Re: [PATCH 1/2] libfuse: don't use SYNC_INIT unless asked for

[Bernd Schubert <bernd@bsbernd.com>]

On 5/5/26 09:30, Bernd Schubert wrote:
> 
> 
> On 5/5/26 07:23, Darrick J. Wong wrote:
>> From: Darrick J. Wong <djwong@kernel.org>
>>
>> If we didn't ask for SYNC_INIT, don't enable it.  This is needed to
>> maintain compatibility with older fuse servers that only support
>> asynchronous FUSE_INIT.
>>
>> Fixes: 3e1101057aea57 ("fuse mount: Support synchronous FUSE_INIT (privileged daemon)")
>> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
>> ---
>>  lib/fuse_lowlevel.c |    6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>>
>> diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
>> index 0e16845d2f14ff..0a801132590079 100644
>> --- a/lib/fuse_lowlevel.c
>> +++ b/lib/fuse_lowlevel.c
>> @@ -4475,9 +4475,9 @@ static int session_start_sync_init(struct fuse_session *se, int fd)
>>  {
>>  	int err, res;
>>  
>> -	if (!se->want_sync_init &&
>> -		(se->uring.enable && !fuse_daemonize_is_used())) {
>> -		if (se->debug)
>> +	if (!se->want_sync_init) {
>> +		/* SYNC_INIT is required for io_uring(?) */
>> +		if ((se->uring.enable && !fuse_daemonize_is_used()) || se->debug)
>>  			fuse_log(FUSE_LOG_DEBUG,
>>  					"fuse: sync init not enabled\n");
>>  		return 0;
>>
> 
> Hmm, but mounting is kind of a libuse internal part? If this is really
> needed the commit message should mention the exact reason - what is the
> issue with old fuse servers and sync init?
> 

One reason I can think off is if the ->init() method starts new threads.
In that case we could still do allow the new mount API when the new
daemonize API is used.