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Date:	Mon, 01 Sep 2014 17:02:04 +0900
From:	Gioh Kim <gioh.kim@....com>
To:	Jan Kara <jack@...e.cz>
CC:	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>,
	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, Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <js1304@...il.com>,
	이건호 <gunho.lee@....com>
Subject: Re: [PATCHv3 1/3] fs/buffer.c: allocate buffer cache with user specific
 flag



2014-09-01 오후 4:53, Jan Kara 쓴 글:
> On Fri 29-08-14 13:48:27, Gioh Kim wrote:
>> What about below?: add gfp for __getblk_slow, change __getblk into __getblk_gfp,
>> getblk_unmovable and __getblk are, I think, symmetric.
>>
>> If you say OK, I'm going to send v4 with tabs ;-)
>    Yes, this looks like what I wanted. I've just spotted two typos in
> comments and one function which should be inline (see below). Thanks for
> work!
>
> 								Honza

Thank you too!
I'm going to report the next spin soon.

>
>> diff --git a/fs/buffer.c b/fs/buffer.c
>> index 8f05111..21711c78 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;
>> @@ -1002,10 +1002,10 @@ 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
>> +        * XXX: __getblk_gfp() can not really deal with failure and
>    You can leave __getblk_slow() here I believe.

I got it. It's my mistake.

>
>
>>           * will endlessly loop on improvised global reclaim.  Prefer
>>           * looping in the allocator rather than here, at least that
>>           * code knows what it's doing.
>> @@ -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
>    _gfp should be before () in the line above.

I got it.

>
>> + * 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..
>> @@ -1410,18 +1413,39 @@ 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 *
>>   __bread(struct block_device *bdev, sector_t block, unsigned size)
>>   {
>> -       struct buffer_head *bh = __getblk(bdev, block, size);
>> +       return __bread_gfp(bdev, block, size, __GFP_MOVABLE);
>> +}
>> +EXPORT_SYMBOL(__bread);
>    This can be just inline defined in buffer_head.h.

I got it.

>
>
>> +
>> +/**
>> + *  __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_gfp(struct block_device *bdev, sector_t block,
>> +                  unsigned size, gfp_t gfp)
>> +{
>> +       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.
>> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
>> index 324329c..6073f5d 100644
>> --- a/include/linux/buffer_head.h
>> +++ b/include/linux/buffer_head.h
>> @@ -175,12 +175,14 @@ 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);
>> @@ -295,7 +297,13 @@ 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
>> @@ -307,7 +315,7 @@ 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 *
>> @@ -344,6 +352,20 @@ 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);
>> +}
>> +
>>   extern int __set_page_dirty_buffers(struct page *page);
>>
>>   #else /* CONFIG_BLOCK */
>> --
>> 1.7.9.5
>>
--
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