[Devel] Re: [PATCH][SHMEM] Factor out sbi->free_inodes manipulations

[Pavel Emelyanov]

Hugh Dickins wrote:
> Looks good, but we can save slightly more there (depending on config),
> and I found your inc/dec names a little confusing, since the count is
> going the other way: how do you feel about this version?  (I'd like it

This is perfect =) Thanks for the masterclass!

> better if those helpers could take a struct inode *, but they cannot.)
> Hugh
> 
> 
> From: Pavel Emelyanov <xemul at openvz.org>
> 
> The shmem_sb_info structure has a number of free_inodes. This
> value is altered in appropriate places under spinlock and with
> the sbi->max_inodes != 0 check.
> 
> Consolidate these manipulations into two helpers.
> 
> This is minus 42 bytes of shmem.o and minus 4 :) lines of code.
> 
> Signed-off-by: Pavel Emelyanov <xemul at openvz.org>
> Signed-off-by: Hugh Dickins <hugh at veritas.com>
> ---
> 
>  mm/shmem.c |   72 ++++++++++++++++++++++++---------------------------
>  1 file changed, 34 insertions(+), 38 deletions(-)
> 
> --- 2.6.24-rc3/mm/shmem.c	2007-11-07 04:21:45.000000000 +0000
> +++ linux/mm/shmem.c	2007-11-23 12:43:28.000000000 +0000
> @@ -207,6 +207,31 @@ static void shmem_free_blocks(struct ino
>  	}
>  }
>  
> +static int shmem_reserve_inode(struct super_block *sb)
> +{
> +	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
> +	if (sbinfo->max_inodes) {
> +		spin_lock(&sbinfo->stat_lock);
> +		if (!sbinfo->free_inodes) {
> +			spin_unlock(&sbinfo->stat_lock);
> +			return -ENOMEM;
> +		}
> +		sbinfo->free_inodes--;
> +		spin_unlock(&sbinfo->stat_lock);
> +	}
> +	return 0;
> +}
> +
> +static void shmem_free_inode(struct super_block *sb)
> +{
> +	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
> +	if (sbinfo->max_inodes) {
> +		spin_lock(&sbinfo->stat_lock);
> +		sbinfo->free_inodes++;
> +		spin_unlock(&sbinfo->stat_lock);
> +	}
> +}
> +
>  /*
>   * shmem_recalc_inode - recalculate the size of an inode
>   *
> @@ -762,7 +787,6 @@ static int shmem_notify_change(struct de
>  
>  static void shmem_delete_inode(struct inode *inode)
>  {
> -	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
>  	struct shmem_inode_info *info = SHMEM_I(inode);
>  
>  	if (inode->i_op->truncate == shmem_truncate) {
> @@ -777,11 +801,7 @@ static void shmem_delete_inode(struct in
>  		}
>  	}
>  	BUG_ON(inode->i_blocks);
> -	if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		sbinfo->free_inodes++;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	shmem_free_inode(inode->i_sb);
>  	clear_inode(inode);
>  }
>  
> @@ -1398,15 +1418,8 @@ shmem_get_inode(struct super_block *sb, 
>  	struct shmem_inode_info *info;
>  	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
>  
> -	if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		if (!sbinfo->free_inodes) {
> -			spin_unlock(&sbinfo->stat_lock);
> -			return NULL;
> -		}
> -		sbinfo->free_inodes--;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	if (shmem_reserve_inode(sb))
> +		return NULL;
>  
>  	inode = new_inode(sb);
>  	if (inode) {
> @@ -1450,11 +1463,8 @@ shmem_get_inode(struct super_block *sb, 
>  						NULL);
>  			break;
>  		}
> -	} else if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		sbinfo->free_inodes++;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	} else
> +		shmem_free_inode(sb);
>  	return inode;
>  }
>  
> @@ -1797,22 +1807,14 @@ static int shmem_create(struct inode *di
>  static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
>  {
>  	struct inode *inode = old_dentry->d_inode;
> -	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
>  
>  	/*
>  	 * No ordinary (disk based) filesystem counts links as inodes;
>  	 * but each new link needs a new dentry, pinning lowmem, and
>  	 * tmpfs dentries cannot be pruned until they are unlinked.
>  	 */
> -	if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		if (!sbinfo->free_inodes) {
> -			spin_unlock(&sbinfo->stat_lock);
> -			return -ENOSPC;
> -		}
> -		sbinfo->free_inodes--;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	if (shmem_reserve_inode(inode->i_sb))
> +		return -ENOSPC;
>  
>  	dir->i_size += BOGO_DIRENT_SIZE;
>  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
> @@ -1827,14 +1829,8 @@ static int shmem_unlink(struct inode *di
>  {
>  	struct inode *inode = dentry->d_inode;
>  
> -	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
> -		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
> -		if (sbinfo->max_inodes) {
> -			spin_lock(&sbinfo->stat_lock);
> -			sbinfo->free_inodes++;
> -			spin_unlock(&sbinfo->stat_lock);
> -		}
> -	}
> +	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
> +		shmem_free_inode(inode->i_sb);
>  
>  	dir->i_size -= BOGO_DIRENT_SIZE;
>  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
>