common/attr: Reduce MAX_ATTRS to leave some overhead for 64K blocksize

[xfstests-dev.git] / common / attr

diff --git a/common/attr b/common/attr
index d3902346e45bae02658108249d3d06d6ed0c051b..35682d7c56cdf7af91b488fcf60853ee93d4e0de 100644 (file)
--- a/common/attr
+++ b/common/attr
@@ -256,6 +256,45 @@ case "$FSTYP" in
 xfs|udf|pvfs2|9p|ceph|nfs)
        MAX_ATTRS=1000
        ;;
+ext2|ext3|ext4)
+       # For 4k blocksizes, most of the attributes have an attr_name of
+       # "attribute_NN" which is 12, and "value_NN" which is 8.
+       # But for larger block sizes, we start having extended attributes of the
+       # form "attribute_NNN" or "attribute_NNNN", and "value_NNN" and
+       # "value_NNNN", which causes the round(len(..), 4) to jump up by 4
+       # bytes.  So round_up(len(attr_name, 4)) becomes 16 instead of 12, and
+       # round_up(len(value, 4)) becomes 12 instead of 8.
+       #
+       # For 64K blocksize the calculation becomes
+       #       max_attrs = (block_size - 32) / (16 + 12 + 16)
+       # or
+       #       max_attrs = (block_size - 32) / 44
+       #
+       # For 4K blocksize:-
+       #       max_attrs = (block_size - 32) / (16 + 8 + 12)
+       # or
+       #       max_attrs = (block_size - 32) / 36
+       #
+       # Note (for 4K bs) above are exact calculations for attrs of type
+       # attribute_NN with values of type value_NN.
+       # With above calculations, for 4k blocksize max_attrs becomes 112.
+       # This means we can have few attrs of type attribute_NNN with values of
+       # type value_NNN. To avoid/handle this we need to add extra 4 bytes of
+       # headroom.
+       #
+       # So for 4K, the calculations becomes:-
+       #       max_attrs = (block_size - 32) / (16 + 8 + 12 + 4)
+       # or
+       #       max_attrs = (block_size - 32) / 40
+       #
+       # Assume max ~1 block of attrs
+       BLOCK_SIZE=`_get_block_size $TEST_DIR`
+       if [ $BLOCK_SIZE -le 4096 ]; then
+               let MAX_ATTRS=$((($BLOCK_SIZE - 32) / (16 + 8 + 12 + 4)))
+       else
+               let MAX_ATTRS=$((($BLOCK_SIZE - 32) / (16 + 12 + 16 )))
+       fi
+       ;;
 *)
        # Assume max ~1 block of attrs
        BLOCK_SIZE=`_get_block_size $TEST_DIR`