Re: [Qemu-devel] [PATCH 2/2] block/nfs: refuse readahead if cache.direct is on

[Peter Lieven <pl@kamp.de>]

Am 18.05.2016 um 15:28 schrieb Jeff Cody:
> On Tue, May 17, 2016 at 04:11:55PM +0200, Peter Lieven wrote:
>> Signed-off-by: Peter Lieven <pl@kamp.de>
>> ---
>>   block/nfs.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/block/nfs.c b/block/nfs.c
>> index 975510f..8b73a35 100644
>> --- a/block/nfs.c
>> +++ b/block/nfs.c
>> @@ -331,6 +331,11 @@ static int64_t nfs_client_open(NFSClient *client, const char *filename,
>>               nfs_set_tcp_syncnt(client->context, val);
>>   #ifdef LIBNFS_FEATURE_READAHEAD
>>           } else if (!strcmp(qp->p[i].name, "readahead")) {
>> +            if (open_flags & BDRV_O_NOCACHE) {
>> +                error_setg(errp, "Cannot enable NFS readahead "
>> +                                 "if cache.direct = on");
>> +                goto fail;
>> +            }
>>               if (val > QEMU_NFS_MAX_READAHEAD_SIZE) {
>>                   error_report("NFS Warning: Truncating NFS readahead"
>>                                " size to %d", QEMU_NFS_MAX_READAHEAD_SIZE);
>> -- 
>> 1.9.1
>>
> Do we to check for cache mode changes now in nfs_reopen_prepare()?

Good point. I guess I have to error out in bdrv_reopen_prepare if we change the cache.direct from off to on and
have readahead or pagecache enabled. Will send an update.

Thanks,
Peter