[LTP] [PATCH] lapi/fs.h: Replace MAX_LFS_FILESIZE constant with own implementation

[Li Wang]

On Tue, Aug 20, 2019 at 5:10 PM Yang Xu <xuyang2018.jy@cn.fujitsu.com> wrote:
...
> >
> > But I don't understand why to define MAX_OFF as (MAX_LEN - MIN_OFF),
> > the failure indicates that not to write at a position past the maximum
> > allowed offset. Shouldn't we give a dst_off large than
> > MAX_LFS_FILESIZE?
> Yes, we should use a dst_off large than MAX_LFS_FILESIZE because it used pos to compare
> in kernel code as below:
>
> mm/filemap.c
>   static int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
> ...
> if (unlikely(pos>= max_size))
>    return -EFBIG;
> ...
>
> I strace xfstest generic/564 code( I follow this test code to ltp), as below:
> #max_off=$((8 * 2**60 - 65536 - 1))
> #min_off=65537
> #xfs_io -f -c "pwrite -S 0x61 0 128k" file
> #touch copy
> #strace xfs_io -c "copy_range -l $min_off -s 0 -d $max_off file" copy
> ....
>   openat(AT_FDCWD, "file", O_RDONLY)      = 4
>   copy_file_range(4, [0], 3, [9223372036854710271], 65537, 0) = 65536
>   copy_file_range(4, [65536], 3, [9223372036854775807], 1, 0) = -1 EFBIG (File too large)
> ....
>
> xfsprogs used a loop to call copy_file_range, and get EFBIG when pos greater than LLONG_MAX.
>
> I think we should  use tst_max_lfs_filesize instead of (tst_max_lfs_filesize -MIN_OFF)
> and this case will pass whether xfs,btrfs and ext4.

Good job, Xu. I think you can format a new patch to fix this problem.
Because Petr's patch is used for solving the cross-compiling issue and
looks good.

@Petr Vorel Hi Petr, what do you think? any more comments?

-- 
Regards,
Li Wang