[13/45] xfs: encode the rtbitmap in little endian format

Commit Message

Darrick J. Wong Dec. 30, 2022, 10:19 p.m. UTC

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

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.

The natural format of a bitmap is (IMHO) little endian, because the byte
offsets of the bitmap data should always increase in step with the
information being indexed.

Signed-off-by: Darrick J. Wong <[e-mail]>
---
 libxfs/xfs_format.h   |    4 +++-
 libxfs/xfs_rtbitmap.c |    8 +++++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

Patch

diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 4096d3f069a..c7752aaa447 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -738,10 +738,12 @@  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 le32 ondisk.
  */
 union xfs_rtword_ondisk {
 	__u32		raw;
+	__le32		rtg;
 };
 
 /*
diff --git a/libxfs/xfs_rtbitmap.c b/libxfs/xfs_rtbitmap.c
index 2e286a22196..db80f740151 100644
--- a/libxfs/xfs_rtbitmap.c
+++ b/libxfs/xfs_rtbitmap.c
@@ -173,6 +173,9 @@  xfs_rtbitmap_getword(
 	struct xfs_mount	*mp,
 	union xfs_rtword_ondisk	*wordptr)
 {
+	if (xfs_has_rtgroups(mp))
+		return le32_to_cpu(wordptr->rtg);
+
 	return wordptr->raw;
 }
 
@@ -183,7 +186,10 @@  xfs_rtbitmap_setword(
 	union xfs_rtword_ondisk	*wordptr,
 	xfs_rtword_t		incore)
 {
-	wordptr->raw = incore;
+	if (xfs_has_rtgroups(mp))
+		wordptr->rtg = cpu_to_le32(incore);
+	else
+		wordptr->raw = incore;
 }
 
 /*