[RESEND PATCH V6] ceph:Implement readv/preadv for sync operation

[majianpeng <majianpeng@gmail.com>]

For readv/preadv sync-operatoin, ceph only do the first iov.
It don't think other iovs.Now implement this.

V6:
   Fix some bugs;
V5:
  -before getattr,it must put caps which already holded avoid deadlock.
  -only do generic_segment_checks for sync-read avoid do again in func
   generic_file_aio_read
V4:
  -modify one bug.
V3:
  -modify some bugs.
V2:
  -add generic_segment_checks
  -using struct iov_iter replace cloning the iovs.
  -return previous successfully copied if ceph_copy_page_vector_to_user
   met error.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 fs/ceph/file.c | 164 +++++++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 118 insertions(+), 46 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 3de8982..b64aa33 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;
 }
@@ -647,55 +690,84 @@ 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_nbytes;
 	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;
 
+again:
 	dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
-	     inode, ceph_vinop(inode), pos, (unsigned)len, inode);
-again:
+	     inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len, inode);
+
 	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;
-	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));
+		return ret;
 
 	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;
+
+		dout("aio_sync_read %p %llx.%llx %llu~%u got cap refs on %s\n",
+		     inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len,
+		     ceph_cap_string(got));
+
+		if (!read) {
+			ret = generic_segment_checks(iov, &nr_segs,
+							&len, VERIFY_WRITE);
+			if (ret)
+				goto out;
+		}
+
+		iocb->ki_left = len;
+		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 = generic_file_aio_read(iocb, iov, nr_segs, pos);
+		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;
+			read = 0;
+		}
+		dout("aio_read %p %llx.%llx %llu~%u got cap refs on %s\n",
+		     inode, ceph_vinop(inode), pos, (unsigned)iocb->ki_nbytes,
+		     ceph_cap_string(got));
 
+		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)
 		ret += read;
 
-- 
1.8.4-rc0