[PATCH 2/2] page cache: Mask off unwanted GFP flags

From: Matthew Wilcox
Date: Tue Apr 10 2018 - 08:54:16 EST


From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>

The page cache has used the mapping's GFP flags for allocating
radix tree nodes for a long time. It took care to always mask off the
__GFP_HIGHMEM flag, and masked off other flags in other paths, but the
__GFP_ZERO flag was still able to sneak through. The __GFP_DMA and
__GFP_DMA32 flags would also have been able to sneak through if they
were ever used. Fix them all by using GFP_RECLAIM_MASK at the innermost
location, and remove it from earlier in the callchain.

Fixes: 19f99cee206c ("f2fs: add core inode operations")
Reported-by: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
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)
--
2.16.3