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Message-ID: <20230426070101epcms2p7dd8faf06f26216c6e99b1aa0e1dbcbbf@epcms2p7>
Date:   Wed, 26 Apr 2023 16:01:01 +0900
From:   Daejun Park <daejun7.park@...sung.com>
To:     Chao Yu <chao@...nel.org>, Daejun Park <daejun7.park@...sung.com>,
        "jaegeuk@...nel.org" <jaegeuk@...nel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "mhiramat@...nel.org" <mhiramat@...nel.org>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-trace-kernel@...r.kernel.org" 
        <linux-trace-kernel@...r.kernel.org>
CC:     Seokhwan Kim <sukka.kim@...sung.com>,
        Yonggil Song <yonggil.song@...sung.com>,
        beomsu kim <beomsu7.kim@...sung.com>
Subject: RE:(2) [PATCH v2] f2fs: add async reset zone command support

Thank you for your review. I have responded in the comments below.

> On 2023/4/25 16:10, Daejun Park wrote:
> > Changelog:
> > 
> > v1 -> v2
> > Changed to apply the optional async reset write pointer by default.
> > 
> > 
> > This patch enables submit reset zone command asynchornously. It helps
> > decrease average latency of write IOs in high utilization scenario by
> > faster checkpointing.
> > 
> > Signed-off-by: Daejun Park <daejun7.park@...sung.com>
> > ---
> >   fs/f2fs/segment.c           | 95 ++++++++++++++++++++++++++++++++++---
> >   include/trace/events/f2fs.h | 18 ++++++-
> >   2 files changed, 105 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 82430f80c5da..27074a6eaf20 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1195,6 +1195,46 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi,
> >   static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
> >                                   struct block_device *bdev, block_t lstart,
> >                                   block_t start, block_t len);
> > +
> > +#ifdef CONFIG_BLK_DEV_ZONED
> > +static int __submit_zone_reset_cmd(struct f2fs_sb_info *sbi,
> > +                                   struct discard_cmd *dc, blk_opf_t flag,
> > +                                   struct list_head *wait_list,
> > +                                   unsigned int *issued)
> > +{
> > +        struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info;
> > +        struct block_device *bdev = dc->bdev;
> > +        struct bio *bio = bio_alloc(bdev, 0, REQ_OP_ZONE_RESET | flag, GFP_NOFS);
> > +        unsigned long flags;
> > +
> > +        trace_f2fs_issue_reset_zone(bdev, SECTOR_FROM_BLOCK(dc->di.start));
> 
> trace_f2fs_issue_reset_zone(bdev, dc->di.start); ?

I will change it. 

> 
> > +
> > +        spin_lock_irqsave(&dc->lock, flags);
> > +        dc->state = D_SUBMIT;
> > +        dc->bio_ref++;
> > +        spin_unlock_irqrestore(&dc->lock, flags);
> > +
> > +        if (issued)
> > +                (*issued)++;
> > +
> > +        atomic_inc(&dcc->queued_discard);
> > +        dc->queued++;
> > +        list_move_tail(&dc->list, wait_list);
> > +
> > +        /* sanity check on discard range */
> > +        __check_sit_bitmap(sbi, dc->di.lstart, dc->di.lstart + dc->di.len);
> > +
> > +        bio->bi_iter.bi_sector = SECTOR_FROM_BLOCK(dc->di.start);
> > +        bio->bi_private = dc;
> > +        bio->bi_end_io = f2fs_submit_discard_endio;
> > +        submit_bio(bio);
> > +
> > +        atomic_inc(&dcc->issued_discard);
> > +
> > +        return 0;
> 
> Unneeded return value?

I will change return type of this function as void.

