On Tue, Jan 10, 2017 at 07:57:31AM -0500, Jeff Layton wrote: > v2: fix bug in offset handling in iov_iter_pvec_size > > xfstest generic/095 triggers soft lockups in kcephfs. Basically it uses > fio to drive some I/O via vmsplice ane splice. Ceph then ends up trying > to access an ITER_BVEC type iov_iter as a ITER_IOVEC one. That causes it > to pick up a wrong offset and get stuck in an infinite loop while trying > to populate the page array. dio_get_pagev_size has a similar problem. > > To fix the first problem, add a new iov_iter helper to determine the > offset into the page for the current segment and have ceph call that. > I would just replace dio_get_pages_alloc with iov_iter_get_pages_alloc, > but that will only return a single page at a time for ITER_BVEC and > it's better to make larger requests when possible. > > For the second problem, we simply replace it with a new helper that does > what it does, but properly for all iov_iter types. > > Since we're moving that into generic code, we can also utilize the > iterate_all_kinds macro to simplify this. That means that we need to > rework the logic a bit since we can't advance to the next vector while > checking the current one. Yecchhh... That really looks like exposing way too low-level stuff instead of coming up with saner primitive ;-/ Is page vector + offset in the first page + number of bytes really what ceph wants? Would e.g. an array of bio_vec be saner? Because _that_ would make a lot more natural iov_iter_get_pages_alloc() analogue... And yes, I realize that you have ->pages wired into the struct ceph_osd_request; how painful would it be to have it switched to struct bio_vec array instead? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
