[21/46] xfs: encode the rtbitmap in big endian format

Commit Message

Darrick J. Wong Dec. 6, 2024, 11:56 p.m. UTC

From: Darrick J. Wong <[e-mail]>

Source kernel commit: eba42c2c53c8b8905307b702c93dffef0719a896

Currently, the ondisk realtime bitmap file is accessed in units of
32-bit words.  There's no endian translation of the contents of this
file, which means that the Bad Things Happen(tm) if you go from (say)
x86 to powerpc.  Since we have a new feature flag, let's take the
opportunity to enforce an endianness on the file.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
---
 libxfs/xfs_format.h   |    4 +++-
 libxfs/xfs_rtbitmap.h |    7 ++++++-
 2 files changed, 9 insertions(+), 2 deletions(-)

Patch

diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 016ee4ff537440..cd9457ed5873fe 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -709,10 +709,12 @@  struct xfs_agfl {
 
 /*
  * Realtime bitmap information is accessed by the word, which is currently
- * stored in host-endian format.
+ * stored in host-endian format.  Starting with the realtime groups feature,
+ * the words are stored in be32 ondisk.
  */
 union xfs_rtword_raw {
 	__u32		old;
+	__be32		rtg;
 };
 
 /*
diff --git a/libxfs/xfs_rtbitmap.h b/libxfs/xfs_rtbitmap.h
index 2286a98ecb32bb..f9c0d241590104 100644
--- a/libxfs/xfs_rtbitmap.h
+++ b/libxfs/xfs_rtbitmap.h
@@ -210,6 +210,8 @@  xfs_rtbitmap_getword(
 {
 	union xfs_rtword_raw	*word = xfs_rbmblock_wordptr(args, index);
 
+	if (xfs_has_rtgroups(args->mp))
+		return be32_to_cpu(word->rtg);
 	return word->old;
 }
 
@@ -222,7 +224,10 @@  xfs_rtbitmap_setword(
 {
 	union xfs_rtword_raw	*word = xfs_rbmblock_wordptr(args, index);
 
-	word->old = value;
+	if (xfs_has_rtgroups(args->mp))
+		word->rtg = cpu_to_be32(value);
+	else
+		word->old = value;
 }
 
 /*