fs/buffer.c: support buffer cache allocations with gfp modifiers

A buffer cache is allocated from movable area because it is referred
for a while and released soon.  But some filesystems are taking buffer
cache for a long time and it can disturb page migration.

New APIs are introduced to allocate buffer cache with user specific
flag.  *_gfp APIs are for user want to set page allocation flag for
page cache allocation.  And *_unmovable APIs are for the user wants to
allocate page cache from non-movable area.

Signed-off-by: Gioh Kim <gioh.kim@lge.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

1 files changed, 26 insertions, 19 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 8f05111bbb8b..9a6029e0dd71 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -993,7 +993,7 @@ init_page_buffers(struct page *page, struct block_device *bdev,
  */
 static int
 grow_dev_page(struct block_device *bdev, sector_t block,
-                pgoff_t index, int size, int sizebits)
+              pgoff_t index, int size, int sizebits, gfp_t gfp)
 {
         struct inode *inode = bdev->bd_inode;
         struct page *page;
@@ -1002,8 +1002,8 @@ 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_mask |= __GFP_MOVABLE;
+        gfp_mask = (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp;
+
         /*
          * XXX: __getblk_slow() can not really deal with failure and
          * will endlessly loop on improvised global reclaim.  Prefer
@@ -1058,7 +1058,7 @@ failed:
  * that page was dirty, the buffers are set dirty also.
  */
 static int
-grow_buffers(struct block_device *bdev, sector_t block, int size)
+grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
 {
         pgoff_t index;
         int sizebits;
@@ -1085,11 +1085,12 @@ grow_buffers(struct block_device *bdev, sector_t block, int size)
         }
 
         /* Create a page with the proper size buffers.. */
-        return grow_dev_page(bdev, block, index, size, sizebits);
+        return grow_dev_page(bdev, block, index, size, sizebits, gfp);
 }
 
-static struct buffer_head *
-__getblk_slow(struct block_device *bdev, sector_t block, int size)
+struct buffer_head *
+__getblk_slow(struct block_device *bdev, sector_t block,
+             unsigned size, gfp_t gfp)
 {
         /* Size must be multiple of hard sectorsize */
         if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
@@ -1111,13 +1112,14 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
                 if (bh)
                         return bh;
 
-                ret = grow_buffers(bdev, block, size);
+                ret = grow_buffers(bdev, block, size, gfp);
                 if (ret < 0)
                         return NULL;
                 if (ret == 0)
                         free_more_memory();
         }
 }
+EXPORT_SYMBOL(__getblk_slow);
 
 /*
  * The relationship between dirty buffers and dirty pages:
@@ -1371,24 +1373,25 @@ __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
 EXPORT_SYMBOL(__find_get_block);
 
 /*
- * __getblk will locate (and, if necessary, create) the buffer_head
+ * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
  * which corresponds to the passed block_device, block and size. The
  * returned buffer has its reference count incremented.
  *
- * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
- * attempt is failing.  FIXME, perhaps?
+ * __getblk_gfp() will lock up the machine if grow_dev_page's
+ * try_to_free_buffers() attempt is failing.  FIXME, perhaps?
  */
 struct buffer_head *
-__getblk(struct block_device *bdev, sector_t block, unsigned size)
+__getblk_gfp(struct block_device *bdev, sector_t block,
+             unsigned size, gfp_t gfp)
 {
         struct buffer_head *bh = __find_get_block(bdev, block, size);
 
         might_sleep();
         if (bh == NULL)
-                bh = __getblk_slow(bdev, block, size);
+                bh = __getblk_slow(bdev, block, size, gfp);
         return bh;
 }
-EXPORT_SYMBOL(__getblk);
+EXPORT_SYMBOL(__getblk_gfp);
 
 /*
  * Do async read-ahead on a buffer..
@@ -1404,24 +1407,28 @@ void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
 EXPORT_SYMBOL(__breadahead);
 
 /**
- *  __bread() - reads a specified block and returns the bh
+ *  __bread_gfp() - reads a specified block and returns the bh
  *  @bdev: the block_device to read from
  *  @block: number of block
  *  @size: size (in bytes) to read
- * 
+ *  @gfp: page allocation flag
+ *
  *  Reads a specified block, and returns buffer head that contains it.
+ *  The page cache can be allocated from non-movable area
+ *  not to prevent page migration if you set gfp to zero.
  *  It returns NULL if the block was unreadable.
  */
 struct buffer_head *
-__bread(struct block_device *bdev, sector_t block, unsigned size)
+__bread_gfp(struct block_device *bdev, sector_t block,
+                   unsigned size, gfp_t gfp)
 {
-        struct buffer_head *bh = __getblk(bdev, block, size);
+        struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
 
         if (likely(bh) && !buffer_uptodate(bh))
                 bh = __bread_slow(bh);
         return bh;
 }
-EXPORT_SYMBOL(__bread);
+EXPORT_SYMBOL(__bread_gfp);
 
 /*
  * invalidate_bh_lrus() is called rarely - but not only at unmount.