[Ocfs2-devel] [PATCH 4/4] ocfs2: do not use ocfs2_zero_extend during direct IO

[Joseph Qi <joseph.qi@huawei.com>]

In ocfs2_direct_IO_write, we use ocfs2_zero_extend to zero allocated
clusters in case of cluster not aligned. But ocfs2_zero_extend uses page
cache, this may happen that it clears the data which blockdev_direct_IO
has already witten.
We should use blkdev_issue_zeroout instead of ocfs2_zero_extend
during direct IO.
So fix this issue by introducing ocfs2_direct_IO_zero_extend and
ocfs2_direct_IO_extend_no_holes.

Reported-by: Yiwen Jiang <jiangyiwen@huawei.com>
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Tested-by: Yiwen Jiang <jiangyiwen@huawei.com>
---
 fs/ocfs2/aops.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 130 insertions(+), 8 deletions(-)

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 973a636..1b0463a 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -663,6 +663,117 @@ static int ocfs2_is_overwrite(struct ocfs2_super *osb,
 	return 0;
 }

+static int ocfs2_direct_IO_zero_extend(struct ocfs2_super *osb,
+		struct inode *inode, loff_t offset,
+		u64 zero_len, int cluster_align)
+{
+	u32 p_cpos = 0;
+	u32 v_cpos = ocfs2_bytes_to_clusters(osb->sb, i_size_read(inode));
+	unsigned int num_clusters = 0;
+	unsigned int ext_flags = 0;
+	int ret = 0;
+
+	if (offset <= i_size_read(inode) || cluster_align)
+		return 0;
+
+	ret = ocfs2_get_clusters(inode, v_cpos, &p_cpos, &num_clusters,
+			&ext_flags);
+	if (ret < 0) {
+		mlog_errno(ret);
+		return ret;
+	}
+
+	if (p_cpos && !(ext_flags & OCFS2_EXT_UNWRITTEN)) {
+		u64 s = i_size_read(inode);
+		sector_t sector = (p_cpos << (osb->s_clustersize_bits - 9)) +
+			(do_div(s, osb->s_clustersize) >> 9);
+
+		ret = blkdev_issue_zeroout(osb->sb->s_bdev, sector,
+				zero_len >> 9, GFP_NOFS, false);
+		if (ret < 0)
+			mlog_errno(ret);
+	}
+
+	return ret;
+}
+
+static int ocfs2_direct_IO_extend_no_holes(struct ocfs2_super *osb,
+		struct inode *inode, loff_t offset)
+{
+	u64 zero_start, zero_len, total_zero_len;
+	u32 p_cpos = 0, clusters_to_add;
+	u32 v_cpos = ocfs2_bytes_to_clusters(osb->sb, i_size_read(inode));
+	unsigned int num_clusters = 0;
+	unsigned int ext_flags = 0;
+	u32 size_div, offset_div;
+	int ret = 0;
+
+	{
+		u64 o = offset;
+		u64 s = i_size_read(inode);
+
+		offset_div = do_div(o, osb->s_clustersize);
+		size_div = do_div(s, osb->s_clustersize);
+	}
+
+	if (offset <= i_size_read(inode))
+		return 0;
+
+	clusters_to_add = ocfs2_bytes_to_clusters(inode->i_sb, offset) -
+		ocfs2_bytes_to_clusters(inode->i_sb, i_size_read(inode));
+	total_zero_len = offset - i_size_read(inode);
+	if (clusters_to_add)
+		total_zero_len -= offset_div;
+
+	/* Allocate clusters to fill out holes, and this is only needed
+	 * when we add more than one clusters. Otherwise the cluster will
+	 * be allocated during direct IO */
+	if (clusters_to_add > 1) {
+		ret = ocfs2_extend_allocation(inode,
+				OCFS2_I(inode)->ip_clusters,
+				clusters_to_add - 1, 0);
+		if (ret) {
+			mlog_errno(ret);
+			goto out;
+		}
+	}
+
+	while (total_zero_len) {
+		ret = ocfs2_get_clusters(inode, v_cpos, &p_cpos, &num_clusters,
+				&ext_flags);
+		if (ret < 0) {
+			mlog_errno(ret);
+			goto out;
+		}
+
+		zero_start = ocfs2_clusters_to_bytes(osb->sb, p_cpos) +
+			size_div;
+		zero_len = ocfs2_clusters_to_bytes(osb->sb, num_clusters) -
+			size_div;
+		zero_len = min(total_zero_len, zero_len);
+
+		if (p_cpos && !(ext_flags & OCFS2_EXT_UNWRITTEN)) {
+			ret = blkdev_issue_zeroout(osb->sb->s_bdev,
+					zero_start >> 9, zero_len >> 9,
+					GFP_NOFS, false);
+			if (ret < 0) {
+				mlog_errno(ret);
+				goto out;
+			}
+		}
+
+		total_zero_len -= zero_len;
+		v_cpos += ocfs2_bytes_to_clusters(osb->sb, zero_len + size_div);
+
+		/* Only at first iteration can be cluster not aligned.
+		 * So set size_div to 0 for the rest */
+		size_div = 0;
+	}
+
+out:
+	return ret;
+}
+
 static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
 		struct iov_iter *iter,
 		loff_t offset)
@@ -677,8 +788,8 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
 	struct buffer_head *di_bh = NULL;
 	size_t count = iter->count;
 	journal_t *journal = osb->journal->j_journal;
-	u32 zero_len;
-	int cluster_align;
+	u64 zero_len_head, zero_len_tail;
+	int cluster_align_head, cluster_align_tail;
 	loff_t final_size = offset + count;
 	int append_write = offset >= i_size_read(inode) ? 1 : 0;
 	unsigned int num_clusters = 0;
@@ -686,9 +797,16 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,

