[Ocfs2-devel] [patch 10/11] ocfs2: add ocfs2_overwrite_io()

[alex chen <alex.chen@huawei.com>]

Hi Gang,

On 2017/12/1 6:24, akpm at linux-foundation.org wrote:
> From: Gang He <ghe@suse.com>
> Subject: ocfs2: add ocfs2_overwrite_io()
> 
> Add ocfs2_overwrite_io(), which is used to judge if overwrite allocated
> blocks, otherwise, the write will bring extra block allocation overhead.
> 
> [ghe at suse.com: v2]
>   Link: https://urldefense.proofpoint.com/v2/url?u=http-3A__lkml.kernel.org_r_1511944612-2D9629-2D3-2Dgit-2Dsend-2Demail-2Dghe-40suse.com&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=C7gAd4uDxlAvTdc0vmU6X8CMk6L2iDY8-HD0qT6Fo7Y&m=C4AZ7lGI2-gfFtbla8puNvYIA3a9Cr_XOH6oyx94oGo&s=QhxdPyP9gdEJZTa2UhuSk0x7ENXyGXUOIBV_LyP8oZw&e=
> Link: https://urldefense.proofpoint.com/v2/url?u=http-3A__lkml.kernel.org_r_1511775987-2D841-2D3-2Dgit-2Dsend-2Demail-2Dghe-40suse.com&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=C7gAd4uDxlAvTdc0vmU6X8CMk6L2iDY8-HD0qT6Fo7Y&m=C4AZ7lGI2-gfFtbla8puNvYIA3a9Cr_XOH6oyx94oGo&s=T9Ljku-nipBqCaeXWukY2hAwcHQL95gtlU7pS3l1fgs&e=
> Signed-off-by: Gang He <ghe@suse.com>
> Cc: Mark Fasheh <mfasheh@versity.com>
> Cc: Joel Becker <jlbec@evilplan.org>
> Cc: Junxiao Bi <junxiao.bi@oracle.com>
> Cc: Joseph Qi <jiangqi903@gmail.com>
> Cc: Changwei Ge <ge.changwei@h3c.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  fs/ocfs2/extent_map.c |   41 ++++++++++++++++++++++++++++++++++++++++
>  fs/ocfs2/extent_map.h |    3 ++
>  2 files changed, 44 insertions(+)
> 
> diff -puN fs/ocfs2/extent_map.c~ocfs2-add-ocfs2_overwrite_io-function fs/ocfs2/extent_map.c
> --- a/fs/ocfs2/extent_map.c~ocfs2-add-ocfs2_overwrite_io-function
> +++ a/fs/ocfs2/extent_map.c
> @@ -832,6 +832,47 @@ out:
>  	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)
> +{
> +	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) &&
> +	   ((map_start + map_len) <= i_size_read(inode)))
> +		goto out;
> +
Should we return -EAGAIN directly when the condition ((OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) && ((map_start + map_len) > i_size_read(inode)))
is true?

Thanks,
Alex
> +	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 -puN fs/ocfs2/extent_map.h~ocfs2-add-ocfs2_overwrite_io-function fs/ocfs2/extent_map.h
> --- a/fs/ocfs2/extent_map.h~ocfs2-add-ocfs2_overwrite_io-function
> +++ a/fs/ocfs2/extent_map.h
> @@ -53,6 +53,9 @@ int ocfs2_extent_map_get_blocks(struct i
>  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,
> _
> 
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> .
>