From 0c1d6bf173a51afd708e6b45d66b2f5655778206 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Fri, 15 Nov 2019 17:16:23 -0500
Subject: [PATCH] xfs: add a xfs_valid_startblock helper

Source kernel commit: eb77b23b565e7e1d2cc3a7d9e4cc186fb54e81a8

Add a helper that validates the startblock is valid.  This checks for a
non-zero block on the main device, but skips that check for blocks on
the realtime device.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net
---
 libxfs/xfs_bmap.c | 2 +-
 libxfs/xfs_bmap.h | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index d3b5e348a..d95f0de01 100644
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -4508,7 +4508,7 @@ xfs_bmapi_convert_delalloc(
 	if (WARN_ON_ONCE(bma.blkno == NULLFSBLOCK))
 		goto out_finish;
 	error = -EFSCORRUPTED;
-	if (WARN_ON_ONCE(!bma.got.br_startblock && !XFS_IS_REALTIME_INODE(ip)))
+	if (WARN_ON_ONCE(!xfs_valid_startblock(ip, bma.got.br_startblock)))
 		goto out_finish;
 
 	XFS_STATS_ADD(mp, xs_xstrat_bytes, XFS_FSB_TO_B(mp, bma.length));
diff --git a/libxfs/xfs_bmap.h b/libxfs/xfs_bmap.h
index c409871a0..5bb446d80 100644
--- a/libxfs/xfs_bmap.h
+++ b/libxfs/xfs_bmap.h
@@ -171,6 +171,13 @@ static inline bool xfs_bmap_is_real_extent(struct xfs_bmbt_irec *irec)
 		!isnullstartblock(irec->br_startblock);
 }
 
+/*
+ * Check the mapping for obviously garbage allocations that could trash the
+ * filesystem immediately.
+ */
+#define xfs_valid_startblock(ip, startblock) \
+	((startblock) != 0 || XFS_IS_REALTIME_INODE(ip))
+
 void	xfs_trim_extent(struct xfs_bmbt_irec *irec, xfs_fileoff_t bno,
 		xfs_filblks_t len);
 int	xfs_bmap_add_attrfork(struct xfs_inode *ip, int size, int rsvd);
-- 
2.50.1