Re: [PATCH] btrfs-progs: Fix the issues btrfs-convert don't recognition ext4 i_{a,c,a}time_extra

[David Sterba <dsterba@suse.cz>]

On Wed, Aug 25, 2021 at 01:04:47AM +0800, Li Zhang wrote:
> Hi, I ran convert-tests.sh, and it reported that the
> 019-ext4-copy-timestamps test failed. The log  is as
> follows
> 
> ...
> mount -o loop -t ext4 btrfs-progs/tests/test.img btrfs-progs/tests/mnt
> ====== RUN CHECK touch btrfs-progs/tests/mnt/file
> ====== RUN CHECK stat btrfs-progs/tests/mnt/file
> File: 'btrfs-progs/tests/mnt/file'
> Size: 0           Blocks: 0          IO Block: 4096   regular empty file
> Device: 700h/1792d  Inode: 13          Links: 1
> Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
> Context: unconfined_u:object_r:unlabeled_t:s0
> Access: 2021-08-24 22:10:21.999209679 +0800
> Modify: 2021-08-24 22:10:21.999209679 +0800
> Change: 2021-08-24 22:10:21.999209679 +0800
> ...
> btrfs-progs/btrfs-convert btrfs-progs/tests/test.img
> ...
> ====== RUN CHECK mount -t btrfs -o loop btrfs-progs/tests/test.img btrfs-progs/tests/mnt
> ====== RUN CHECK stat btrfs-progs/tests/mnt/file
> File: 'btrfs-progs/tests/mnt/file'
> Size: 0           Blocks: 0          IO Block: 4096   regular empty file
> Device: 2ch/44d Inode: 267         Links: 1
> Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
> Context: unconfined_u:object_r:unlabeled_t:s0
> Access: 2021-08-24 22:10:21.000000000 +0800
> Modify: 2021-08-24 22:10:21.000000000 +0800
> Change: 2021-08-24 22:10:21.000000000 +0800
> ...
> atime on converted inode does not match
> test failed for case 019-ext4-copy-timestamps
> 
> Obviously, the log says that btrfs-convert does not
> support nanoseconds. I looked at the source code and
> found that only if ext2_fs.h defines EXT4_EPOCH_MASK
> btrfs-convert to support nanoseconds. But in e2fsprogs,
> EXT4_EPOCH_MASK was introduced in v1.43, but in some
> older versions, such as v1.40, e2fsprogs actually
> supports nanoseconds. It seems that if struct ext2_inode_large
> contains the i_atime_extra member, ext4 is supports
> nanoseconds, so I updated the logic to determine whether the
> current ext4 file system supports nanosecond precision.
> In addition, I imported some definitions to encode and
> decode tv_nsec (copied from e2fsprogs source code).

So it's supportable even up to the old versions (1.40 was released in
2007) with the updated detection, nice.

> ---
>  configure.ac | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/configure.ac b/configure.ac
> index c4fa461..20297c5 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -253,7 +253,21 @@ AX_CHECK_DEFINE([linux/fiemap.h], [FIEMAP_EXTENT_SHARED], [],
>  AX_CHECK_DEFINE([ext2fs/ext2_fs.h], [EXT4_EPOCH_MASK],
>  		[AC_DEFINE([HAVE_EXT4_EPOCH_MASK_DEFINE], [1],
>  			   [Define to 1 if e2fsprogs defines EXT4_EPOCH_MASK])],
> -		[AC_MSG_WARN([no definition of EXT4_EPOCH_MASK found, probably old e2fsprogs, no 64bit time precision of converted images])])
> +        [have_ext4_epoch_mask_define=no])
> +
> +AS_IF([test "x$have_ext4_epoch_mask_define" = xno], [
> +    AC_CHECK_MEMBERS([struct ext2_inode_large.i_atime_extra],
> +        [
> +            AC_DEFINE([HAVE_EXT4_EPOCH_MASK_DEFINE], [1], [Define to 1 if ext2_inode_large includes i_atime_extra]),
> +            AC_DEFINE([EXT4_EPOCH_BITS], [2],[for encode and decode tv_nsec in ext2 inode]),
> +            AC_DEFINE([EXT4_EPOCH_MASK], [((1 << EXT4_EPOCH_BITS) - 1)], [For encode and decode tv_nsec info in ext2 inode]),
> +            AC_DEFINE([EXT4_NSEC_MASK],  [(~0UL << EXT4_EPOCH_BITS)], [For encode and decode tv_nsec info in ext2 inode]),
> +            AC_DEFINE([inode_includes(size, field)],[m4_normalize[(size >= (sizeof(((struct ext2_inode_large *)0)->field) + offsetof(struct ext2_inode_large, field)))]],

The "," can't be at the end of the AC_DEFINE lines, this does not
produce valid ./configure and fails with

checking for FIEMAP_EXTENT_SHARED defined in linux/fiemap.h... yes                                        
checking for EXT4_EPOCH_MASK defined in ext2fs/ext2_fs.h... yes                                           
checking for struct ext2_inode_large.i_atime_extra... yes     
./configure: line 6487: ,: command not found         
./configure: line 6490: ,: command not found        
./configure: line 6493: ,: command not found                                                              
./configure: line 6496: ,: command not found

because the "," appear in the final file as separate commands. Removing them
produces valid script and the detection works.

Added to devel, thanks.