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fs/buffer.c: support buffer cache allocations with gfp modifiers
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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>
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Gioh Kim authored and Theodore Ts'o committed Sep 5, 2014
1 parent d26e2c4 commit 3b5e645
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Showing 2 changed files with 68 additions and 24 deletions.
45 changes: 26 additions & 19 deletions fs/buffer.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand All @@ -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
Expand Down Expand Up @@ -1058,7 +1058,7 @@ grow_dev_page(struct block_device *bdev, sector_t block,
* 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;
Expand All @@ -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) ||
Expand All @@ -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:
Expand Down Expand Up @@ -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..
Expand All @@ -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.
Expand Down
47 changes: 42 additions & 5 deletions include/linux/buffer_head.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -175,12 +175,13 @@ void __wait_on_buffer(struct buffer_head *);
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);
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_gfp(struct block_device *bdev, sector_t block,
unsigned size, gfp_t gfp);
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_gfp(struct block_device *,
sector_t block, unsigned size, gfp_t gfp);
void invalidate_bh_lrus(void);
struct buffer_head *alloc_buffer_head(gfp_t gfp_flags);
void free_buffer_head(struct buffer_head * bh);
Expand Down Expand Up @@ -295,7 +296,13 @@ static inline void bforget(struct buffer_head *bh)
static inline struct buffer_head *
sb_bread(struct super_block *sb, sector_t block)
{
return __bread(sb->s_bdev, block, sb->s_blocksize);
return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
}

static inline struct buffer_head *
sb_bread_unmovable(struct super_block *sb, sector_t block)
{
return __bread_gfp(sb->s_bdev, block, sb->s_blocksize, 0);
}

static inline void
Expand All @@ -307,7 +314,7 @@ sb_breadahead(struct super_block *sb, sector_t block)
static inline struct buffer_head *
sb_getblk(struct super_block *sb, sector_t block)
{
return __getblk(sb->s_bdev, block, sb->s_blocksize);
return __getblk_gfp(sb->s_bdev, block, sb->s_blocksize, __GFP_MOVABLE);
}

static inline struct buffer_head *
Expand Down Expand Up @@ -344,6 +351,36 @@ static inline void lock_buffer(struct buffer_head *bh)
__lock_buffer(bh);
}

static inline struct buffer_head *getblk_unmovable(struct block_device *bdev,
sector_t block,
unsigned size)
{
return __getblk_gfp(bdev, block, size, 0);
}

static inline struct buffer_head *__getblk(struct block_device *bdev,
sector_t block,
unsigned size)
{
return __getblk_gfp(bdev, block, size, __GFP_MOVABLE);
}

/**
* __bread() - 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 movable area so that it can be migrated.
* It returns NULL if the block was unreadable.
*/
static inline struct buffer_head *
__bread(struct block_device *bdev, sector_t block, unsigned size)
{
return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
}

extern int __set_page_dirty_buffers(struct page *page);

#else /* CONFIG_BLOCK */
Expand Down

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