[PATCH v2 02/13] mm: Introduce do_generic_perform_write

[Stefan Roesch <shr@fb.com>]

This splits off the do generic_perform_write() function, so an
additional flags parameter can be specified. It uses the new flag
parameter to support async buffered writes.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 include/linux/fs.h |  1 +
 mm/filemap.c       | 20 +++++++++++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2d892b201b0..b7dd5bd701c0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -278,6 +278,7 @@ enum positive_aop_returns {
 #define AOP_FLAG_NOFS			0x0002 /* used by filesystem to direct
 						* helper code (eg buffer layer)
 						* to clear GFP_FS from alloc */
+#define AOP_FLAG_NOWAIT			0x0004 /* async nowait buffered writes */
 
 /*
  * oh the beauties of C type declarations.
diff --git a/mm/filemap.c b/mm/filemap.c
index ad8c39d90bf9..5bd692a327d0 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3725,14 +3725,13 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
 }
 EXPORT_SYMBOL(generic_file_direct_write);
 
-ssize_t generic_perform_write(struct file *file,
-				struct iov_iter *i, loff_t pos)
+static ssize_t do_generic_perform_write(struct file *file, struct iov_iter *i,
+					loff_t pos, int flags)
 {
 	struct address_space *mapping = file->f_mapping;
 	const struct address_space_operations *a_ops = mapping->a_ops;
 	long status = 0;
 	ssize_t written = 0;
-	unsigned int flags = 0;
 
 	do {
 		struct page *page;
@@ -3801,6 +3800,12 @@ ssize_t generic_perform_write(struct file *file,
 
 	return written ? written : status;
 }
+
+ssize_t generic_perform_write(struct file *file,
+				struct iov_iter *i, loff_t pos)
+{
+	return do_generic_perform_write(file, i, pos, 0);
+}
 EXPORT_SYMBOL(generic_perform_write);
 
 /**
@@ -3832,6 +3837,10 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t		written = 0;
 	ssize_t		err;
 	ssize_t		status;
+	int		flags = 0;
+
+	if (iocb->ki_flags & IOCB_NOWAIT)
+		flags |= AOP_FLAG_NOWAIT;
 
 	/* We can write back this queue in page reclaim */
 	current->backing_dev_info = inode_to_bdi(inode);
@@ -3857,7 +3866,8 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
 			goto out;
 
-		status = generic_perform_write(file, from, pos = iocb->ki_pos);
+		status = do_generic_perform_write(file, from, pos = iocb->ki_pos, flags);
+
 		/*
 		 * If generic_perform_write() returned a synchronous error
 		 * then we want to return the number of bytes which were
@@ -3889,7 +3899,7 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			 */
 		}
 	} else {
-		written = generic_perform_write(file, from, iocb->ki_pos);
+		written = do_generic_perform_write(file, from, iocb->ki_pos, flags);
 		if (likely(written > 0))
 			iocb->ki_pos += written;
 	}
-- 
2.30.2