From: Matthew Wilcox mawilcox@microsoft.com

f2fs specifies the __GFP_ZERO flag for allocating some of its pages. Unfortunately, the page cache also uses the mapping's GFP flags for allocating radix tree nodes. It always masked off the __GFP_HIGHMEM flag, and masks off __GFP_ZERO in some paths, but not all. That causes radix tree nodes to be allocated with a NULL list_head, which causes backtraces like:

[<ffffff80086f4de0>] __list_del_entry+0x30/0xd0 [<ffffff8008362018>] list_lru_del+0xac/0x1ac [<ffffff800830f04c>] page_cache_tree_insert+0xd8/0x110

The __GFP_DMA and __GFP_DMA32 flags would also be able to sneak through if they are ever used. Fix them all by using GFP_RECLAIM_MASK at the innermost location, and remove it from earlier in the callchain.

Fixes: 449dd6984d0e ("mm: keep page cache radix tree nodes in check") Reported-by: Chris Fries cfries@google.com Debugged-by: Minchan Kim minchan@kernel.org Signed-off-by: Matthew Wilcox mawilcox@microsoft.com Acked-by: Johannes Weiner hannes@cmpxchg.org Acked-by: Michal Hocko mhocko@suse.com Reviewed-by: Jan Kara jack@suse.cz Cc: stable@vger.kernel.org --- mm/filemap.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c index c2147682f4c3..1a4bfc5ed3dc 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -785,7 +785,7 @@ int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) VM_BUG_ON_PAGE(!PageLocked(new), new); VM_BUG_ON_PAGE(new->mapping, new);

- error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); + error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK); if (!error) { struct address_space *mapping = old->mapping; void (*freepage)(struct page *); @@ -841,7 +841,7 @@ static int __add_to_page_cache_locked(struct page *page, return error; }

- error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM); + error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK); if (error) { if (!huge) mem_cgroup_cancel_charge(page, memcg, false); @@ -1574,8 +1574,7 @@ struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset, if (fgp_flags & FGP_ACCESSED) __SetPageReferenced(page);

- err = add_to_page_cache_lru(page, mapping, offset, - gfp_mask & GFP_RECLAIM_MASK); + err = add_to_page_cache_lru(page, mapping, offset, gfp_mask); if (unlikely(err)) { put_page(page); page = NULL; @@ -2378,7 +2377,7 @@ static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask) if (!page) return -ENOMEM;

- ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL); + ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask); if (ret == 0) ret = mapping->a_ops->readpage(file, page); else if (ret == -EEXIST)