On Tue, Oct 11, 2016 at 05:40:31PM +0200, Jan Kara wrote: > On Thu 15-09-16 14:54:53, Kirill A. Shutemov wrote: > > We want page to be isolated from the rest of the system before spliting > > it. We rely on page count to be 2 for file pages to make sure nobody > > uses the page: one pin to caller, one to radix-tree. > > > > Filesystems with backing storage can have page count increased if it has > > buffers. > > > > Let's try to free them, before attempt split. And remove one guarding > > VM_BUG_ON_PAGE(). > > > > Signed-off-by: Kirill A. Shutemov <[email protected]> > ... > > @@ -2041,6 +2041,23 @@ int split_huge_page_to_list(struct page *page, > > struct list_head *list) > > goto out; > > } > > > > + /* Try to free buffers before attempt split */ > > + if (!PageSwapBacked(head) && PagePrivate(page)) { > > + /* > > + * We cannot trigger writeback from here due possible > > + * recursion if triggered from vmscan, only wait. > > + * > > + * Caller can trigger writeback it on its own, if safe. > > + */ > > + wait_on_page_writeback(head); > > + > > + if (page_has_buffers(head) && > > + !try_to_free_buffers(head)) { > > + ret = -EBUSY; > > + goto out; > > + } > > Shouldn't you rather use try_to_release_page() here? Because filesystems > have their ->releasepage() callbacks for freeing data associated with a > page. It is not guaranteed page private data are buffers although it is > true for ext4...
Fair enough. Will fix this. -- Kirill A. Shutemov
