Re: [PATCH] Make invalidate_inode_pages2() work again

[Nick Piggin <nickpiggin@yahoo.com.au>]

Chuck Lever wrote:

>A recent change to fix a problem with invalidate_inode_pages() has weakened
>the behavior of invalidate_inode_pages2() inadvertently.  Add a flag to
>tell the helper routines when stronger invalidation semantics are desired.
>

Question: if invalidate_inode_pages2 cares about not invalidating dirty
pages, how can one avoid the page_count check and it still be correct
(ie. not randomly lose dirty bits in some situations)?

>Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
>---
>
> mm/truncate.c |    8 ++++----
> 1 files changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/mm/truncate.c b/mm/truncate.c
>index c6ab55e..b3097a2 100644
>--- a/mm/truncate.c
>+++ b/mm/truncate.c
>@@ -59,7 +59,7 @@ truncate_complete_page(struct address_sp
>  * Returns non-zero if the page was successfully invalidated.
>  */
> static int
>-invalidate_complete_page(struct address_space *mapping, struct page *page)
>+invalidate_complete_page(struct address_space *mapping, struct page *page, int try_harder)
> {
> 	if (page->mapping != mapping)
> 		return 0;
>@@ -70,7 +70,7 @@ invalidate_complete_page(struct address_
> 	write_lock_irq(&mapping->tree_lock);
> 	if (PageDirty(page))
> 		goto failed;
>-	if (page_count(page) != 2)	/* caller's ref + pagecache ref */
>+	if (!try_harder && page_count(page) != 2)	/* caller's ref + pagecache ref */
> 		goto failed;
> 
> 	BUG_ON(PagePrivate(page));
>@@ -255,7 +255,7 @@ unsigned long invalidate_mapping_pages(s
> 				goto unlock;
> 			if (page_mapped(page))
> 				goto unlock;
>-			ret += invalidate_complete_page(mapping, page);
>+			ret += invalidate_complete_page(mapping, page, 0);
> unlock:
> 			unlock_page(page);
> 			if (next > end)
>@@ -339,7 +339,7 @@ int invalidate_inode_pages2_range(struct
> 				}
> 			}
> 			was_dirty = test_clear_page_dirty(page);
>-			if (!invalidate_complete_page(mapping, page)) {
>+			if (!invalidate_complete_page(mapping, page, 1)) {
> 				if (was_dirty)
> 					set_page_dirty(page);
> 				ret = -EIO;
>
>--
>  
>

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