renegade-project/linux-next
2
0
Fork 0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-02 10:23:55 +08:00
Code

Fix dirty page accounting leak with ext3 data=journal

Browse Source 
In 46d2277c79 ("Clean up and make
try_to_free_buffers() not race with dirty pages"), try_to_free_buffers
was changed to bail out if the page was dirty.

That in turn 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 3e67c0987d ("truncate:
clear page dirtiness before running try_to_free_buffers()").

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.

As a result, in ecdfc9787f ("Resurrect
'try_to_free_buffers()' VM hackery") the changes to try_to_free_buffers
were reverted, so the original reason for the massive memory leak is
gone, and we can also revert the move of the call to cancel_dirty_page
from truncate_complete_page and get the accounting right again.

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.

Signed-off-by: Björn Steinbrink <B.Steinbrink@gmx.de>
Tested-by: Krzysztof Piotr Oledzki <ole@ans.pl>
Cc: Jan Kara <jack@ucw.cz>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Osterried <osterried@jesse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Bjorn Steinbrink 2008-02-04 22:29:28 -08:00 committed by Linus Torvalds
parent ae1276b934
commit a2b345642f
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
mm/truncate.c
View File

@ -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);