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nbd-server: Use a separate BlockBackend

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The builtin NBD server uses its own BlockBackend now instead of reusing
the monitor/guest device one.

This means that it has its own writethrough setting now. The builtin
NBD server always uses writeback caching now regardless of whether the
guest device has WCE enabled. qemu-nbd respects the cache mode given on
the command line.

We still need to keep a reference to the monitor BB because we put an
eject notifier on it, but we don't use it for any I/O.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2016-07-06 11:22:39 +02:00
parent 0524e93a3f
commit cd7fca952c
5 changed files with 28 additions and 10 deletions
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25
nbd/server.c
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@ -69,6 +69,7 @@ struct NBDExport {
AioContext *ctx;
BlockBackend *eject_notifier_blk;
Notifier eject_notifier;
};
@ -807,11 +808,18 @@ static void nbd_eject_notifier(Notifier *n, void *data)
nbd_export_close(exp);
}
NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
NBDExport *nbd_export_new(BlockDriverState *bs, off_t dev_offset, off_t size,
uint16_t nbdflags, void (*close)(NBDExport *),
bool writethrough, BlockBackend *on_eject_blk,
Error **errp)
{
BlockBackend *blk;
NBDExport *exp = g_malloc0(sizeof(NBDExport));
blk = blk_new();
blk_insert_bs(blk, bs);
blk_set_enable_write_cache(blk, !writethrough);
exp->refcount = 1;
QTAILQ_INIT(&exp->clients);
exp->blk = blk;
@ -827,11 +835,14 @@ NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
exp->close = close;
exp->ctx = blk_get_aio_context(blk);
blk_ref(blk);
blk_add_aio_context_notifier(blk, blk_aio_attached, blk_aio_detach, exp);
exp->eject_notifier.notify = nbd_eject_notifier;
blk_add_remove_bs_notifier(blk, &exp->eject_notifier);
if (on_eject_blk) {
blk_ref(on_eject_blk);
exp->eject_notifier_blk = on_eject_blk;
exp->eject_notifier.notify = nbd_eject_notifier;
blk_add_remove_bs_notifier(on_eject_blk, &exp->eject_notifier);
}
/*
* NBD exports are used for non-shared storage migration. Make sure
@ -844,6 +855,7 @@ NBDExport *nbd_export_new(BlockBackend *blk, off_t dev_offset, off_t size,
return exp;
fail:
blk_unref(blk);
g_free(exp);
return NULL;
}
@ -914,7 +926,10 @@ void nbd_export_put(NBDExport *exp)
}
if (exp->blk) {
notifier_remove(&exp->eject_notifier);
if (exp->eject_notifier_blk) {
notifier_remove(&exp->eject_notifier);
blk_unref(exp->eject_notifier_blk);
}
blk_remove_aio_context_notifier(exp->blk, blk_aio_attached,
blk_aio_detach, exp);
blk_unref(exp->blk);