Date:	Tue, 07 Jun 2011 09:50:16 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH] ext4: remove deprecated oldalloc

On 6/7/11 8:35 AM, Lukas Czerner wrote:
> For a long time now orlov is the default block allocator in the ext4. It
> performs better than the old one and no one seems to claim otherwise so
> we can safely drop it and make oldalloc and orlov mount option
> deprecated.
> 
> This is a part of the effort to reduce number of ext4 options hence the
> test matrix.
> 
> Signed-off-by: Lukas Czerner <lczerner@...hat.com>

Seems like a good idea to me.

But I'm doing a little digging into why find_group_flex() was there;
why all that flex_bg-related inode allocation work for a deprecated option?

commit 772cb7c83ba256a11c7bf99a11bef3858d23767c
Author: Jose R. Santos <jrs@...ibm.com>
Date:   Fri Jul 11 19:27:31 2008 -0400

    ext4: New inode allocation for FLEX_BG meta-data groups.
    
    This patch mostly controls the way inode are allocated in order to
    make ialloc aware of flex_bg block group grouping.  It achieves this
    by bypassing the Orlov allocator when block group meta-data are packed
    toghether through mke2fs. <snip>

find_group_flex() used to be called by ext4_new_inode() regardless of
OLDALLOC, (I think) so just want to see for sure what happened to that plan...

