Re: [f2fs-dev] [PATCH 4/5] f2fs: do not stop GC when requiring a free section

From: Jaegeuk Kim
Date: Wed May 11 2022 - 12:48:01 EST

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In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 4/5] f2fs: do not stop GC when requiring a free section"
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On 05/11, Chao Yu wrote:
> On 2022/5/10 0:55, Jaegeuk Kim wrote:
> > On 05/08, Chao Yu wrote:
> > > On 2022/5/7 7:20, Jaegeuk Kim wrote:
> > > > The f2fs_gc uses a bitmap to indicate pinned sections, but when disabling
> > > > chckpoint, we call f2fs_gc() with NULL_SEGNO which selects the same dirty
> > > > segment as a victim all the time, resulting in checkpoint=disable failure,
> > > > for example. Let's pick another one, if we fail to collect it.
> > > >
> > > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > > > ---
> > > > fs/f2fs/f2fs.h | 1 +
> > > > fs/f2fs/file.c | 12 ++++++++----
> > > > fs/f2fs/gc.c | 11 +++++++----
> > > > fs/f2fs/segment.c | 3 ++-
> > > > fs/f2fs/super.c | 3 ++-
> > > > include/trace/events/f2fs.h | 11 ++++++++---
> > > > 6 files changed, 28 insertions(+), 13 deletions(-)
> > > >
> > > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > > index d49b9b476592..27871f6efb01 100644
> > > > --- a/fs/f2fs/f2fs.h
> > > > +++ b/fs/f2fs/f2fs.h
> > > > @@ -1282,6 +1282,7 @@ struct f2fs_gc_control {
> > > > bool no_bg_gc; /* check the space and stop bg_gc */
> > > > bool should_migrate_blocks; /* should migrate blocks */
> > > > bool err_gc_skipped; /* return EAGAIN if GC skipped */
> > > > + unsigned int nr_free_secs; /* # of free sections to do GC */
> > > > };
> > > > /* For s_flag in struct f2fs_sb_info */
> > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > > index 0e7d101c3e65..7072c2b86b2f 100644
> > > > --- a/fs/f2fs/file.c
> > > > +++ b/fs/f2fs/file.c
> > > > @@ -1650,7 +1650,8 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
> > > > struct f2fs_gc_control gc_control = { .victim_segno = NULL_SEGNO,
> > > > .init_gc_type = FG_GC,
> > > > .should_migrate_blocks = false,
> > > > - .err_gc_skipped = true };
> > > > + .err_gc_skipped = true,
> > > > + .nr_free_secs = 0 };
> > > > pgoff_t pg_start, pg_end;
> > > > loff_t new_size = i_size_read(inode);
> > > > loff_t off_end;
> > > > @@ -2453,7 +2454,8 @@ static int f2fs_ioc_gc(struct file *filp, unsigned long arg)
> > > > struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> > > > struct f2fs_gc_control gc_control = { .victim_segno = NULL_SEGNO,
> > > > .no_bg_gc = false,
> > > > - .should_migrate_blocks = false };
> > > > + .should_migrate_blocks = false,
> > > > + .nr_free_secs = 0 };
> > > > __u32 sync;
> > > > int ret;
> > > > @@ -2494,7 +2496,8 @@ static int __f2fs_ioc_gc_range(struct file *filp, struct f2fs_gc_range *range)
> > > > .init_gc_type = range->sync ? FG_GC : BG_GC,
> > > > .no_bg_gc = false,
> > > > .should_migrate_blocks = false,
> > > > - .err_gc_skipped = range->sync };
> > > > + .err_gc_skipped = range->sync,
> > > > + .nr_free_secs = 0 };
> > > > u64 end;
> > > > int ret;
> > > > @@ -2940,7 +2943,8 @@ static int f2fs_ioc_flush_device(struct file *filp, unsigned long arg)
> > > > struct f2fs_gc_control gc_control = {
> > > > .init_gc_type = FG_GC,
> > > > .should_migrate_blocks = true,
> > > > - .err_gc_skipped = true };
> > > > + .err_gc_skipped = true,
> > > > + .nr_free_secs = 0 };
> > > > int ret;
> > > > if (!capable(CAP_SYS_ADMIN))
> > > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > > > index ec3f6f876e76..f63576ff1c2d 100644
> > > > --- a/fs/f2fs/gc.c
> > > > +++ b/fs/f2fs/gc.c
> > > > @@ -147,6 +147,7 @@ static int gc_thread_func(void *data)
> > > > gc_control.init_gc_type = sync_mode ? FG_GC : BG_GC;
> > > > gc_control.no_bg_gc = foreground;
> > > > + gc_control.nr_free_secs = foreground ? 1 : 0;
> > >
> > > if init_gc_type is BG_GC, sec_freed won't increase for background GC due to
> > > below statement:
> > >
> > > if (gc_type == FG_GC &&
> > > get_valid_blocks(sbi, segno, false) == 0)
> > > seg_freed++;
> > >
> > > It may cause gc thread migrates lots of segments in each round?
> >
> > BG_GC include two cases, f2fs_balance_fs and gc thread for GC_MERGE, both of
> > which are no_bg_gc=true. So, I think this would be enough. Other cases that sets
> > nr_free_secs to 1 should be FG_GC only.
>
> What I mean is, in below check condition, for BG_GC cases,
> if !has_not_enough_free_secs(sbi, sec_freed, 0) is true, since sec_freed will
> never be increased due to above condition, so it will goto gc_more label all
> the time, result in looping until migrating all dirty segments.

