Re: [PATCH v7 1/6] Btrfs: heuristic make use compression workspaces

From: David Sterba <dsterba@suse.cz>
To: Timofey Titovets <nefelim4ag@gmail.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v7 1/6] Btrfs: heuristic make use compression workspaces
Date: Wed, 27 Sep 2017 15:12:49 +0200	[thread overview]
Message-ID: <20170927131249.GA31640@twin.jikos.cz> (raw)
In-Reply-To: <20170825091845.4120-2-nefelim4ag@gmail.com>

On Fri, Aug 25, 2017 at 12:18:40PM +0300, Timofey Titovets wrote:
> Move heuristic to external file
> Implement compression workspaces support for
> heuristic resources

I think the file compression.c is suitable, there's not that much code
the heuristic adds and it its only related to compresession.

> Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>
> ---
>  fs/btrfs/Makefile      |  2 +-
>  fs/btrfs/compression.c | 18 +++++--------
>  fs/btrfs/compression.h |  7 ++++-
>  fs/btrfs/heuristic.c   | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 87 insertions(+), 13 deletions(-)
>  create mode 100644 fs/btrfs/heuristic.c
> 
> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> index 128ce17a80b0..6fa8479dff43 100644
> --- a/fs/btrfs/Makefile
> +++ b/fs/btrfs/Makefile
> @@ -9,7 +9,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
>  	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \
>  	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
>  	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
> -	   uuid-tree.o props.o hash.o free-space-tree.o
> +	   uuid-tree.o props.o hash.o free-space-tree.o heuristic.o
> 
>  btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
>  btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
> diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
> index 883ecc58fd0d..f0aaf27bcc95 100644
> --- a/fs/btrfs/compression.c
> +++ b/fs/btrfs/compression.c
> @@ -704,6 +704,7 @@ static struct {
>  static const struct btrfs_compress_op * const btrfs_compress_op[] = {
>  	&btrfs_zlib_compress,
>  	&btrfs_lzo_compress,
> +	&btrfs_heuristic,
>  };
> 
>  void __init btrfs_init_compress(void)
> @@ -1065,18 +1066,13 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
>   */
>  int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
>  {
> -	u64 index = start >> PAGE_SHIFT;
> -	u64 end_index = end >> PAGE_SHIFT;
> -	struct page *page;
> -	int ret = 1;
> +	int ret;
> +	enum btrfs_compression_type type = BTRFS_HEURISTIC;
> +	struct list_head *workspace = find_workspace(type);
> 
> -	while (index <= end_index) {
> -		page = find_get_page(inode->i_mapping, index);
> -		kmap(page);
> -		kunmap(page);
> -		put_page(page);
> -		index++;
> -	}
> +	ret = btrfs_compress_op[type-1]->heuristic(workspace, inode,
> +						   start, end);
> 
> +	free_workspace(type, workspace);
>  	return ret;
>  }
> diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
> index 3b1b0ac15fdc..10e9ffa6dfa4 100644
> --- a/fs/btrfs/compression.h
> +++ b/fs/btrfs/compression.h
> @@ -99,7 +99,8 @@ enum btrfs_compression_type {
>  	BTRFS_COMPRESS_NONE  = 0,
>  	BTRFS_COMPRESS_ZLIB  = 1,
>  	BTRFS_COMPRESS_LZO   = 2,
> -	BTRFS_COMPRESS_TYPES = 2,
> +	BTRFS_HEURISTIC = 3,
> +	BTRFS_COMPRESS_TYPES = 3,

Compression cannot be another type, I get it's for the workspace
management, that would need to be managed in another way anyway.

>  };
> 
>  struct btrfs_compress_op {
> @@ -123,10 +124,14 @@ struct btrfs_compress_op {
>  			  struct page *dest_page,
>  			  unsigned long start_byte,
>  			  size_t srclen, size_t destlen);
> +
> +	int (*heuristic)(struct list_head *workspace,
> +			 struct inode *inode, u64 start, u64 end);
>  };
> 
>  extern const struct btrfs_compress_op btrfs_zlib_compress;
>  extern const struct btrfs_compress_op btrfs_lzo_compress;
> +extern const struct btrfs_compress_op btrfs_heuristic;
> 
>  int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end);
> 
> diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
> new file mode 100644
> index 000000000000..92f9335bafd4
> --- /dev/null
> +++ b/fs/btrfs/heuristic.c
> @@ -0,0 +1,73 @@
> +/*
> + * Copyright (c) 2017
> + * All rights reserved.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public
> + * License v2 as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/sizes.h>
> +#include <linux/pagemap.h>
> +#include <linux/string.h>
> +#include <linux/bio.h>
> +#include "compression.h"
> +
> +struct workspace {
> +	struct list_head list;
> +};
> +
> +static void heuristic_free_workspace(struct list_head *ws)
> +{
> +	struct workspace *workspace = list_entry(ws, struct workspace, list);
> +	kfree(workspace);
> +}
> +
> +static struct list_head *heuristic_alloc_workspace(void)
> +{
> +	struct workspace *workspace;
> +
> +	workspace = kzalloc(sizeof(*workspace), GFP_KERNEL);
> +	if (!workspace)
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&workspace->list);
> +
> +	return &workspace->list;
> +}
> +
> +static int heuristic(struct list_head *ws, struct inode *inode,
> +		     u64 start, u64 end)
> +{
> +	struct page *page;
> +	u64 index, index_end;
> +
> +	index = start >> PAGE_SHIFT;
> +	index_end = end >> PAGE_SHIFT;
> +
> +	/* Don't miss unaligned end */
> +	if (!IS_ALIGNED(end, PAGE_SIZE))
> +		index_end++;
> +
> +	for (; index < index_end; index++) {
> +		page = find_get_page(inode->i_mapping, index);
> +		kmap(page);
> +		kunmap(page);
> +		put_page(page);
> +	}
> +
> +	return 1;
> +}
> +
> +const struct btrfs_compress_op btrfs_heuristic = {
> +	.alloc_workspace	= heuristic_alloc_workspace,
> +	.free_workspace		= heuristic_free_workspace,
> +	.heuristic              = heuristic,
> +};
> --
> 2.14.1
> --
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