On Wed, 13 Dec 2006 19:48:34 +0100
Peter Zijlstra <[email protected]> wrote:
> --- linux-2.6-git.orig/mm/truncate.c 2006-12-13 19:41:09.000000000 +0100
> +++ linux-2.6-git/mm/truncate.c 2006-12-13 19:42:56.000000000 +0100
> @@ -306,19 +306,14 @@ invalidate_complete_page2(struct address
> if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
> return 0;
>
> + test_clear_page_dirty(page);
> 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;
> }
>
> /**
> @@ -350,7 +345,6 @@ int invalidate_inode_pages2_range(struct
> for (i = 0; !ret && i < pagevec_count(&pvec); i++) {
> struct page *page = pvec.pages[i];
> pgoff_t page_index;
> - int was_dirty;
>
> lock_page(page);
> if (page->mapping != mapping) {
> @@ -386,12 +380,8 @@ int invalidate_inode_pages2_range(struct
> PAGE_CACHE_SIZE, 0);
> }
> }
> - was_dirty = test_clear_page_dirty(page);
> - if (!invalidate_complete_page2(mapping, page)) {
> - if (was_dirty)
> - set_page_dirty(page);
> + if (!invalidate_complete_page2(mapping, page))
> ret = -EIO;
> - }
> unlock_page(page);
> }
> pagevec_release(&pvec);
a) we're now calling try_to_release_page() with a potentially-dirty
page, whereas it was previously clean.
I wouldn't expect ->releasepage() implementations to go looking at
PG_Dirty, because that's not what they're suppoed to be interested in.
But they might do, dunno.
b) If invalidate_complete_page2() failed due to, say, dirty buffer_heads
then we now have a clean page with dirty buffers. That is an illegal
state and the page will leak permanently.
I _think_ that's what the was_dirty logic is in there for: to
preserve the correct page-vs-buffers dirtiness coherency. But I'd need
to do some 2.5.x changelog-dumpster-diving to be sure.
Sigh. I don't know what invalidate_inode_pages2() is *supposed to do*.
What are its semantics wrt unfreeable page metadata? Against page
dirtiness?
It was written for direct-io and had one set of semantics for that, then
NFS came along and seemed to require a slightly different set of semantics,
even though the earlier semantics weren't really defined, leading to a
belief that the present semantics are "wrong", without a definition of what
semantics NFS actually desires.
So let's start again.
Trond, please define precisely and completely and without reference to
the existing implementation: what behaviour does NFS want?
-
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