I am on Openwrt 18.06.1 running on an EA8500, which is also an ipq806x device. When I boot or run block info, I also get similar errors, such as below. This happens regardless of whether I have a USB drive plugged in or not. If I uninstall block-mount, these errors disappear from the log.
print_req_error: I/O error, dev mtdblock0, sector 0
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.517064] print_req_error: I/O error, dev mtdblock0, sector 8
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.522744] print_req_error: I/O error, dev mtdblock0, sector 16
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.528473] print_req_error: I/O error, dev mtdblock0, sector 24
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.534890] print_req_error: I/O error, dev mtdblock0, sector 0
Tue Aug 21 10:37:57 2018 kern.warn kernel: [ 830.540038] buffer_io_error: 8 callbacks suppressed
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.540042] Buffer I/O error on dev mtdblock0, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.552617] print_req_error: I/O error, dev mtdblock0, sector 32
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.558394] print_req_error: I/O error, dev mtdblock0, sector 40
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.564641] print_req_error: I/O error, dev mtdblock0, sector 48
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.570550] print_req_error: I/O error, dev mtdblock0, sector 56
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.576638] print_req_error: I/O error, dev mtdblock0, sector 64
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.584046] Buffer I/O error on dev mtdblock0, logical block 1, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.590546] Buffer I/O error on dev mtdblock1, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.624789] Buffer I/O error on dev mtdblock1, logical block 1, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.920680] Buffer I/O error on dev mtdblock2, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.925736] Buffer I/O error on dev mtdblock2, logical block 1, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.929753] Buffer I/O error on dev mtdblock3, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.937309] Buffer I/O error on dev mtdblock3, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.945523] Buffer I/O error on dev mtdblock4, logical block 0, async page read
Tue Aug 21 10:37:57 2018 kern.err kernel: [ 830.954858] Buffer I/O error on dev mtdblock4, logical block 0, async page read