Fix overlap io_u into outside regions
authorJens Axboe <jaxboe@fusionio.com>
Tue, 24 May 2011 09:26:16 +0000 (11:26 +0200)
committerJens Axboe <jaxboe@fusionio.com>
Tue, 24 May 2011 09:26:16 +0000 (11:26 +0200)
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

diff --git a/io_u.c b/io_u.c
index d35b844..51da223 100644 (file)
--- 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;
 }