ext4: use s_csum_seed instead of i_csum_seed for xattr block
In xattr block operation, we use h_refcount to indicate whether the xattr block is shared among many inodes. And xattr block csum uses s_csum_seed if it is shared and i_csum_seed if it belongs to one inode. But this has a problem. So consider the block is shared first bewteen inode A and B, and B has some xattr update and CoW the xattr block. When it updates the *old* xattr block(because of the h_refcount change) and calls ext4_xattr_release_block, we has no idea that inode A is the real owner of the *old* xattr block and we can't use the i_csum_seed of inode A either in xattr block csum calculation. And I don't think we have an easy way to find inode A. So this patch just removes the tricky i_csum_seed and we now uses s_csum_seed every time for the xattr block csum. The corresponding patch for the e2fsprogs will be sent in another patch. This is spotted by xfstests 117. Signed-off-by: NTao Ma <boyu.mt@taobao.com> Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu> Acked-by: NDarrick J. Wong <djwong@us.ibm.com>
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