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

[Daeho Jeong]

On Tue, Jan 16, 2024 at 2:58 PM Daeho Jeong <daeho43@xxxxxxxxx> wrote:
>
> On Tue, Jan 16, 2024 at 6:36 AM Wenjie Qi <qwjhust@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> >  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?

Sorry, I was confused. It would work. However, it might be a little clumsy.
How about using a data structure like a counting semaphore?
We can decrease it as we open a zone and increase it as we close a zone.

>
> >
> >  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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