linux-kernel - Re: [f2fs-dev] [PATCH 2/3] f2fs: run GCs synchronously given user requests

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Message-ID: <Yq+kiXPyBsXgdYb2@google.com>
Date:   Sun, 19 Jun 2022 15:34:49 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/3] f2fs: run GCs synchronously given user
 requests

On 06/19, Chao Yu wrote:
> On 2022/6/18 6:31, Jaegeuk Kim wrote:
> > When users set GC_URGENT or GC_MID, they expected to do GCs right away.
> > But, there's a condition to bypass it. Let's indicate we need to do now
> > in the thread.
> 
> .should_migrate_blocks is used to force migrating blocks in full
> section, so what is the condition here? GC should not never select
> a full section, right?

I think it'll move a full section given .victim_segno is not NULL_SEGNO,
as __get_victim will give a dirty segment all the time. wdyt?

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> > ---
> >   fs/f2fs/gc.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index d5fb426e0747..f4aa3c88118b 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -37,7 +37,6 @@ static int gc_thread_func(void *data)
> >   	unsigned int wait_ms;
> >   	struct f2fs_gc_control gc_control = {
> >   		.victim_segno = NULL_SEGNO,
> > -		.should_migrate_blocks = false,
> >   		.err_gc_skipped = false };
> >   	wait_ms = gc_th->min_sleep_time;
> > @@ -113,7 +112,10 @@ static int gc_thread_func(void *data)
> >   				sbi->gc_mode == GC_URGENT_MID) {
> >   			wait_ms = gc_th->urgent_sleep_time;
> >   			f2fs_down_write(&sbi->gc_lock);
> > +			gc_control.should_migrate_blocks = true;
> >   			goto do_gc;
> > +		} else {
> > +			gc_control.should_migrate_blocks = false;
> >   		}
> >   		if (foreground) {
> > @@ -139,7 +141,9 @@ static int gc_thread_func(void *data)
> >   		if (!foreground)
> >   			stat_inc_bggc_count(sbi->stat_info);
> > -		sync_mode = F2FS_OPTION(sbi).bggc_mode == BGGC_MODE_SYNC;
> > +		sync_mode = F2FS_OPTION(sbi).bggc_mode == BGGC_MODE_SYNC ||
> > +				sbi->gc_mode == GC_URGENT_HIGH ||
> > +				sbi->gc_mode == GC_URGENT_MID;
> >   		/* foreground GC was been triggered via f2fs_balance_fs() */
> >   		if (foreground)