 	{
 		u64 o = offset;
+		u64 s = i_size_read(inode);
+
+		zero_len_head = do_div(o, 1 << osb->s_clustersize_bits);
+		cluster_align_head = !zero_len_head;

-		zero_len = do_div(o, 1 << osb->s_clustersize_bits);
-		cluster_align = !zero_len;
+		zero_len_tail = osb->s_clustersize -
+			do_div(s, osb->s_clustersize);
+		if ((offset - i_size_read(inode)) < zero_len_tail)
+			zero_len_tail = offset - i_size_read(inode);
+		cluster_align_tail = !zero_len_tail;
 	}

 	/*
@@ -712,10 +830,13 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
 			goto clean_orphan;
 		}

+		/* zeroing out the previously allocated cluster tail
+		 * that but not zeroed */
 		if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
-			ret = ocfs2_zero_extend(inode, di_bh, offset);
+			ret = ocfs2_direct_IO_zero_extend(osb, inode, offset,
+					zero_len_tail, cluster_align_tail);
 		else
-			ret = ocfs2_extend_no_holes(inode, di_bh, offset,
+			ret = ocfs2_direct_IO_extend_no_holes(osb, inode,
 					offset);
 		if (ret < 0) {
 			mlog_errno(ret);
@@ -768,7 +889,8 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
 				mlog_errno(ret);
 		}
 	} else if (written > 0 && append_write && !is_overwrite &&
-			!cluster_align) {
+			!cluster_align_head) {
+		/* zeroing out the allocated cluster head */
 		u32 p_cpos = 0;
 		u32 v_cpos = ocfs2_bytes_to_clusters(osb->sb, offset);

@@ -790,7 +912,7 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,

 		ret = blkdev_issue_zeroout(osb->sb->s_bdev,
 				p_cpos << (osb->s_clustersize_bits - 9),
-				zero_len >> 9, GFP_NOFS, false);
+				zero_len_head >> 9, GFP_NOFS, false);
 		if (ret < 0)
 			mlog_errno(ret);

-- 
1.8.4.3