> > +}
> > +#endif
> > +
> >   /* this function is copied from blkdev_issue_discard from block/blk-lib.c */
> >   static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
> >                                   struct discard_policy *dpolicy,
> > @@ -1216,6 +1256,11 @@ static int __submit_discard_cmd(struct f2fs_sb_info *sbi,
> >           if (is_sbi_flag_set(sbi, SBI_NEED_FSCK))
> >                   return 0;
> >   
> > +#ifdef CONFIG_BLK_DEV_ZONED
> > +        if (f2fs_sb_has_blkzoned(sbi) && bdev_is_zoned(bdev))
> > +                return __submit_zone_reset_cmd(sbi, dc, flag, wait_list, issued);
> > +#endif
> > +
> >           trace_f2fs_issue_discard(bdev, dc->di.start, dc->di.len);
> >   
> >           lstart = dc->di.lstart;
> > @@ -1460,21 +1505,42 @@ static void __update_discard_tree_range(struct f2fs_sb_info *sbi,
> >           }
> >   }
> >   
> > +#ifdef CONFIG_BLK_DEV_ZONED
> > +static void __queue_zone_reset_cmd(struct f2fs_sb_info *sbi,
> > +                struct block_device *bdev, block_t blkstart, block_t blklen)
> 
> block_t lblkstart,
> 
> > +{
> > +        block_t lblkstart = blkstart;
> 
> block_t blkstart = lblkstart;

I refactored this function as follows.

static void __queue_zone_reset_cmd(struct f2fs_sb_info *sbi,
		struct block_device *bdev, block_t blkstart, block_t lblkstart,
		block_t blklen)
{
	trace_f2fs_queue_reset_zone(bdev, blkstart);

	mutex_lock(&SM_I(sbi)->dcc_info->cmd_lock);
	__insert_discard_cmd(sbi, bdev, lblkstart, blkstart, blklen);
	mutex_unlock(&SM_I(sbi)->dcc_info->cmd_lock);
}

> 
> > +
> > +        if (f2fs_is_multi_device(sbi)) {
> > +                int devi = f2fs_target_device_index(sbi, blkstart);
> > +
> > +                blkstart -= FDEV(devi).start_blk;
> > +        }
> > +
> > +        trace_f2fs_queue_reset_zone(bdev, blkstart);
> > +
> > +        mutex_lock(&SM_I(sbi)->dcc_info->cmd_lock);
> > +        __insert_discard_cmd(sbi, bdev, lblkstart, blkstart, blklen);
> > +        mutex_unlock(&SM_I(sbi)->dcc_info->cmd_lock);
> > +}
> > +#endif
> > +
> >   static void __queue_discard_cmd(struct f2fs_sb_info *sbi,
> >                   struct block_device *bdev, block_t blkstart, block_t blklen)
> >   {
> >           block_t lblkstart = blkstart;
> >   
> > +        trace_f2fs_queue_discard(bdev, blkstart, blklen);
> 
> If device doesn't support discard, it's better not show above tracepoint?

This issue was caused by a mistake during the merge process. I have fixed it.

> > +
> >           if (!f2fs_bdev_support_discard(bdev))
> >                   return;
> >   
> > -        trace_f2fs_queue_discard(bdev, blkstart, blklen);
> > -
> >           if (f2fs_is_multi_device(sbi)) {
> >                   int devi = f2fs_target_device_index(sbi, blkstart);
> >   
> >                   blkstart -= FDEV(devi).start_blk;
> >           }
> > +
> >           mutex_lock(&SM_I(sbi)->dcc_info->cmd_lock);
> >           __update_discard_tree_range(sbi, bdev, lblkstart, blkstart, blklen);
> >           mutex_unlock(&SM_I(sbi)->dcc_info->cmd_lock);
> > @@ -1725,7 +1791,18 @@ static void f2fs_wait_discard_bio(struct f2fs_sb_info *sbi, block_t blkaddr)
> >           dc = __lookup_discard_cmd(sbi, blkaddr);
> >           if (dc) {
> >                   if (dc->state == D_PREP) {
> > -                        __punch_discard_cmd(sbi, dc, blkaddr);
> > +                        if (f2fs_sb_has_blkzoned(sbi) &&
> > +                            bdev_is_zoned(dc->bdev)) {
> > +                                struct discard_policy dpolicy;
> > +                                /* force submit zone reset */
> > +                                __init_discard_policy(sbi, &dpolicy,
> > +                                                      DPOLICY_FORCE, 1);
> > +                                __submit_discard_cmd(sbi, &dpolicy, dc, NULL);
> 
> Can we call __submit_zone_reset_cmd() directly?