-eric

> ---
>  Documentation/filesystems/ext4.txt |    8 --
>  fs/ext4/ext4.h                     |    1 -
>  fs/ext4/ialloc.c                   |  136 +-----------------------------------
>  fs/ext4/super.c                    |    8 +-
>  4 files changed, 7 insertions(+), 146 deletions(-)
> 
> diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
> index 3ae9bc9..ec469fa 100644
> --- a/Documentation/filesystems/ext4.txt
> +++ b/Documentation/filesystems/ext4.txt
> @@ -201,14 +201,6 @@ inode_readahead_blks=n	This tuning parameter controls the maximum
>  			table readahead algorithm will pre-read into
>  			the buffer cache.  The default value is 32 blocks.
>  
> -orlov		(*)	This enables the new Orlov block allocator. It is
> -			enabled by default.
> -
> -oldalloc		This disables the Orlov block allocator and enables
> -			the old block allocator.  Orlov should have better
> -			performance - we'd like to get some feedback if it's
> -			the contrary for you.
> -
>  user_xattr		Enables Extended User Attributes.  Additionally, you
>  			need to have extended attribute support enabled in the
>  			kernel configuration (CONFIG_EXT4_FS_XATTR).  See the
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1921392..7e0b8aa 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -884,7 +884,6 @@ struct ext4_inode_info {
>  /*
>   * Mount flags
>   */
> -#define EXT4_MOUNT_OLDALLOC		0x00002  /* Don't use the new Orlov allocator */
>  #define EXT4_MOUNT_GRPID		0x00004	/* Create files with directory's group */
>  #define EXT4_MOUNT_DEBUG		0x00008	/* Some debugging messages */
>  #define EXT4_MOUNT_ERRORS_CONT		0x00010	/* Continue on errors */
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index 21bb2f6..0b5ec23 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -293,118 +293,6 @@ error_return:
>  	ext4_std_error(sb, fatal);
>  }
>  
> -/*
> - * There are two policies for allocating an inode.  If the new inode is
> - * a directory, then a forward search is made for a block group with both
> - * free space and a low directory-to-inode ratio; if that fails, then of
> - * the groups with above-average free space, that group with the fewest
> - * directories already is chosen.
> - *
> - * For other inodes, search forward from the parent directory\'s block
> - * group to find a free inode.
> - */
> -static int find_group_dir(struct super_block *sb, struct inode *parent,
> -				ext4_group_t *best_group)
> -{
> -	ext4_group_t ngroups = ext4_get_groups_count(sb);
> -	unsigned int freei, avefreei;
> -	struct ext4_group_desc *desc, *best_desc = NULL;
> -	ext4_group_t group;
> -	int ret = -1;
> -
> -	freei = percpu_counter_read_positive(&EXT4_SB(sb)->s_freeinodes_counter);
> -	avefreei = freei / ngroups;
> -
> -	for (group = 0; group < ngroups; group++) {
> -		desc = ext4_get_group_desc(sb, group, NULL);
> -		if (!desc || !ext4_free_inodes_count(sb, desc))
> -			continue;
> -		if (ext4_free_inodes_count(sb, desc) < avefreei)
> -			continue;
> -		if (!best_desc ||
> -		    (ext4_free_blks_count(sb, desc) >
> -		     ext4_free_blks_count(sb, best_desc))) {
> -			*best_group = group;
> -			best_desc = desc;
> -			ret = 0;
> -		}
> -	}
> -	return ret;
> -}
> -
> -#define free_block_ratio 10
> -
> -static int find_group_flex(struct super_block *sb, struct inode *parent,
> -			   ext4_group_t *best_group)
> -{
> -	struct ext4_sb_info *sbi = EXT4_SB(sb);
> -	struct ext4_group_desc *desc;
> -	struct flex_groups *flex_group = sbi->s_flex_groups;
> -	ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
> -	ext4_group_t parent_fbg_group = ext4_flex_group(sbi, parent_group);
> -	ext4_group_t ngroups = ext4_get_groups_count(sb);
> -	int flex_size = ext4_flex_bg_size(sbi);
> -	ext4_group_t best_flex = parent_fbg_group;
> -	int blocks_per_flex = sbi->s_blocks_per_group * flex_size;
> -	int flexbg_free_blocks;
> -	int flex_freeb_ratio;
> -	ext4_group_t n_fbg_groups;
> -	ext4_group_t i;
> -
> -	n_fbg_groups = (ngroups + flex_size - 1) >>
> -		sbi->s_log_groups_per_flex;
> -
> -find_close_to_parent:
> -	flexbg_free_blocks = atomic_read(&flex_group[best_flex].free_blocks);
> -	flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;
> -	if (atomic_read(&flex_group[best_flex].free_inodes) &&
> -	    flex_freeb_ratio > free_block_ratio)
> -		goto found_flexbg;
> -
> -	if (best_flex && best_flex == parent_fbg_group) {
> -		best_flex--;
> -		goto find_close_to_parent;
> -	}
> -
> -	for (i = 0; i < n_fbg_groups; i++) {
> -		if (i == parent_fbg_group || i == parent_fbg_group - 1)
> -			continue;
> -
> -		flexbg_free_blocks = atomic_read(&flex_group[i].free_blocks);
> -		flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;
> -
> -		if (flex_freeb_ratio > free_block_ratio &&
> -		    (atomic_read(&flex_group[i].free_inodes))) {
> -			best_flex = i;
> -			goto found_flexbg;
> -		}
> -
> -		if ((atomic_read(&flex_group[best_flex].free_inodes) == 0) ||
> -		    ((atomic_read(&flex_group[i].free_blocks) >
> -		      atomic_read(&flex_group[best_flex].free_blocks)) &&
> -		     atomic_read(&flex_group[i].free_inodes)))
> -			best_flex = i;
> -	}
> -
> -	if (!atomic_read(&flex_group[best_flex].free_inodes) ||
> -	    !atomic_read(&flex_group[best_flex].free_blocks))
> -		return -1;
> -
> -found_flexbg:
> -	for (i = best_flex * flex_size; i < ngroups &&
> -		     i < (best_flex + 1) * flex_size; i++) {
> -		desc = ext4_get_group_desc(sb, i, NULL);
> -		if (ext4_free_inodes_count(sb, desc)) {
> -			*best_group = i;
> -			goto out;
> -		}
> -	}
> -
> -	return -1;
> -out:
> -	return 0;
> -}
> -
>  struct orlov_stats {
>  	__u32 free_inodes;
>  	__u32 free_blocks;
> @@ -817,7 +705,6 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
>  	struct inode *ret;
>  	ext4_group_t i;
>  	int free = 0;
> -	static int once = 1;
>  	ext4_group_t flex_group;
>  
>  	/* Cannot create files in a deleted directory */
> @@ -843,26 +730,9 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode,
>  		goto got_group;
>  	}
>  
> -	if (sbi->s_log_groups_per_flex && test_opt(sb, OLDALLOC)) {
> -		ret2 = find_group_flex(sb, dir, &group);
> -		if (ret2 == -1) {
> -			ret2 = find_group_other(sb, dir, &group, mode);
> -			if (ret2 == 0 && once) {
> -				once = 0;
> -				printk(KERN_NOTICE "ext4: find_group_flex "
> -				       "failed, fallback succeeded dir %lu\n",
> -				       dir->i_ino);
> -			}
> -		}
> -		goto got_group;
> -	}
> -
> -	if (S_ISDIR(mode)) {
> -		if (test_opt(sb, OLDALLOC))
> -			ret2 = find_group_dir(sb, dir, &group);
> -		else
> -			ret2 = find_group_orlov(sb, dir, &group, mode, qstr);
> -	} else
> +	if (S_ISDIR(mode))
> +		ret2 = find_group_orlov(sb, dir, &group, mode, qstr);
> +	else
>  		ret2 = find_group_other(sb, dir, &group, mode);
>  
>  got_group:
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index cc5c157..e1f8f73 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1031,8 +1031,6 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
>  		seq_puts(seq, ",nouid32");
>  	if (test_opt(sb, DEBUG) && !(def_mount_opts & EXT4_DEFM_DEBUG))
>  		seq_puts(seq, ",debug");
> -	if (test_opt(sb, OLDALLOC))
> -		seq_puts(seq, ",oldalloc");
>  #ifdef CONFIG_EXT4_FS_XATTR
>  	if (test_opt(sb, XATTR_USER))
>  		seq_puts(seq, ",user_xattr");
> @@ -1541,10 +1539,12 @@ static int parse_options(char *options, struct super_block *sb,
>  			set_opt(sb, DEBUG);
>  			break;
>  		case Opt_oldalloc:
> -			set_opt(sb, OLDALLOC);
> +			ext4_msg(sb, KERN_WARNING,
> +				 "Ignoring deprecated oldalloc option");
>  			break;
>  		case Opt_orlov:
> -			clear_opt(sb, OLDALLOC);
> +			ext4_msg(sb, KERN_WARNING,
> +				 "Ignoring deprecated orlov option");
>  			break;
>  #ifdef CONFIG_EXT4_FS_XATTR
>  		case Opt_user_xattr:

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