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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>
This commit is contained in:
Michal Hocko 2016-07-26 15:24:53 -07:00 committed by Linus Torvalds
parent e5e3f4c4f0
commit 8a5c743e30
8 changed files with 19 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/btrfs/extent_io.c
View File

@ -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;
}

2
fs/cifs/file.c
View File

@ -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);

2
fs/ext4/readpage.c
View File

@ -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;
}

3
fs/f2fs/data.c
View File

@ -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;
}

4
fs/mpage.c
View File

@ -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;

2
fs/orangefs/inode.c
View File

@ -80,7 +80,7 @@ static int orangefs_readpages(struct file *file,
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",

6
include/linux/pagemap.h
View File

@ -209,10 +209,10 @@ static inline struct page *page_cache_alloc_cold(struct address_space *x)
return __page_cache_alloc(mapping_gfp_mask(x)|__GFP_COLD);
}
static inline struct page *page_cache_alloc_readahead(struct address_space *x)
static inline gfp_t readahead_gfp_mask(struct address_space *x)
{
return __page_cache_alloc(mapping_gfp_mask(x) |
__GFP_COLD | __GFP_NORETRY | __GFP_NOWARN);
return mapping_gfp_mask(x) |
__GFP_COLD | __GFP_NORETRY | __GFP_NOWARN;
}
typedef int filler_t(void *, struct page *);

13
mm/readahead.c
View File

@ -89,7 +89,7 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages,
page = lru_to_page(pages);
list_del(&page->lru);
if (add_to_page_cache_lru(page, mapping, page->index,
mapping_gfp_constraint(mapping, GFP_KERNEL))) {
readahead_gfp_mask(mapping))) {
read_cache_pages_invalidate_page(mapping, page);
continue;
}
@ -108,7 +108,7 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages,
EXPORT_SYMBOL(read_cache_pages);
static int read_pages(struct address_space *mapping, struct file *filp,
struct list_head *pages, unsigned nr_pages)
struct list_head *pages, unsigned int nr_pages, gfp_t gfp)
{
struct blk_plug plug;
unsigned page_idx;
@ -126,10 +126,8 @@ static int read_pages(struct address_space *mapping, struct file *filp,
for (page_idx = 0; page_idx < nr_pages; page_idx++) {
struct page *page = lru_to_page(pages);
list_del(&page->lru);
if (!add_to_page_cache_lru(page, mapping, page->index,
mapping_gfp_constraint(mapping, GFP_KERNEL))) {
if (!add_to_page_cache_lru(page, mapping, page->index, gfp))
mapping->a_ops->readpage(filp, page);
}
put_page(page);
}
ret = 0;
@ -159,6 +157,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
int page_idx;
int ret = 0;
loff_t isize = i_size_read(inode);
gfp_t gfp_mask = readahead_gfp_mask(mapping);
if (isize == 0)
goto out;
@ -180,7 +179,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
if (page && !radix_tree_exceptional_entry(page))
continue;
page = page_cache_alloc_readahead(mapping);
page = __page_cache_alloc(gfp_mask);
if (!page)
break;
page->index = page_offset;
@ -196,7 +195,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
* will then handle the error.
*/
if (ret)
read_pages(mapping, filp, &page_pool, ret);
read_pages(mapping, filp, &page_pool, ret, gfp_mask);
BUG_ON(!list_empty(&page_pool));
out:
return ret;