cancel_dirty_page() had some issues and b9ea25152e56 ("page_writeback:
clean up mess around cancel_dirty_page()") replaced it with
account_page_cleaned() which makes the caller responsible for clearing
the dirty bit; unfortunately, the planned changes for cgroup writeback
support requires synchronization between dirty bit manipulation and
stat updates. While we can open-code such synchronization in each
account_page_cleaned() callsite, that's gonna be unnecessarily awkward
and verbose.
This patch revives cancel_dirty_page() but in a more restricted form.
All it does is TestClearPageDirty() followed by account_page_cleaned()
invocation if the page was dirty. This helper covers all
account_page_cleaned() usages except for __delete_from_page_cache()
which is a special case anyway and left alone. As this leaves no
module user for account_page_cleaned(), EXPORT_SYMBOL() is dropped
from it.
This patch just revives cancel_dirty_page() as a trivial wrapper to
replace equivalent usages and doesn't introduce any functional
changes.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
.../lustre/include/linux/lustre_patchless_compat.h | 4 +---
fs/buffer.c | 4 ++--
include/linux/mm.h | 1 +
mm/page-writeback.c | 27 ++++++++++++++++------
mm/truncate.c | 4 +---
5 files changed, 25 insertions(+), 15 deletions(-)
diff --git a/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h b/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h
index d726058..1456278 100644
--- a/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h
+++ b/drivers/staging/lustre/lustre/include/linux/lustre_patchless_compat.h
@@ -55,9 +55,7 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
if (PagePrivate(page))
page->mapping->a_ops->invalidatepage(page, 0, PAGE_CACHE_SIZE);
- if (TestClearPageDirty(page))
- account_page_cleaned(page, mapping);
-
+ cancel_dirty_page(page);
ClearPageMappedToDisk(page);
ll_delete_from_page_cache(page);
}
diff --git a/fs/buffer.c b/fs/buffer.c
index efd85e0..e776bec 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3233,8 +3233,8 @@ int try_to_free_buffers(struct page *page)
* to synchronise against __set_page_dirty_buffers and prevent the
* dirty bit from being lost.
*/
- if (ret && TestClearPageDirty(page))
- account_page_cleaned(page, mapping);
+ if (ret)
+ cancel_dirty_page(page);
spin_unlock(&mapping->private_lock);
out:
if (buffers_to_free) {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0755b9f..a83cf3a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1215,6 +1215,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping);
void account_page_cleaned(struct page *page, struct address_space *mapping);
int set_page_dirty(struct page *page);
int set_page_dirty_lock(struct page *page);
+void cancel_dirty_page(struct page *page);
int clear_page_dirty_for_io(struct page *page);
int get_cmdline(struct task_struct *task, char *buffer, int buflen);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5daf556..227b867 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2112,12 +2112,6 @@ EXPORT_SYMBOL(account_page_dirtied);
/*
* Helper function for deaccounting dirty page without writeback.
- *
- * Doing this should *normally* only ever be done when a page
- * is truncated, and is not actually mapped anywhere at all. However,
- * fs/buffer.c does this when it notices that somebody has cleaned
- * out all the buffers on a page without actually doing it through
- * the VM. Can you say "ext3 is horribly ugly"? Thought you could.
*/
void account_page_cleaned(struct page *page, struct address_space *mapping)
{
@@ -2127,7 +2121,6 @@ void account_page_cleaned(struct page *page, struct address_space *mapping)
task_io_account_cancelled_write(PAGE_CACHE_SIZE);
}
}
-EXPORT_SYMBOL(account_page_cleaned);
/*
* For address_spaces which do not use buffers. Just tag the page as dirty in
@@ -2266,6 +2259,26 @@ int set_page_dirty_lock(struct page *page)
EXPORT_SYMBOL(set_page_dirty_lock);
/*
+ * This cancels just the dirty bit on the kernel page itself, it does NOT
+ * actually remove dirty bits on any mmap's that may be around. It also
+ * leaves the page tagged dirty, so any sync activity will still find it on
+ * the dirty lists, and in particular, clear_page_dirty_for_io() will still
+ * look at the dirty bits in the VM.
+ *
+ * Doing this should *normally* only ever be done when a page is truncated,
+ * and is not actually mapped anywhere at all. However, fs/buffer.c does
+ * this when it notices that somebody has cleaned out all the buffers on a
+ * page without actually doing it through the VM. Can you say "ext3 is
+ * horribly ugly"? Thought you could.
+ */
+void cancel_dirty_page(struct page *page)
+{
+ if (TestClearPageDirty(page))
+ account_page_cleaned(page, page_mapping(page));
+}
+EXPORT_SYMBOL(cancel_dirty_page);
+
+/*
* Clear a page's dirty flag, while caring for dirty memory accounting.
* Returns true if the page was previously dirty.
*
diff --git a/mm/truncate.c b/mm/truncate.c
index 66af903..0c36025 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -116,9 +116,7 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
* the VM has canceled the dirty bit (eg ext3 journaling).
* Hence dirty accounting check is placed after invalidation.
*/
- if (TestClearPageDirty(page))
- account_page_cleaned(page, mapping);
-
+ cancel_dirty_page(page);
ClearPageMappedToDisk(page);
delete_from_page_cache(page);
return 0;
--
2.4.0
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