[PATCH 5/6] xfs: maintain a sequence count for inode fork manipulations

[Christoph Hellwig <hch@lst.de>]

Add a simple 32-bit unsigned integer as the sequence count for
modifications to the extent list in the inode fork.  This will be
used to optimize away extent list lookups in the writeback code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_iext_tree.c  | 4 ++++
 fs/xfs/libxfs/xfs_inode_fork.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_iext_tree.c b/fs/xfs/libxfs/xfs_iext_tree.c
index b80c63faace2..cce7e8024f46 100644
--- a/fs/xfs/libxfs/xfs_iext_tree.c
+++ b/fs/xfs/libxfs/xfs_iext_tree.c
@@ -650,6 +650,7 @@ xfs_iext_insert(
 		cur->leaf->recs[i] = cur->leaf->recs[i - 1];
 	xfs_iext_set(cur_rec(cur), irec);
 	ifp->if_bytes += sizeof(struct xfs_iext_rec);
+	ifp->if_seq++;
 
 	trace_xfs_iext_insert(ip, cur, state, _RET_IP_);
 
@@ -869,6 +870,7 @@ xfs_iext_remove(
 		leaf->recs[i] = leaf->recs[i + 1];
 	xfs_iext_rec_clear(&leaf->recs[nr_entries]);
 	ifp->if_bytes -= sizeof(struct xfs_iext_rec);
+	ifp->if_seq++;
 
 	if (cur->pos == 0 && nr_entries > 0) {
 		xfs_iext_update_node(ifp, offset, xfs_iext_leaf_key(leaf, 0), 1,
@@ -983,6 +985,8 @@ xfs_iext_update_extent(
 	trace_xfs_bmap_pre_update(ip, cur, state, _RET_IP_);
 	xfs_iext_set(cur_rec(cur), new);
 	trace_xfs_bmap_post_update(ip, cur, state, _RET_IP_);
+
+	ifp->if_seq++;
 }
 
 /*
diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
index 1492143371f3..f20b2468ca35 100644
--- a/fs/xfs/libxfs/xfs_inode_fork.h
+++ b/fs/xfs/libxfs/xfs_inode_fork.h
@@ -14,6 +14,7 @@ struct xfs_dinode;
  */
 struct xfs_ifork {
 	int			if_bytes;	/* bytes in if_u1 */
+	unsigned int		if_seq;
 	struct xfs_btree_block	*if_broot;	/* file's incore btree root */
 	short			if_broot_bytes;	/* bytes allocated for root */
 	unsigned char		if_flags;	/* per-fork flags */
-- 
2.18.0