[PATCH 2/2] jffs2: Provide jffs2_sync files to track gc POLL progress

[Theuns.Verwoerd@xxxxxxxxxxxxxxxxxxx (Theuns Verwoerd)]

On 07/20/2018 12:04 PM, Al Viro wrote:
> On Fri, Jul 20, 2018 at 11:50:12AM +1200, Theuns Verwoerd wrote:
>
>> +ssize_t jffs2_sync_file_read(struct file *f,
>> +	      char __user *b, size_t len, loff_t *ofs)
>> +{
>> +	struct jffs2_sb_info *c = file_inode(f)->i_private;
>> +
>> +	while (c->tidemark)
>> +		schedule();
>> +
>> +	return 0;
>> +}
> Brilliant.  So when that gets called with c->tidemark being true and
> need_resched() - false, we shall...
By my reading, schedule() will happily force a reschedule (once) when 
need_resched() is false.? Every time the process is granted a time 
slice, it'll check the condition and surrender if not ready.

What do you believe will happen?
> Bonus question: what happens if that is called after that jffs2_sb_info
> gets freed?
That is probably a valid critique - if jffs2_kill_sb() gets called the 
cleanup in exit_jffs2_fs() is not sufficient.

Regards,

Theuns
KRN