From: Eric Sandeen <sandeen@sandeen.net>
Date: Mon, 14 Apr 2014 06:13:54 +0000 (+1000)
Subject: xfs_io: fix random pread/pwrite to honor offset
X-Git-Tag: v3.2.0-rc1~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=033777858aa2f24750d23ab80b9e5e6e080d0fb5;p=thirdparty%2Fxfsprogs-dev.git

xfs_io: fix random pread/pwrite to honor offset

xfs_io's pread & pwrite claim to support a random IO mode
where it will do random IOs between offset & offset+len.

However, offset was ignored, and we did the IOs between 0
and len instead.

Clang caught this by pointing out that the calculated/normalized
"offset" variable was never read.

(NB: If the range is larger than RAND_MAX, these functions don't
work, but that's always been true, so I'll leave it for another
day...)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
---

diff --git a/io/pread.c b/io/pread.c
index a42baeddd..cff327575 100644
--- a/io/pread.c
+++ b/io/pread.c
@@ -246,7 +246,7 @@ read_random(
 
 	*total = 0;
 	while (count > 0) {
-		off = ((random() % range) / buffersize) * buffersize;
+		off = ((offset + (random() % range)) / buffersize) * buffersize;
 		bytes = do_pread(fd, off, buffersize, buffersize);
 		if (bytes == 0)
 			break;
diff --git a/io/pwrite.c b/io/pwrite.c
index a2f0a81e3..0674c01b2 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -129,7 +129,7 @@ write_random(
 
 	*total = 0;
 	while (count > 0) {
-		off = ((random() % range) / buffersize) * buffersize;
+		off = ((offset + (random() % range)) / buffersize) * buffersize;
 		bytes = do_pwrite(file->fd, off, buffersize, buffersize);
 		if (bytes == 0)
 			break;