From 48753c414169f92c3d7bce02cd7c10dbb52c75b5 Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Tue, 8 Mar 2011 11:54:40 -0500
Subject: [PATCH] --- yaml --- r: 234091 b: refs/heads/master c:
 ea8efc74bd0402b4d5f663d007b4e25fa29ea778 h: refs/heads/master i:   234089:
 6d6663bbc5f6c6d8eb49eea27e2bb8af418920ab   234087:
 b28f6fc8f9d955e8a97f4746e6b31f37905bff01 v: v3

---
 [refs]                     |  2 +-
 trunk/fs/btrfs/extent_io.c | 33 +++++++++++++++++++++++++++------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index c3d09b791aad..2d6e983840af 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 31339acd07b4ba687906702085127895a56eb920
+refs/heads/master: ea8efc74bd0402b4d5f663d007b4e25fa29ea778
diff --git a/trunk/fs/btrfs/extent_io.c b/trunk/fs/btrfs/extent_io.c
index ff45b80d90f0..9fcb5ede6b72 100644
--- a/trunk/fs/btrfs/extent_io.c
+++ b/trunk/fs/btrfs/extent_io.c
@@ -3046,17 +3046,38 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	}
 
 	while (!end) {
-		off = extent_map_end(em);
-		if (off >= max)
-			end = 1;
+		u64 offset_in_extent;
+
+		/* break if the extent we found is outside the range */
+		if (em->start >= max || extent_map_end(em) < off)
+			break;
+
+		/*
+		 * get_extent may return an extent that starts before our
+		 * requested range.  We have to make sure the ranges
+		 * we return to fiemap always move forward and don't
+		 * overlap, so adjust the offsets here
+		 */
+		em_start = max(em->start, off);
 
-		em_start = em->start;
-		em_len = em->len;
+		/*
+		 * record the offset from the start of the extent
+		 * for adjusting the disk offset below
+		 */
+		offset_in_extent = em_start - em->start;
 		em_end = extent_map_end(em);
+		em_len = em_end - em_start;
 		emflags = em->flags;
 		disko = 0;
 		flags = 0;
 
+		/*
+		 * bump off for our next call to get_extent
+		 */
+		off = extent_map_end(em);
+		if (off >= max)
+			end = 1;
+
 		if (em->block_start == EXTENT_MAP_LAST_BYTE) {
 			end = 1;
 			flags |= FIEMAP_EXTENT_LAST;
@@ -3067,7 +3088,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 			flags |= (FIEMAP_EXTENT_DELALLOC |
 				  FIEMAP_EXTENT_UNKNOWN);
 		} else {
-			disko = em->block_start;
+			disko = em->block_start + offset_in_extent;
 		}
 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
 			flags |= FIEMAP_EXTENT_ENCODED;