Re: [PATCH] ext4: refactor duplicated block placement code

[Eric Sandeen <sandeen@redhat.com>]

On 6/22/11 10:16 PM, Andreas Dilger wrote:
> On 2011-06-22, at 12:37 PM, Eric Sandeen wrote:
>> I found that ext4_ext_find_goal() and ext4_find_near()
>> share the same code for returning a coloured start block
>> based on i_block_group.
>>
>> We can refactor this into a common function so that they
>> don't diverge in the future.
>>
>> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
>> ---
>>
>> ext4.h    |    1 
>> extents.c |   37 ---------------------------------
>> inode.c   |   69 +++++++++++++++++++++++++++++++++++++-------------------------
>> 3 files changed, 44 insertions(+), 63 deletions(-)
>>
>> I don't know that I like the new function name too much,
>> I'm open to suggestions...
> 
> What about ext4_goal_block_from_inode() or ext4_start_block_from_inode() or
> ext4_inode_to_{goal,start}_block()?  One of last ones might be good since
> it makes it clear this function is related to other ext4_inode_*() functions.

ext4_inode_to_goal_block sounds good to me, I'll resend, thanks.

-Eric

>> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
>> index 1921392..1d79fbc 100644
>> --- a/fs/ext4/ext4.h
>> +++ b/fs/ext4/ext4.h
>> @@ -1812,6 +1812,7 @@ extern int  ext4_getattr(struct vfsmount *mnt, struct dentry *dentry,
>> 				struct kstat *stat);
>> extern void ext4_evict_inode(struct inode *);
>> extern void ext4_clear_inode(struct inode *);
>> +ext4_fsblk_t ext4_inode_group_start(struct inode *);
>> extern int  ext4_sync_inode(handle_t *, struct inode *);
>> extern void ext4_dirty_inode(struct inode *, int);
>> extern int ext4_change_inode_journal_flag(struct inode *, int);
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 5199bac..23cf7dd 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -114,12 +114,6 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
>> 			      struct ext4_ext_path *path,
>> 			      ext4_lblk_t block)
>> {
>> -	struct ext4_inode_info *ei = EXT4_I(inode);
>> -	ext4_fsblk_t bg_start;
>> -	ext4_fsblk_t last_block;
>> -	ext4_grpblk_t colour;
>> -	ext4_group_t block_group;
>> -	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
>> 	int depth;
>>
>> 	if (path) {
>> @@ -161,36 +155,7 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode,
>> 	}
>>
>> 	/* OK. use inode's group */
>> -	block_group = ei->i_block_group;
>> -	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
>> -		/*
>> -		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
>> -		 * block groups per flexgroup, reserve the first block
>> -		 * group for directories and special files.  Regular
>> -		 * files will start at the second block group.  This
>> -		 * tends to speed up directory access and improves
>> -		 * fsck times.
>> -		 */
>> -		block_group &= ~(flex_size-1);
>> -		if (S_ISREG(inode->i_mode))
>> -			block_group++;
>> -	}
>> -	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
>> -	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
>> -
>> -	/*
>> -	 * If we are doing delayed allocation, we don't need take
>> -	 * colour into account.
>> -	 */
>> -	if (test_opt(inode->i_sb, DELALLOC))
>> -		return bg_start;
>> -
>> -	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
>> -		colour = (current->pid % 16) *
>> -			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
>> -	else
>> -		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
>> -	return bg_start + colour + block;
>> +	return ext4_inode_group_start(inode);
>> }
>>
>> /*
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index a5763e3..5784809 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -466,6 +466,47 @@ no_block:
>> 	return p;
>> }
>>
>> +ext4_fsblk_t ext4_inode_group_start(struct inode *inode)
>> +{
>> +	struct ext4_inode_info *ei = EXT4_I(inode);
>> +	ext4_group_t block_group;
>> +	ext4_grpblk_t colour;
>> +	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
>> +	ext4_fsblk_t bg_start;
>> +	ext4_fsblk_t last_block;
>> +
>> +	block_group = ei->i_block_group;
>> +	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
>> +		/*
>> +		 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
>> +		 * block groups per flexgroup, reserve the first block
>> +		 * group for directories and special files.  Regular
>> +		 * files will start at the second block group.  This
>> +		 * tends to speed up directory access and improves
>> +		 * fsck times.
>> +		 */
>> +		block_group &= ~(flex_size-1);
>> +		if (S_ISREG(inode->i_mode))
>> +			block_group++;
>> +	}
>> +	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
>> +	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
>> +
>> +	/*
>> +	 * If we are doing delayed allocation, we don't need take
>> +	 * colour into account.
>> +	 */
>> +	if (test_opt(inode->i_sb, DELALLOC))
>> +		return bg_start;
>> +
>> +	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
>> +		colour = (current->pid % 16) *
>> +			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
>> +	else
>> +		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
>> +	return bg_start + colour;
>> +}
>> +
>> /**
>> *	ext4_find_near - find a place for allocation with sufficient locality
>> *	@inode: owner
>> @@ -491,11 +532,6 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
>> 	struct ext4_inode_info *ei = EXT4_I(inode);
>> 	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
>> 	__le32 *p;
>> -	ext4_fsblk_t bg_start;
>> -	ext4_fsblk_t last_block;
>> -	ext4_grpblk_t colour;
>> -	ext4_group_t block_group;
>> -	int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
>>
>> 	/* Try to find previous block */
>> 	for (p = ind->p - 1; p >= start; p--) {
>> @@ -511,28 +547,7 @@ static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
>> 	 * It is going to be referred to from the inode itself? OK, just put it
>> 	 * into the same cylinder group then.
>> 	 */
>> -	block_group = ei->i_block_group;
>> -	if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
>> -		block_group &= ~(flex_size-1);
>> -		if (S_ISREG(inode->i_mode))
>> -			block_group++;
>> -	}
>> -	bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
>> -	last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
>> -
>> -	/*
>> -	 * If we are doing delayed allocation, we don't need take
>> -	 * colour into account.
>> -	 */
>> -	if (test_opt(inode->i_sb, DELALLOC))
>> -		return bg_start;
>> -
>> -	if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
>> -		colour = (current->pid % 16) *
>> -			(EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
>> -	else
>> -		colour = (current->pid % 16) * ((last_block - bg_start) / 16);
>> -	return bg_start + colour;
>> +	return ext4_inode_group_start(inode);
>> }
>>
>> /**
>> --
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> 
> 
> Cheers, Andreas
> 
> 
> 
> 
>