Btrfs: Endianess bug fix for v0.13 with kernels

Fix for a endianess BUG when using btrfs v0.13 with kernels older than 2.6.23

Problem:

Has of v0.13, btrfs-progs is using crc32c.c equivalent to the one found on
linux-2.6.23/lib/libcrc32c.c Since crc32c_le() changed in linux-2.6.23, when
running btrfs v0.13 with older kernels we have a missmatch between the versions
of crc32c_le() from btrfs-progs and libcrc32c in the kernel.  This missmatch
causes a bug when using btrfs on big endian machines.

Solution:
btrfs_crc32c() macro that when compiling for kernels older than 2.6.23, does
endianess conversion to parameters and return value of crc32c().
This endianess conversion nullifies the differences in implementation
of crc32c_le().
If kernel 2.6.23 or better, it calls crc32c().

Signed-off-by: Miguel Sousa Filipe <miguel.filipe@gmail.com>
---

Signed-off-by: Chris Mason <chris.mason@oracle.com>

3 files changed, 24 insertions, 9 deletions

diff --git a/fs/btrfs/crc32c.h b/fs/btrfs/crc32c.h
new file mode 100644
index 000000000000..a93255b4ee27
--- /dev/null
+++ b/fs/btrfs/crc32c.h
@@ -0,0 +1,17 @@
+#include <asm/byteorder.h>
+#include <linux/crc32c.h>
+#include <linux/version.h>
+
+/**
+ * implementation of crc32c_le() changed in linux-2.6.23,
+ * has of v0.13 btrfs-progs is using the latest version.
+ * We must workaround older implementations of crc32c_le()
+ * found on older kernel versions.
+ */
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,23)
+#define btrfs_crc32c(seed, data, length) \
+        __cpu_to_le32( crc32c( __le32_to_cpu(seed), data, length) )
+#else
+#define btrfs_crc32c(seed, data, length) \
+        crc32c(seed, data, length)
+#endif
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e22960e23501..0bfcc31d94d7 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -18,13 +18,13 @@
 
 #include <linux/fs.h>
 #include <linux/blkdev.h>
-#include <linux/crc32c.h>
 #include <linux/scatterlist.h>
 #include <linux/swap.h>
 #include <linux/radix-tree.h>
 #include <linux/writeback.h>
 #include <linux/buffer_head.h> // for block_sync_page
 #include <linux/workqueue.h>
+#include "crc32c.h"
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
@@ -100,7 +100,7 @@ out:
 
 u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len)
 {
-        return crc32c(seed, data, len);
+        return btrfs_crc32c(seed, data, len);
 }
 
 void btrfs_csum_final(u32 crc, char *result)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 283b08a32a43..a056a2df689a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -15,11 +15,10 @@
  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  * Boston, MA 021110-1307, USA.
  */
-
 #include <linux/sched.h>
-#include <linux/crc32c.h>
 #include <linux/pagemap.h>
 #include "hash.h"
+#include "crc32c.h"
 #include "ctree.h"
 #include "disk-io.h"
 #include "print-tree.h"
@@ -398,16 +397,15 @@ static u64 hash_extent_ref(u64 root_objectid, u64 ref_generation,
         u32 high_crc = ~(u32)0;
         u32 low_crc = ~(u32)0;
         __le64 lenum;
-
         lenum = cpu_to_le64(root_objectid);
-        high_crc = crc32c(high_crc, &lenum, sizeof(lenum));
+        high_crc = btrfs_crc32c(high_crc, &lenum, sizeof(lenum));
         lenum = cpu_to_le64(ref_generation);
-        low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
+        low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
         if (owner >= BTRFS_FIRST_FREE_OBJECTID) {
                 lenum = cpu_to_le64(owner);
-                low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
+                low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
                 lenum = cpu_to_le64(owner_offset);
-                low_crc = crc32c(low_crc, &lenum, sizeof(lenum));
+                low_crc = btrfs_crc32c(low_crc, &lenum, sizeof(lenum));
         }
         return ((u64)high_crc << 32) | (u64)low_crc;
 }