Hi guys, We were looking at testing the new IO polling improvements and we built a kernel from the 'for-4.10/dio' (64ead7d) branch in linux-block. However this branch seems to cause hung tasks when booted. Most noticeably, dhclient seems to always hang as it tries to read from it's leases file, and that means networking does not work on the computers we tested on. Other tasks seemed to hang occasionally and randomly. We tested on two machines with radically different hardware but both running Debian Jessie. (One is a dual-socket server system with the root FS on an HDD and the other is an off the shelf commodity motherboard with root on an SSD.) We performed a bisect to find the culprit commit to be: [b685d3d65ac791406e0dfd8779cc9b3707fea5a3] block: treat REQ_FUA and REQ_PREFLUSH as synchronous I've attached a bisect log. Thanks, Logan
git bisect start # good: [1001354ca34179f3db924eb66672442a173147dc] Linux 4.9-rc1 git bisect good 1001354ca34179f3db924eb66672442a173147dc # bad: [64ead7d24b34ed40e85577e9be8bd203835e57c4] blk-mq: make the polling code adaptive git bisect bad 64ead7d24b34ed40e85577e9be8bd203835e57c4 # bad: [70fd76140a6cb63262bd47b68d57b42e889c10ee] block,fs: use REQ_* flags directly git bisect bad 70fd76140a6cb63262bd47b68d57b42e889c10ee # good: [2552e3f878c2b43b41d7728a328821d8220c28da] blk-mq: get rid of confusing blk_map_ctx structure git bisect good 2552e3f878c2b43b41d7728a328821d8220c28da # good: [aa39ebd404423e62f74cfd3e27e9ffe7e38b2a25] cfq-iosched: use op_is_sync instead of opencoding it git bisect good aa39ebd404423e62f74cfd3e27e9ffe7e38b2a25 # good: [67f055c798c72c49ee0c844eae0cd6e9c83b1b16] btrfs: use op_is_sync to check for synchronous requests git bisect good 67f055c798c72c49ee0c844eae0cd6e9c83b1b16 # bad: [b685d3d65ac791406e0dfd8779cc9b3707fea5a3] block: treat REQ_FUA and REQ_PREFLUSH as synchronous git bisect bad b685d3d65ac791406e0dfd8779cc9b3707fea5a3 # good: [6f6b29171a192e84b666c816e49d2175afbbb09f] block: don't use REQ_SYNC in the READ_SYNC definition git bisect good 6f6b29171a192e84b666c816e49d2175afbbb09f # first bad commit: [b685d3d65ac791406e0dfd8779cc9b3707fea5a3] block: treat REQ_FUA and REQ_PREFLUSH as synchronous
