xfs: create function to scan and clear EOFBLOCKS inodes

xfs_inodes_free_eofblocks() implements scanning functionality for
EOFBLOCKS inodes. It uses the AG iterator to walk the tagged inodes
and free post-EOF blocks via the xfs_inode_free_eofblocks() execute
function. The scan can be invoked in best-effort mode or wait
(force) mode.

A best-effort scan (default) handles all inodes that do not have a
dirty cache and we successfully acquire the io lock via trylock. In
wait mode, we continue to cycle through an AG until all inodes are
handled.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_icache.c

@@ -1170,6 +1170,49 @@ xfs_reclaim_inodes_count(
 	return reclaimable;
 }
 
+STATIC int
+xfs_inode_free_eofblocks(
+	struct xfs_inode	*ip,
+	struct xfs_perag	*pag,
+	int			flags,
+	void			*args)
+{
+	int ret;
+
+	if (!xfs_can_free_eofblocks(ip, false)) {
+		/* inode could be preallocated or append-only */
+		trace_xfs_inode_free_eofblocks_invalid(ip);
+		xfs_inode_clear_eofblocks_tag(ip);
+		return 0;
+	}
+
+	/*
+	 * If the mapping is dirty the operation can block and wait for some
+	 * time. Unless we are waiting, skip it.
+	 */
+	if (!(flags & SYNC_WAIT) &&
+	    mapping_tagged(VFS_I(ip)->i_mapping, PAGECACHE_TAG_DIRTY))
+		return 0;
+
+	ret = xfs_free_eofblocks(ip->i_mount, ip, true);
+
+	/* don't revisit the inode if we're not waiting */
+	if (ret == EAGAIN && !(flags & SYNC_WAIT))
+		ret = 0;
+
+	return ret;
+}
+
+int
+xfs_icache_free_eofblocks(
+	struct xfs_mount	*mp,
+	int			flags)
+{
+	ASSERT((flags & ~(SYNC_TRYLOCK|SYNC_WAIT)) == 0);
+	return xfs_inode_ag_iterator_tag(mp, xfs_inode_free_eofblocks, flags,
+					 NULL, XFS_ICI_EOFBLOCKS_TAG);
+}
+
 void
 xfs_inode_set_eofblocks_tag(
 	xfs_inode_t	*ip)

fs/xfs/xfs_icache.h

@@ -37,6 +37,7 @@ void xfs_inode_set_reclaim_tag(struct xfs_inode *ip);
 
 void xfs_inode_set_eofblocks_tag(struct xfs_inode *ip);
 void xfs_inode_clear_eofblocks_tag(struct xfs_inode *ip);
+int xfs_icache_free_eofblocks(struct xfs_mount *, int);
 
 int xfs_sync_inode_grab(struct xfs_inode *ip);
 int xfs_inode_ag_iterator(struct xfs_mount *mp,

fs/xfs/xfs_trace.h

@@ -589,6 +589,7 @@ DEFINE_INODE_EVENT(xfs_dquot_dqdetach);
 
 DEFINE_INODE_EVENT(xfs_inode_set_eofblocks_tag);
 DEFINE_INODE_EVENT(xfs_inode_clear_eofblocks_tag);
+DEFINE_INODE_EVENT(xfs_inode_free_eofblocks_invalid);
 
 DECLARE_EVENT_CLASS(xfs_iref_class,
 	TP_PROTO(struct xfs_inode *ip, unsigned long caller_ip),