mm, memcg: use consistent gfp flags during readahead
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>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 75533ad..e91d558 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4180,7 +4180,8 @@
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;
}
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index d4890b6..579e41b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3366,7 +3366,7 @@
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);
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index dc54a4b..c75b66a 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -166,7 +166,7 @@
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;
}
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 9a8bbc1..c80dda4 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -996,7 +996,8 @@
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;
}
diff --git a/fs/mpage.c b/fs/mpage.c
index eedc644..c8a0590 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -71,6 +71,8 @@
{
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 @@
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;
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index 85640e9..06a8da7 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -80,7 +80,7 @@
if (!add_to_page_cache(page,
mapping,
page->index,
- GFP_KERNEL)) {
+ readahead_gfp_mask(mapping))) {
ret = read_one_page(page);
gossip_debug(GOSSIP_INODE_DEBUG,
"failure adding page to cache, read_one_page returned: %d\n",