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SubjectRe: 2.4.0-test10-pre3:Oops in mm/filemap.c:filemap_write_pa


On Mon, 23 Oct 2000, Linus Torvalds wrote:

> On Mon, 23 Oct 2000, Alexander Viro wrote:
> >
> > That's fine, but I'm afraid that we'll need a bit more than that. A couple of
> > obvious ones:
> > * filemap_nopage() needs the second check for ->i_size. Upon exit.
>
> Nope, that just makes the race window smaller. We should check for i_size
> after we've gotten the page table lock and just before actually entering
> the page into the page tables. Otherwise we'll still race on SMP (a _very_
> hard window to get into, admittedly).

Umm... I would probably remove Uptodate upon truncate() and check _that_
in the place you've mentioned.

> So how about this truncate_complete_page() implementation:
>
> /*
> * Try to get rid of a page.. Clear it if it fails
> * for some reason. The page must be locked upon calling
> * this function.
> *
> * We remove the page from the page cache _after_ we have
> * destroyed all buffer-cache references to it. Otherwise some
> * other process might think this inode page is not in the
> * page cache and creates a buffer-cache alias to it causing
> * all sorts of fun problems ...
> */
> static inline void truncate_complete_page(struct page *page)
> {
> /* Try to get rid of buffers */
> if (page->buffers)
> block_flushpage(page, 0);
>
> spin_lock(&pagecache_lock);
> spin_lock(&pagemap_lru_lock);
>
> if (page_count(page) != 1) {
> memclear_highpage_flush(page, 0, PAGE_CACHE_SIZE);
> } else {
> ClearPageDirty(page);
ClearPageUptodate(page);

How about that?

> __lru_cache_del(page);
> __remove_inode_page(page);
> page_cache_release(page);
> }
> spin_unlock(&pagemap_lru_lock);
> spin_unlock(&pagecache_lock);
> }
>
> we should probably special-case the "block_flushpage()" failed case, but
> the above should do reasonable things with it (because page_count() will
> be > 1 due to buffers).

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