[PATCH] xfs_io: Prevent devide by zero from {pread,pwrite}_random

[Dmitry Monakhov]

Math is wrong if range requested is less or equals to block size

xfs_io -c 'pwrite -b 4k 8k 4k -R' \
       -c 'pread -b 4k  4k 4k -R' -f file

Signed-off-by: Dmitry Monakhov <dmonakhov at openvz.org>
---
 io/pread.c  | 6 +++++-
 io/pwrite.c | 6 +++++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/io/pread.c b/io/pread.c
index f16c86c..b98355f 100644
--- a/io/pread.c
+++ b/io/pread.c
@@ -245,7 +245,11 @@ read_random(
 
 	*total = 0;
 	while (count > 0) {
-		off = ((offset + (random() % range)) / buffersize) * buffersize;
+		if (range)
+			off = ((offset + (random() % range)) / buffersize) *
+				buffersize;
+		else
+			off = offset;
 		bytes = do_pread(fd, off, buffersize, buffersize);
 		if (bytes == 0)
 			break;
diff --git a/io/pwrite.c b/io/pwrite.c
index 4fc8de6..67631ce 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -128,7 +128,11 @@ write_random(
 
 	*total = 0;
 	while (count > 0) {
-		off = ((offset + (random() % range)) / buffersize) * buffersize;
+		if (range)
+			off = ((offset + (random() % range)) / buffersize) *
+				buffersize;
+		else
+			off = offset;
 		bytes = do_pwrite(file->fd, off, buffersize, buffersize);
 		if (bytes == 0)
 			break;
-- 
1.8.3.1