Re: Re: [PATCH 1/2] ceph: Implement readv/preadv for sync operation.

[majianpeng <majianpeng@gmail.com>]

>On 09/03/2013 04:52 PM, majianpeng wrote:
>> For readv/preadv sync-operatoin, ceph only do the first iov.
>> It don't think other iovs.Now implement this.
>> 
>> Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
>> ---
>>  fs/ceph/file.c | 175 ++++++++++++++++++++++++++++++++++++++++-----------------
>>  1 file changed, 123 insertions(+), 52 deletions(-)
>> 
>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>> index 3de8982..7d6a3ee 100644
>> --- a/fs/ceph/file.c
>> +++ b/fs/ceph/file.c
>> @@ -408,51 +408,95 @@ 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 iovec *iov,
>> +			      unsigned long nr_segs, int *checkeof)
>>  {
>> +	struct file *file = iocb->ki_filp;
>>  	struct inode *inode = file_inode(file);
>>  	struct page **pages;
>> -	u64 off = *poff;
>> -	int num_pages, ret;
>> +	u64 off = iocb->ki_pos;
>> +	int num_pages, ret, i;
>>  
>> -	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) {
>> +		for (i = 0; i < nr_segs; i++) {
>> +			void __user *data = iov[i].iov_base;
>> +			size_t len = iov[i].iov_len;
>> +
>> +			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;
>> +			if (ret < len)
>> +				break;
>> +		}
>> +		if (off > iocb->ki_pos) {
>> +			ret = off - iocb->ki_pos;
>> +			iocb->ki_pos = off;
>> +			iocb->ki_left -= ret;
>> +		}
>> +	} 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);
>> +		len = ret;
>> +		if (len) {
>> +			int i, l, k = 0;
>> +			size_t left = len;
>> +
>> +			for (i = 0; i < nr_segs && left; i++) {
>> +				void __user *data = iov[i].iov_base;
>> +				l = min(left, iov[i].iov_len);
>> +				ret = ceph_copy_page_vector_to_user(&pages[k],
>> +								    data, off,
>> +								    l);
>> +				if (ret > 0) {
>> +					left -= ret;
>> +					off += ret;
>> +					k = calc_pages_for(iocb->ki_pos,
>> +							   len - left + 1) - 1;
>> +					BUG_ON(k >= num_pages && left);
>> +				} else
>> +					break;
>> +			}
>> +
>> +			if (left == 0) {
>> +				iocb->ki_pos += len;
>> +				iocb->ki_left -= len;
>> +				ret = len;
>> +			}
>
>If user program provides invalid buffer to readv syscall. 'left' can be larger than 0.
>For this case, we should return size of data that were successfully copied
Ok, we should add this code, before "if (left == 0)"
left = len - left;

>
>> +		}
>>  		ceph_release_page_vector(pages, num_pages);
>> +	}
>> +
>>  	dout("sync_read result %d\n", ret);
>>  	return ret;
>>  }
>> @@ -647,55 +691,82 @@ 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 = iocb->ki_left;
>>  	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;
>>  
>> +
>>  	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;
>>  	else
>>  		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)) {
>> +		unsigned long curr_seg = 0;
>> +		struct iovec *iov_clone;
>> +
>> +		iov_clone = kmalloc(nr_segs * sizeof(struct iovec), GFP_KERNEL);
>> +		if (iov_clone == NULL) {
>> +			ret = -ENOMEM;
>> +			goto out;
>> +		}
>> +		memcpy(iov_clone, iov, nr_segs * sizeof(struct iovec));
>
>why do we need to clone the iov ?
>
I noticed in patch2,you asked the same question.
The reason is i need modify iov,but the iov is const.So i only clone it.
Or should you have better method?

>Regards
>Yan, Zheng
>
>> +again:
>>  		/* hmm, this isn't really async... */
>> -		ret = ceph_sync_read(filp, base, len, ppos, &checkeof);
>> -	else
>> -		ret = generic_file_aio_read(iocb, iov, nr_segs, pos);
>> +		ret = ceph_sync_read(iocb, &iov_clone[curr_seg],
>> +					nr_segs - curr_seg, &checkeof);
>> +
>> +		if (checkeof && ret >= 0) {
>> +			int statret = ceph_do_getattr(inode,
>> +						      CEPH_STAT_CAP_SIZE);
>> +
>> +			/* hit EOF or hole? */
>> +			if (statret == 0 && iocb->ki_pos < inode->i_size &&
>> +				iocb->ki_left) {
>> +				size_t tmp = 0;
>> +				dout("%s sync_read hit hole, ppos %lld < size %lld"
>> +				     ", reading more\n", __func__, iocb->ki_pos,
>> +				     inode->i_size);
>> +
>> +				read += ret;
>> +				for (; curr_seg < nr_segs; curr_seg++) {
>> +					if ((tmp + iov_clone[curr_seg].iov_len)
>> +						> ret)
>> +						break;
>> +					tmp += iov_clone[curr_seg].iov_len;
>> +				}
>> +
>> +				BUG_ON(curr_seg == nr_segs);
>> +				iov_clone[curr_seg].iov_base += ret - tmp;
>> +				iov_clone[curr_seg].iov_len -= ret - tmp;
>> +				checkeof = 0;
>> +				goto again;
>> +			}
>> +		}
>> +		kfree(iov_clone);
>>  
>> +	} else
>> +		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);
>> -
>> -		/* 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);
>> -			read += ret;
>> -			base += ret;
>> -			len -= ret;
>> -			checkeof = 0;
>> -			goto again;
>> -		}
>> -	}
>>  	if (ret >= 0)
>>  		ret += read;
>>  
>> 
>