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>

1 files changed, 17 insertions, 0 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