On 09/18, Chao Yu wrote: > On 2019/9/18 4:55, Jaegeuk Kim wrote: > > On 09/17, Chao Yu wrote: > >> On 2019/9/16 23:37, Jaegeuk Kim wrote: > >>> On 09/16, Chao Yu wrote: > >>>> On 2019/9/9 20:04, Jaegeuk Kim wrote: > >>>>> On 09/09, Chao Yu wrote: > >>>>>> On 2019/9/9 16:06, Jaegeuk Kim wrote: > >>>>>>> On 09/09, Chao Yu wrote: > >>>>>>>> On 2019/9/9 9:25, Jaegeuk Kim wrote: > >>>>>>>>> GC must avoid select the same victim again. > >>>>>>>> > >>>>>>>> Blocks in previous victim will occupy addition free segment, I doubt > >>>>>>>> after this > >>>>>>>> change, FGGC may encounter out-of-free space issue more frequently. > >>>>>>> > >>>>>>> Hmm, actually this change seems wrong by sec_usage_check(). > >>>>>>> We may be able to avoid this only in the suspicious loop? > >>>>>>> > >>>>>>> --- > >>>>>>> fs/f2fs/gc.c | 2 +- > >>>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>>>>> > >>>>>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c > >>>>>>> index e88f98ddf396..5877bd729689 100644 > >>>>>>> --- a/fs/f2fs/gc.c > >>>>>>> +++ b/fs/f2fs/gc.c > >>>>>>> @@ -1326,7 +1326,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, bool sync, > >>>>>>> round++; > >>>>>>> } > >>>>>>> > >>>>>>> - if (gc_type == FG_GC) > >>>>>>> + if (gc_type == FG_GC && seg_freed) > >>>>>> > >>>>>> That's original solution Sahitya provided to avoid infinite loop of > >>>>>> GC, but I > >>>>>> suggest to find the root cause first, then we added .invalid_segmap > >>>>>> for that > >>>>>> purpose. > >>>>> > >>>>> I've checked the Sahitya's patch. So, it seems the problem can happen > >>>>> due to > >>>>> is_alive or atomic_file. > >>>> > >>>> For some conditions, this doesn't help, for example, two sections > >>>> contain the > >>>> same fewest valid blocks, it will cause to loop selecting them if it > >>>> fails to > >>>> migrate blocks. > >>>> > >>>> How about keeping it as it is to find potential bug. > >>> > >>> I think it'd be fine to merge this. Could you check the above scenario in > >>> more > >>> detail? > >> > >> I haven't saw this in real scenario yet. > >> > >> What I mean is if there is a bug (maybe in is_alive()) failing us to GC on > >> one > >> section, when that bug happens in two candidates, there could be the same > >> condition that GC will run into loop (select A, fail to migrate; select B, > >> fail > >> to migrate, select A...). > >> > >> But I guess the benefit of this change is, if FGGC fails to migrate block > >> due to > >> i_gc_rwsem race, selecting another section and later retrying previous one > >> may > >> avoid lock race, right? > > > > In any case, I think this can avoid potenial GC loop. At least to me, it'd > > be > > quite risky, if we remain this just for debugging purpose only. > > Yup, > > One more concern is would this cur_victim_sec remain after FGGC? then BGGC/SSR > will always skip the section cur_victim_sec points to.
Then, we can get another loop before using it by BGGC/SSR. > > So could we reset cur_victim_sec in the end of FGGC? > > Thanks, > > > > >> > >> Thanks, > >> > >>> > >>> Thanks, > >>> > >>>> > >>>> Thanks, > >>>> > >>>>> > >>>>>> > >>>>>> Thanks, > >>>>>> > >>>>>>> sbi->cur_victim_sec = NULL_SEGNO; > >>>>>>> > >>>>>>> if (sync) > >>>>>>> > >>>>> . > >>>>> > >>> . > >>> > > . > >
