mm, fs: introduce mapping_gfp_constraint()

There are many places which use mapping_gfp_mask to restrict a more
generic gfp mask which would be used for allocations which are not
directly related to the page cache but they are performed in the same
context.

Let's introduce a helper function which makes the restriction explicit and
easier to track.  This patch doesn't introduce any functional changes.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

19 files changed, 36 insertions, 30 deletions

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 3c2d4abd71c5..1d47d2e9487c 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -491,7 +491,7 @@ struct page **drm_gem_get_pages(struct drm_gem_object *obj)
                  * __GFP_DMA32 to be set in mapping_gfp_mask(inode->i_mapping)
                  * so shmem can relocate pages during swapin if required.
                  */
-                BUG_ON((mapping_gfp_mask(mapping) & __GFP_DMA32) &&
+                BUG_ON(mapping_gfp_constraint(mapping, __GFP_DMA32) &&
                                 (page_to_pfn(p) >= 0x00100000UL));
         }
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 7e505d4be7c0..399aab265db3 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2214,9 +2214,8 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
          * Fail silently without starting the shrinker
          */
         mapping = file_inode(obj->base.filp)->i_mapping;
-        gfp = mapping_gfp_mask(mapping);
+        gfp = mapping_gfp_constraint(mapping, ~(__GFP_IO | __GFP_RECLAIM));
         gfp |= __GFP_NORETRY | __GFP_NOWARN;
-        gfp &= ~(__GFP_IO | __GFP_RECLAIM);
         sg = st->sgl;
         st->nents = 0;
         for (i = 0; i < page_count; i++) {
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 57ee8ca29b06..36dfeff2c1f4 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -482,13 +482,12 @@ static noinline int add_ra_bio_pages(struct inode *inode,
                         goto next;
                 }
 
-                page = __page_cache_alloc(mapping_gfp_mask(mapping) &
-                                                                ~__GFP_FS);
+                page = __page_cache_alloc(mapping_gfp_constraint(mapping,
+                                                                 ~__GFP_FS));
                 if (!page)
                         break;
 
-                if (add_to_page_cache_lru(page, mapping, pg_index,
-                                                                GFP_NOFS)) {
+                if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
                         page_cache_release(page);
                         goto next;
                 }
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 938efe33be80..eb90f0f1a124 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3316,7 +3316,7 @@ static inline bool btrfs_mixed_space_info(struct btrfs_space_info *space_info)
 
 static inline gfp_t btrfs_alloc_write_mask(struct address_space *mapping)
 {
-        return mapping_gfp_mask(mapping) & ~__GFP_FS;
+        return mapping_gfp_constraint(mapping, ~__GFP_FS);
 }
 
 /* extent-tree.c */
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index abe3a66bd3ba..ed05da1b977e 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -85,8 +85,8 @@ static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
         }
 
         mapping_set_gfp_mask(inode->i_mapping,
-                        mapping_gfp_mask(inode->i_mapping) &
-                        ~(__GFP_FS | __GFP_HIGHMEM));
+                        mapping_gfp_constraint(inode->i_mapping,
+                        ~(__GFP_FS | __GFP_HIGHMEM)));
 
         return inode;
 }
diff --git a/fs/buffer.c b/fs/buffer.c
index 82283abb2795..51aff0296ce2 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -999,7 +999,7 @@ grow_dev_page(struct block_device *bdev, sector_t block,
         int ret = 0;            /* Will call free_more_memory() */
         gfp_t gfp_mask;
 
-        gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp;
+        gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
 
