Fix access-outside-array of o->rwmix[]

gcc 4.9 rightfully complains about it, though in a very obtuse way:

     CC cconv.o
In file included from thread_options.h:5:0,
                  from cconv.c:3:
cconv.c: In function 'convert_thread_options_to_cpu':
os/os.h:197:16: warning: iteration 2u invokes undefined behavior
[-Waggressive-loop-optimizations]
   __le32_to_cpu(*__val);   \
                 ^
os/os.h:176:28: note: in definition of macro '__le32_to_cpu'
  #define __le32_to_cpu(x)  (x)
                             ^
cconv.c:78:17: note: in expansion of macro 'le32_to_cpu'
    o->rwmix[i] = le32_to_cpu(top->rwmix[i]);
                  ^
cconv.c:63:2: note: containing loop
   for (i = 0; i < DDIR_RWDIR_CNT; i++) {
   ^
In file included from thread_options.h:5:0,
                  from cconv.c:3:
cconv.c: In function 'convert_thread_options_to_net':
os/os.h:209:16: warning: iteration 2u invokes undefined behavior
[-Waggressive-loop-optimizations]
   __cpu_to_le32(*__val);   \
                 ^
os/os.h:179:28: note: in definition of macro '__cpu_to_le32'
  #define __cpu_to_le32(x)  (x)
                             ^
cconv.c:372:19: note: in expansion of macro 'cpu_to_le32'
    top->rwmix[i] = cpu_to_le32(o->rwmix[i]);
                    ^
cconv.c:352:2: note: containing loop
   for (i = 0; i < DDIR_RWDIR_CNT; i++) {
   ^
In file included from thread_options.h:5:0,
                  from cconv.c:3:
cconv.c: In function 'fio_test_cconv':
os/os.h:209:16: warning: iteration 2u invokes undefined behavior
[-Waggressive-loop-optimizations]
   __cpu_to_le32(*__val);   \
                 ^
os/os.h:179:28: note: in definition of macro '__cpu_to_le32'
  #define __cpu_to_le32(x)  (x)
                             ^
cconv.c:372:19: note: in expansion of macro 'cpu_to_le32'
    top->rwmix[i] = cpu_to_le32(o->rwmix[i]);
                    ^
cconv.c:352:2: note: containing loop
   for (i = 0; i < DDIR_RWDIR_CNT; i++) {
   ^
In file included from thread_options.h:5:0,
                  from cconv.c:3:
os/os.h:197:16: warning: iteration 2u invokes undefined behavior
[-Waggressive-loop-optimizations]
   __le32_to_cpu(*__val);   \
                 ^
os/os.h:176:28: note: in definition of macro '__le32_to_cpu'
  #define __le32_to_cpu(x)  (x)
                             ^
cconv.c:78:17: note: in expansion of macro 'le32_to_cpu'
    o->rwmix[i] = le32_to_cpu(top->rwmix[i]);
                  ^
cconv.c:63:2: note: containing loop
   for (i = 0; i < DDIR_RWDIR_CNT; i++) {
   ^

Fix it by extending the rwmix indexes to the full rwdir count,
even though it doesn't support trim as part of the mix (yet).

Reported-by: Bruce Cran <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

server.h

@@ -38,7 +38,7 @@ struct fio_net_cmd_reply {
 };
 
 enum {
-	FIO_SERVER_VER			= 25,
+	FIO_SERVER_VER			= 26,
 
 	FIO_SERVER_MAX_FRAGMENT_PDU	= 1024,
 

thread_options.h

@@ -157,7 +157,7 @@ struct thread_options {
 #endif
 	unsigned int iolog;
 	unsigned int rwmixcycle;
-	unsigned int rwmix[2];
+	unsigned int rwmix[DDIR_RWDIR_CNT];
 	unsigned int nice;
 	unsigned int ioprio;
 	unsigned int ioprio_class;
@@ -362,7 +362,7 @@ struct thread_options_pack {
 	uint32_t verify_cpumask_set;
 	uint32_t iolog;
 	uint32_t rwmixcycle;
-	uint32_t rwmix[2];
+	uint32_t rwmix[DDIR_RWDIR_CNT];
 	uint32_t nice;
 	uint32_t ioprio;
 	uint32_t ioprio_class;