xfs: don't check agf_btreeblks on pre-lazysbcount filesystems

mainline-inclusion
from mainline-v5.12-rc4
commit e6c01077
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4KIAO
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e6c01077ec2d28fe8b6e0bc79eddea8d788f6ea3



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The AGF free space btree block counter wasn't added until the
lazysbcount feature was added to XFS midway through the life of the V4
format, so ignore the field when checking.  Online AGF repair requires
rmapbt, so it doesn't need the feature check.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Guo Xuenan <guoxuenan@huawei.com>
Reviewed-by: Lihong Kou <koulihong@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>