xfs: make xfs_inode_set_eofblocks_tag cheaper for the common case

For long growing file writes we will usually already have the
eofblocks tag set when adding more speculative preallocations.  Add
a flag in the inode to allow us to skip the the fairly expensive
AG-wide spinlocks and multiple radix tree operations in that case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>


diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index e1a411e..8f30d25 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -216,6 +216,7 @@
 #define __XFS_IPINNED_BIT	8	 /* wakeup key for zero pin count */
 #define XFS_IPINNED		(1 << __XFS_IPINNED_BIT)
 #define XFS_IDONTCACHE		(1 << 9) /* don't cache the inode long term */
+#define XFS_IEOFBLOCKS		(1 << 10)/* has the preallocblocks tag set */
 
 /*
  * Per-lifetime flags need to be reset when re-using a reclaimable inode during