linux-kernel - [PATCH] fs: prefer read_iter over read and write

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Date:   Fri, 20 May 2022 15:51:03 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     viro@...iv.linux.org.uk, linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH] fs: prefer read_iter over read and write_iter over write

Most kernel code prefers read_iter over read and write_iter over write,
yet the read function pointer is tested first. Reverse these so that the
iter function is always used first.

Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 fs/read_write.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index e643aec2b0ef..78a81aa5fa76 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -476,10 +476,10 @@ ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
 
-	if (file->f_op->read)
-		ret = file->f_op->read(file, buf, count, pos);
-	else if (file->f_op->read_iter)
+	if (file->f_op->read_iter)
 		ret = new_sync_read(file, buf, count, pos);
+	else if (file->f_op->read)
+		ret = file->f_op->read(file, buf, count, pos);
 	else
 		ret = -EINVAL;
 	if (ret > 0) {
@@ -585,10 +585,10 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
 	file_start_write(file);
-	if (file->f_op->write)
-		ret = file->f_op->write(file, buf, count, pos);
-	else if (file->f_op->write_iter)
+	if (file->f_op->write_iter)
 		ret = new_sync_write(file, buf, count, pos);
+	else if (file->f_op->write)
+		ret = file->f_op->write(file, buf, count, pos);
 	else
 		ret = -EINVAL;
 	if (ret > 0) {
-- 
2.35.1