At 05:06 08/08/13, Mingming Cao wrote:
>> With that said, I don't have strong feelings against falling back to
>> buffered IO when the invalidate fails.
>>
>>
>It seems a little odd that we have to back to buffered IO in this case.
>The pages are all flushed, DIO just want to make sure the
>journaltransactions who still keep those buffers are removed from their
>list. It did that, the only reason to keep DIO fail is someone else
>hasn't release the bh.
>
>Current code enforce all the buffers have to be freed and pages are
>removed from page cache, in order to force later read are from disk. I
>am not sure why can't we just leave the page in the cache, just clear it
>uptodate flag, without reduce the page ref count? I think DIO should
>proceed it's IO in this case...
Like this?
Following patch just clears PG_uptodate when try_to_release_page fails.
diff -Nrup linux-2.6.27-rc3.org/mm/truncate.c linux-2.6.27-rc3/mm/truncate.c
--- linux-2.6.27-rc3.org/mm/truncate.c 2008-08-13 13:48:48.000000000 +0900
+++ linux-2.6.27-rc3/mm/truncate.c 2008-08-13 14:24:47.000000000 +0900
@@ -345,8 +345,10 @@ invalidate_complete_page2(struct address
if (page->mapping != mapping)
return 0;
- if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL))
- return 0;
+ if (PagePrivate(page) && !try_to_release_page(page, GFP_KERNEL)) {
+ ClearPageUptodate(page);
+ return 1;
+ }
spin_lock_irq(&mapping->tree_lock);
if (PageDirty(page))
But this patch may cause some issue.
See,
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=84209e02de48d72289650cc5a7ae8dd18223620f;hp=2b12a4c524812fb3f6ee590a02e65b95c8c32229
ClearPageUptodate in truncate.c was removed at 2.6.27-rc2 because this triggers some
problems around NFS,FUSE,madvice.
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