
*/

87
nbd/server.c
View File

@ -1457,9 +1457,9 @@ static void nbd_eject_notifier(Notifier *n, void *data)
NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
const char *name, const char *description,
uint16_t nbdflags, void (*close)(NBDExport *),
bool writethrough, BlockBackend *on_eject_blk,
Error **errp)
const char *bitmap, uint16_t nbdflags,
void (*close)(NBDExport *), bool writethrough,
BlockBackend *on_eject_blk, Error **errp)
{
AioContext *ctx;
BlockBackend *blk;
@ -1507,6 +1507,43 @@ NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
}
exp->size -= exp->size % BDRV_SECTOR_SIZE;
if (bitmap) {
BdrvDirtyBitmap *bm = NULL;
BlockDriverState *bs = blk_bs(blk);
while (true) {
bm = bdrv_find_dirty_bitmap(bs, bitmap);
if (bm != NULL || bs->backing == NULL) {
break;
}
bs = bs->backing->bs;
}
if (bm == NULL) {
error_setg(errp, "Bitmap '%s' is not found", bitmap);
goto fail;
}
if ((nbdflags & NBD_FLAG_READ_ONLY) && bdrv_is_writable(bs) &&
bdrv_dirty_bitmap_enabled(bm)) {
error_setg(errp,
"Enabled bitmap '%s' incompatible with readonly export",
bitmap);
goto fail;
}
if (bdrv_dirty_bitmap_user_locked(bm)) {
error_setg(errp, "Bitmap '%s' is in use", bitmap);
goto fail;
}
bdrv_dirty_bitmap_set_qmp_locked(bm, true);
exp->export_bitmap = bm;
exp->export_bitmap_context = g_strdup_printf("qemu:dirty-bitmap:%s",
bitmap);
}
exp->close = close;
exp->ctx = blk_get_aio_context(blk);
blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
@ -2424,47 +2461,3 @@ void nbd_client_new(QIOChannelSocket *sioc,
co = qemu_coroutine_create(nbd_co_client_start, client);
qemu_coroutine_enter(co);
}
void nbd_export_bitmap(NBDExport *exp, const char *bitmap,
const char *bitmap_export_name, Error **errp)
{
BdrvDirtyBitmap *bm = NULL;
BlockDriverState *bs = blk_bs(exp->blk);
if (exp->export_bitmap) {
error_setg(errp, "Export bitmap is already set");
return;
}
while (true) {
bm = bdrv_find_dirty_bitmap(bs, bitmap);
if (bm != NULL || bs->backing == NULL) {
break;
}
bs = bs->backing->bs;
}
if (bm == NULL) {
error_setg(errp, "Bitmap '%s' is not found", bitmap);
return;
}
if ((exp->nbdflags & NBD_FLAG_READ_ONLY) && bdrv_is_writable(bs) &&
bdrv_dirty_bitmap_enabled(bm)) {
error_setg(errp,
"Enabled bitmap '%s' incompatible with readonly export",
bitmap);
return;
}
if (bdrv_dirty_bitmap_user_locked(bm)) {
error_setg(errp, "Bitmap '%s' is in use", bitmap);
return;
}
bdrv_dirty_bitmap_set_qmp_locked(bm, true);
exp->export_bitmap = bm;
exp->export_bitmap_context =
g_strdup_printf("qemu:dirty-bitmap:%s", bitmap_export_name);
}

5
qemu-nbd.c
View File

@ -1016,8 +1016,9 @@ int main(int argc, char **argv)
}
export = nbd_export_new(bs, dev_offset, fd_size, export_name,
export_description, nbdflags, nbd_export_closed,
writethrough, NULL, &error_fatal);
export_description, NULL, nbdflags,
nbd_export_closed, writethrough, NULL,
&error_fatal);
if (device) {
#if HAVE_NBD_DEVICE