xfs: replace do_mod with native operations

do_mod() is a hold-over from when we have different sizes for file
offsets and and other internal values for 40 bit XFS filesystems.
Hence depending on build flags variables passed to do_mod() could
change size. We no longer support those small format filesystems and
hence everything is of fixed size theses days, even on 32 bit
platforms.

As such, we can convert all the do_mod() callers to platform
optimised modulus operations as defined by linux/math64.h.
Individual conversions depend on the types of variables being used.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

7 files changed, 66 insertions, 50 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 6a79a07528cf..01628f0c9a0c 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -2923,7 +2923,7 @@ xfs_bmap_extsize_align(
 	 * perform this alignment, or if a truncate shot us in the
 	 * foot.
 	 */
-	temp = do_mod(orig_off, extsz);
+	div_u64_rem(orig_off, extsz, &temp);
 	if (temp) {
 		align_alen += temp;
 		align_off -= temp;
@@ -3497,15 +3497,17 @@ xfs_bmap_btalloc(
 	/* apply extent size hints if obtained earlier */
 	if (align) {
 		args.prod = align;
-		if ((args.mod = (xfs_extlen_t)do_mod(ap->offset, args.prod)))
-			args.mod = (xfs_extlen_t)(args.prod - args.mod);
+		div_u64_rem(ap->offset, args.prod, &args.mod);
+		if (args.mod)
+			args.mod = args.prod - args.mod;
 	} else if (mp->m_sb.sb_blocksize >= PAGE_SIZE) {
 		args.prod = 1;
 		args.mod = 0;
 	} else {
 		args.prod = PAGE_SIZE >> mp->m_sb.sb_blocklog;
-		if ((args.mod = (xfs_extlen_t)(do_mod(ap->offset, args.prod))))
-			args.mod = (xfs_extlen_t)(args.prod - args.mod);
+		div_u64_rem(ap->offset, args.prod, &args.mod);
+		if (args.mod)
+			args.mod = args.prod - args.mod;
 	}
 	/*
 	 * If we are not low on available data blocks, and the
@@ -4953,13 +4955,15 @@ xfs_bmap_del_extent_real(
 	if (whichfork == XFS_DATA_FORK && XFS_IS_REALTIME_INODE(ip)) {
 		xfs_fsblock_t	bno;
 		xfs_filblks_t	len;
+		xfs_extlen_t	mod;
+
+		bno = div_u64_rem(del->br_startblock, mp->m_sb.sb_rextsize,
+				  &mod);
+		ASSERT(mod == 0);
+		len = div_u64_rem(del->br_blockcount, mp->m_sb.sb_rextsize,
+				  &mod);
+		ASSERT(mod == 0);
 
-		ASSERT(do_mod(del->br_blockcount, mp->m_sb.sb_rextsize) == 0);
-		ASSERT(do_mod(del->br_startblock, mp->m_sb.sb_rextsize) == 0);
-		bno = del->br_startblock;
-		len = del->br_blockcount;
-		do_div(bno, mp->m_sb.sb_rextsize);
-		do_div(len, mp->m_sb.sb_rextsize);
 		error = xfs_rtfree_extent(tp, bno, (xfs_extlen_t)len);
 		if (error)
 			goto done;
@@ -5296,9 +5300,12 @@ __xfs_bunmapi(
 			del.br_blockcount = max_len;
 		}
 
+		if (!isrt)
+			goto delete;
+
 		sum = del.br_startblock + del.br_blockcount;
-		if (isrt &&
-		    (mod = do_mod(sum, mp->m_sb.sb_rextsize))) {
+		div_u64_rem(sum, mp->m_sb.sb_rextsize, &mod);
+		if (mod) {
 			/*
 			 * Realtime extent not lined up at the end.
 			 * The extent could have been split into written
@@ -5345,7 +5352,8 @@ __xfs_bunmapi(
 				goto error0;
 			goto nodelete;
 		}
-		if (isrt && (mod = do_mod(del.br_startblock, mp->m_sb.sb_rextsize))) {
+		div_u64_rem(del.br_startblock, mp->m_sb.sb_rextsize, &mod);
+		if (mod) {
 			/*
 			 * Realtime extent is lined up at the end but not
 			 * at the front.  We'll get rid of full extents if
@@ -5414,6 +5422,7 @@ __xfs_bunmapi(
 			}
 		}
 
