From 584c362ba46cf711c9ef19b27c89ea216f7eb804 Mon Sep 17 00:00:00 2001
From: Andrea Mazzoleni <amadvance@gmail.com>
Date: Sun, 20 Dec 2015 17:19:57 +0100
Subject: [PATCH] Handle correctly files without offset

This avoid the warnings about duplicate offsets.
---
 HISTORY        |  3 +++
 cmdline/unix.c | 20 +++++++++++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/HISTORY b/HISTORY
index 2308f603..b9edf694 100644
--- a/HISTORY
+++ b/HISTORY
@@ -6,6 +6,9 @@ SnapRAID HISTORY
  * Fixes support for symlinks pointing to an empty target. Before they
    were only partially supported, and their presence could result in
    a content file not readable.
+ * Improves the physical offset ordering for the Btrfs filesystem,
+   correctly detecting files that have not a physical offset, for
+   whatever reason.
  * Adds UUID support to Btrfs filesystems. It's present only if the
    libblkid library is available on the system.
 
diff --git a/cmdline/unix.c b/cmdline/unix.c
index 29c23ecf..743a5170 100644
--- a/cmdline/unix.c
+++ b/cmdline/unix.c
@@ -210,7 +210,25 @@ int filephy(const char* path, uint64_t size, uint64_t* physical)
 	fm.fiemap.fm_extent_count = 1; /* we are interested only at the first block */
 
 	if (ioctl(f, FS_IOC_FIEMAP, &fm) != -1) {
-		*physical = fm.fiemap.fm_extents[0].fe_physical + FILEPHY_REAL_OFFSET;
+		uint32_t flags = fm.fiemap.fm_extents[0].fe_flags;
+		uint64_t offset = fm.fiemap.fm_extents[0].fe_physical;
+
+		/* check some condition for validating the offset */
+		if (flags & FIEMAP_EXTENT_DATA_INLINE) {
+			/* if the data is inline, we don't have an offset to report */
+			*physical = FILEPHY_WITHOUT_OFFSET;
+		} else if (flags & FIEMAP_EXTENT_UNKNOWN) {
+			/* if the offset is unknown, we don't have an offset to report */
+			*physical = FILEPHY_WITHOUT_OFFSET;
+		} else if (offset == 0) {
+			/* 0 is the general fallback for filesystems when */
+			/* they don't have an offset to report */
+			*physical = FILEPHY_WITHOUT_OFFSET;
+		} else {
+			/* finally report the real offset */
+			*physical = offset + FILEPHY_REAL_OFFSET;
+		}
+
 		if (close(f) == -1)
 			return -1;
 		return 0;