On Sun, Sep 01, 2019 at 01:51:22PM +0800, Gao Xiang wrote:
> From: Gao Xiang <gaoxian...@huawei.com>
> 
> As Christoph pointed out [1], "erofs_grab_bio tries to
> handle a bio_alloc failure, except that the function will
> not actually fail due the mempool backing it."
> 
> Sorry about useless code, fix it now.

A lot of file systems used to have this, it is a classic that gets
copy and pasted everywhere.  If you feel like doing a little project
it might make sense to check for other places that do the same.

> +             bio = erofs_grab_bio(sb, blkaddr, 1, sb, read_endio);
>  
>               if (bio_add_page(bio, page, PAGE_SIZE, 0) != PAGE_SIZE) {
>                       err = -EFAULT;
> @@ -275,13 +270,7 @@ static inline struct bio *erofs_read_raw_page(struct bio 
> *bio,
>               if (nblocks > BIO_MAX_PAGES)
>                       nblocks = BIO_MAX_PAGES;
>  
> -             bio = erofs_grab_bio(sb, blknr, nblocks, sb,
> -                                  read_endio, false);
> -             if (IS_ERR(bio)) {
> -                     err = PTR_ERR(bio);
> -                     bio = NULL;
> -                     goto err_out;
> -             }
> +             bio = erofs_grab_bio(sb, blknr, nblocks, sb, read_endio);

Btw, I think you should remove erofs_grab_bio in its current form.
The full code in data.c is indeed used in two places, so a local
erofs_raw_page_alloc_bio (or whatever name you prefer) helper here
that hardcodes the sb amd read_endio argument to simplify it a bit
makes sense.

> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index f06a2fad7af2..abe28565d6c0 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -1265,7 +1265,7 @@ static bool z_erofs_vle_submit_all(struct super_block 
> *sb,
>               if (!bio) {
>                       bio = erofs_grab_bio(sb, first_index + i,
>                                            BIO_MAX_PAGES, bi_private,
> -                                          z_erofs_vle_read_endio, true);
> +                                          z_erofs_vle_read_endio);

But I think here you might as well open code it entirely, or at least
us a separate (and local to zdata.c) helper.
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