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Date: Thu, 11 Jan 2018 09:59:42 +0800
From: alex chen <alex.chen@...wei.com>
To: Gang He <ghe@...e.com>
CC: <jlbec@...lplan.org>, <ocfs2-devel@....oracle.com>,
<mfasheh@...sity.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [Ocfs2-devel] [PATCH v3 2/3] ocfs2: add ocfs2_overwrite_io function
Hi Gang,
On 2018/1/4 11:32, Gang He wrote:
> Hi Alex,
>
>
>>>>
>> Hi Gang,
>>
>> On 2018/1/3 13:14, Gang He wrote:
>>> Hi Alex,
>>>
>>>
>>>>>>
>>>> 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@...e.com>
>>>>> ---
>>>>> 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?
>>> I prefer to use the detailed types for file start address and length in
>> ocfs2_overwrite_io() function declaration,
>>> then here will be a potential type conversion (loff_t -> u64, size_t -> u64), I
>> think this conversion should be considered as expectation.
>>> Since our OCFS2 is a 64 bit file system, the related data types do not
>> change, but loff_t and size_t type can change under different architectures
>> (e.g. x86_32, x86_64, etc.).
>>>
>> The type conversion (loff_t -> u64, size_t -> u64) has been made before calling
>> the function ocfs2_overwrite_io().
>> So it doesn't matter which type we use for file start address and length in
>> ocfs2_overwrite_io(), Right?
>> To be consistent with the context, is it better to use struct loff_t for
>> 'map_start' and struct size_t for 'map_len'?
> I am not sure if I describe my thought clearly.
> In VFS layer, loff_t, size_t and other related data types are used for all architectures, that means these kinds of data type's lengths
> will change based on different CPU bits.
> But, for a specific file system, the file system bit is fixed, e.g. ocfs2 is a 64 bits file system, this bit length is determined by file system layout (not CPU bits).
> Then, in this layer we should use fixed-length (or common) data type in the code, the VFS layer data types should be converted into our data types potentially (but except pointer type).
>
I agree about you to use fixed-length data type in OCFS2 layer, but now we already use the loff_t for pos in ocfs2_prepare_inode_for_write(), I don't
think it's going to work whatever data type we use. Right ?
Anyway, I accept it if you think it is better to use fixed-length type here.
Reviewed-by: Alex Chen <alex.chen@...wei.com>
Thanks,
Alex
>
> Thanks
> Gang
>
>>
>> Thanks,
>> Alex
>>
>>> Thanks
>>> Gang
>>>
>>>>
>>>> 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,
>>>>>
>>>
>>>
>>> .
>>>
>
> .
>
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