On 2017/12/26 16:19, alex chen wrote:
> Hi Changwei,
>
> On 2017/12/26 15:03, Changwei Ge wrote:
>> The intention of this patch is to provide an option to ocfs2 users whether
>> to allocate disk space while doing dio write.
>>
>> Whether to make ocfs2 fall back to buffer io is up to ocfs2 users through
>> toggling append-dio feature. It rather makes ocfs2 configurable and
>> flexible.
>>
> It is too strange to make ocfs2 fall back to buffer io by toggling append-dio
> feature.
>
>> So if something bad happens to dio write with space allocation, we can
>> still make ocfs2 fall back to buffer io. It's an option not a mandatory
>> action.:)
> Now the ocfs2 supports fill holes during direct io whether or not supporting
> append-dio feature
> and we can directly fix the problem.
> I think it is meaningless to provide an temporary option to turn off it.
>
I have the same opinion with Alex. And probablly the better way is
providing a new feature for user, not just reuse 'append-dio'.
>>
>> Besides, append-dio feature is key to whether to allocate space with dio
>> writing. So writing to file hole and enlarging file(appending file) should
>> have the same reflection to append-dio feature.
>>
>> Signed-off-by: Changwei Ge <ge.chang...@h3c.com>
>> ---
>> fs/ocfs2/aops.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++---
>> 1 file changed, 50 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>> index d151632..32e60c0 100644
>> --- a/fs/ocfs2/aops.c
>> +++ b/fs/ocfs2/aops.c
>> @@ -2414,12 +2414,52 @@ static int ocfs2_dio_end_io(struct kiocb *iocb,
>> return ret;
>> }
>>
>> +/*
>> + * Will look for holes and unwritten extents in the range starting at
>> + * pos for count bytes (inclusive).
>> + * Return value 1 indicates hole exists, 0 not exists, others indicate
>> error.
>> + */
>> +static int ocfs2_range_has_holes(struct inode *inode, loff_t pos,
>> + size_t count)
>> +{
>> + int ret = 0;
>> + unsigned int extent_flags;
>> + u32 cpos, clusters, extent_len, phys_cpos;
>> + struct super_block *sb = inode->i_sb;
>> +
>> + cpos = pos >> OCFS2_SB(sb)->s_clustersize_bits;
>> + clusters = ocfs2_clusters_for_bytes(sb, pos + count) - cpos;
>> +
>> + while (clusters) {
>> + ret = ocfs2_get_clusters(inode, cpos, &phys_cpos, &extent_len,
>> + &extent_flags);
>> + if (ret < 0) {
>> + mlog_errno(ret);
>> + goto out;
>> + }
>> +
>> + if (phys_cpos == 0) {
>> + ret = 1;
>> + goto out;
>> + }
>> +
>> + if (extent_len > clusters)
>> + extent_len = clusters;
>> +
>> + clusters -= extent_len;
>> + cpos += extent_len;
>> + }
>> +out:
>> + return ret;
>> +}
>> +
>> static ssize_t ocfs2_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>> {
>> struct file *file = iocb->ki_filp;
>> struct inode *inode = file->f_mapping->host;
>> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>> get_block_t *get_block;
>> + int ret;
>>
>> /*
>> * Fallback to buffered I/O if we see an inode without
>> @@ -2429,9 +2469,16 @@ static ssize_t ocfs2_direct_IO(struct kiocb *iocb,
>> struct iov_iter *iter)
>> return 0;
>>
>> /* Fallback to buffered I/O if we do not support append dio. */
>> - if (iocb->ki_pos + iter->count > i_size_read(inode) &&
>> - !ocfs2_supports_append_dio(osb))
>> - return 0;
>> + if (!ocfs2_supports_append_dio(osb)) {
>> + if (iocb->ki_pos + iter->count > i_size_read(inode))
>> + return 0;
>> +
>> + ret = ocfs2_range_has_holes(inode, iocb->ki_pos, iter->count);
>> + if (ret == 1)
>> + return 0;
>> + else if (ret < 0)
>> + return ret;
>> + }
>>
>> if (iov_iter_rw(iter) == READ)
>> get_block = ocfs2_lock_get_block;
>>
>
>
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