Revert "block: do not notify urgent request, when flush with data in flight"

This reverts commit 72859c360d425f3cd38bad71f4e4044bc55b48d9.
Revert "block: Reserve only one queue tag for sync IO if only 3 tags are available"

This reverts commit 68b9f69deac11cd0f9d5fe472f37a220144626f7.
Revert "writeback: fix race that cause writeback hung"

This reverts commit 2fbd04ac174794c131eb6c4679df12ab56c28a31.
Revert "block: account iowait time when waiting for completion of IO request"

This reverts commit cb974269e033ad31725abc061fd9d06fcb436720.
Revert "writeback: fix writeback cache thrashing"

This reverts commit ccbdb95d7fba1879e5548def48bb3814cb5c2c16.
Revert "mm: slub: Default slub_max_order to 0"

This reverts commit d5f26525c33a33535b9b924a2e83e4aff07bb49e.
Revert "block: disable add_random for more performance on SSD's"

This reverts commit 0942412bf2abbb0623265e21b2bd6afba129e3e0.
Revert "readahead: make context readahead more conservative"

This reverts commit bfd35532a4989ba16f6db0f04a8b3c6053f1be52.
Revert "writeback: fix occasional slow sync(1)"

This reverts commit 43d66c81ac7732c8f92fe16c4e6714baaaf3a64c.