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Message-Id: <1166031601.9127.1.camel@lade.trondhjem.org>
Date: Wed, 13 Dec 2006 12:40:01 -0500
From: Trond Myklebust <trond.myklebust@....uio.no>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Andrew Morton <akpm@...l.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [PATCH] nfs: fix NR_FILE_DIRTY underflow
On Wed, 2006-12-13 at 16:01 +0100, Peter Zijlstra wrote:
> On Wed, 2006-12-13 at 07:26 -0500, Trond Myklebust wrote:
> > On Wed, 2006-12-13 at 13:12 +0100, Peter Zijlstra wrote:
> > > Still testing this patch, but it looks good so far.
> > >
> > > ---
> > > Just setting PG_dirty can cause NR_FILE_DIRTY to underflow
> > > which is bad (TM).
> > >
> > > Use set_page_dirty() which will do the right thing.
> >
> > Actually, I'd prefer to have it do the right thing by getting rid of
> > that call to test_clear_page_dirty() inside
> > invalidate_inode_pages2_range(). That is causing loss of data integrity,
> > and is what is causing us to have to hack NFS in the first place.
>
> Ah, I think I see what your problem is there.
> How about this totally untested patch:
>
> ---
> Delay clearing the dirty page state till after removing it from the
> mapping in invalidate_inode_pages2_range(). This will give
> try_to_release_pages() a shot to flush dirty data.
>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
> fs/nfs/file.c | 2 --
> include/linux/page-flags.h | 2 ++
> mm/page-writeback.c | 17 +++++++++++------
> mm/truncate.c | 11 +++--------
> 4 files changed, 16 insertions(+), 16 deletions(-)
>
> Index: linux-2.6-git/fs/nfs/file.c
> ===================================================================
> --- linux-2.6-git.orig/fs/nfs/file.c 2006-12-13 15:31:26.000000000 +0100
> +++ linux-2.6-git/fs/nfs/file.c 2006-12-13 15:39:33.000000000 +0100
> @@ -320,8 +320,6 @@ static int nfs_release_page(struct page
> */
> if (!(gfp & __GFP_FS))
> return 0;
> - /* Hack... Force nfs_wb_page() to write out the page */
> - SetPageDirty(page);
> return !nfs_wb_page(page_file_mapping(page)->host, page);
> }
>
> Index: linux-2.6-git/include/linux/page-flags.h
> ===================================================================
> --- linux-2.6-git.orig/include/linux/page-flags.h 2006-12-13 15:35:50.000000000 +0100
> +++ linux-2.6-git/include/linux/page-flags.h 2006-12-13 15:36:14.000000000 +0100
> @@ -252,7 +252,9 @@ static inline void SetPageUptodate(struc
> #define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
>
> struct page; /* forward declaration */
> +struct address_space;
>
> +int __test_clear_page_dirty(struct address_space *mapping, struct page *page);
> int test_clear_page_dirty(struct page *page);
> int test_clear_page_writeback(struct page *page);
> int test_set_page_writeback(struct page *page);
> Index: linux-2.6-git/mm/page-writeback.c
> ===================================================================
> --- linux-2.6-git.orig/mm/page-writeback.c 2006-12-13 15:34:15.000000000 +0100
> +++ linux-2.6-git/mm/page-writeback.c 2006-12-13 15:39:41.000000000 +0100
> @@ -850,13 +850,8 @@ int set_page_dirty_lock(struct page *pag
> }
> EXPORT_SYMBOL(set_page_dirty_lock);
>
> -/*
> - * Clear a page's dirty flag, while caring for dirty memory accounting.
> - * Returns true if the page was previously dirty.
> - */
> -int test_clear_page_dirty(struct page *page)
> +int __test_clear_page_dirty(struct address_space *mapping, struct page *page)
> {
> - struct address_space *mapping = page_mapping(page);
> unsigned long flags;
>
> if (!mapping)
> @@ -880,6 +875,16 @@ int test_clear_page_dirty(struct page *p
> write_unlock_irqrestore(&mapping->tree_lock, flags);
> return 0;
> }
> +
> +/*
> + * Clear a page's dirty flag, while caring for dirty memory accounting.
> + * Returns true if the page was previously dirty.
> + */
> +int test_clear_page_dirty(struct page *page)
> +{
> + struct address_space *mapping = page_mapping(page);
> + return __test_clear_page_dirty(mapping, page);
> +}
> EXPORT_SYMBOL(test_clear_page_dirty);
>
> /*
> Index: linux-2.6-git/mm/truncate.c
> ===================================================================
> --- linux-2.6-git.orig/mm/truncate.c 2006-12-13 15:36:38.000000000 +0100
> +++ linux-2.6-git/mm/truncate.c 2006-12-13 15:44:01.000000000 +0100
> @@ -307,18 +307,12 @@ invalidate_complete_page2(struct address
> return 0;
>
> write_lock_irq(&mapping->tree_lock);
> - if (PageDirty(page))
> - goto failed;
> -
> BUG_ON(PagePrivate(page));
> __remove_from_page_cache(page);
> write_unlock_irq(&mapping->tree_lock);
> ClearPageUptodate(page);
> page_cache_release(page); /* pagecache ref */
> return 1;
> -failed:
> - write_unlock_irq(&mapping->tree_lock);
> - return 0;
> }
>
> /**
> @@ -386,12 +380,13 @@ int invalidate_inode_pages2_range(struct
> PAGE_CACHE_SIZE, 0);
> }
> }
> - was_dirty = test_clear_page_dirty(page);
> + was_dirty = PageDirty(page);
> if (!invalidate_complete_page2(mapping, page)) {
> if (was_dirty)
> set_page_dirty(page);
^^^^^^^^^^^^^^^^^^^^^
Why would you still need this?
> ret = -EIO;
> - }
> + } else
> + __test_clear_page_dirty(mapping, page);
> unlock_page(page);
> }
> pagevec_release(&pvec);
>
Cheers
Trond
-
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