In 46d2277c796f9f4937bfa668c40b2e3f43e93dd0, try_to_free_buffers was
changed to bail out if the page was dirty. That caused
truncate_complete_page to leak massive amounts of memory, because the
dirty bit was only cleared after the call to try_to_free_buffers. So the
call to cancel_dirty_page was moved up to have the dirty bit cleared
early in 3e67c0987d7567ad666641164a153dca9a43b11d.
The problem with that fix is, that the page can be redirtied after
cancel_dirty_page was called, eg. like this:
truncate_complete_page()
cancel_dirty_page() // PG_dirty cleared, decr. dirty pages
do_invalidatepage()
ext3_invalidatepage()
journal_invalidatepage()
journal_unmap_buffer()
__dispose_buffer()
__journal_unfile_buffer()
__journal_temp_unlink_buffer()
mark_buffer_dirty(); // PG_dirty set, incr. dirty pages
And then we end up with dirty pages being wrongly accounted.
In ecdfc9787fe527491baefc22dce8b2dbd5b2908d the changes to
try_to_free_buffers were reverted, so the original reason for the
massive memory leak is gone, so we can also revert the move of
the call to cancel_dirty_page from truncate_complete_page and get the
accounting right again.
Signed-off-by: Björn Steinbrink <B.Steinbrink@xxxxxx>
Tested-by: Krzysztof Piotr Oledzki <ole@xxxxxx>
---
I'm not sure if it matters, but opposed to the final check in
__remove_from_page_cache, this one also cares about the task io
accounting, so maybe we want to use this instead, although it's not
quite the clean fix either.
diff --git a/mm/truncate.c b/mm/truncate.c
index cadc156..2974903 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -98,11 +98,11 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
if (page->mapping != mapping)
return;
- cancel_dirty_page(page, PAGE_CACHE_SIZE);
-
if (PagePrivate(page))
do_invalidatepage(page, 0);
+ cancel_dirty_page(page, PAGE_CACHE_SIZE);
+
remove_from_page_cache(page);
ClearPageUptodate(page);
ClearPageMappedToDisk(page);
-
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