* [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
@ 2015-10-12 12:24 ` Liao Tonglang
0 siblings, 0 replies; 6+ messages in thread
From: Liao Tonglang @ 2015-10-12 12:24 UTC (permalink / raw)
To: tj, axboe, akpm, jack, hannes; +Cc: linux-mm, linux-kernel, Liao Tonglang
Variables m_thresh and m_dirty in function balance_dirty_pages() may use
uninitialized. GCC throws a warning on it. Fixed by assigned to 0 as
initial value.
Signed-off-by: Liao Tonglang <liaotonglang@gmail.com>
---
mm/page-writeback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0a931cd..288db45 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1534,7 +1534,7 @@ static void balance_dirty_pages(struct address_space *mapping,
for (;;) {
unsigned long now = jiffies;
unsigned long dirty, thresh, bg_thresh;
- unsigned long m_dirty, m_thresh, m_bg_thresh;
+ unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh;
/*
* Unstable writes are a feature of certain networked
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
@ 2015-10-12 12:24 ` Liao Tonglang
0 siblings, 0 replies; 6+ messages in thread
From: Liao Tonglang @ 2015-10-12 12:24 UTC (permalink / raw)
To: tj, axboe, akpm, jack, hannes; +Cc: linux-mm, linux-kernel, Liao Tonglang
Variables m_thresh and m_dirty in function balance_dirty_pages() may use
uninitialized. GCC throws a warning on it. Fixed by assigned to 0 as
initial value.
Signed-off-by: Liao Tonglang <liaotonglang@gmail.com>
---
mm/page-writeback.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0a931cd..288db45 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1534,7 +1534,7 @@ static void balance_dirty_pages(struct address_space *mapping,
for (;;) {
unsigned long now = jiffies;
unsigned long dirty, thresh, bg_thresh;
- unsigned long m_dirty, m_thresh, m_bg_thresh;
+ unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh;
/*
* Unstable writes are a feature of certain networked
--
1.8.3.1
--
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
2015-10-12 12:24 ` Liao Tonglang
@ 2015-10-12 12:58 ` Jan Kara
-1 siblings, 0 replies; 6+ messages in thread
From: Jan Kara @ 2015-10-12 12:58 UTC (permalink / raw)
To: Liao Tonglang; +Cc: tj, axboe, akpm, jack, hannes, linux-mm, linux-kernel
On Mon 12-10-15 20:24:58, Liao Tonglang wrote:
> Variables m_thresh and m_dirty in function balance_dirty_pages() may use
> uninitialized. GCC throws a warning on it. Fixed by assigned to 0 as
> initial value.
The code is correct - m_dirty & m_thresh gets set & used only if mdtc is
set. So the warning is false positive (and e.g. my gcc doesn't warn). What
gcc version are you using?
Honza
>
> Signed-off-by: Liao Tonglang <liaotonglang@gmail.com>
> ---
> mm/page-writeback.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0a931cd..288db45 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1534,7 +1534,7 @@ static void balance_dirty_pages(struct address_space *mapping,
> for (;;) {
> unsigned long now = jiffies;
> unsigned long dirty, thresh, bg_thresh;
> - unsigned long m_dirty, m_thresh, m_bg_thresh;
> + unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh;
>
> /*
> * Unstable writes are a feature of certain networked
> --
> 1.8.3.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
@ 2015-10-12 12:58 ` Jan Kara
0 siblings, 0 replies; 6+ messages in thread
From: Jan Kara @ 2015-10-12 12:58 UTC (permalink / raw)
To: Liao Tonglang; +Cc: tj, axboe, akpm, jack, hannes, linux-mm, linux-kernel
On Mon 12-10-15 20:24:58, Liao Tonglang wrote:
> Variables m_thresh and m_dirty in function balance_dirty_pages() may use
> uninitialized. GCC throws a warning on it. Fixed by assigned to 0 as
> initial value.
The code is correct - m_dirty & m_thresh gets set & used only if mdtc is
set. So the warning is false positive (and e.g. my gcc doesn't warn). What
gcc version are you using?
Honza
>
> Signed-off-by: Liao Tonglang <liaotonglang@gmail.com>
> ---
> mm/page-writeback.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index 0a931cd..288db45 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1534,7 +1534,7 @@ static void balance_dirty_pages(struct address_space *mapping,
> for (;;) {
> unsigned long now = jiffies;
> unsigned long dirty, thresh, bg_thresh;
> - unsigned long m_dirty, m_thresh, m_bg_thresh;
> + unsigned long m_dirty = 0, m_thresh = 0, m_bg_thresh;
>
> /*
> * Unstable writes are a feature of certain networked
> --
> 1.8.3.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
2015-10-12 12:58 ` Jan Kara
@ 2015-10-13 1:41 ` Liao Tonglang
-1 siblings, 0 replies; 6+ messages in thread
From: Liao Tonglang @ 2015-10-13 1:41 UTC (permalink / raw)
To: Jan Kara; +Cc: tj, axboe, akpm, hannes, linux-mm, linux-kernel
On 2015/10/12 20:58, Jan Kara wrote:
> What
> gcc version are you using?
It is the last line of my gcc -v command.
gcc version 4.8.3 20140911 (Red Hat 4.8.3-9) (GCC)
And it warn like this:
mm/page-writeback.c: In function ‘balance_dirty_pages.isra.26’:
mm/page-writeback.c:1537:26: warning: ‘m_thresh’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
unsigned long m_dirty, m_thresh, m_bg_thresh;
^
mm/page-writeback.c:1537:17: warning: ‘m_dirty’ may be used
uninitialized in this function [-Wmaybe-uninitialized]
unsigned long m_dirty, m_thresh, m_bg_thresh;
^
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized
@ 2015-10-13 1:41 ` Liao Tonglang
0 siblings, 0 replies; 6+ messages in thread
From: Liao Tonglang @ 2015-10-13 1:41 UTC (permalink / raw)
To: Jan Kara; +Cc: tj, axboe, akpm, hannes, linux-mm, linux-kernel
On 2015/10/12 20:58, Jan Kara wrote:
> What
> gcc version are you using?
It is the last line of my gcc -v command.
gcc version 4.8.3 20140911 (Red Hat 4.8.3-9) (GCC)
And it warn like this:
mm/page-writeback.c: In function ?balance_dirty_pages.isra.26?:
mm/page-writeback.c:1537:26: warning: ?m_thresh? may be used
uninitialized in this function [-Wmaybe-uninitialized]
unsigned long m_dirty, m_thresh, m_bg_thresh;
^
mm/page-writeback.c:1537:17: warning: ?m_dirty? may be used
uninitialized in this function [-Wmaybe-uninitialized]
unsigned long m_dirty, m_thresh, m_bg_thresh;
^
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-10-13 1:42 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-10-12 12:24 [PATCH] mm: cleanup balance_dirty_pages() that leave variables uninitialized Liao Tonglang
2015-10-12 12:24 ` Liao Tonglang
2015-10-12 12:58 ` Jan Kara
2015-10-12 12:58 ` Jan Kara
2015-10-13 1:41 ` Liao Tonglang
2015-10-13 1:41 ` Liao Tonglang
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