Re: [PATCH 1/1] fanotify: read(2) error handling

[Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>]

On 03.05.2014 21:21, Michael Kerrisk (man-pages) wrote:
> [CC += Eric]
>
> Hello Heinrich,
>
> On 05/03/2014 06:57 PM, Heinrich Schuchardt wrote:
>> The last lines of fanotify_read() in fanotify_user.c are:
>> 	if (start != buf && ret != -EFAULT)
>> 		ret = buf - start;
>> 	return ret;
>>
>> This implies that an error code is only returned, if reading the first
>> event on the queue fails or if EFAULT occurs.
>
> I'm not quite sure if this text is needed. What sort of errors
> are we talking about here that are not reported?

EMFILE The per-process limit on the number of open files has been 
reached.  See the description of RLIMIT_NOFILE in getrlimit(2).

ENFILE The system-wide limit on the number of open files has been 
reached.  See /proc/sys/fs/file-max in proc(5).

ETXTBSY This error is returned by read(2) if O_RDWR or O_WRONLY was 
specified in the event_f_flags argument when calling fanotify_init(2) 
and  an event occurred for a monitored file that is currently being 
executed.

Cheers

Heinrich

>
> Cheers,
>
> Michael
>
>
>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk-Mmb7MZpHnFY@public.gmane.org>
>> ---
>>   man7/fanotify.7 | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/man7/fanotify.7 b/man7/fanotify.7
>> index 083244f..6936b88 100644
>> --- a/man7/fanotify.7
>> +++ b/man7/fanotify.7
>> @@ -131,6 +131,14 @@ until either a file event occurs or the call is interrupted by a signal
>>   The return value of
>>   .BR read (2)
>>   is the length of the filled buffer, or \-1 in case of an error.
>> +If multiple events are on the fanotify queue,
>> +.BR read (2)
>> +will only report an error, if reading the first event fails or an error
>> +.B EFAULT
>> +occurs.
>> +If reading the first event is successful but reading any further event fails,
>> +.BR read (2)
>> +returns the length of the buffer filled with all prior events.
>>   After a successful
>>   .BR read (2),
>>   the read buffer contains one or more of the following structures:
>>
>
>

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