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SubjectRe: [Ocfs2-devel] [PATCH 2/3] ocfs2: add ocfs2_overwrite_io function
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Hi Gang,

If ocfs2_overwrite_io is only called in 'nowait' scenarios, I wonder if
we can discard 'int wait' just as ext4 does:

static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len);

thans,
Jun

On 2017/11/27 17:46, 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@suse.com>
> ---
> fs/ocfs2/extent_map.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++
> fs/ocfs2/extent_map.h | 3 +++
> 2 files changed, 70 insertions(+)
>
> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
> index e4719e0..98bf325 100644
> --- a/fs/ocfs2/extent_map.c
> +++ b/fs/ocfs2/extent_map.c
> @@ -832,6 +832,73 @@ 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, u64 map_start, u64 map_len,
> + int wait)
> +{
> + int ret = 0, is_last;
> + u32 mapping_end, cpos;
> + struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
> + struct buffer_head *di_bh = NULL;
> + struct ocfs2_extent_rec rec;
> +
> + if (wait)
> + ret = ocfs2_inode_lock(inode, &di_bh, 0);
> + else
> + ret = ocfs2_try_inode_lock(inode, &di_bh, 0);
> + if (ret)
> + goto out;
> +
> + if (wait)
> + down_read(&OCFS2_I(inode)->ip_alloc_sem);
> + else {
> + if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) {
> + ret = -EAGAIN;
> + goto out_unlock1;
> + }
> + }
> +
> + if ((OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) &&
> + ((map_start + map_len) <= i_size_read(inode)))
> + goto out_unlock2;
> +
> + 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_unlock2;
> + }
> +
> + 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 = 1;
> +
> +out_unlock2:
> + brelse(di_bh);
> +
> + up_read(&OCFS2_I(inode)->ip_alloc_sem);
> +
> +out_unlock1:
> + ocfs2_inode_unlock(inode, 0);
> +
> +out:
> + return (ret ? 0 : 1);
> +}
> +
> 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..fd9e86a 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, u64 map_start, u64 map_len,
> + int wait);
> +
> 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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