+delete:
 		if (wasdel) {
 			error = xfs_bmap_del_extent_delay(ip, whichfork, &icur,
 					&got, &del);
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 7d26933a542f..c35009a86699 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -80,6 +80,7 @@ xfs_bmap_rtalloc(
 	int		error;		/* error return value */
 	xfs_mount_t	*mp;		/* mount point structure */
 	xfs_extlen_t	prod = 0;	/* product factor for allocators */
+	xfs_extlen_t	mod = 0;	/* product factor for allocators */
 	xfs_extlen_t	ralen = 0;	/* realtime allocation length */
 	xfs_extlen_t	align;		/* minimum allocation alignment */
 	xfs_rtblock_t	rtb;
@@ -99,7 +100,8 @@ xfs_bmap_rtalloc(
 	 * If the offset & length are not perfectly aligned
 	 * then kill prod, it will just get us in trouble.
 	 */
-	if (do_mod(ap->offset, align) || ap->length % align)
+	div_u64_rem(ap->offset, align, &mod);
+	if (mod || ap->length % align)
 		prod = 1;
 	/*
 	 * Set ralen to be the actual requested length in rtextents.
@@ -936,9 +938,11 @@ xfs_alloc_file_space(
 			do_div(s, extsz);
 			s *= extsz;
 			e = startoffset_fsb + allocatesize_fsb;
-			if ((temp = do_mod(startoffset_fsb, extsz)))
+			div_u64_rem(startoffset_fsb, extsz, &temp);
+			if (temp)
 				e += temp;
-			if ((temp = do_mod(e, extsz)))
+			div_u64_rem(e, extsz, &temp);
+			if (temp)
 				e += extsz - temp;
 		} else {
 			s = 0;
@@ -1099,7 +1103,7 @@ xfs_adjust_extent_unmap_boundaries(
 
 	if (nimap && imap.br_startblock != HOLESTARTBLOCK) {
 		ASSERT(imap.br_startblock != DELAYSTARTBLOCK);
-		mod = do_mod(imap.br_startblock, mp->m_sb.sb_rextsize);
+		div_u64_rem(imap.br_startblock, mp->m_sb.sb_rextsize, &mod);
 		if (mod)
 			*startoffset_fsb += mp->m_sb.sb_rextsize - mod;
 	}
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 6cda0f08b045..4a2e5e13c569 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2258,7 +2258,7 @@ xfs_ifree_cluster(
 		 */
 		ioffset = inum - xic->first_ino;
 		if ((xic->alloc & XFS_INOBT_MASK(ioffset)) == 0) {
-			ASSERT(do_mod(ioffset, inodes_per_cluster) == 0);
+			ASSERT(ioffset % inodes_per_cluster == 0);
 			continue;
 		}
 
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index b0c98d4faa5b..83474c9cede9 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -30,10 +30,10 @@ xfs_aligned_fsb_count(
 	if (extsz) {
 		xfs_extlen_t	align;
 
-		align = do_mod(offset_fsb, extsz);
+		div_u64_rem(offset_fsb, extsz, &align);
 		if (align)
 			count_fsb += align;
-		align = do_mod(count_fsb, extsz);
+		div_u64_rem(count_fsb, extsz, &align);
 		if (align)
 			count_fsb += extsz - align;
 	}
diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
index 0fcb6295aa5d..edbd5a210df2 100644
--- a/fs/xfs/xfs_linux.h
+++ b/fs/xfs/xfs_linux.h
@@ -207,25 +207,6 @@ static inline xfs_dev_t linux_to_xfs_dev_t(dev_t dev)
 #define xfs_sort(a,n,s,fn)	sort(a,n,s,fn,NULL)
 #define xfs_stack_trace()	dump_stack()
 
