Re: [PATCH 15/17] gfs2: use bdev_rw_virt in gfs2_read_super

Damien Le Moal
2025-04-24T06:23:17Z

On 4/22/25 23:26, Christoph Hellwig wrote:
> Switch gfs2_read_super to allocate the superblock buffer using kmalloc
> which falls back to the page allocator for PAGE_SIZE allocation but
> gives us a kernel virtual address and then use bdev_rw_virt to perform
> the synchronous read into it.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

One nit below.

> ---
> fs/gfs2/ops_fstype.c | 24 +++++++++---------------
> 1 file changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
> index e83d293c3614..7c1014ba7ac7 100644
> --- a/fs/gfs2/ops_fstype.c
> +++ b/fs/gfs2/ops_fstype.c
> @@ -226,28 +226,22 @@ static void gfs2_sb_in(struct gfs2_sbd *sdp, const struct gfs2_sb *str)
>
> static int gfs2_read_super(struct gfs2_sbd *sdp, sector_t sector, int silent)
> {
> - struct super_block *sb = sdp->sd_vfs;
> - struct page *page;
> - struct bio_vec bvec;
> - struct bio bio;
> + struct gfs2_sb *sb;
> int err;
>
> - page = alloc_page(GFP_KERNEL);
> - if (unlikely(!page))
> + sb = kmalloc(PAGE_SIZE, GFP_KERNEL);
> + if (unlikely(!sb))
> return -ENOMEM;
> -
> - bio_init(&bio, sb->s_bdev, &bvec, 1, REQ_OP_READ | REQ_META);
> - bio.bi_iter.bi_sector = sector * (sb->s_blocksize >> 9);
> - __bio_add_page(&bio, page, PAGE_SIZE, 0);
> -
> - err = submit_bio_wait(&bio);
> + err = bdev_rw_virt(sdp->sd_vfs->s_bdev,
> + sector * (sdp->sd_vfs->s_blocksize >> 9), sb, PAGE_SIZE,

While at it, use SECTOR_SHIFT here ?

> + REQ_OP_READ | REQ_META);
> if (err) {
> pr_warn("error %d reading superblock\n", err);
> - __free_page(page);
> + kfree(sb);
> return err;
> }
> - gfs2_sb_in(sdp, page_address(page));
> - __free_page(page);
> + gfs2_sb_in(sdp, sb);
> + kfree(sb);
> return gfs2_check_sb(sdp, silent);
> }
>

--
Damien Le Moal
Western Digital Research