[PATCH 02/21] xfs: add helper to decide if an inode has allocated cow blocks

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

Add a helper to decide if an inode has real or unwritten extents in the
CoW fork.  The upcoming repair freeze functionality will have to know if
it's safe to iput an inode -- if the inode has incore any state that
would require a transaction to unwind during iput, we'll have to defer
the iput.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/xfs/xfs_inode.c |   19 +++++++++++++++++++
 fs/xfs/xfs_inode.h |    1 +
 2 files changed, 20 insertions(+)


diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 7a96c4e0ab5c..e6859dfc29af 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -3689,3 +3689,22 @@ xfs_iflush_int(
 corrupt_out:
 	return -EFSCORRUPTED;
 }
+
+/* Decide if there are real or unwritten extents in the CoW fork. */
+bool
+xfs_inode_has_cow_blocks(
+	struct xfs_inode		*ip)
+{
+	struct xfs_iext_cursor		icur;
+	struct xfs_bmbt_irec		irec;
+	struct xfs_ifork		*ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+
+	if (!ifp)
+		return false;
+
+	for_each_xfs_iext(ifp, &icur, &irec) {
+		if (!isnullstartblock(irec.br_startblock))
+			return true;
+	}
+	return false;
+}
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 2ed63a49e890..735d0788bfdb 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -503,5 +503,6 @@ extern struct kmem_zone	*xfs_inode_zone;
 #define XFS_DEFAULT_COWEXTSZ_HINT 32
 
 bool xfs_inode_verify_forks(struct xfs_inode *ip);
+bool xfs_inode_has_cow_blocks(struct xfs_inode *ip);
 
 #endif	/* __XFS_INODE_H__ */