Re: [Ocfs2-devel] [PATCH v3 2/3] ocfs2: add ocfs2_overwrite_io function

[alex chen]

Hi Gang,

On 2017/12/28 18:07, Gang He wrote:
> Add ocfs2_overwrite_io function, which is used to judge if
> overwrite allocated blocks, otherwise, the write will bring extra
> block allocation overhead.
> 
> Signed-off-by: Gang He <ghe@xxxxxxxx>
> ---
>  fs/ocfs2/extent_map.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  fs/ocfs2/extent_map.h |  3 +++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
> index e4719e0..06cb964 100644
> --- a/fs/ocfs2/extent_map.c
> +++ b/fs/ocfs2/extent_map.c
> @@ -38,6 +38,7 @@
>  #include "inode.h"
>  #include "super.h"
>  #include "symlink.h"
> +#include "aops.h"
>  #include "ocfs2_trace.h"
>  
>  #include "buffer_head_io.h"
> @@ -832,6 +833,50 @@ int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  	return ret;
>  }
>  
> +/* Is IO overwriting allocated blocks? */
> +int ocfs2_overwrite_io(struct inode *inode, struct buffer_head *di_bh,
> +		       u64 map_start, u64 map_len)
Here can the type of 'map_start' is struct loff_t and map_len is struct size_t?

Thanks,
Alex
> +{
> +	int ret = 0, is_last;
> +	u32 mapping_end, cpos;
> +	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> +	struct ocfs2_extent_rec rec;
> +
> +	if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
> +		if (ocfs2_size_fits_inline_data(di_bh, map_start + map_len))
> +			return ret;
> +		else
> +			return -EAGAIN;
> +	}
> +
> +	cpos = map_start >> osb->s_clustersize_bits;
> +	mapping_end = ocfs2_clusters_for_bytes(inode->i_sb,
> +					       map_start + map_len);
> +	is_last = 0;
> +	while (cpos < mapping_end && !is_last) {
> +		ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos,
> +						 NULL, &rec, &is_last);
> +		if (ret) {
> +			mlog_errno(ret);
> +			goto out;
> +		}
> +
> +		if (rec.e_blkno == 0ULL)
> +			break;
> +
> +		if (rec.e_flags & OCFS2_EXT_REFCOUNTED)
> +			break;
> +
> +		cpos = le32_to_cpu(rec.e_cpos) +
> +			le16_to_cpu(rec.e_leaf_clusters);
> +	}
> +
> +	if (cpos < mapping_end)
> +		ret = -EAGAIN;
> +out:
> +	return ret;
> +}
> +
>  int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int whence)
>  {
>  	struct inode *inode = file->f_mapping->host;
> diff --git a/fs/ocfs2/extent_map.h b/fs/ocfs2/extent_map.h
> index 67ea57d..1057586 100644
> --- a/fs/ocfs2/extent_map.h
> +++ b/fs/ocfs2/extent_map.h
> @@ -53,6 +53,9 @@ int ocfs2_extent_map_get_blocks(struct inode *inode, u64 v_blkno, u64 *p_blkno,
>  int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>  		 u64 map_start, u64 map_len);
>  
> +int ocfs2_overwrite_io(struct inode *inode, struct buffer_head *di_bh,
> +		       u64 map_start, u64 map_len);
> +
>  int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int origin);
>  
>  int ocfs2_xattr_get_clusters(struct inode *inode, u32 v_cluster,
>