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Message-ID: <53EC45FC.7050508@lge.com>
Date: Thu, 14 Aug 2014 14:15:40 +0900
From: Gioh Kim <gioh.kim@....com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Peter Zijlstra <peterz@...radead.org>, Jan Kara <jack@...e.cz>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>,
linux-ext4@...r.kernel.org
CC: Minchan Kim <minchan@...nel.org>, Joonsoo Kim <js1304@...il.com>,
ÀÌ°ÇÈ£ <gunho.lee@....com>
Subject: [PATCH 1/2] fs/buffer.c: allocate buffer cache from non-movable area
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.
A new API should be introduced to allocate buffer cache from
non-movable area.
Signed-off-by: Gioh Kim <gioh.kim@....com>
---
fs/buffer.c | 63 ++++++++++++++++++++++++++++++++++++++-----
include/linux/buffer_head.h | 10 +++++++
2 files changed, 66 insertions(+), 7 deletions(-)
diff --git a/fs/buffer.c b/fs/buffer.c
index 8f05111..7ef658f 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 movable_mask)
{
struct inode *inode = bdev->bd_inode;
struct page *page;
@@ -1003,7 +1003,8 @@ grow_dev_page(struct block_device *bdev, sector_t block,
gfp_t gfp_mask;
gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS;
- gfp_mask |= __GFP_MOVABLE;
+ if (movable_mask & __GFP_MOVABLE)
+ gfp_mask |= __GFP_MOVABLE;
/*
* XXX: __getblk_slow() can not really deal with failure and
* will endlessly loop on improvised global reclaim. Prefer
@@ -1058,7 +1059,8 @@ 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 movable_mask)
{
pgoff_t index;
int sizebits;
@@ -1085,11 +1087,12 @@ 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, movable_mask);
}
static struct buffer_head *
-__getblk_slow(struct block_device *bdev, sector_t block, int size)
+__getblk_slow(struct block_device *bdev, sector_t block,
+ int size, gfp_t movable_mask)
{
/* Size must be multiple of hard sectorsize */
if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
@@ -1111,7 +1114,7 @@ __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, movable_mask);
if (ret < 0)
return NULL;
if (ret == 0)
@@ -1385,11 +1388,34 @@ __getblk(struct block_device *bdev, sector_t block, unsigned size)
might_sleep();
if (bh == NULL)
- bh = __getblk_slow(bdev, block, size);
+ bh = __getblk_slow(bdev, block, size, __GFP_MOVABLE);
return bh;
}
EXPORT_SYMBOL(__getblk);
+ /*
+ * __getblk_nonmovable 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.
+ *
+ * The page cache is allocated from non-movable area
+ * not to prevent page migration.
+ *
+ * __getblk()_nonmovable will lock up the machine
+ * if grow_dev_page's try_to_free_buffers() attempt is failing. FIXME, perhaps?
+ */
+struct buffer_head *
+__getblk_nonmovable(struct block_device *bdev, sector_t block, unsigned size)
+{
+ struct buffer_head *bh = __find_get_block(bdev, block, size);
+
+ might_sleep();
+ if (bh == NULL)
+ bh = __getblk_slow(bdev, block, size, 0);
+ return bh;
+}
+EXPORT_SYMBOL(__getblk_nonmovable);
+
/*
* Do async read-ahead on a buffer..
*/
@@ -1410,6 +1436,7 @@ EXPORT_SYMBOL(__breadahead);
* @size: size (in bytes) to read
*
* Reads a specified block, and returns buffer head that contains it.
+ * The page cache is allocated from movable area so that it can be migrated.
* It returns NULL if the block was unreadable.
*/
struct buffer_head *
@@ -1423,6 +1450,28 @@ __bread(struct block_device *bdev, sector_t block, unsigned size)
}
EXPORT_SYMBOL(__bread);
+/**
+ * __bread_nonmovable() - 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
+ *
+ * Reads a specified block, and returns buffer head that contains it.
+ * The page cache is allocated from non-movable area
+ * not to prevent page migration.
+ * It returns NULL if the block was unreadable.
+ */
+struct buffer_head *
+__bread_nonmovable(struct block_device *bdev, sector_t block, unsigned size)
+{
+ struct buffer_head *bh = __getblk_slow(bdev, block, size, 0);
+
+ if (likely(bh) && !buffer_uptodate(bh))
+ bh = __bread_slow(bh);
+ return bh;
+}
+EXPORT_SYMBOL(__bread_nonmovable);
+
/*
* invalidate_bh_lrus() is called rarely - but not only at unmount.
* This doesn't race because it runs in each cpu either in irq
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 324329c..3f52370 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -177,10 +177,14 @@ struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
unsigned size);
struct buffer_head *__getblk(struct block_device *bdev, sector_t block,
unsigned size);
+struct buffer_head *__getblk_nonmovable(struct block_device *bdev,
+ sector_t block, unsigned size);
void __brelse(struct buffer_head *);
void __bforget(struct buffer_head *);
void __breadahead(struct block_device *, sector_t block, unsigned int size);
struct buffer_head *__bread(struct block_device *, sector_t block, unsigned size);
+struct buffer_head *__bread_nonmovable(struct block_device *,
+ sector_t block, unsigned size);
void invalidate_bh_lrus(void);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
@@ -298,6 +302,12 @@ sb_bread(struct super_block *sb, sector_t block)
return __bread(sb->s_bdev, block, sb->s_blocksize);
}
+static inline struct buffer_head *
+sb_bread_nonmovable(struct super_block *sb, sector_t block)
+{
+ return __bread_nonmovable(sb->s_bdev, block, sb->s_blocksize);
+}
+
static inline void
sb_breadahead(struct super_block *sb, sector_t block)
{
--
1.7.9.5
--
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