> On Sep 1, 2016, at 09:13, NeilBrown <neilb@xxxxxxxx> wrote: > > On Wed, Aug 31 2016, Yan, Zheng wrote: > >> On Wed, Aug 31, 2016 at 10:56 AM, NeilBrown <neilb@xxxxxxxx> wrote: >>> >>> Hi, >>> it is quite possible for O_DIRECT and buffered writes to a file to >>> race. >>> The xfstests test suite has a test - generic/036 - which tests this >>> case. >>> >>> Unlike most filesystems, cephfs does not hold inode_lock() across >>> direct writes. This means that buffer pages can become dirty while >>> direct writes are happening. This confused ceph a little. >> >> how about make ceph_write_iter() hold inode_lock() for direct/sync write? > > You could probably do that. You could even use inode_lock_shared() to > allow multiple writers to perform O_DIRECT writes to the same file in > parallel. > > But I don't know why ceph did this differently from every other > filesystem, and the git commit message doesn't shine any light on that > question. I didn't want to propose a change that I didn't understand > the consequences of. > > If you did extend the locking over ceph_direct_read_write(), it would > probably make sense to remove the truncate_inode_pages_range() call as > it should be redundant. both patches applied Regards Yan, Zheng > > Thanks, > NeilBrown > > >> >> Regards >> Yan, Zheng >>> >>> The following two patches allow ceph to handle this possibility a >>> little more cleanly. The more important patch removes a WARN_ON() for >>> a circumstance which can easily be triggered. >>> >>> Thanks, >>> NeilBrown -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
