RE: [PATCH v2] f2fs: fix to correct freed section number during gc

From: Chao Yu
Date: Mon Sep 28 2015 - 05:41:31 EST


> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@xxxxxxxxxx]
> Sent: Saturday, September 26, 2015 2:04 AM
> To: Chao Yu
> Cc: linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2] f2fs: fix to correct freed section number during gc
>
> On Fri, Sep 25, 2015 at 05:50:55PM +0800, Chao Yu wrote:
> > This patch fixes to maintain the right section count freed in garbage
> > collecting when triggering a foreground gc.
> >
> > Besides, when a foreground gc is running on current selected section, once
> > we fail to gc one segment, it's better to abandon gcing the left segments
> > in current section, because anyway we will select next victim for
> > foreground gc, so gc on the left segments in previous section will become
> > overhead and also cause the long latency for caller.
> >
> > Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
> > ---
> > v2:
> > o avoid calc the wrong value when freed segments across sections.
> > fs/f2fs/gc.c | 22 +++++++++++++++++-----
> > 1 file changed, 17 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index e932740..256ebd4 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -802,7 +802,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi)
> > unsigned int segno = NULL_SEGNO;
> > unsigned int i;
> > int gc_type = BG_GC;
> > - int nfree = 0;
> > + int sec_freed = 0, seg_freed;
> > int ret = -1;
> > struct cp_control cpc;
> > struct gc_inode_list gc_list = {
> > @@ -817,7 +817,7 @@ gc_more:
> > if (unlikely(f2fs_cp_error(sbi)))
> > goto stop;
> >
> > - if (gc_type == BG_GC && has_not_enough_free_secs(sbi, nfree)) {
> > + if (gc_type == BG_GC && has_not_enough_free_secs(sbi, sec_freed)) {
> > gc_type = FG_GC;
> > if (__get_victim(sbi, &segno, gc_type) || prefree_segments(sbi))
> > write_checkpoint(sbi, &cpc);
> > @@ -833,13 +833,25 @@ gc_more:
> > ra_meta_pages(sbi, GET_SUM_BLOCK(sbi, segno), sbi->segs_per_sec,
> > META_SSA);
> >
> > - for (i = 0; i < sbi->segs_per_sec; i++)
> > - nfree += do_garbage_collect(sbi, segno + i, &gc_list, gc_type);
> > + for (i = 0, seg_freed = 0; i < sbi->segs_per_sec; i++) {
> > + /*
> > + * for FG_GC case, halt gcing left segments once failed one
> > + * of segments in selected section to avoid long latency.
> > + */
> > + if (!do_garbage_collect(sbi, segno + i, &gc_list, gc_type) &&
> > + gc_type == FG_GC)
> > + break;
> > + if (gc_type == FG_GC)
> > + seg_freed++;
> > + }
>
> How about?
>
> if (i == sbi->segs_per_sec && gc_type == FG_GC)
> sec_free++;

I'll update it. See the following v3 patch.

Thanks,

>
> > +
> > + if (seg_freed == sbi->segs_per_sec)
> > + sec_freed++;
> >
> > if (gc_type == FG_GC)
> > sbi->cur_victim_sec = NULL_SEGNO;
> >
> > - if (has_not_enough_free_secs(sbi, nfree))
> > + if (has_not_enough_free_secs(sbi, sec_freed))
> > goto gc_more;
> >
> > if (gc_type == FG_GC)
> > --
> > 2.5.2

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