[RFC] 3.16-rc6 -- fs/direct-io.c:1011 from and to uninitialized.

[Ian Kumlien <ian.kumlien@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1401 bytes --]

This is a resend, try two... 

---
Hi,

While playing around compiling the kernel i noticed the following:
fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in
this function [-Wmaybe-uninitialized]
    ret = submit_page_section(dio, sdio, page,
                             ^
fs/direct-io.c:913:10: note: ‘from’ was declared here
   size_t from, to;
          ^
fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this
function [-Wmaybe-uninitialized]
    u = (to - from) >> blkbits;
            ^
fs/direct-io.c:913:16: note: ‘to’ was declared here
   size_t from, to;
                ^
---


And while the fix is simple, something along the lines of:
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 98040ba..64a8286 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct
dio_submit *sdi
 
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);
---

I however don't know if it's in the correct C standard, it compiles fine
though... (or if this is more gcc speific)




[-- Attachment #2: direct-io-init.patch --]
[-- Type: text/x-patch, Size: 1528 bytes --]

commit f94d05ce10d869c418d3271bd028fc33bfd25e6f
Author: Ian Kumlien <ian.kumlien@gmail.com>
Date:   Tue Jul 22 20:57:50 2014 +0200

    Initialize the to and from fields
    
    While compliling the 3.16-rc6 kernel I saw this:
    fs/direct-io.c: In function ‘do_blockdev_direct_IO’:
    fs/direct-io.c:1022:29: warning: ‘from’ may be used uninitialized in this function [-Wmaybe-uninitialized]
        ret = submit_page_section(dio, sdio, page,
                                 ^
    fs/direct-io.c:913:10: note: ‘from’ was declared here
       size_t from, to;
              ^
    fs/direct-io.c:1011:12: warning: ‘to’ may be used uninitialized in this function [-Wmaybe-uninitialized]
        u = (to - from) >> blkbits;
                ^
    fs/direct-io.c:913:16: note: ‘to’ was declared here
       size_t from, to;
                    ^
    ---
    
    This small changes makes sure that the values are initialized.
    
    Signed-off-by: Ian Kumlien <ian.kumlien@gmail.com>

diff --git a/fs/direct-io.c b/fs/direct-io.c
index 98040ba..64a8286 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -910,7 +910,7 @@ static int do_direct_IO(struct dio *dio, struct dio_submit *sdio,
 
        while (sdio->block_in_file < sdio->final_block_in_request) {
                struct page *page;
-               size_t from, to;
+               size_t from, to = {0};
                page = dio_get_page(dio, sdio, &from, &to);
                if (IS_ERR(page)) {
                        ret = PTR_ERR(page);