From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id A66C36B004D for ; Fri, 12 Jun 2009 09:26:35 -0400 (EDT) Date: Fri, 12 Jun 2009 21:27:14 +0800 From: Wu Fengguang Subject: Re: [PATCH 2/5] HWPOISON: fix tasklist_lock/anon_vma locking order Message-ID: <20090612132714.GB6751@localhost> References: <20090611142239.192891591@intel.com> <20090611144430.540500784@intel.com> <20090612100308.GD25568@one.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090612100308.GD25568@one.firstfloor.org> Sender: owner-linux-mm@kvack.org To: Andi Kleen Cc: Andrew Morton , LKML , Nick Piggin , Hugh Dickins , "riel@redhat.com" , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: On Fri, Jun 12, 2009 at 06:03:08PM +0800, Andi Kleen wrote: > On Thu, Jun 11, 2009 at 10:22:41PM +0800, Wu Fengguang wrote: > > To avoid possible deadlock. Proposed by Nick Piggin: > > I disagree with the description. There's no possible deadlock right now. > It would be purely out of paranoia. > > > > > You have tasklist_lock(R) nesting outside i_mmap_lock, and inside anon_vma > > lock. And anon_vma lock nests inside i_mmap_lock. > > > > This seems fragile. If rwlocks ever become FIFO or tasklist_lock changes > > I was a bit dubious on this reasoning. If rwlocks become FIFO a lot of > stuff will likely break. > > > type (maybe -rt kernels do it), then you could have a task holding > > I think they tried but backed off quickly again > > It's ok with a less scare-mongering description. Why not merge it into the original patch and add a simple changelog line there? I tried the last 6.5 patchset and it didn't apply cleanly to the latest -mm tree. And this patch was updated: --- HWPOISON: Refactor truncate to allow direct truncating of page v3 From: Nick Piggin 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 v3: add comments Signed-off-by: Nick Piggin Signed-off-by: Andi Kleen --- include/linux/mm.h | 2 ++ mm/truncate.c | 34 ++++++++++++++++++++++------------ 2 files changed, 24 insertions(+), 12 deletions(-) --- linux.orig/mm/truncate.c +++ linux/mm/truncate.c @@ -135,6 +135,26 @@ invalidate_complete_page(struct address_ return ret; } +/* + * Remove one page from its pagecache mapping. The page must be locked. + * This does not truncate the file on disk, it performs the pagecache + * side of the truncate operation. Dirty data will be discarded, and + * concurrent page references are ignored. + * + * Generic mm/fs code cannot call this on filesystem metadata mappings + * because those can assume that a page reference is enough to pin the + * page to its mapping. + */ +void 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); + } + truncate_complete_page(mapping, page); +} + /** * truncate_inode_pages - truncate range of pages specified by start & end byte offsets * @mapping: mapping to truncate @@ -196,12 +216,7 @@ void truncate_inode_pages_range(struct a unlock_page(page); continue; } - if (page_mapped(page)) { - unmap_mapping_range(mapping, - (loff_t)page_index<index<index > next) next = page->index; next++; - truncate_complete_page(mapping, page); unlock_page(page); } pagevec_release(&pvec); --- linux.orig/include/linux/mm.h +++ linux/include/linux/mm.h @@ -808,6 +808,8 @@ 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); +void 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, int write_access); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org