linux-ext4 - Re: [PATCH] ext4: fall back to vmalloc() for large allocations

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Date:	Sun, 17 Jul 2011 21:25:56 -0400
From:	Ted Ts'o <tytso@....edu>
To:	Andreas Dilger <adilger@...mcloud.com>
Cc:	linux-ext4@...r.kernel.org, Yu Jian <yujian@...mcloud.com>
Subject: Re: [PATCH] ext4: fall back to vmalloc() for large allocations

On Tue, Jul 12, 2011 at 03:40:46PM -0600, Andreas Dilger wrote:
> For very large ext4 filesystems (128TB and larger) kmalloc() of
> some per-group structures can fail at mount time due to memory
> fragmentation.  If kmalloc() fails, fall back to vmalloc() for
> the s_group_info and s_group_desc arrays.
> 
> Signed-off-by: Yu Jian <yujian@...mcloud.com>
> Signed-off-by: Andreas Dilger <adilger@...mcloud.com>

Andras, was this patch authored by Yu Jian or by you?

>  	sbi->s_buddy_cache = new_inode(sb);
>  	if (sbi->s_buddy_cache == NULL) {
> -		printk(KERN_ERR "EXT4-fs: can't get new inode\n");
> +		ext4_msg(sb, KERN_ERR, "can't get new inode\n");
>  		goto err_freesgi;
>  	}

Using ext4_msg instead of printk is good, but that really should be a
separate patch.


> -	sbi->s_buddy_cache->i_ino = get_next_ino();
> +	/* To avoid potentially colliding with an valid on-disk inode number,
> +	 * use EXT4_BAD_INO for the buddy cache inode number.  This inode is
> +	 * not in the inode hash, so it should never be found by iget(), but
> +	 * this will avoid confusion if it ever shows up during debugging. */
> +	sbi->s_buddy_cache->i_ino = EXT4_BAD_INO;

This should be a separate patch.

> @@ -2457,12 +2472,6 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
>  		i++;
>  	} while (i <= sb->s_blocksize_bits + 1);
>  
> -	/* init file for buddy data */
> -	ret = ext4_mb_init_backend(sb);
> -	if (ret != 0) {
> -		goto out;
> -	}
> -
>  	spin_lock_init(&sbi->s_md_lock);
>  	spin_lock_init(&sbi->s_bal_lock);
>  
> @@ -2487,6 +2496,11 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
>  		spin_lock_init(&lg->lg_prealloc_lock);
>  	}
>  
> +	/* init file for buddy data */
> +	ret = ext4_mb_init_backend(sb);
> +	if (ret != 0)
> +		goto out;
> +
>  	if (sbi->s_proc)
>  		proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
>  				 &ext4_mb_seq_groups_fops, sb);

Why are you moving ext4_mb_init_backend()?  This should be a separate
patch, with an explanation of what is going on....

       	       		      	      	    - Ted
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