linux-kernel - Re: [PATCH 03/15] md: use folio for bb

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Message-ID: <CALTww28tZDgBVy=G=doJQ3yfWtuiLk5QoMMyL1cmveacXHLynA@mail.gmail.com>
Date: Mon, 19 Jan 2026 11:03:56 +0800
From: Xiao Ni <xni@...hat.com>
To: linan666@...weicloud.com
Cc: song@...nel.org, yukuai@...as.com, linux-raid@...r.kernel.org, 
	linux-kernel@...r.kernel.org, yangerkun@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH 03/15] md: use folio for bb_folio

On Wed, Dec 17, 2025 at 8:11 PM <linan666@...weicloud.com> wrote:
>
> From: Li Nan <linan122@...wei.com>
>
> Convert bio_page to bio_folio and use it throughout.
>
> Signed-off-by: Li Nan <linan122@...wei.com>
> ---
>  drivers/md/md.h |  3 ++-
>  drivers/md/md.c | 25 +++++++++++++------------
>  2 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/md/md.h b/drivers/md/md.h
> index 410f8a6b75e7..aa6d9df50fd0 100644
> --- a/drivers/md/md.h
> +++ b/drivers/md/md.h
> @@ -144,7 +144,8 @@ struct md_rdev {
>         struct block_device *bdev;      /* block device handle */
>         struct file *bdev_file;         /* Handle from open for bdev */
>
> -       struct page     *sb_page, *bb_page;
> +       struct page     *sb_page;
> +       struct folio    *bb_folio;
>         int             sb_loaded;
>         __u64           sb_events;
>         sector_t        data_offset;    /* start of data in array */
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 9dfd6f8da5b8..0732bbcdb95d 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -1073,9 +1073,9 @@ void md_rdev_clear(struct md_rdev *rdev)
>                 rdev->sb_start = 0;
>                 rdev->sectors = 0;
>         }
> -       if (rdev->bb_page) {
> -               put_page(rdev->bb_page);
> -               rdev->bb_page = NULL;
> +       if (rdev->bb_folio) {
> +               folio_put(rdev->bb_folio);
> +               rdev->bb_folio = NULL;
>         }
>         badblocks_exit(&rdev->badblocks);
>  }
> @@ -1909,9 +1909,10 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
>
>         rdev->desc_nr = le32_to_cpu(sb->dev_number);
>
> -       if (!rdev->bb_page) {
> -               rdev->bb_page = alloc_page(GFP_KERNEL);
> -               if (!rdev->bb_page)
> +       if (!rdev->bb_folio) {
> +               rdev->bb_folio = folio_alloc(GFP_KERNEL, 0);
> +
> +               if (!rdev->bb_folio)
>                         return -ENOMEM;
>         }
>         if ((le32_to_cpu(sb->feature_map) & MD_FEATURE_BAD_BLOCKS) &&
> @@ -1930,10 +1931,10 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
>                 if (offset == 0)
>                         return -EINVAL;
>                 bb_sector = (long long)offset;
> -               if (!sync_page_io(rdev, bb_sector, sectors << 9,
> -                                 rdev->bb_page, REQ_OP_READ, true))
> +               if (!sync_folio_io(rdev, bb_sector, sectors << 9, 0,
> +                                 rdev->bb_folio, REQ_OP_READ, true))
>                         return -EIO;
> -               bbp = (__le64 *)page_address(rdev->bb_page);
> +               bbp = (__le64 *)folio_address(rdev->bb_folio);
>                 rdev->badblocks.shift = sb->bblog_shift;
>                 for (i = 0 ; i < (sectors << (9-3)) ; i++, bbp++) {
>                         u64 bb = le64_to_cpu(*bbp);
> @@ -2300,7 +2301,7 @@ static void super_1_sync(struct mddev *mddev, struct md_rdev *rdev)
>                 md_error(mddev, rdev);
>         else {
>                 struct badblocks *bb = &rdev->badblocks;
> -               __le64 *bbp = (__le64 *)page_address(rdev->bb_page);
> +               __le64 *bbp = (__le64 *)folio_address(rdev->bb_folio);
>                 u64 *p = bb->page;
>                 sb->feature_map |= cpu_to_le32(MD_FEATURE_BAD_BLOCKS);
>                 if (bb->changed) {
> @@ -2953,7 +2954,7 @@ void md_update_sb(struct mddev *mddev, int force_change)
>                                 md_write_metadata(mddev, rdev,
>                                                   rdev->badblocks.sector,
>                                                   rdev->badblocks.size << 9,
> -                                                 rdev->bb_page, 0);
> +                                                 folio_page(rdev->bb_folio, 0), 0);
>                                 rdev->badblocks.size = 0;
>                         }
>
> @@ -3809,7 +3810,7 @@ int md_rdev_init(struct md_rdev *rdev)
>         rdev->sb_events = 0;
>         rdev->last_read_error = 0;
>         rdev->sb_loaded = 0;
> -       rdev->bb_page = NULL;
> +       rdev->bb_folio = NULL;
>         atomic_set(&rdev->nr_pending, 0);
>         atomic_set(&rdev->read_errors, 0);
>         atomic_set(&rdev->corrected_errors, 0);
> --
> 2.39.2
>

Hi Nan

Bad block page is only one single page. I don't think it's necessary
to use folio here. And it uses folio_page to get the page again. Or do
you plan to replace all page apis to folio apis? Looking through all
patches, sync_page_io is not removed. In patch02, it says sync_page_io
will be removed. So maybe it's better to switch bb_page to bb_folio in
your second patch set? And this patch set only focuses on replacing
sync pages with folio. It's my 2 cents point. If you think it's better
to change the bad block page here, I'm still ok.

Best Regards
Xiao