Re: [PATCH v2 1/3] Revert "squashfs: provide backing_dev_info in order to disable read-ahead"

[Xiongwei Song <sxwjean@gmail.com>]

On Tue, May 17, 2022 at 4:27 PM Hsin-Yi Wang <hsinyi@chromium.org> wrote:
>
> This reverts commit 9eec1d897139e5de287af5d559a02b811b844d82.
>
> Revert closing the readahead to squashfs since the readahead callback
> for squashfs is implemented.
>
> Suggested-by: Xiongwei Song <sxwjean@gmail.com>

I'd like to use "xiongwei.song@windriver.com" in my tag.

> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> ---
>  fs/squashfs/super.c | 33 ---------------------------------
>  1 file changed, 33 deletions(-)
>
> diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
> index 6d594ba2ed28..32565dafa7f3 100644
> --- a/fs/squashfs/super.c
> +++ b/fs/squashfs/super.c
> @@ -29,7 +29,6 @@
>  #include <linux/module.h>
>  #include <linux/magic.h>
>  #include <linux/xattr.h>
> -#include <linux/backing-dev.h>
>
>  #include "squashfs_fs.h"
>  #include "squashfs_fs_sb.h"
> @@ -113,24 +112,6 @@ static const struct squashfs_decompressor *supported_squashfs_filesystem(
>         return decompressor;
>  }
>
> -static int squashfs_bdi_init(struct super_block *sb)
> -{
> -       int err;
> -       unsigned int major = MAJOR(sb->s_dev);
> -       unsigned int minor = MINOR(sb->s_dev);
> -
> -       bdi_put(sb->s_bdi);
> -       sb->s_bdi = &noop_backing_dev_info;
> -
> -       err = super_setup_bdi_name(sb, "squashfs_%u_%u", major, minor);
> -       if (err)
> -               return err;
> -
> -       sb->s_bdi->ra_pages = 0;
> -       sb->s_bdi->io_pages = 0;
> -
> -       return 0;
> -}
>
>  static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
>  {
> @@ -146,20 +127,6 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc)
>
>         TRACE("Entered squashfs_fill_superblock\n");
>
> -       /*
> -        * squashfs provides 'backing_dev_info' in order to disable read-ahead. For
> -        * squashfs, I/O is not deferred, it is done immediately in read_folio,
> -        * which means the user would always have to wait their own I/O. So the effect
> -        * of readahead is very weak for squashfs. squashfs_bdi_init will set
> -        * sb->s_bdi->ra_pages and sb->s_bdi->io_pages to 0 and close readahead for
> -        * squashfs.
> -        */
> -       err = squashfs_bdi_init(sb);
> -       if (err) {
> -               errorf(fc, "squashfs init bdi failed");
> -               return err;
> -       }
> -
>         sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
>         if (sb->s_fs_info == NULL) {
>                 ERROR("Failed to allocate squashfs_sb_info\n");
> --
> 2.36.0.550.gb090851708-goog
>
>