Linux 4.8 compat #4892

behlendorf · 2016-07-27T18:19:49Z

Compatibility patches for Linux 4.8.

The rw argument has been removed from submit_bio/submit_bio_wait. Callers are now expected to set bio->bi_rw instead of passing it in. See torvalds/linux/commit/4e49ea4a for complete details. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

New REQ_OP_* definitions have been introduced to separate the WRITE, READ, and DISCARD operations from the flags. See torvalds/linux/commit/f2150821 for complete details. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

The REQ_FLUSH flag was renamed REQ_PREFLUSH to avoid confusion with REQ_OP_FLUSH. See torvalds/linux/commit/28a8f0d3 for complete details. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Requires-spl: refs/pull/564/head

behlendorf · 2016-07-27T18:21:18Z

@tuxoko @dweeezil along with openzfs/spl#564 compatibility patches for Linux 4.8 for review. Thus far the required changes have been very minor.

dweeezil · 2016-07-28T01:54:31Z

@behlendorf Running a kernel at torvalds/linux@8448cefe, SPL at openzfs/spl@0484fbb and ZFS at 0a4e3b6, writes to disk vdevs aren't actually writing anything. I'm investigating the BIO changes further.

dweeezil · 2016-07-28T15:25:34Z

Something has broken the way we're using the BIO layer in the newest kernels but nothing obvious has jumped out. So, I've been looking at all the kernel commits tagged with "block:" and am doing a little pseudo-bisection to see if I can narrow it down a bit. Backing off the kernel to torvalds/linux@43b62ce makes writes work again which leaves about 40 relevant commits to examine.

behlendorf · 2016-07-28T19:42:41Z

@dweeezil thanks digging in to this. I haven't had a chance to boot a kernel with these changes yet but I certainly will look in to it. Definitely let me know if you identify the issue.

dweeezil · 2016-07-28T19:57:02Z

@behlendorf I've gotten a few more bisection steps done so I should be getting close.

tuxoko · 2016-07-28T21:24:37Z

I think we cannot use bio->bi_rw = XXX, we need to use bio_set_op_attrs.

tuxoko · 2016-07-28T21:31:14Z

torvalds/linux@f215082
This one introduced bio_set_op_attrs helper but didn't change the encoding of bi_rw
torvalds/linux@4e1b2d5
This one changed the encoding of bi_rw

dweeezil · 2016-07-28T21:39:31Z

@tuxoko For some reason, I was under the impression that they kept the encoding of bi_rw compatible with legacy code which used assignments but apparently that's not the case.

dweeezil · 2016-07-28T21:46:24Z

@behlendorf There's one other change I think we ought to make and that's to streamline the handling of bi_rw. See dweeezil/zfs@eef4b2e for a patch which I layered on to your PR. Of course, in light of the need to use the new accessor helpers, it'll have to change even a bit more.

tuxoko · 2016-07-28T21:50:10Z

My kernel build is so unstable, I couldn't even boot it now...
I'll probably wait a bit before working on or testing this issue.

behlendorf · 2016-07-28T21:51:06Z

Yes, that's almost certainly the issue. The initial commit I was looking at didn't change that encoding, that happened latter in torvalds/linux@4e1b2d5 as @tuxoko points out. Sorry about that.

@dweeezil streamlining the bi_rw handling makes sense. Rather than me trying to incorporate your fixes perhaps you could open a new PR when you're ready with your proposed updated version.

tuxoko · 2016-07-28T23:56:10Z

#4899

The rw argument has been removed from submit_bio/submit_bio_wait. Callers are now expected to set bio->bi_rw instead of passing it in. See torvalds/linux@4e49ea4a for complete details. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#4892 Issue openzfs#4899

The REQ_FLUSH flag was renamed REQ_PREFLUSH to avoid confusion with REQ_OP_FLUSH. See torvalds/linux@28a8f0d3 for complete details. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#4892 Issue openzfs#4899

The rw argument has been removed from submit_bio/submit_bio_wait. Callers are now expected to set bio->bi_rw instead of passing it in. See torvalds/linux@4e49ea4a for complete details. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#4892 Issue openzfs#4899

The REQ_FLUSH flag was renamed REQ_PREFLUSH to avoid confusion with REQ_OP_FLUSH. See torvalds/linux@28a8f0d3 for complete details. Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue openzfs#4892 Issue openzfs#4899

New REQ_OP_* definitions have been introduced to separate the WRITE, READ, and DISCARD operations from the flags. This included changing the encoding of bi_rw. It places REQ_OP_* in high order bits and other stuff in low order bits. This encoding is done through the new helper function bio_set_op_attrs. For complete details refer to: torvalds/linux@f215082 torvalds/linux@4e1b2d5 Signed-off-by: Tim Chase <tim@chase2k.com> Signed-off-by: Chunwei Chen <david.chen@osnexus.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes openzfs#4892 Closes openzfs#4899