From 799441286648bdced4f42d3040f37fd2e35eaf1d Mon Sep 17 00:00:00 2001
From: Jens Axboe <jaxboe@fusionio.com>
Date: Tue, 24 May 2011 11:26:16 +0200
Subject: [PATCH] Fix overlap io_u into outside regions

Test case is a job file ala this:

[global]
ioengine=posixaio
direct=0
filename=testfile
iodepth=128
size=50M
loops=10000000000
group_reporting=1
readwrite=randwrite
do_verify=1
verify=md5
verify_fatal=1
numjobs=1
thread
bsrange=4k:1M

[thread0]
offset=0G

[thread1]
offset=50M

[thread2]
offset=100M

[thread3]
offset=150M

[thread4]
offset=200M

[thread5]
offset=250M

[thread6]
offset=300M

[thread7]
offset=350M

where io_u units from threadN ends up crossing into the zone of threadN+1.
This is due to using file->real_file_size as the boundary check for the
buffer length, where the offset itself is correctly calculated. When
using mixed block sizes, this can cause a blocksize larger than the
minimum size to span into the next region.

Fix this by using file->io_size + offset as the end delimeter. Also
improve the logic of dropping to a smaller allowed block size if we do
end up being close to spanning into the next region.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
---
 io_u.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/io_u.c b/io_u.c
index d35b8441..51da223d 100644
--- a/io_u.c
+++ b/io_u.c
@@ -341,6 +341,14 @@ static int get_next_offset(struct thread_data *td, struct io_u *io_u)
 	return __get_next_offset(td, io_u);
 }
 
+static inline int io_u_fits(struct thread_data *td, struct io_u *io_u,
+			    unsigned int buflen)
+{
+	struct fio_file *f = io_u->file;
+
+	return io_u->offset + buflen <= f->io_size + td->o.start_offset;
+}
+
 static unsigned int __get_next_buflen(struct thread_data *td, struct io_u *io_u)
 {
 	const int ddir = io_u->ddir;
@@ -353,14 +361,15 @@ static unsigned int __get_next_buflen(struct thread_data *td, struct io_u *io_u)
 	minbs = td->o.min_bs[ddir];
 	maxbs = td->o.max_bs[ddir];
 
+	if (minbs == maxbs)
+		return minbs;
+
 	if (td->o.use_os_rand)
 		rand_max = OS_RAND_MAX;
 	else
 		rand_max = FRAND_MAX;
 
-	if (minbs == maxbs)
-		buflen = minbs;
-	else {
+	do {
 		if (td->o.use_os_rand)
 			r = os_random_long(&td->bsrange_state);
 		else
@@ -380,19 +389,16 @@ static unsigned int __get_next_buflen(struct thread_data *td, struct io_u *io_u)
 
 				buflen = bsp->bs;
 				perc += bsp->perc;
-				if (r <= ((rand_max / 100L) * perc))
+				if ((r <= ((rand_max / 100L) * perc)) &&
+				    io_u_fits(td, io_u, buflen))
 					break;
 			}
 		}
+
 		if (!td->o.bs_unaligned && is_power_of_2(minbs))
 			buflen = (buflen + minbs - 1) & ~(minbs - 1);
-	}
 
-	if (io_u->offset + buflen > io_u->file->real_file_size) {
-		dprint(FD_IO, "lower buflen %u -> %u (ddir=%d)\n", buflen,
-						minbs, ddir);
-		buflen = minbs;
-	}
+	} while (!io_u_fits(td, io_u, buflen));
 
 	return buflen;
 }
-- 
2.25.1