[v1,02/14] mm: Introduce do_generic_perform_write

Commit Message

Stefan Roesch Feb. 14, 2022, 5:43 p.m. UTC

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 <[e-mail]>
---
 include/linux/fs.h |  1 +
 mm/filemap.c       | 20 +++++++++++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)

Comments

Matthew Wilcox Feb. 14, 2022, 7:06 p.m. UTC | #1

On Mon, Feb 14, 2022 at 09:43:51AM -0800, Stefan Roesch wrote:
> 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.

It would seem simpler to pass the iocb pointer to generic_perform_write()
(in place of the struct file pointer) instead of inventing a new flag.

Patch

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2d892b201b0..e62dba6ed453 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_FLAGS_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..d2fb817c0845 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_FLAGS_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;
 	}