         /*
          * XXX: __getblk_slow() can not really deal with failure and
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 9d23e788d1df..b7d218a168fb 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -1283,8 +1283,8 @@ static int ceph_filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
                 int ret1;
                 struct address_space *mapping = inode->i_mapping;
                 struct page *page = find_or_create_page(mapping, 0,
-                                                mapping_gfp_mask(mapping) &
-                                                ~__GFP_FS);
+                                                mapping_gfp_constraint(mapping,
+                                                ~__GFP_FS));
                 if (!page) {
                         ret = VM_FAULT_OOM;
                         goto out;
@@ -1428,7 +1428,8 @@ void ceph_fill_inline_data(struct inode *inode, struct page *locked_page,
                 if (i_size_read(inode) == 0)
                         return;
                 page = find_or_create_page(mapping, 0,
-                                           mapping_gfp_mask(mapping) & ~__GFP_FS);
+                                           mapping_gfp_constraint(mapping,
+                                           ~__GFP_FS));
                 if (!page)
                         return;
                 if (PageUptodate(page)) {
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 47c5c97e2dd3..0068e82217c3 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -3380,7 +3380,7 @@ 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 = GFP_KERNEL & mapping_gfp_mask(mapping);
+        gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
 
         INIT_LIST_HEAD(tmplist);
 
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 612fbcf76b5c..60aaecd5598b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3344,7 +3344,7 @@ static int __ext4_block_zero_page_range(handle_t *handle,
         int err = 0;
 
         page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT,
-                                   mapping_gfp_mask(mapping) & ~__GFP_FS);
+                                   mapping_gfp_constraint(mapping, ~__GFP_FS));
         if (!page)
                 return -ENOMEM;
 
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 560af0437704..1061611ae14d 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -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,
-                                        GFP_KERNEL & mapping_gfp_mask(mapping)))
+                                  mapping_gfp_constraint(mapping, GFP_KERNEL)))
                                 goto next_page;
                 }
 
diff --git a/fs/logfs/segment.c b/fs/logfs/segment.c
index 7f9b096d8d57..6de0fbfc6c00 100644
--- a/fs/logfs/segment.c
+++ b/fs/logfs/segment.c
@@ -57,7 +57,7 @@ static struct page *get_mapping_page(struct super_block *sb, pgoff_t index,
         filler_t *filler = super->s_devops->readpage;
         struct page *page;
 
-        BUG_ON(mapping_gfp_mask(mapping) & __GFP_FS);
+        BUG_ON(mapping_gfp_constraint(mapping, __GFP_FS));
         if (use_filler)
                 page = read_cache_page(mapping, index, filler, sb);
         else {
diff --git a/fs/mpage.c b/fs/mpage.c
index 09abba7653aa..1480d3a18037 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -361,7 +361,7 @@ 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 = GFP_KERNEL & mapping_gfp_mask(mapping);
+        gfp_t gfp = mapping_gfp_constraint(mapping, GFP_KERNEL);
 
         map_bh.b_state = 0;
         map_bh.b_size = 0;
@@ -397,7 +397,7 @@ int mpage_readpage(struct page *page, get_block_t get_block)
         sector_t last_block_in_bio = 0;
         struct buffer_head map_bh;
         unsigned long first_logical_block = 0;
-        gfp_t gfp = GFP_KERNEL & mapping_gfp_mask(page->mapping);
+        gfp_t gfp = mapping_gfp_constraint(page->mapping, GFP_KERNEL);
 
         map_bh.b_state = 0;
         map_bh.b_size = 0;
diff --git a/fs/namei.c b/fs/namei.c
index 0d3340b32e14..3c18970a8899 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4604,7 +4604,7 @@ EXPORT_SYMBOL(__page_symlink);
 int page_symlink(struct inode *inode, const char *symname, int len)
 {
         return __page_symlink(inode, symname, len,
-                        !(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
+                        !mapping_gfp_constraint(inode->i_mapping, __GFP_FS));
 }
 EXPORT_SYMBOL(page_symlink);
 
