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Date: Thu, 27 Aug 2015 14:57:46 +0100
From: Luis Henriques <luis.henriques@...onical.com>
To: Ben Hutchings <ben@...adent.org.uk>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
akpm@...ux-foundation.org, Gioh Kim <gioh.kim@....com>,
Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 3.2 060/110] fs/buffer.c: support buffer cache
allocations with gfp modifiers
On Mon, Aug 10, 2015 at 12:12:31PM +0200, Ben Hutchings wrote:
> 3.2.71-rc1 review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Gioh Kim <gioh.kim@....com>
>
> commit 3b5e6454aaf6b4439b19400d8365e2ec2d24e411 upstream.
>
> 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@....com>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> Reviewed-by: Jan Kara <jack@...e.cz>
> [bwh: Prerequisite for "bufferhead: Add _gfp version for sb_getblk()".
> Backported to 3.2: adjust context]
Great, I'll queue this and bd7ade3cd9b0 ("bufferhead: Add _gfp version
for sb_getblk()") for the 3.16 as well.
Cheers,
--
Luís
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> ---
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -1002,7 +1002,7 @@ init_page_buffers(struct page *page, str
> */
> 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;
> @@ -1011,7 +1011,7 @@ grow_dev_page(struct block_device *bdev,
> int ret = 0; /* Will call free_more_memory() */
>
> page = find_or_create_page(inode->i_mapping, index,
> - (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
> + (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS) | gfp);
> if (!page)
> return ret;
>
> @@ -1059,7 +1059,7 @@ 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;
> @@ -1086,11 +1086,12 @@ grow_buffers(struct block_device *bdev,
> }
>
> /* 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) ||
> @@ -1112,13 +1113,14 @@ __getblk_slow(struct block_device *bdev,
> 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:
> @@ -1369,24 +1371,25 @@ __find_get_block(struct block_device *bd
> 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..
> @@ -1402,24 +1405,28 @@ void __breadahead(struct block_device *b
> 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.
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -166,12 +166,13 @@ 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);
> @@ -286,7 +287,13 @@ static inline void bforget(struct buffer
> 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
> @@ -298,7 +305,7 @@ sb_breadahead(struct super_block *sb, se
> 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 *
> @@ -335,6 +342,36 @@ static inline void lock_buffer(struct bu
> __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 */
>
> --
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