Re: [PATCH 1/5] [XFS] Use xfs_sync_inodes() for device flushing

Dave Chinner
2009-03-16T10:51:56Z

On Mon, Mar 16, 2009 at 05:08:47AM -0400, Christoph Hellwig wrote:
> On Sun, Mar 15, 2009 at 10:31:43PM +1100, Dave Chinner wrote:
> > index 5aeb777..08be36d 100644
> > --- a/fs/xfs/linux-2.6/xfs_fs_subr.c
> > +++ b/fs/xfs/linux-2.6/xfs_fs_subr.c
> > @@ -74,14 +74,14 @@ xfs_flush_pages(
> >
> > if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
> > xfs_iflags_clear(ip, XFS_ITRUNCATED);
> > - ret = filemap_fdatawrite(mapping);
> > - if (flags & XFS_B_ASYNC)
> > - return -ret;
> > - ret2 = filemap_fdatawait(mapping);
> > - if (!ret)
> > - ret = ret2;
> > + ret = -filemap_fdatawrite(mapping);
> > }
> > - return -ret;
> > + if (flags & XFS_B_ASYNC)
> > + return ret;
> > + ret2 = xfs_wait_on_pages(ip, first, last);
> > + if (!ret)
> > + ret = ret2;
> > + return ret;
> > }
>
> How does this belong into this patch series?

So xfs_flush_pages waits on writeback pages which aren't caught by
mapping_tagged(mapping, PAGECACHE_TAG_DIRTY). If we are waiting for
a flush to complete, we should be waiting for all pages under IO to
complete regardless of whether there are dirty pages or not. That
matters if we are doing 2 passes to flush everything and then wait;
the wait won't see dirty mappings, but there might still be pages
under IO....

> Also I think the sync code should just use filemap_fdatawait and
> filemap_fdatawait directly. It's at a high enough level that we don't
> need all these obsfucations.

OK. I'll rework it so that:

> > + if (flags & SYNC_DELWRI) {
> > + if (VN_DIRTY(inode)) {
> > + if (flags & SYNC_TRYLOCK) {
> > + if (xfs_ilock_nowait(ip, XFS_IOLOCK_SHARED))
> > + lock_flags |= XFS_IOLOCK_SHARED;
> > + } else {
> > + xfs_ilock(ip, XFS_IOLOCK_SHARED);
> > + lock_flags |= XFS_IOLOCK_SHARED;
> > + }
>
> > + if (lock_flags & XFS_IOLOCK_SHARED) {
>
> Too long line and pretty ugly use of the lock_flags variable, but given
> that it gets sorted out in the sync series I think we can leave it that way.

This gets done early and the later patches become simpler.

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com