btrfs: populate otime when logging an inode item

btrfs: populate otime when logging an inode item

[TEST FAILURE WITH EXPERIMENTAL FEATURES]
When running test case generic/508, the test case will fail with the new
btrfs shutdown support:

generic/508       - output mismatch (see /home/adam/xfstests/results//generic/508.out.bad)
    --- tests/generic/508.out	2022-05-11 11:25:30.806666664 +0930
    +++ /home/adam/xfstests/results//generic/508.out.bad	2025-07-02 14:53:22.401824212 +0930
    @@ -1,2 +1,6 @@
     QA output created by 508
     Silence is golden
    +Before:
    +After : stat.btime = Thu Jan  1 09:30:00 1970
    +Before:
    +After : stat.btime = Wed Jul  2 14:53:22 2025
    ...
    (Run 'diff -u /home/adam/xfstests/tests/generic/508.out /home/adam/xfstests/results//generic/508.out.bad'  to see the entire diff)
Ran: generic/508
Failures: generic/508
Failed 1 of 1 tests

Please note that the test case requires shutdown support, thus the test
case will be skipped using the current upstream kernel, as it doesn't
have shutdown ioctl support.

[CAUSE]
The direct cause the 0 time stamp in the log tree:

leaf 30507008 items 2 free space 16057 generation 9 owner TREE_LOG
leaf 30507008 flags 0x1(WRITTEN) backref revision 1
checksum stored e522548d
checksum calced e522548d
fs uuid 57d45451-481e-43e4-aa93-289ad707a3a0
chunk uuid d52bd3fd-5163-4337-98a7-7986993ad398
	item 0 key (257 INODE_ITEM 0) itemoff 16123 itemsize 160
		generation 9 transid 9 size 0 nbytes 0
		block group 0 mode 100644 links 1 uid 0 gid 0 rdev 0
		sequence 1 flags 0x0(none)
		atime 1751432947.492000000 (2025-07-02 14:39:07)
		ctime 1751432947.492000000 (2025-07-02 14:39:07)
		mtime 1751432947.492000000 (2025-07-02 14:39:07)
		otime 0.0 (1970-01-01 09:30:00) <<<

But the old fs tree has all the correct time stamp:

btrfs-progs v6.12
fs tree key (FS_TREE ROOT_ITEM 0)
leaf 30425088 items 2 free space 16061 generation 5 owner FS_TREE
leaf 30425088 flags 0x1(WRITTEN) backref revision 1
checksum stored 48f6c57e
checksum calced 48f6c57e
fs uuid 57d45451-481e-43e4-aa93-289ad707a3a0
chunk uuid d52bd3fd-5163-4337-98a7-7986993ad398
	item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160
		generation 3 transid 0 size 0 nbytes 16384
		block group 0 mode 40755 links 1 uid 0 gid 0 rdev 0
		sequence 0 flags 0x0(none)
		atime 1751432947.0 (2025-07-02 14:39:07)
		ctime 1751432947.0 (2025-07-02 14:39:07)
		mtime 1751432947.0 (2025-07-02 14:39:07)
		otime 1751432947.0 (2025-07-02 14:39:07) <<<

The root cause is that fill_inode_item() in tree-log.c is only
populating a/c/m time, not the otime (or btime in statx output).

Part of the reason is that, the vfs inode only has a/c/m time, no native
btime support yet.

[FIX]
Thankfully btrfs has its otime stored in btrfs_inode::i_otime_sec and
btrfs_inode::i_otime_nsec.

So what we really need is just fill the otime time stamp in
fill_inode_item() of tree-log.c

There is another fill_inode_item() in inode.c, which is doing the proper
otime population.

Fixes: 94edf4ae43a5 ("Btrfs: don't bother committing delayed inode updates when fsyncing")
CC: stable@vger.kernel.org
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>