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


>>>

>
> On 17/11/28 11:35, Gang He wrote:
>> Hello Joseph,
>>
>>
>>>>>
>>> Hi Gang,
>>>
>>> On 17/11/27 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:
>>> Should brelse(di_bh) be here?
>> If the code jumps to out_unlock1 directly, the di_bh pointer should be NULL,
> it is not necessary to release.
>>
> Umm... No, once going out here, we have already taken inode lock. So
> di_bh should be released.
Sorry, you are right.

>
>>>
>>>> + ocfs2_inode_unlock(inode, 0);
>>>> +
>>>> +out:
>>>> + return (ret ? 0 : 1);
>>> I don't think EAGAIN and other error code can be handled the same. We
>>> have to distinguish them.
>> Ok, I think we can add one line log to report the error in case the error is
> not EAGAIN.
>>
> My point is, there is no need to try again in several cases, e.g. EROFS
> returned by ocfs2_get_clusters_nocache.
In this function ocfs2_overwrite_io() only can return True(1) or False(0), then I think we can only give a error print before return true/false.
It is not necessary to return another value, but should let the user know any possible error message.

Thanks
Gang

>
>>>
>>> Thanks,
>>> Joseph
>>>
>>>> +}
>>>> +
>>>> 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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