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Date:   Thu, 27 Oct 2022 20:22:57 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     Yangtao Li <frank.li@vivo.com>,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] f2fs: introducr gc_urgent_idle_remaining sysfs
 node and mark gc_urgent_high_remaining node deprecated
Message-ID: <Y1tLEVYQjj2qC3I7@google.com>
References: <20221025065025.35017-1-frank.li@vivo.com>
 <20221025065025.35017-2-frank.li@vivo.com>
 <cd6d15e3-b692-d3c1-0f01-33e632f5f94c@kernel.org>
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On 10/28, Chao Yu wrote:
> On 2022/10/25 14:50, Yangtao Li wrote:
> > Added a new sysfs node called gc_urgent_idle_remaining.
> > The user can set the trial count limit for GC urgent and
> > idle mode with this value. If GC thread gets to the limit,
> > the mode will turn back to GC normal mode finally.
> > 
> > This method is not only applicable to gc_urgent_high,
> > but applicable to all gc modes. Also mark
> > gc_urgent_high_remaining as deprecated, so that the node
> > can be removed in the future.
> > 
> > Signed-off-by: Yangtao Li <frank.li@vivo.com>
> > ---
> >   Documentation/ABI/testing/sysfs-fs-f2fs |  8 ++++++++
> >   fs/f2fs/f2fs.h                          |  6 ++++--
> >   fs/f2fs/gc.c                            | 12 ++++++------
> >   fs/f2fs/super.c                         |  2 +-
> >   fs/f2fs/sysfs.c                         | 14 ++++++++++----
> >   5 files changed, 29 insertions(+), 13 deletions(-)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> > index 483639fb727b..859c4e53a846 100644
> > --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> > +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> > @@ -598,6 +598,14 @@ Contact:	"Daeho Jeong" <daehojeong@google.com>
> >   Description:	You can set the trial count limit for GC urgent high mode with this value.
> >   		If GC thread gets to the limit, the mode will turn back to GC normal mode.
> >   		By default, the value is zero, which means there is no limit like before.
> > +		<deprecated>
> > +
> > +What:		/sys/fs/f2fs/<disk>/gc_urgent_idle_remaining
> > +Date:		October 2022
> > +Contact:	"Yangtao Li" <frank.li@vivo.com>
> > +Description:	You can set the trial count limit for GC urgent and idle mode with this value.
> > +		If GC thread gets to the limit, the mode will turn back to GC normal mode.
> > +		By default, the value is zero, which means there is no limit like before.
> >   What:		/sys/fs/f2fs/<disk>/max_roll_forward_node_blocks
> >   Date:		January 2022
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index e6355a5683b7..2bad69cf9fd9 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1734,8 +1734,10 @@ struct f2fs_sb_info {
> >   	unsigned int cur_victim_sec;		/* current victim section num */
> >   	unsigned int gc_mode;			/* current GC state */
> >   	unsigned int next_victim_seg[2];	/* next segment in victim section */
> > -	spinlock_t gc_urgent_high_lock;
> > -	unsigned int gc_urgent_high_remaining;	/* remaining trial count for GC_URGENT_HIGH */
> > +	spinlock_t gc_urgent_idle_lock;
> > +	/* remaining trial count for GC_URGENT_* and GC_IDLE_* */
> > +	unsigned int gc_urgent_idle_remaining;
> > +	unsigned int gc_urgent_high_remaining;	/* deprecated */
> >   	/* for skip statistic */
> >   	unsigned long long skipped_gc_rwsem;		/* FG_GC only */
> > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> > index e0ff99c7e3f2..0ed5b3c5922c 100644
> > --- a/fs/f2fs/gc.c
> > +++ b/fs/f2fs/gc.c
> > @@ -152,14 +152,14 @@ static int gc_thread_func(void *data)
> >   		/* balancing f2fs's metadata periodically */
> >   		f2fs_balance_fs_bg(sbi, true);
> >   next:
> > -		if (sbi->gc_mode == GC_URGENT_HIGH) {
