xfs: use accessor functions for summary info wordsrefactor-rtbitmap-accessors-6.7_2023-10-19

Create get and set functions for rtsummary words so that we can redefine
the ondisk format with a specific endianness.  Note that this requires
the definition of a distinct type for ondisk summary info words so that
the compiler can perform proper typechecking.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

3 files changed, 42 insertions, 9 deletions

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 2af891d5d171..9a88aba1589f 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -699,6 +699,14 @@ union xfs_rtword_raw {
 };
 
 /*
+ * Realtime summary counts are accessed by the word, which is currently
+ * stored in host-endian format.
+ */
+union xfs_suminfo_raw {
+	__u32		old;
+};
+
+/*
  * XFS Timestamps
  * ==============
  *
diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index fb05ea0177ec..4221f539615f 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -451,7 +451,6 @@ xfs_rtmodify_summary_int(
 	int		error;		/* error value */
 	xfs_fileoff_t	sb;		/* summary fsblock */
 	xfs_rtsumoff_t	so;		/* index into the summary file */
-	xfs_suminfo_t	*sp;		/* pointer to returned data */
 	unsigned int	infoword;
 
 	/*
@@ -490,19 +489,21 @@ xfs_rtmodify_summary_int(
 	 * Point to the summary information, modify/log it, and/or copy it out.
 	 */
 	infoword = xfs_rtsumoffs_to_infoword(mp, so);
-	sp = xfs_rsumblock_infoptr(bp, infoword);
 	if (delta) {
-		*sp += delta;
+		xfs_suminfo_t	val = xfs_suminfo_add(bp, infoword, delta);
+
 		if (mp->m_rsum_cache) {
-			if (*sp == 0 && log == mp->m_rsum_cache[bbno])
+			if (val == 0 && log == mp->m_rsum_cache[bbno])
 				mp->m_rsum_cache[bbno]++;
-			if (*sp != 0 && log < mp->m_rsum_cache[bbno])
+			if (val != 0 && log < mp->m_rsum_cache[bbno])
 				mp->m_rsum_cache[bbno] = log;
 		}
 		xfs_trans_log_rtsummary(tp, bp, infoword);
+		if (sum)
+			*sum = val;
+	} else if (sum) {
+		*sum = xfs_suminfo_get(bp, infoword);
 	}
-	if (sum)
-		*sum = *sp;
 	return 0;
 }
 
diff --git a/fs/xfs/libxfs/xfs_rtbitmap.h b/fs/xfs/libxfs/xfs_rtbitmap.h
index a3e8288bedea..fdfa98e0ee52 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.h
+++ b/fs/xfs/libxfs/xfs_rtbitmap.h
@@ -232,16 +232,40 @@ xfs_rtsumoffs_to_infoword(
 }
 
 /* Return a pointer to a summary info word within a rt summary block. */
-static inline xfs_suminfo_t *
+static inline union xfs_suminfo_raw *
 xfs_rsumblock_infoptr(
 	struct xfs_buf		*bp,
 	unsigned int		index)
 {
-	xfs_suminfo_t		*info = bp->b_addr;
+	union xfs_suminfo_raw	*info = bp->b_addr;
 
 	return info + index;
 }
 
+/* Get the current value of a summary counter. */
+static inline xfs_suminfo_t
+xfs_suminfo_get(
+	struct xfs_buf		*bp,
+	unsigned int		index)
+{
+	union xfs_suminfo_raw	*info = xfs_rsumblock_infoptr(bp, index);
+
+	return info->old;
+}
+
+/* Add to the current value of a summary counter and return the new value. */
+static inline xfs_suminfo_t
+xfs_suminfo_add(
+	struct xfs_buf		*bp,
+	unsigned int		index,
+	int			delta)
+{
+	union xfs_suminfo_raw	*info = xfs_rsumblock_infoptr(bp, index);
+
+	info->old += delta;
+	return info->old;
+}
+
 /*
  * Functions for walking free space rtextents in the realtime bitmap.
  */