[LTP] [PATCH v2] syscalls/ioctl_loop05: Use correct blockdev to get logical_block_size

Jan Stancek jstancek@redhat.com
Wed Jun 10 15:04:03 CEST 2020

----- Original Message -----
> >>
> >> What I had in mind when I referred to df was something like:
> >>    stat("test.img", &statbuf);
> >>    SAFE_MKNOD("blkdev", S_IFBLK | S_IRWXU, statbuf.st_dev);
> >>    block_devfd = SAFE_OPEN("blkdev", O_RDWR);
> >> What do you think?
> >>
> It works well on ext4 or xfs filesystem(user may mount wanted filesystem
> on tmpdir). But if we use btrfs, this
> BLKSSZGET will fail because major dev numer is 0. When we meet this
> situation, we don't need to call this ioctl and we can directly test
> becuase it doesn' t have backing file block device align limit.
> What do you thin about it?

This I didn't expect. If it's not reliable then perhaps your method
in v1 that incrementally increases it until it works is perhaps most
universal approach. Sorry for the detour to get there.

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