[PATCH 4/8] filemap: add a kiocb_write_and_wait helper

[Christoph Hellwig <hch@xxxxxx>]

Factor out a helper that does filemap_write_and_wait_range for the range
covered by a read kiocb, or returns -EAGAIN if the kiocb is marked as
nowait and there would be pages to write.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
Acked-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 block/fops.c            | 18 +++---------------
 include/linux/pagemap.h |  2 ++
 mm/filemap.c            | 30 ++++++++++++++++++------------
 3 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index 58d0aebc7313a8..575171049c5d83 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -576,21 +576,9 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		goto reexpand; /* skip atime */
 
 	if (iocb->ki_flags & IOCB_DIRECT) {
-		struct address_space *mapping = iocb->ki_filp->f_mapping;
-
-		if (iocb->ki_flags & IOCB_NOWAIT) {
-			if (filemap_range_needs_writeback(mapping, pos,
-							  pos + count - 1)) {
-				ret = -EAGAIN;
-				goto reexpand;
-			}
-		} else {
-			ret = filemap_write_and_wait_range(mapping, pos,
-							   pos + count - 1);
-			if (ret < 0)
-				goto reexpand;
-		}
-
+		ret = kiocb_write_and_wait(iocb, count);
+		if (ret < 0)
+			goto reexpand;
 		file_accessed(iocb->ki_filp);
 
 		ret = blkdev_direct_IO(iocb, to);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index a56308a9d1a450..36fc2cea13ce20 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -30,6 +30,7 @@ static inline void invalidate_remote_inode(struct inode *inode)
 int invalidate_inode_pages2(struct address_space *mapping);
 int invalidate_inode_pages2_range(struct address_space *mapping,
 		pgoff_t start, pgoff_t end);
+
 int write_inode_now(struct inode *, int sync);
 int filemap_fdatawrite(struct address_space *);
 int filemap_flush(struct address_space *);
@@ -54,6 +55,7 @@ int filemap_check_errors(struct address_space *mapping);
 void __filemap_set_wb_err(struct address_space *mapping, int err);
 int filemap_fdatawrite_wbc(struct address_space *mapping,
 			   struct writeback_control *wbc);
+int kiocb_write_and_wait(struct kiocb *iocb, size_t count);
 
 static inline int filemap_write_and_wait(struct address_space *mapping)
 {
diff --git a/mm/filemap.c b/mm/filemap.c
index 15907af4a57ff5..5fcd5227f9cae2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2762,6 +2762,21 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
 }
 EXPORT_SYMBOL_GPL(filemap_read);
 
+int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
+{
+	struct address_space *mapping = iocb->ki_filp->f_mapping;
+	loff_t pos = iocb->ki_pos;
+	loff_t end = pos + count - 1;
+
+	if (iocb->ki_flags & IOCB_NOWAIT) {
+		if (filemap_range_needs_writeback(mapping, pos, end))
+			return -EAGAIN;
+		return 0;
+	}
+
+	return filemap_write_and_wait_range(mapping, pos, end);
+}
+
 /**
  * generic_file_read_iter - generic filesystem read routine
  * @iocb:	kernel I/O control block
@@ -2797,18 +2812,9 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 		struct address_space *mapping = file->f_mapping;
 		struct inode *inode = mapping->host;
 
-		if (iocb->ki_flags & IOCB_NOWAIT) {
-			if (filemap_range_needs_writeback(mapping, iocb->ki_pos,
-						iocb->ki_pos + count - 1))
-				return -EAGAIN;
-		} else {
-			retval = filemap_write_and_wait_range(mapping,
-						iocb->ki_pos,
-					        iocb->ki_pos + count - 1);
-			if (retval < 0)
-				return retval;
-		}
-
+		retval = kiocb_write_and_wait(iocb, count);
+		if (retval < 0)
+			return retval;
 		file_accessed(file);
 
 		retval = mapping->a_ops->direct_IO(iocb, iter);
-- 
2.39.2