-/* Side effect free 64 bit mod operation */
-static inline __u32 xfs_do_mod(void *a, __u32 b, int n)
-{
-	switch (n) {
-		case 4:
-			return *(__u32 *)a % b;
-		case 8:
-			{
-			__u64	c = *(__u64 *)a;
-			return do_div(c, b);
-			}
-	}
-
-	/* NOTREACHED */
-	return 0;
-}
-
-#define do_mod(a, b)	xfs_do_mod(&(a), (b), sizeof(a))
-
 static inline uint64_t roundup_64(uint64_t x, uint32_t y)
 {
 	x += y - 1;
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index b1aedf73d09d..b181b5f57a19 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -1236,6 +1236,25 @@ xlog_verify_head(
 }
 
 /*
+ * We need to make sure we handle log wrapping properly, so we can't use the
+ * calculated logbno directly. Make sure it wraps to the correct bno inside the
+ * log.
+ *
+ * The log is limited to 32 bit sizes, so we use the appropriate modulus
+ * operation here and cast it back to a 64 bit daddr on return.
+ */
+static inline xfs_daddr_t
+xlog_wrap_logbno(
+	struct xlog		*log,
+	xfs_daddr_t		bno)
+{
+	int			mod;
+
+	div_s64_rem(bno, log->l_logBBsize, &mod);
+	return mod;
+}
+
+/*
  * Check whether the head of the log points to an unmount record. In other
  * words, determine whether the log is clean. If so, update the in-core state
  * appropriately.
@@ -1283,12 +1302,13 @@ xlog_check_unmount_rec(
 	} else {
 		hblks = 1;
 	}
-	after_umount_blk = rhead_blk + hblks + BTOBB(be32_to_cpu(rhead->h_len));
-	after_umount_blk = do_mod(after_umount_blk, log->l_logBBsize);
+
+	after_umount_blk = xlog_wrap_logbno(log,
+			rhead_blk + hblks + BTOBB(be32_to_cpu(rhead->h_len)));
+
 	if (*head_blk == after_umount_blk &&
 	    be32_to_cpu(rhead->h_num_logops) == 1) {
-		umount_data_blk = rhead_blk + hblks;
-		umount_data_blk = do_mod(umount_data_blk, log->l_logBBsize);
+		umount_data_blk = xlog_wrap_logbno(log, rhead_blk + hblks);
 		error = xlog_bread(log, umount_data_blk, 1, bp, &offset);
 		if (error)
 			return error;
@@ -5459,9 +5479,7 @@ xlog_do_recovery_pass(
 			 */
 			if (blk_no + bblks <= log->l_logBBsize ||
 			    blk_no >= log->l_logBBsize) {
-				/* mod blk_no in case the header wrapped and
-				 * pushed it beyond the end of the log */
-				rblk_no = do_mod(blk_no, log->l_logBBsize);
+				rblk_no = xlog_wrap_logbno(log, blk_no);
 				error = xlog_bread(log, rblk_no, bblks, dbp,
 						   &offset);
 				if (error)
diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
index 80bbfe604ce0..329d4d26c13e 100644
--- a/fs/xfs/xfs_rtalloc.c
+++ b/fs/xfs/xfs_rtalloc.c
@@ -301,8 +301,12 @@ xfs_rtallocate_extent_block(
 		/*
 		 * If size should be a multiple of prod, make that so.
 		 */
-		if (prod > 1 && (p = do_mod(bestlen, prod)))
-			bestlen -= p;
+		if (prod > 1) {
+			div_u64_rem(bestlen, prod, &p);
+			if (p)
+				bestlen -= p;
+		}
+
 		/*
 		 * Allocate besti for bestlen & return that.
 		 */
@@ -1263,7 +1267,7 @@ xfs_rtpick_extent(
 		b = (mp->m_sb.sb_rextents * ((resid << 1) + 1ULL)) >>
 		    (log2 + 1);
 		if (b >= mp->m_sb.sb_rextents)
-			b = do_mod(b, mp->m_sb.sb_rextents);
+			div64_u64_rem(b, mp->m_sb.sb_rextents, &b);
 		if (b + len > mp->m_sb.sb_rextents)
 			b = mp->m_sb.sb_rextents - len;
 	}