Re: [RESEND PATCH V5] ceph:Implement readv/preadv for sync operation

["Yan, Zheng" <zheng.z.yan@intel.com>]

On 09/24/2013 04:54 PM, majianpeng wrote:
>> On 09/24/2013 04:05 PM, majianpeng wrote:
>>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>>> index 3de8982..5422d8e 100644
>>> --- a/fs/ceph/file.c
>>> +++ b/fs/ceph/file.c
>>> @@ -408,51 +408,94 @@ more:
>>>   *
>>>   * If the read spans object boundary, just do multiple reads.
>>>   */
>>> -static ssize_t ceph_sync_read(struct file *file, char __user *data,
>>> -			      unsigned len, loff_t *poff, int *checkeof)
>>> +static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *i,
>>> +				int *checkeof)
>>>  {
>>> +	struct file *file = iocb->ki_filp;
>>>  	struct inode *inode = file_inode(file);
>>>  	struct page **pages;
>>> -	u64 off = *poff;
>>> +	u64 off = iocb->ki_pos;
>>>  	int num_pages, ret;
>>>  
>>> -	dout("sync_read on file %p %llu~%u %s\n", file, off, len,
>>> +	dout("sync_read on file %p %llu~%u %s\n", file, off,
>>> +	     (unsigned)iocb->ki_left,
>>>  	     (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");
>>> -
>>> -	if (file->f_flags & O_DIRECT) {
>>> -		num_pages = calc_pages_for((unsigned long)data, len);
>>> -		pages = ceph_get_direct_page_vector(data, num_pages, true);
>>> -	} else {
>>> -		num_pages = calc_pages_for(off, len);
>>> -		pages = ceph_alloc_page_vector(num_pages, GFP_NOFS);
>>> -	}
>>> -	if (IS_ERR(pages))
>>> -		return PTR_ERR(pages);
>>> -
>>>  	/*
>>>  	 * flush any page cache pages in this range.  this
>>>  	 * will make concurrent normal and sync io slow,
>>>  	 * but it will at least behave sensibly when they are
>>>  	 * in sequence.
>>>  	 */
>>> -	ret = filemap_write_and_wait(inode->i_mapping);
>>> +	ret = filemap_write_and_wait_range(inode->i_mapping, off,
>>> +						off + iocb->ki_left);
>>>  	if (ret < 0)
>>> -		goto done;
>>> -
>>> -	ret = striped_read(inode, off, len, pages, num_pages, checkeof,
>>> -			   file->f_flags & O_DIRECT,
>>> -			   (unsigned long)data & ~PAGE_MASK);
>>> +		return ret;
>>>  
>>> -	if (ret >= 0 && (file->f_flags & O_DIRECT) == 0)
>>> -		ret = ceph_copy_page_vector_to_user(pages, data, off, ret);
>>> -	if (ret >= 0)
>>> -		*poff = off + ret;
>>> +	if (file->f_flags & O_DIRECT) {
>>> +		while (iov_iter_count(i)) {
>>> +			void __user *data = i->iov[0].iov_base + i->iov_offset;
>>> +			size_t len = i->iov[0].iov_len - i->iov_offset;
>>> +
>>> +			num_pages = calc_pages_for((unsigned long)data, len);
>>> +			pages = ceph_get_direct_page_vector(data,
>>> +							    num_pages, true);
>>> +			if (IS_ERR(pages))
>>> +				return PTR_ERR(pages);
>>> +
>>> +			ret = striped_read(inode, off, len,
>>> +					   pages, num_pages, checkeof,
>>> +					   1, (unsigned long)data & ~PAGE_MASK);
>>> +			ceph_put_page_vector(pages, num_pages, true);
>>> +
>>> +			if (ret <= 0)
>>> +				break;
>>> +			off += ret;
>>> +			iov_iter_advance(i, ret);
>>> +			if (ret < len)
>>> +				break;
>>> +		}
>>> +	} else {
>>> +		size_t len = iocb->ki_left;
>>>  
>>> -done:
>>> -	if (file->f_flags & O_DIRECT)
>>> -		ceph_put_page_vector(pages, num_pages, true);
>>> -	else
>>> +		num_pages = calc_pages_for(off, len);
>>> +		pages = ceph_alloc_page_vector(num_pages, GFP_NOFS);
>>> +		if (IS_ERR(pages))
>>> +			return PTR_ERR(pages);
>>> +		ret = striped_read(inode, off, len, pages,
>>> +					num_pages, checkeof, 0, 0);
>>> +		if (ret > 0) {
>>> +			int l, k = 0;
>>> +			size_t left = len = ret;
>>> +
>>> +			while (left) {
>>> +				void __user *data = i->iov[0].iov_base
>>> +							+ i->iov_offset;
>>> +				l = min(i->iov[0].iov_len - i->iov_offset,
>>> +					left);
>>> +
>>> +				ret = ceph_copy_page_vector_to_user(&pages[k],
>>> +								    data, off,
>>> +								    l);
>>> +				if (ret > 0) {
>>> +					iov_iter_advance(i, ret);
>>> +					left -= ret;
>>> +					off += ret;
>>> +					k = calc_pages_for(iocb->ki_pos,
>>> +							   len - left + 1) - 1;
>>> +					BUG_ON(k >= num_pages && left);
>>> +				} else
>>> +					break;
>>> +			}
>>> +		}
>>>  		ceph_release_page_vector(pages, num_pages);
>>> +	}
>>> +
>>> +	if (off > iocb->ki_pos) {
>>> +		ret = off - iocb->ki_pos;
>>> +		iocb->ki_pos = off;
>>> +		iocb->ki_left -= ret;
>>> +	}
>>> +
>>>  	dout("sync_read result %d\n", ret);
>>>  	return ret;
>>>  }
>>> @@ -647,17 +690,16 @@ static ssize_t ceph_aio_read(struct kiocb *iocb, const struct iovec *iov,
>>>  {
>>>  	struct file *filp = iocb->ki_filp;
>>>  	struct ceph_file_info *fi = filp->private_data;
>>> -	loff_t *ppos = &iocb->ki_pos;
>>> -	size_t len = iov->iov_len;
>>> +	size_t len = 0;
>>
>> len = iocb->ki_left;
> Yes, the dout need this.
> 
>>
>>>  	struct inode *inode = file_inode(filp);
>>>  	struct ceph_inode_info *ci = ceph_inode(inode);
>>> -	void __user *base = iov->iov_base;
>>>  	ssize_t ret;
>>>  	int want, got = 0;
>>>  	int checkeof = 0, read = 0;
>>>  
>>
>> I think we should put label 'again' here.
> Ok
> 
>>
>>>  	dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
>>>  	     inode, ceph_vinop(inode), pos, (unsigned)len, inode);
>>> +
>>>  again:
>>>  	if (fi->fmode & CEPH_FILE_MODE_LAZY)
>>>  		want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
>>> @@ -665,38 +707,61 @@ again:
>>>  		want = CEPH_CAP_FILE_CACHE;
>>>  	ret = ceph_get_caps(ci, CEPH_CAP_FILE_RD, want, &got, -1);
>>>  	if (ret < 0)
>>> -		goto out;
>>> +		return ret;
>>> +
>>>  	dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
>>>  	     inode, ceph_vinop(inode), pos, (unsigned)len,
>>>  	     ceph_cap_string(got));
>>>  
>>>  	if ((got & (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) == 0 ||
>>>  	    (iocb->ki_filp->f_flags & O_DIRECT) ||
>>> -	    (fi->flags & CEPH_F_SYNC))
>>> +	    (fi->flags & CEPH_F_SYNC)) {
>>> +		struct iov_iter i;
>>> +
>>> +		if (!read) {
>>> +			ret = generic_segment_checks(iov, &nr_segs,
>>> +							&len, VERIFY_WRITE);
>>> +			if (ret)
>>> +				goto out;
>>> +		}
>>> +
>>> +		iocb->ki_left = len;
>>
>> iocb->ki_left = len - read ?
> Before goto again, i let 'len -= ret'.
> len mean the left size.
>>
>>
>>> +		iov_iter_init(&i, iov, nr_segs, len, read);
>>>  		/* hmm, this isn't really async... */
>>> -		ret = ceph_sync_read(filp, base, len, ppos, &checkeof);
>>> -	else
>>> +		ret = ceph_sync_read(iocb, &i, &checkeof);
>>> +	} else {
>>> +		/*
>>> +		 * We can't modify the content of iov,
>>> +		 * so we only read from beginning.
>>> +		 */
>>> +		if (read)
>>> +			iocb->ki_pos = pos;
>>
>> forget to set 'read' to 0 ?
> When define read, i set read = 0.
>   >int checkeof = 0, read = 0;

