On Sat, Feb 04, 2017 at 10:56:06AM +0100, Christoph Hellwig wrote: > On Fri, Feb 03, 2017 at 11:22:43AM -0500, Brian Foster wrote: > > I didn't catch this until looking through everything after the next > > patch, but I think there's a problem with the wakeup here as well. If we > > have a busy extent with XFS_EXTENT_BUSY_SKIP_DISCARD set, we immediately > > issue a wake from the first xfs_extent_busy_clear() in the cil committed > > handler, regardless of whether !SKIP_DISCARD extents exist as well > > under the current gen value. I think that means we'd get a premature > > wake any time a busy_list has at least one of each type..? > > We'll need to wake as soon as a previously busy extent in the AG > becomes available, and that includes XFS_EXTENT_BUSY_SKIP_DISCARD > ones. Otherwise e.g. a transaction only containing > XFS_EXTENT_BUSY_SKIP_DISCARD will never wake at all. > Hmm, Ok. I suppose that isn't a problem so long as we don't ever wait for a particular extent based on a particular generation number. The current code is just retrying allocations and whatnot, so is probably safe. That said, that limitation should be noted somewhere. Can we add a comment in xfs_extent_busy_clear() right above the hunk where we do the SKIP_DISCARD wake? E.g., something that points out the gen number for any particular extent could be bumped in such a situation.. (or something along those lines)? Brian > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