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 4a73d6dffabf..ac2f64943ff4 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -356,7 +356,7 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
                 goto failed;
 
         mapping_set_gfp_mask(inode->i_mapping,
-                             mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
+                           mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS));
 
         root = NILFS_I(dir)->i_root;
         ii = NILFS_I(inode);
@@ -522,7 +522,7 @@ static int __nilfs_read_inode(struct super_block *sb,
         up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
         nilfs_set_inode_flags(inode);
         mapping_set_gfp_mask(inode->i_mapping,
-                             mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
+                           mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS));
         return 0;
 
  failed_unmap:
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index 262561fea923..9d383e5eff0e 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -525,8 +525,8 @@ static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
                                 }
                         }
                         err = add_to_page_cache_lru(*cached_page, mapping,
-                                        index,
-                                        GFP_KERNEL & mapping_gfp_mask(mapping));
+                                   index,
+                                   mapping_gfp_constraint(mapping, GFP_KERNEL));
                         if (unlikely(err)) {
                                 if (err == -EEXIST)
                                         continue;
diff --git a/fs/splice.c b/fs/splice.c
index 5fc1e50a7f30..801c21cd77fe 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -360,7 +360,7 @@ __generic_file_splice_read(struct file *in, loff_t *ppos,
                                 break;
 
                         error = add_to_page_cache_lru(page, mapping, index,
-                                        GFP_KERNEL & mapping_gfp_mask(mapping));
+                                   mapping_gfp_constraint(mapping, GFP_KERNEL));
                         if (unlikely(error)) {
                                 page_cache_release(page);
                                 if (error == -EEXIST)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a6c78e00ea96..26eabf5ec718 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -69,6 +69,13 @@ static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
         return (__force gfp_t)mapping->flags & __GFP_BITS_MASK;
 }
 
+/* Restricts the given gfp_mask to what the mapping allows. */
+static inline gfp_t mapping_gfp_constraint(struct address_space *mapping,
+                gfp_t gfp_mask)
+{
+        return mapping_gfp_mask(mapping) & gfp_mask;
+}
+
 /*
  * This is non-atomic.  Only to be used before the mapping is activated.
  * Probably needs a barrier...
diff --git a/mm/filemap.c b/mm/filemap.c
index 6ef3674c0763..1bb007624b53 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1722,7 +1722,7 @@ no_cached_page:
                         goto out;
                 }
                 error = add_to_page_cache_lru(page, mapping, index,
-                                        GFP_KERNEL & mapping_gfp_mask(mapping));
+                                mapping_gfp_constraint(mapping, GFP_KERNEL));
                 if (error) {
                         page_cache_release(page);
                         if (error == -EEXIST) {
@@ -1824,7 +1824,7 @@ static int page_cache_read(struct file *file, pgoff_t offset)
                         return -ENOMEM;
 
                 ret = add_to_page_cache_lru(page, mapping, offset,
-                                GFP_KERNEL & mapping_gfp_mask(mapping));
+                                mapping_gfp_constraint(mapping, GFP_KERNEL));
                 if (ret == 0)
                         ret = mapping->a_ops->readpage(file, page);
                 else if (ret == -EEXIST)
diff --git a/mm/readahead.c b/mm/readahead.c
index 998ad592f408..ba22d7fe0afb 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -90,7 +90,7 @@ int read_cache_pages(struct address_space *mapping, struct list_head *pages,
                 page = list_to_page(pages);
                 list_del(&page->lru);
                 if (add_to_page_cache_lru(page, mapping, page->index,
-                                GFP_KERNEL & mapping_gfp_mask(mapping))) {
+                                mapping_gfp_constraint(mapping, GFP_KERNEL))) {
                         read_cache_pages_invalidate_page(mapping, page);
                         continue;
                 }
@@ -128,7 +128,7 @@ static int read_pages(struct address_space *mapping, struct file *filp,
                 struct page *page = list_to_page(pages);
                 list_del(&page->lru);
                 if (!add_to_page_cache_lru(page, mapping, page->index,
-                                GFP_KERNEL & mapping_gfp_mask(mapping))) {
+                                mapping_gfp_constraint(mapping, GFP_KERNEL))) {
                         mapping->a_ops->readpage(filp, page);
                 }
                 page_cache_release(page);