On Sat, Feb 04, 2017 at 10:59:54AM +0100, Christoph Hellwig wrote: > On Fri, Feb 03, 2017 at 11:22:38AM -0500, Brian Foster wrote: > > On Sun, Jan 29, 2017 at 07:43:41PM +0100, Christoph Hellwig wrote: > > > Instead we submit the discard requests and use another workqueue to > > > release the extents from the extent busy list. > > > > > > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > > > --- > > > fs/xfs/xfs_discard.c | 29 ------------------ > > > fs/xfs/xfs_discard.h | 1 - > > > fs/xfs/xfs_log_cil.c | 84 ++++++++++++++++++++++++++++++++++++++++++++++----- > > > fs/xfs/xfs_log_priv.h | 1 + > > > fs/xfs/xfs_mount.c | 1 + > > > fs/xfs/xfs_super.c | 8 +++++ > > > fs/xfs/xfs_super.h | 2 ++ > > > 7 files changed, 88 insertions(+), 38 deletions(-) > > > > > ... > > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c > > > index 4e9feb1..7a74c9f 100644 > > > --- a/fs/xfs/xfs_mount.c > > > +++ b/fs/xfs/xfs_mount.c > > > @@ -1057,6 +1057,7 @@ xfs_unmountfs( > > > cancel_delayed_work_sync(&mp->m_cowblocks_work); > > > > > > xfs_fs_unreserve_ag_blocks(mp); > > > + flush_workqueue(xfs_discard_wq); > > > > Shouldn't this happen after we force the log? > > Yes. > > > Also, now that discards are async with respect to log flush, what > > prevents breaking down the fs completely before we ever get a reply from > > disk? E.g., don't we have to wait on in-flight discards before we bother > > to wait on the wq? > > Can you explain in which contex you mean this? I'm a bit lost on this > comment unfortunately. Sorry.. what I'm concerned about is waiting on in-flight discards during unmount. The current discard code issues the discards synchronously and so the log force is sufficient to drain in-flight I/O before we start breaking down core data structures in the unmount path that would be referenced by end_io handlers and such. With this change, the log force can return with discards still in flight. In fact, a subsequent flush of the workqueue is not sufficient since there's no guarantee the work item has been queued by that point either. If we don't have unmount serialization against in-flight I/Os, this can lead to unmount crashes (see the I/O accounting infrastructure added in commit 9c7504aa7 for an example of this problem with async buffer I/Os). Am I missing something that protects us from this problem here? 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
