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



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);
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