Messages in this thread Patch in this message | | | 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 |
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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 <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 v3: add comments
Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Andi Kleen <ak@linux.intel.com> --- 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<<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 +253,10 @@ 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); --- 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);
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