linux-kernel - Re: [f2fs-dev] [PATCH 5/6] f2fs: implement iomap operations

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Date:   Thu, 2 Dec 2021 11:10:41 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Cc:     Eric Biggers <ebiggers@...gle.com>
Subject: Re: [f2fs-dev] [PATCH 5/6] f2fs: implement iomap operations

On 2021/11/17 5:45, Jaegeuk Kim wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Implement 'struct iomap_ops' for f2fs, in preparation for making f2fs
> use iomap for direct I/O.
> 
> Note that this may be used for other things besides direct I/O in the
> future; however, for now I've only tested it for direct I/O.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
>   fs/f2fs/Kconfig |  1 +
>   fs/f2fs/data.c  | 58 +++++++++++++++++++++++++++++++++++++++++++++++++
>   fs/f2fs/f2fs.h  |  1 +
>   3 files changed, 60 insertions(+)
> 
> diff --git a/fs/f2fs/Kconfig b/fs/f2fs/Kconfig
> index 7eea3cfd894d..f46a7339d6cf 100644
> --- a/fs/f2fs/Kconfig
> +++ b/fs/f2fs/Kconfig
> @@ -7,6 +7,7 @@ config F2FS_FS
>   	select CRYPTO_CRC32
>   	select F2FS_FS_XATTR if FS_ENCRYPTION
>   	select FS_ENCRYPTION_ALGS if FS_ENCRYPTION
> +	select FS_IOMAP
>   	select LZ4_COMPRESS if F2FS_FS_LZ4
>   	select LZ4_DECOMPRESS if F2FS_FS_LZ4
>   	select LZ4HC_COMPRESS if F2FS_FS_LZ4HC
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 7ac1a39fcad2..43b3ca7cabe0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -21,6 +21,7 @@
>   #include <linux/cleancache.h>
>   #include <linux/sched/signal.h>
>   #include <linux/fiemap.h>
> +#include <linux/iomap.h>
>   
>   #include "f2fs.h"
>   #include "node.h"
> @@ -4236,3 +4237,60 @@ void f2fs_destroy_bio_entry_cache(void)
>   {
>   	kmem_cache_destroy(bio_entry_slab);
>   }
> +
> +static int f2fs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> +			    unsigned int flags, struct iomap *iomap,
> +			    struct iomap *srcmap)
> +{
> +	struct f2fs_map_blocks map = {};
> +	pgoff_t next_pgofs = 0;
> +	int err;
> +
> +	map.m_lblk = bytes_to_blks(inode, offset);
> +	map.m_len = bytes_to_blks(inode, offset + length - 1) - map.m_lblk + 1;
> +	map.m_next_pgofs = &next_pgofs;
> +	map.m_seg_type = f2fs_rw_hint_to_seg_type(inode->i_write_hint);
> +	if (flags & IOMAP_WRITE)
> +		map.m_may_create = true;
> +
> +	err = f2fs_map_blocks(inode, &map, flags & IOMAP_WRITE,
> +			      F2FS_GET_BLOCK_DIO);
> +	if (err)
> +		return err;
> +
> +	iomap->offset = blks_to_bytes(inode, map.m_lblk);
> +
> +	if (map.m_flags & (F2FS_MAP_MAPPED | F2FS_MAP_UNWRITTEN)) {
> +		iomap->length = blks_to_bytes(inode, map.m_len);
> +		if (map.m_flags & F2FS_MAP_MAPPED) {
> +			iomap->type = IOMAP_MAPPED;
> +			iomap->flags |= IOMAP_F_MERGED;
> +		} else {
> +			iomap->type = IOMAP_UNWRITTEN;
> +		}
> +		if (WARN_ON_ONCE(!__is_valid_data_blkaddr(map.m_pblk)))
> +			return -EINVAL;
> +		iomap->addr = blks_to_bytes(inode, map.m_pblk);
> +
> +		if (WARN_ON_ONCE(f2fs_is_multi_device(F2FS_I_SB(inode))))
> +			return -EINVAL;

Why not relocating this check before f2fs_map_blocks()?

Thanks,

> +		iomap->bdev = inode->i_sb->s_bdev;
> +	} else {
> +		iomap->length = blks_to_bytes(inode, next_pgofs) -
> +				iomap->offset;
> +		iomap->type = IOMAP_HOLE;
> +		iomap->addr = IOMAP_NULL_ADDR;
> +	}
> +
> +	if (map.m_flags & F2FS_MAP_NEW)
> +		iomap->flags |= IOMAP_F_NEW;
> +	if ((inode->i_state & I_DIRTY_DATASYNC) ||
> +	    offset + length > i_size_read(inode))
> +		iomap->flags |= IOMAP_F_DIRTY;
> +
> +	return 0;
> +}
> +
> +const struct iomap_ops f2fs_iomap_ops = {
> +	.iomap_begin	= f2fs_iomap_begin,
> +};
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 14bea669f87e..0d199e8f2c1d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -3654,6 +3654,7 @@ int f2fs_init_post_read_processing(void);
>   void f2fs_destroy_post_read_processing(void);
>   int f2fs_init_post_read_wq(struct f2fs_sb_info *sbi);
>   void f2fs_destroy_post_read_wq(struct f2fs_sb_info *sbi);
> +extern const struct iomap_ops f2fs_iomap_ops;
>   
>   /*
>    * gc.c
>