Re: "bad tree block start" when trying to mount on ARM

[Erik Jensen]

On Wed, Feb 17, 2021 at 9:24 PM Qu Wenruo <quwenruo.bt...@gmx.com> wrote:
> Got it now.
>
> [  295.249182] read_extent_buffer_pages: eb->start=26207780683776 mirror=0
> [  295.249188] __btrfs_map_block: logical=8615594639360 chunk
> start=8614760677376 len=4294967296 type=0x81
> [  295.249189] __btrfs_map_block: stripe[0] devid=3 phy=2118735708160
>
> Note that, the initial request is to read from 26207780683776.
> But inside btrfs_map_block(), we want to read from 8615594639360.
>
> This is totally screwed up in a unexpected way.
>
> 26207780683776 = 0x17d5f9754000
> 8615594639360  = 0x07d5f9754000
>
> See the missing leading 1, which screws up the result.
>
> The problem should be the logical calculation part, which doesn't do
> proper u64 conversion which could cause the problem.
>
> Would you like to test the single line fix below?
>
> Thanks,
> Qu
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index b8fab44394f5..69d728f5ff9e 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -6575,7 +6575,7 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info
> *fs_info, struct bio *bio,
>   {
>          struct btrfs_device *dev;
>          struct bio *first_bio = bio;
> -       u64 logical = bio->bi_iter.bi_sector << 9;
> +       u64 logical = ((u64)bio->bi_iter.bi_sector) << 9;
>          u64 length = 0;
>          u64 map_length;
>          int ret;

So… it appears my kernel tree (Arch32's 5.10.14-arch1) already has that:

blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
                           int mirror_num)
{
        struct btrfs_device *dev;
        struct bio *first_bio = bio;
        u64 logical = (u64)bio->bi_iter.bi_sector << 9;
        u64 length = 0;
        u64 map_length;
        int ret;
        int dev_nr;
        int total_devs;
        struct btrfs_bio *bbio = NULL;