Hi Changwei,
On 2017/12/19 11:05, Changwei Ge wrote:
> Hi Jun,
>
> On 2017/12/19 9:48, piaojun wrote:
>> Hi Changwei,
>>
>> On 2017/12/18 20:06, Changwei Ge wrote:
>>> Before ocfs2 supporting allocating clusters while doing append-dio, all
>>> append
>>> dio will fall back to buffer io to allocate clusters firstly. Also, when it
>>> steps on a file hole, it will fall back to buffer io, too. But for current
>>> code, writing to file hole will leverage dio to allocate clusters. This is
>>> not
>>> right, since whether append-io is enabled tells the capability whether
>>> ocfs2 can
>>> allocate space while doing dio.
>>> So introduce file hole check function back into ocfs2.
>>> Once ocfs2 is doing dio upon a file hole with append-dio disabled, it will
>>> fall
>>> back to buffer IO to allocate clusters.
>>>
>> 1. Do you mean that filling hole can't go with dio when append-dio is
>> disabled?
>
> Yes, direct IO will fall back to buffer IO with _append-dio_ disabled.
Why does dio need fall back to buffer-io when append-dio disabled?
Could 'common-dio' on file hole go through direct io process? If not,
could you please point out the necessity.
>
>> 2. Is your checking-hole just for 'append-dio' or for 'all-common-dio'?
>
> Just for append-dio
>
If your patch is just for 'append-dio', I wonder that will have impact
on 'common-dio'.
thanks,
Jun
>>> Signed-off-by: Changwei Ge <ge.chang...@h3c.com>
>>> ---
>>> fs/ocfs2/aops.c | 44 ++++++++++++++++++++++++++++++++++++++++++--
>>> 1 file changed, 42 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
>>> index d151632..a982cf6 100644
>>> --- a/fs/ocfs2/aops.c
>>> +++ b/fs/ocfs2/aops.c
>>> @@ -2414,6 +2414,44 @@ 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).
>>> + */
>>> +static int ocfs2_check_range_for_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 || (extent_flags & OCFS2_EXT_UNWRITTEN)) {
>>> + ret = 1;
>>> + break;
>>> + }
>>> +
>>> + 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;
>>> @@ -2429,8 +2467,10 @@ 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))
>>> + if (!ocfs2_supports_append_dio(osb) &&
>>> + (iocb->ki_pos + iter->count > i_size_read(inode) ||
>>> + ocfs2_check_range_for_holes(inode, iocb->ki_pos,
>>> + iter->count)))
>> we should check error here, right?
>
> Accept this point.
>
> Thanks,
> Changwei
>
>>
>> thanks,
>> Jun
>>> return 0;
>>>
>>> if (iov_iter_rw(iter) == READ)
>>>
>>
>
> .
>
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