Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

Wu Fengguang
2009-08-05T12:38:00Z

On Wed, Aug 05, 2009 at 06:20:08PM +0800, Nick Piggin wrote:
> On Wed, Aug 05, 2009 at 11:36:38AM +0200, Andi Kleen wrote:
> >
> > From: Nick Piggin <npiggin@suse.de>
> >
> > Extract out truncate_inode_page() out of the truncate path so that
> > it can be used by memory-failure.c
> >
> > [AK: description, headers, fix typos]
> > v2: Some white space changes from Fengguang Wu
> >
> > Signed-off-by: Andi Kleen <ak@linux.intel.com>
> >
> > ---
> > include/linux/mm.h | 2 ++
> > mm/truncate.c | 29 +++++++++++++++--------------
> > 2 files changed, 17 insertions(+), 14 deletions(-)
> >
> > Index: linux/mm/truncate.c
> > ===================================================================
> > --- linux.orig/mm/truncate.c
> > +++ linux/mm/truncate.c
> > @@ -93,11 +93,11 @@ EXPORT_SYMBOL(cancel_dirty_page);
> > * its lock, b) when a concurrent invalidate_mapping_pages got there first and
> > * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
> > */
> > -static void
> > +static int
> > truncate_complete_page(struct address_space *mapping, struct page *page)
> > {
> > if (page->mapping != mapping)
> > - return;
> > + return -EIO;
>
> Hmm, at this point, the page must have been removed from pagecache,
> so I don't know if you need to pass an error back?

Me think so too. When called from hwpoison, the page count and lock
have both be taken, so at least _in this case_,

(page->mapping != mapping)

can be equally written as

(page->mapping == NULL)

But anyway, the return value is now ignored in upper layer :)

Thanks,
Fengguang

>
> > if (page_has_private(page))
> > do_invalidatepage(page, 0);
> > @@ -108,6 +108,7 @@ truncate_complete_page(struct address_sp
> > remove_from_page_cache(page);
> > ClearPageMappedToDisk(page);
> > page_cache_release(page); /* pagecache ref */
> > + return 0;
> > }
> >
> > /*
> > @@ -135,6 +136,16 @@ invalidate_complete_page(struct address_
> > return ret;
> > }
> >
> > +int truncate_inode_page(struct address_space *mapping, struct page *page)
> > +{
> > + if (page_mapped(page)) {
> > + unmap_mapping_range(mapping,
> > + (loff_t)page->index << PAGE_CACHE_SHIFT,
> > + PAGE_CACHE_SIZE, 0);
> > + }
> > + return truncate_complete_page(mapping, page);
> > +}
> > +
> > /**
> > * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
> > * @mapping: mapping to truncate
> > @@ -196,12 +207,7 @@ void truncate_inode_pages_range(struct a
> > unlock_page(page);
> > continue;
> > }
> > - if (page_mapped(page)) {
> > - unmap_mapping_range(mapping,
> > - (loff_t)page_index<<PAGE_CACHE_SHIFT,
> > - PAGE_CACHE_SIZE, 0);
> > - }
> > - truncate_complete_page(mapping, page);
> > + truncate_inode_page(mapping, page);
> > unlock_page(page);
> > }
> > pagevec_release(&pvec);
> > @@ -238,15 +244,10 @@ void truncate_inode_pages_range(struct a
> > break;
> > lock_page(page);
> > wait_on_page_writeback(page);
> > - if (page_mapped(page)) {
> > - unmap_mapping_range(mapping,
> > - (loff_t)page->index<<PAGE_CACHE_SHIFT,
> > - PAGE_CACHE_SIZE, 0);
> > - }
> > + truncate_inode_page(mapping, page);
> > if (page->index > next)
> > next = page->index;
> > next++;
> > - truncate_complete_page(mapping, page);
> > unlock_page(page);
> > }
> > pagevec_release(&pvec);
> > Index: linux/include/linux/mm.h
> > ===================================================================
> > --- linux.orig/include/linux/mm.h
> > +++ linux/include/linux/mm.h
> > @@ -809,6 +809,8 @@ static inline void unmap_shared_mapping_
> > extern int vmtruncate(struct inode * inode, loff_t offset);
> > extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end);
> >
> > +int truncate_inode_page(struct address_space *mapping, struct page *page);
> > +
> > #ifdef CONFIG_MMU
> > extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> > unsigned long address, unsigned int flags);