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Message-ID: <42c23c83-1914-e8dd-c765-df3d6d872532@kernel.org>
Date: Wed, 11 May 2022 16:53:41 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 4/5] f2fs: do not stop GC when requiring a free
section
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@...nel.org>
>>> ---
>>> 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.
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,
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