xfs: add online discard support

Now that we have reliably tracking of deleted extents in a
transaction we can easily implement "online" discard support
which calls blkdev_issue_discard once a transaction commits.

The actual discard is a two stage operation as we first have
to mark the busy extent as not available for reuse before we
can start the actual discard.  Note that we don't bother
supporting discard for the non-delaylog mode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index da0a561ffba2..8d52ba4c87e5 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -187,6 +187,8 @@ struct xfs_busy_extent {
         xfs_agnumber_t  agno;
         xfs_agblock_t   bno;
         xfs_extlen_t    length;
+        unsigned int    flags;
+#define XFS_ALLOC_BUSY_DISCARDED        0x01    /* undergoing a discard op. */
 };
 
 /*