xfs: look at m_frextents in xfs_iomap_prealloc_size for RT allocations

Add a check for files on the RT subvolume and use m_frextents instead
of m_fdblocks to adjust the preallocation size.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

fs/xfs/xfs_iomap.c

@@ -28,6 +28,7 @@
 #include "xfs_dquot.h"
 #include "xfs_reflink.h"
 #include "xfs_health.h"
+#include "xfs_rtbitmap.h"
 
 #define XFS_ALLOC_ALIGN(mp, off) \
 	(((off) >> mp->m_allocsize_log) << mp->m_allocsize_log)
@@ -404,6 +405,29 @@ xfs_quota_calc_throttle(
 	}
 }
 
+static int64_t
+xfs_iomap_freesp(
+	struct percpu_counter	*counter,
+	uint64_t		low_space[XFS_LOWSP_MAX],
+	int			*shift)
+{
+	int64_t			freesp;
+
+	freesp = percpu_counter_read_positive(counter);
+	if (freesp < low_space[XFS_LOWSP_5_PCNT]) {
+		*shift = 2;
+		if (freesp < low_space[XFS_LOWSP_4_PCNT])
+			(*shift)++;
+		if (freesp < low_space[XFS_LOWSP_3_PCNT])
+			(*shift)++;
+		if (freesp < low_space[XFS_LOWSP_2_PCNT])
+			(*shift)++;
+		if (freesp < low_space[XFS_LOWSP_1_PCNT])
+			(*shift)++;
+	}
+	return freesp;
+}
+
 /*
  * If we don't have a user specified preallocation size, dynamically increase
  * the preallocation size as the size of the file grows.  Cap the maximum size
@@ -486,18 +510,13 @@ xfs_iomap_prealloc_size(
 	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(XFS_MAX_BMBT_EXTLEN),
 				       alloc_blocks);
 
-	freesp = percpu_counter_read_positive(&mp->m_fdblocks);
-	if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
-		shift = 2;
-		if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
-			shift++;
-		if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
-			shift++;
-		if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
-			shift++;
-		if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
-			shift++;
-	}
+	if (unlikely(XFS_IS_REALTIME_INODE(ip)))
+		freesp = xfs_rtx_to_rtb(mp,
+			xfs_iomap_freesp(&mp->m_frextents,
+					mp->m_low_rtexts, &shift));
+	else
+		freesp = xfs_iomap_freesp(&mp->m_fdblocks, mp->m_low_space,
+				&shift);
 
 	/*
 	 * Check each quota to cap the prealloc size, provide a shift value to