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SubjectRe: [Ocfs2-devel] [PATCH v3 2/3] ocfs2: add ocfs2_overwrite_io function
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@suse.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.).

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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