Sure. I refactored as follows.

	if (dc) {
		if (f2fs_sb_has_blkzoned(sbi) && bdev_is_zoned(dc->bdev)) {
			if (dc->state == D_PREP)
				__submit_zone_reset_cmd(sbi, dc, REQ_SYNC,
							&dcc->wait_list, NULL);
			dc->ref++;
			need_wait = true;
		} else {
			if (dc->state == D_PREP) {
				__punch_discard_cmd(sbi, dc, blkaddr);
			} else {
				dc->ref++;
				need_wait = true;
			}
		}
	}

Thanks,

> 
> Thanks,
> 
> > +                                dc->ref++;
> > +                                need_wait = true;
> > +                        } else {
> > +                                __punch_discard_cmd(sbi, dc, blkaddr);
> > +                        }
> >                   } else {
> >                           dc->ref++;
> >                           need_wait = true;
> > @@ -1875,9 +1952,15 @@ static int __f2fs_issue_discard_zone(struct f2fs_sb_info *sbi,
> >                                    blkstart, blklen);
> >                           return -EIO;
> >                   }
> > -                trace_f2fs_issue_reset_zone(bdev, blkstart);
> > -                return blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,
> > -                                        sector, nr_sects, GFP_NOFS);
> > +
> > +                if (unlikely(!is_sbi_flag_set(sbi, SBI_POR_DOING))) {
> > +                        trace_f2fs_issue_reset_zone(bdev, blkstart);
> > +                        return blkdev_zone_mgmt(bdev, REQ_OP_ZONE_RESET,
> > +                                                sector, nr_sects, GFP_NOFS);
> > +                }
> > +
> > +                __queue_zone_reset_cmd(sbi, bdev, lblkstart, blklen);
> > +                return 0;
> >           }
> >   
> >           /* For conventional zones, use regular discard if supported */
> > diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
> > index 99cbc5949e3c..ee1477de8324 100644
> > --- a/include/trace/events/f2fs.h
> > +++ b/include/trace/events/f2fs.h
> > @@ -1512,7 +1512,7 @@ DEFINE_EVENT(f2fs_discard, f2fs_remove_discard,
> >           TP_ARGS(dev, blkstart, blklen)
> >   );
> >   
> > -TRACE_EVENT(f2fs_issue_reset_zone,
> > +DECLARE_EVENT_CLASS(f2fs_reset_zone,
> >   
> >           TP_PROTO(struct block_device *dev, block_t blkstart),
> >   
> > @@ -1528,11 +1528,25 @@ TRACE_EVENT(f2fs_issue_reset_zone,
> >                   __entry->blkstart = blkstart;
> >           ),
> >   
> > -        TP_printk("dev = (%d,%d), reset zone at block = 0x%llx",
> > +        TP_printk("dev = (%d,%d), zone at block = 0x%llx",
> >                   show_dev(__entry->dev),
> >                   (unsigned long long)__entry->blkstart)
> >   );
> >   
> > +DEFINE_EVENT(f2fs_reset_zone, f2fs_queue_reset_zone,
> > +
> > +        TP_PROTO(struct block_device *dev, block_t blkstart),
> > +
> > +        TP_ARGS(dev, blkstart)
> > +);
> > +
> > +DEFINE_EVENT(f2fs_reset_zone, f2fs_issue_reset_zone,
> > +
> > +        TP_PROTO(struct block_device *dev, block_t blkstart),
> > +
> > +        TP_ARGS(dev, blkstart)
> > +);
> > +
> >   TRACE_EVENT(f2fs_issue_flush,
> >   
> >           TP_PROTO(struct block_device *dev, unsigned int nobarrier,

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