I mean gc_control->nr_free_secs should be 0.

>
> Thanks,
>
> >
> > >
> > > if ((gc_control->init_gc_type == FG_GC ||
> > > !has_not_enough_free_secs(sbi, sec_freed, 0))) {
> > > if (sec_freed < gc_control->nr_free_secs)
> > > goto gc_more;
> > > goto stop;
> > > }
> > >
> > > > /* if return value is not zero, no victim was selected */
> > > > if (f2fs_gc(sbi, &gc_control))
> > > > @@ -1776,6 +1777,7 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
> > > > unsigned int skipped_round = 0, round = 0;
> > > > trace_f2fs_gc_begin(sbi->sb, gc_type, gc_control->no_bg_gc,
> > > > + gc_control->nr_free_secs,
> > > > get_pages(sbi, F2FS_DIRTY_NODES),
> > > > get_pages(sbi, F2FS_DIRTY_DENTS),
> > > > get_pages(sbi, F2FS_DIRTY_IMETA),
> > > > @@ -1848,11 +1850,12 @@ int f2fs_gc(struct f2fs_sb_info *sbi, struct f2fs_gc_control *gc_control)
> > > > if (gc_type == FG_GC)
> > > > sbi->cur_victim_sec = NULL_SEGNO;
> > > > - if (gc_control->init_gc_type == FG_GC)
> > > > - goto stop;
> > > > -
> > > > - if (!has_not_enough_free_secs(sbi, sec_freed, 0))
> > > > + if ((gc_control->init_gc_type == FG_GC ||
> > > > + !has_not_enough_free_secs(sbi, sec_freed, 0))) {
> > > > + if (sec_freed < gc_control->nr_free_secs)
> > > > + goto gc_more;
> > > > goto stop;
> > > > + }
> > > > if (skipped_round <= MAX_SKIP_GC_COUNT || skipped_round * 2 < round) {
> > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > > > index bc63f0572c64..d6b9231ab0e1 100644
> > > > --- a/fs/f2fs/segment.c
> > > > +++ b/fs/f2fs/segment.c
> > > > @@ -528,7 +528,8 @@ void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
> > > > .init_gc_type = BG_GC,
> > > > .no_bg_gc = true,
> > > > .should_migrate_blocks = false,
> > > > - .err_gc_skipped = false };
> > > > + .err_gc_skipped = false,
> > > > + .nr_free_secs = 1 };
> > >
> > > .init_gc_type is BG_GC, so !has_not_enough_free_secs(sbi, sec_freed, 0) condition
> > > should be enough to exit?
> > >
> > > if ((gc_control->init_gc_type == FG_GC ||
> > > !has_not_enough_free_secs(sbi, sec_freed, 0))) {
> > > if (sec_freed < gc_control->nr_free_secs)
> > > goto gc_more;
> > > goto stop;
> > > }
> > >
> > > Thanks,
> > >
> > > > f2fs_down_write(&sbi->gc_lock);
> > > > f2fs_gc(sbi, &gc_control);
> > > > }
> > > > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > > > index 8b23fa6fc6b7..5d5b35067c3d 100644
> > > > --- a/fs/f2fs/super.c
> > > > +++ b/fs/f2fs/super.c
> > > > @@ -2084,7 +2084,8 @@ static int f2fs_disable_checkpoint(struct f2fs_sb_info *sbi)
> > > > .victim_segno = NULL_SEGNO,
> > > > .init_gc_type = FG_GC,
> > > > .should_migrate_blocks = false,
> > > > - .err_gc_skipped = true };
> > > > + .err_gc_skipped = true,