> > -			spin_lock(&sbi->gc_urgent_high_lock);
> > -			if (sbi->gc_urgent_high_remaining) {
> > -				sbi->gc_urgent_high_remaining--;
> > -				if (!sbi->gc_urgent_high_remaining)
> > +		if (sbi->gc_mode != GC_NORMAL) {
> > +			spin_lock(&sbi->gc_urgent_idle_lock);
> > +			if (sbi->gc_urgent_idle_remaining) {
> > +				sbi->gc_urgent_idle_remaining--;
> > +				if (!sbi->gc_urgent_idle_remaining)
> >   					sbi->gc_mode = GC_NORMAL;
> >   			}
> > -			spin_unlock(&sbi->gc_urgent_high_lock);
> > +			spin_unlock(&sbi->gc_urgent_idle_lock);
> >   		}
> >   		sb_end_write(sbi->sb);
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 3834ead04620..f90a8c0a53ec 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -3616,7 +3616,7 @@ static void init_sb_info(struct f2fs_sb_info *sbi)
> >   	sbi->seq_file_ra_mul = MIN_RA_MUL;
> >   	sbi->max_fragment_chunk = DEF_FRAGMENT_SIZE;
> >   	sbi->max_fragment_hole = DEF_FRAGMENT_SIZE;
> > -	spin_lock_init(&sbi->gc_urgent_high_lock);
> > +	spin_lock_init(&sbi->gc_urgent_idle_lock);
> >   	atomic64_set(&sbi->current_atomic_write, 0);
> >   	sbi->dir_level = DEF_DIR_LEVEL;
> > diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> > index df27afd71ef4..2b1c653b37cf 100644
> > --- a/fs/f2fs/sysfs.c
> > +++ b/fs/f2fs/sysfs.c
> > @@ -531,10 +531,14 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
> >   		return count;
> >   	}
> > -	if (!strcmp(a->attr.name, "gc_urgent_high_remaining")) {
> > -		spin_lock(&sbi->gc_urgent_high_lock);
> > -		sbi->gc_urgent_high_remaining = t;
> > -		spin_unlock(&sbi->gc_urgent_high_lock);
> > +	/* deprecated */
> > +	if (!strcmp(a->attr.name, "gc_urgent_high_remaining"))
> > +		return -EINVAL;
> 
> How about those users who has already used these interface... it breaks
> the usage.
> 
> It needs to keep old interface and tag as deprecated, and recommend user
> to use new interface you introduced.

I feel that this is not a super critical node, so how about just removing it?

> 
> e.g.:
> 
> What:           /sys/fs/f2fs/<disk>/features
> Date:           July 2017
> Contact:        "Jaegeuk Kim" <jaegeuk@kernel.org>
> Description:    <deprecated: should use /sys/fs/f2fs/<disk>/feature_list/
>                 Shows all enabled features in current device.
>                 Supported features:
>                 encryption, blkzoned, extra_attr, projquota, inode_checksum,
>                 flexible_inline_xattr, quota_ino, inode_crtime, lost_found,
>                 verity, sb_checksum, casefold, readonly, compression, pin_file.
> 
> Thanks,
> 
> > +
> > +	if (!strcmp(a->attr.name, "gc_urgent_idle_remaining")) {
> > +		spin_lock(&sbi->gc_urgent_idle_lock);
> > +		sbi->gc_urgent_idle_remaining = t;
> > +		spin_unlock(&sbi->gc_urgent_idle_lock);
> >   		return count;
> >   	}
> > @@ -826,6 +830,7 @@ F2FS_RW_ATTR(FAULT_INFO_TYPE, f2fs_fault_info, inject_type, inject_type);
> >   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, data_io_flag, data_io_flag);
> >   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, node_io_flag, node_io_flag);
> >   F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_urgent_high_remaining, gc_urgent_high_remaining);
> > +F2FS_RW_ATTR(F2FS_SBI, f2fs_sb_info, gc_urgent_idle_remaining, gc_urgent_idle_remaining);
> >   F2FS_RW_ATTR(CPRC_INFO, ckpt_req_control, ckpt_thread_ioprio, ckpt_thread_ioprio);
> >   F2FS_GENERAL_RO_ATTR(dirty_segments);
> >   F2FS_GENERAL_RO_ATTR(free_segments);
> > @@ -953,6 +958,7 @@ static struct attribute *f2fs_attrs[] = {
> >   	ATTR_LIST(data_io_flag),
> >   	ATTR_LIST(node_io_flag),
> >   	ATTR_LIST(gc_urgent_high_remaining),
> > +	ATTR_LIST(gc_urgent_idle_remaining),
> >   	ATTR_LIST(ckpt_thread_ioprio),
> >   	ATTR_LIST(dirty_segments),
> >   	ATTR_LIST(free_segments),