linux-kernel - Re: [f2fs-dev] [PATCH v1] f2fs: fix max open zone constraints

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Date: Tue, 16 Jan 2024 14:58:54 -0800
From: Daeho Jeong <daeho43@...il.com>
To: Wenjie Qi <qwjhust@...il.com>
Cc: jaegeuk@...nel.org, chao@...nel.org, 
	linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, 
	hustqwj@...t.edu.cn
Subject: Re: [f2fs-dev] [PATCH v1] f2fs: fix max open zone constraints

On Tue, Jan 16, 2024 at 6:36 AM Wenjie Qi <qwjhust@...il.com> wrote:
>
> We can get the number of remaining available zone
> resources by subtracting the number of active logs from
> the number of max active zones of zoned devices. We can
> use these available zone resources to reduce the number
> of pending bio when switching zones.
> If max active zones is 0, there is no limit.
>
> Signed-off-by: Wenjie Qi <qwjhust@...il.com>
> ---
>  fs/f2fs/data.c  | 32 +++++++++++++++++++++++++-------
>  fs/f2fs/f2fs.h  |  2 ++
>  fs/f2fs/super.c | 11 +++++++++++
>  3 files changed, 38 insertions(+), 7 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index dce8defdf4c7..0b62ca296074 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -392,6 +392,19 @@ static void f2fs_zone_write_end_io(struct bio *bio)
>         complete(&io->zone_wait);
>         f2fs_write_end_io(bio);
>  }
> +
> +static void f2fs_zone_write_end_io_nowait(struct bio *bio)
> +{
> +#ifdef CONFIG_F2FS_IOSTAT
> +       struct bio_iostat_ctx *iostat_ctx = bio->bi_private;
> +       struct f2fs_sb_info *sbi = iostat_ctx->sbi;
> +#else
> +       struct f2fs_sb_info *sbi = (struct f2fs_sb_info *)bio->bi_private;
> +#endif
> +
> +       atomic_inc(&sbi->available_active_zones);
> +       f2fs_write_end_io(bio);
> +}
>  #endif

I don't think this works. Let's assume we start with 2
available_active_zones and 4 active logs.
How about 4 active logs reach at the end of the zones at the same time?

>
>  struct block_device *f2fs_target_device(struct f2fs_sb_info *sbi,
> @@ -1085,14 +1098,19 @@ void f2fs_submit_page_write(struct f2fs_io_info *fio)
>                 goto next;
>  out:
>  #ifdef CONFIG_BLK_DEV_ZONED
> -       if (f2fs_sb_has_blkzoned(sbi) && btype < META &&
> +       if (f2fs_sb_has_blkzoned(sbi) && sbi->max_active_zones && btype < META &&
>                         is_end_zone_blkaddr(sbi, fio->new_blkaddr)) {
> -               bio_get(io->bio);
> -               reinit_completion(&io->zone_wait);
> -               io->bi_private = io->bio->bi_private;
> -               io->bio->bi_private = io;
> -               io->bio->bi_end_io = f2fs_zone_write_end_io;
> -               io->zone_pending_bio = io->bio;
> +               if (!atomic_add_negative(-1, &sbi->available_active_zones)) {
> +                       io->bio->bi_end_io = f2fs_zone_write_end_io_nowait;
> +               } else {
> +                       atomic_inc(&sbi->available_active_zones);
> +                       bio_get(io->bio);
> +                       reinit_completion(&io->zone_wait);
> +                       io->bi_private = io->bio->bi_private;
> +                       io->bio->bi_private = io;
> +                       io->bio->bi_end_io = f2fs_zone_write_end_io;
> +                       io->zone_pending_bio = io->bio;
> +               }
>                 __submit_merged_bio(io);
>         }
>  #endif
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 65294e3b0bef..2aade367ac66 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1551,6 +1551,8 @@ struct f2fs_sb_info {
>
>  #ifdef CONFIG_BLK_DEV_ZONED
>         unsigned int blocks_per_blkz;           /* F2FS blocks per zone */
> +       unsigned int max_active_zones;          /* max zone resources of the zoned device */
> +       atomic_t available_active_zones;        /* remaining zone resources for zone switch */
>  #endif
>
>         /* for node-related operations */
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 206d03c82d96..6711283ff187 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -2385,6 +2385,12 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
>         if (err)
>                 goto restore_opts;
>
> +#ifdef CONFIG_BLK_DEV_ZONED
> +       if (sbi->max_active_zones)
> +               atomic_set(&sbi->available_active_zones,
> +                               sbi->max_active_zones - F2FS_OPTION(sbi).active_logs);
> +#endif
> +
>         /* flush outstanding errors before changing fs state */
>         flush_work(&sbi->s_error_work);
>
> @@ -3932,6 +3938,11 @@ static int init_blkz_info(struct f2fs_sb_info *sbi, int devi)
>         if (!f2fs_sb_has_blkzoned(sbi))
>                 return 0;
>
> +       sbi->max_active_zones = bdev_max_active_zones(bdev);
> +       if (sbi->max_active_zones)
> +               atomic_set(&sbi->available_active_zones,
> +                               sbi->max_active_zones - F2FS_OPTION(sbi).active_logs);
> +

Need to make available_active_zones not be negative, right?
Hmm, need to make sure active_logs should be equal or less than
max_active_zones.

>         zone_sectors = bdev_zone_sectors(bdev);
>         if (!is_power_of_2(zone_sectors)) {
>                 f2fs_err(sbi, "F2FS does not support non power of 2 zone sizes\n");
> --
> 2.34.1
>
>
>
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