> > > > + .nr_free_secs = 1 };
> > > > f2fs_down_write(&sbi->gc_lock);
> > > > err = f2fs_gc(sbi, &gc_control);
> > > > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > > > index 6699174977a3..349679a72301 100644
> > > > --- a/include/trace/events/f2fs.h
> > > > +++ b/include/trace/events/f2fs.h
> > > > @@ -653,18 +653,21 @@ TRACE_EVENT(f2fs_background_gc,
> > > > TRACE_EVENT(f2fs_gc_begin,
> > > > TP_PROTO(struct super_block *sb, int gc_type, bool no_bg_gc,
> > > > + unsigned int nr_free_secs,
> > > > long long dirty_nodes, long long dirty_dents,
> > > > long long dirty_imeta, unsigned int free_sec,
> > > > unsigned int free_seg, int reserved_seg,
> > > > unsigned int prefree_seg),
> > > > - TP_ARGS(sb, gc_type, no_bg_gc, dirty_nodes, dirty_dents, dirty_imeta,
> > > > + TP_ARGS(sb, gc_type, no_bg_gc, nr_free_secs, dirty_nodes,
> > > > + dirty_dents, dirty_imeta,
> > > > free_sec, free_seg, reserved_seg, prefree_seg),
> > > > TP_STRUCT__entry(
> > > > __field(dev_t, dev)
> > > > __field(int, gc_type)
> > > > __field(bool, no_bg_gc)
> > > > + __field(unsigned int, nr_free_secs)
> > > > __field(long long, dirty_nodes)
> > > > __field(long long, dirty_dents)
> > > > __field(long long, dirty_imeta)
> > > > @@ -678,6 +681,7 @@ TRACE_EVENT(f2fs_gc_begin,
> > > > __entry->dev = sb->s_dev;
> > > > __entry->gc_type = gc_type;
> > > > __entry->no_bg_gc = no_bg_gc;
> > > > + __entry->nr_free_secs = nr_free_secs;
> > > > __entry->dirty_nodes = dirty_nodes;
> > > > __entry->dirty_dents = dirty_dents;
> > > > __entry->dirty_imeta = dirty_imeta;
> > > > @@ -687,12 +691,13 @@ TRACE_EVENT(f2fs_gc_begin,
> > > > __entry->prefree_seg = prefree_seg;
> > > > ),
> > > > - TP_printk("dev = (%d,%d), gc_type = %s, no_background_GC = %d, nodes = %lld, "
> > > > - "dents = %lld, imeta = %lld, free_sec:%u, free_seg:%u, "
> > > > + TP_printk("dev = (%d,%d), gc_type = %s, no_background_GC = %d, nr_free_secs = %u, "
> > > > + "nodes = %lld, dents = %lld, imeta = %lld, free_sec:%u, free_seg:%u, "
> > > > "rsv_seg:%d, prefree_seg:%u",
> > > > show_dev(__entry->dev),
> > > > show_gc_type(__entry->gc_type),
> > > > __entry->no_bg_gc,
> > > > + __entry->nr_free_secs,
> > > > __entry->dirty_nodes,
> > > > __entry->dirty_dents,
> > > > __entry->dirty_imeta,

Next message: Heiko Carstens: "Re: [PATCH 22/30] panic: Introduce the panic post-reboot notifier list"
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In reply to: Chao Yu: "Re: [f2fs-dev] [PATCH 4/5] f2fs: do not stop GC when requiring a free section"
Next in thread: Chao Yu: "Re: [f2fs-dev] [PATCH 4/5] f2fs: do not stop GC when requiring a free section"
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