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SubjectRe: [PATCH] fix task dirty balancing
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hi,

> On Thursday 10 July 2008 13:10, YAMAMOTO Takashi wrote:
> > hi,
> >
> > thanks for the review.
> >
> > > On Wednesday 09 July 2008 09:38, YAMAMOTO Takashi wrote:
> > > > hi,
> > > >
> > > > > Please beat me to cleaning up this stuff - otherwise I'll have to
> > > > > look at it when I get back from holidays.
> > > >
> > > > how about the following?
> > >
> > > Quite good, however I would like to keep the buffers warning if it isn't
> > > too difficult (it has already caught one or two real bugs).
> >
> > isn't the WARN_ON_ONCE in __set_page_dirty_nobuffers enough?
>
> No, because it will skip warning if the page has buffers (which is a
> very common case for fs/buffer.c :)).

i see. thanks.

> > > Also, we should
> > > split out the bugfix from the cleanup. But yes overall I think the result
> > > looks quite nice.
> >
> > honestly, i don't think it makes much sense to separate the fix and
> > the cleanup in this particular case. trying to keep the bug while
> > the code cleanup naturally fixes it, or vice versa, would be a waste
> > of time.
>
> It always makes sense to separate fix and cleanup IMO. The most important
> reason is that it makes it clearer to review the fix. Secondarily, it
> makes it easier to ensure no unwanted changes in the cleanup part.

ok, i removed the cleanup part because i don't want to participate in
this kind of discussion. is the following patch ok for you?

YAMAMOTO Takashi


Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
---
diff --git a/fs/buffer.c b/fs/buffer.c
index 4ffb5bb..3a89d58 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -708,27 +708,29 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
static int __set_page_dirty(struct page *page,
struct address_space *mapping, int warn)
{
- if (unlikely(!mapping))
- return !TestSetPageDirty(page);

if (TestSetPageDirty(page))
return 0;

- spin_lock_irq(&mapping->tree_lock);
- if (page->mapping) { /* Race with truncate? */
- WARN_ON_ONCE(warn && !PageUptodate(page));
+ if (likely(mapping)) {
+ spin_lock_irq(&mapping->tree_lock);
+ if (page->mapping) { /* Race with truncate? */
+ WARN_ON_ONCE(warn && !PageUptodate(page));

- if (mapping_cap_account_dirty(mapping)) {
- __inc_zone_page_state(page, NR_FILE_DIRTY);
- __inc_bdi_stat(mapping->backing_dev_info,
- BDI_RECLAIMABLE);
- task_io_account_write(PAGE_CACHE_SIZE);
+ if (mapping_cap_account_dirty(mapping)) {
+ __inc_zone_page_state(page, NR_FILE_DIRTY);
+ __inc_bdi_stat(mapping->backing_dev_info,
+ BDI_RECLAIMABLE);
+ task_io_account_write(PAGE_CACHE_SIZE);
+ }
+ radix_tree_tag_set(&mapping->page_tree,
+ page_index(page), PAGECACHE_TAG_DIRTY);
}
- radix_tree_tag_set(&mapping->page_tree,
- page_index(page), PAGECACHE_TAG_DIRTY);
+ spin_unlock_irq(&mapping->tree_lock);
+ __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
}
- spin_unlock_irq(&mapping->tree_lock);
- __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
+
+ task_dirty_inc(current);

return 1;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a4eeb3c..33fd91a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1167,6 +1167,7 @@ extern int filemap_fault(struct vm_area_struct *, struct vm_fault *);

/* mm/page-writeback.c */
int write_one_page(struct page *page, int wait);
+void task_dirty_inc(struct task_struct *tsk);

/* readahead.c */
#define VM_MAX_READAHEAD 128 /* kbytes */
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 29b1d1e..382f742 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -176,10 +176,11 @@ void bdi_writeout_inc(struct backing_dev_info *bdi)
}
EXPORT_SYMBOL_GPL(bdi_writeout_inc);

-static inline void task_dirty_inc(struct task_struct *tsk)
+void task_dirty_inc(struct task_struct *tsk)
{
prop_inc_single(&vm_dirties, &tsk->dirties);
}
+EXPORT_SYMBOL_GPL(task_dirty_inc);

/*
* Obtain an accurate fraction of the BDI's portion.
@@ -1074,8 +1075,13 @@ int __set_page_dirty_no_writeback(struct page *page)
*/
int __set_page_dirty_nobuffers(struct page *page)
{
- if (!TestSetPageDirty(page)) {
- struct address_space *mapping = page_mapping(page);
+ struct address_space *mapping;
+
+ if (TestSetPageDirty(page))
+ return 0;
+
+ mapping = page_mapping(page);
+ if (likely(mapping)) {
struct address_space *mapping2;

if (!mapping)
@@ -1100,9 +1106,11 @@ int __set_page_dirty_nobuffers(struct page *page)
/* !PageAnon && !swapper_space */
__mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
}
- return 1;
}
- return 0;
+
+ task_dirty_inc(current);
+
+ return 1;
}
EXPORT_SYMBOL(__set_page_dirty_nobuffers);

@@ -1122,7 +1130,7 @@ EXPORT_SYMBOL(redirty_page_for_writepage);
* If the mapping doesn't provide a set_page_dirty a_op, then
* just fall through and assume that it wants buffer_heads.
*/
-static int __set_page_dirty(struct page *page)
+int set_page_dirty(struct page *page)
{
struct address_space *mapping = page_mapping(page);

@@ -1140,14 +1148,6 @@ static int __set_page_dirty(struct page *page)
}
return 0;
}
-
-int set_page_dirty(struct page *page)
-{
- int ret = __set_page_dirty(page);
- if (ret)
- task_dirty_inc(current);
- return ret;
-}
EXPORT_SYMBOL(set_page_dirty);

/*

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