mm, memcg: use consistent gfp flags during readahead (8a5c743e) · Commits · 戴 / test

Vladimir has noticed that we might declare memcg oom even during readahead because read_pages only uses GFP_KERNEL (with mapping_gfp restriction) while __do_page_cache_readahead uses page_cache_alloc_readahead which adds __GFP_NORETRY to prevent from OOMs. This gfp mask discrepancy is really unfortunate and easily fixable. Drop page_cache_alloc_readahead() which only has one user and outsource the gfp_mask logic into readahead_gfp_mask and propagate this mask from __do_page_cache_readahead down to read_pages. This alone would have only very limited impact as most filesystems are implementing ->readpages and the common implementation mpage_readpages does GFP_KERNEL (with mapping_gfp restriction) again. We can tell it to use readahead_gfp_mask instead as this function is called only during readahead as well. The same applies to read_cache_pages. ext4 has its own ext4_mpage_readpages but the path which has pages != NULL can use the same gfp mask. Btrfs, cifs, f2fs and orangefs are doing a very similar pattern to mpage_readpages so the same can be applied to them as well. [akpm@linux-foundation.org: coding-style fixes] [mhocko@suse.com: restrict gfp mask in mpage_alloc] Link: http://lkml.kernel.org/r/20160610074223.GC32285@dhcp22.suse.cz Link: http://lkml.kernel.org/r/1465301556-26431-1-git-send-email-mhocko@kernel.org Signed-off-by:

Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@parallels.com> Cc: Chris Mason <clm@fb.com> Cc: Steve French <sfrench@samba.org> Cc: Theodore Ts'o <tytso@mit.edu> Cc: Jan Kara <jack@suse.cz> Cc: Mike Marshall <hubcap@omnibond.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Changman Lee <cm224.lee@samsung.com> Cc: Chao Yu <yuchao0@huawei.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

fs/btrfs/extent_io.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -4180,7 +4180,8 @@ int extent_readpages(struct extent_io_tree *tree,
		prefetchw(&page->flags);
		list_del(&page->lru);
		if (add_to_page_cache_lru(page, mapping,
		page->index, GFP_NOFS)) {
		page->index,
		readahead_gfp_mask(mapping))) {
		put_page(page);
		continue;
		}

fs/cifs/file.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -3366,7 +3366,7 @@ readpages_get_pages(struct address_space mapping, struct list_head page_list,
		struct page page, tpage;
		unsigned int expected_index;
		int rc;
		gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
		gfp_t gfp = readahead_gfp_mask(mapping);

		INIT_LIST_HEAD(tmplist);

fs/ext4/readpage.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -166,7 +166,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
		page = list_entry(pages->prev, struct page, lru);
		list_del(&page->lru);
		if (add_to_page_cache_lru(page, mapping, page->index,
		mapping_gfp_constraint(mapping, GFP_KERNEL)))
		readahead_gfp_mask(mapping)))
		goto next_page;
		}

fs/f2fs/data.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -996,7 +996,8 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
		page = list_entry(pages->prev, struct page, lru);
		list_del(&page->lru);
		if (add_to_page_cache_lru(page, mapping,
		page->index, GFP_KERNEL))
		page->index,
		readahead_gfp_mask(mapping)))
		goto next_page;
		}

fs/mpage.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -71,6 +71,8 @@ mpage_alloc(struct block_device *bdev,
		{
		struct bio *bio;

		/* Restrict the given (page cache) mask for slab allocations */
		gfp_flags &= GFP_KERNEL;
		bio = bio_alloc(gfp_flags, nr_vecs);

		if (bio == NULL && (current->flags & PF_MEMALLOC)) {
		@@ -362,7 +364,7 @@ mpage_readpages(struct address_space mapping, struct list_head pages,
		sector_t last_block_in_bio = 0;
		struct buffer_head map_bh;
		unsigned long first_logical_block = 0;
		gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
		gfp_t gfp = readahead_gfp_mask(mapping);

		map_bh.b_state = 0;
		map_bh.b_size = 0;

Admin message