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

[Li Zhang <zhanglikernel@gmail.com>]

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).
---
 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)))]],
+                [For encode and decode tv_nsec info in ext2 inode])
+        ],
+        [AC_MSG_WARN([It seems that ext2_inode_large don't includes tv_nsec related info, probably old e2fsprogs, no 64bit time precision of converted images])],
+        [[#include <ext2fs/ext2_fs.h>]])
+])
 
 AC_CHECK_HEADER(linux/blkzoned.h, [blkzoned_found=yes], [blkzoned_found=no])
 AC_CHECK_MEMBER([struct blk_zone.capacity], [blkzoned_capacity=yes], [blkzoned_capacity=no], [[#include <linux/blkzoned.h>]])
-- 
1.8.3.1


Best regards,
Li