Re: [Qemu-block] [PATCH v8 06/16] nbd: Switch from close to eject notifier

[Max Reitz]

On 28.01.2016 04:26, Fam Zheng wrote:
> On Wed, 01/27 18:59, Max Reitz wrote:
>> The NBD code uses the BDS close notifier to determine when a medium is
>> ejected. However, now it should use the BB's BDS removal notifier for
>> that instead of the BDS's close notifier.
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>>  blockdev-nbd.c | 40 +++++-----------------------------------
>>  nbd/server.c   | 13 +++++++++++++
>>  2 files changed, 18 insertions(+), 35 deletions(-)
>>
>> diff --git a/blockdev-nbd.c b/blockdev-nbd.c
>> index 4a758ac..9d6a21c 100644
>> --- a/blockdev-nbd.c
>> +++ b/blockdev-nbd.c
>> @@ -45,37 +45,11 @@ void qmp_nbd_server_start(SocketAddress *addr, Error 
>> **errp)
>>      }
>>  }
>>  
>> -/*
>> - * Hook into the BlockBackend notifiers to close the export when the
>> - * backend is closed.
>> - */
>> -typedef struct NBDCloseNotifier {
>> -    Notifier n;
>> -    NBDExport *exp;
>> -    QTAILQ_ENTRY(NBDCloseNotifier) next;
>> -} NBDCloseNotifier;
>> -
>> -static QTAILQ_HEAD(, NBDCloseNotifier) close_notifiers =
>> -    QTAILQ_HEAD_INITIALIZER(close_notifiers);
>> -
>> -static void nbd_close_notifier(Notifier *n, void *data)
>> -{
>> -    NBDCloseNotifier *cn = DO_UPCAST(NBDCloseNotifier, n, n);
>> -
>> -    notifier_remove(&cn->n);
>> -    QTAILQ_REMOVE(&close_notifiers, cn, next);
>> -
>> -    nbd_export_close(cn->exp);
>> -    nbd_export_put(cn->exp);
>> -    g_free(cn);
>> -}
>> -
>>  void qmp_nbd_server_add(const char *device, bool has_writable, bool 
>> writable,
>>                          Error **errp)
>>  {
>>      BlockBackend *blk;
>>      NBDExport *exp;
>> -    NBDCloseNotifier *n;
>>  
>>      if (server_fd == -1) {
>>          error_setg(errp, "NBD server not running");
>> @@ -113,19 +87,15 @@ void qmp_nbd_server_add(const char *device, bool 
>> has_writable, bool writable,
>>  
>>      nbd_export_set_name(exp, device);
>>  
>> -    n = g_new0(NBDCloseNotifier, 1);
>> -    n->n.notify = nbd_close_notifier;
>> -    n->exp = exp;
>> -    blk_add_close_notifier(blk, &n->n);
>> -    QTAILQ_INSERT_TAIL(&close_notifiers, n, next);
>> +    /* The list of named exports has a strong reference to this export now 
>> and
>> +     * our only way of accessing it is through nbd_export_find(), so we can 
>> drop
>> +     * the strong reference that is @exp. */
> 
> Not quite sure about the meaning of "the strong reference that is @exp", I
> guess you mean the one reference born in nbd_export_new(), which would match
> the code.  Other than this,

Yes, the reference returned by nbd_export_new(), which is then stored in
@exp. This is a strong reference, so once @exp goes out of scope, the
reference counter has to be decremented.

Max

> Reviewed-by: Fam Zheng <address@hidden>

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