Messages in this thread Patch in this message | | | Date | Wed, 25 Jun 2008 14:40:39 +0200 | From | Miklos Szeredi <> | Subject | [patch 1/2] mm: dont clear PG_uptodate in invalidate_complete_page2() |
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From: Miklos Szeredi <mszeredi@suse.cz>
Clearing the uptodate page flag will cause page_cache_pipe_buf_confirm() to return -ENODATA if that page was in the buffer. This in turn will cause splice() to return a short or zero count.
This manifested itself in rare I/O errors seen on nfs exported fuse filesystems. This is because nfsd uses splice_direct_to_actor() to read files, and fuse uses invalidate_inode_pages2() to invalidate stale data on open.
Fix this by not clearing PG_uptodate on page invalidation. This will result in the old, invalid page contents being copied. But that's OK, the contents were valid at splice-in time (which is when the the "copy" was conceptually done).
I haven't done an audit of all code that checks the PG_uptodate flags, but I suspect, that this change won't have any harmful effects. Most code checks page->mapping to see if the page was truncated or invalidated, before using it, and retries the find/read on the page if it wasn't. The page_cache_pipe_buf_confirm() code is an exception in this regard.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> --- mm/truncate.c | 1 - 1 file changed, 1 deletion(-)
Index: linux-2.6/mm/truncate.c =================================================================== --- linux-2.6.orig/mm/truncate.c 2008-06-24 20:49:25.000000000 +0200 +++ linux-2.6/mm/truncate.c 2008-06-24 23:28:32.000000000 +0200 @@ -356,7 +356,6 @@ invalidate_complete_page2(struct address 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: --
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