I mean you need to reset 'read' to 0 here, because 'read' is used for calculating the return value.


---
if (read) {
  iocb->ki_pos = pos;
  read = 0;
}


>>
>>
>>>  		ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
>>> -
>>> +	}
>>>  out:
>>>  	dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n",
>>>  	     inode, ceph_vinop(inode), ceph_cap_string(got), (int)ret);
>>>  	ceph_put_cap_refs(ci, got);
>>>  
>>>  	if (checkeof && ret >= 0) {
>>> -		int statret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
>>> +		int statret = ceph_do_getattr(inode,
>>> +					      CEPH_STAT_CAP_SIZE);
>>>  
>>>  		/* hit EOF or hole? */
>>> -		if (statret == 0 && *ppos < inode->i_size) {
>>> -			dout("aio_read sync_read hit hole, ppos %lld < size %lld, reading more\n", *ppos, inode->i_size);
>>> +		if (statret == 0 && iocb->ki_pos < inode->i_size &&
>>> +			iocb->ki_left) {
>>> +			dout("sync_read hit hole, ppos %lld < size %lld"
>>> +			     ", reading more\n", iocb->ki_pos,
>>> +			     inode->i_size);
>>> +
>>>  			read += ret;
>>> -			base += ret;
>>>  			len -= ret;
>>>  			checkeof = 0;
>>>  			goto again;
>>>  		}
>>>  	}
>>> -	if (ret >= 0)
>>> +
>>> +	if (ret > 0)
>>>  		ret += read;
>>
>> what is the purpose of this change ?
> Sorry, i make a mistake.
> 
>>
>> Regards
>> Yan, Zheng
>>>  
>>>  	return ret;
>>> -- 
>>
>