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From: Christoph Hellwig <hch@lst.de>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org
Subject: [PATCH 06/11] fs: don't change the address limit for ->write_iter in __kernel_write
Date: Fri,  8 May 2020 11:22:17 +0200	[thread overview]
Message-ID: <20200508092222.2097-7-hch@lst.de> (raw)
In-Reply-To: <20200508092222.2097-1-hch@lst.de>

If we write to a file that implements ->write_iter there is no need
to change the address limit if we send a kvec down.  Implement that
case, and prefer it over using plain ->write with a changed address
limit if available.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/read_write.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 67a035782874b..8a55e81bd9ac7 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -488,10 +488,9 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
 	return ret;
 }
 
-ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t *pos)
+ssize_t __kernel_write(struct file *file, const void *buf, size_t count,
+		loff_t *pos)
 {
-	mm_segment_t old_fs;
-	const char __user *p;
 	ssize_t ret;
 
 	if (!(file->f_mode & FMODE_WRITE))
@@ -500,18 +499,29 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
 		return -EINVAL;
 
 	file_start_write(file);
-	old_fs = get_fs();
-	set_fs(KERNEL_DS);
-	p = (__force const char __user *)buf;
 	if (count > MAX_RW_COUNT)
 		count =  MAX_RW_COUNT;
-	if (file->f_op->write)
-		ret = file->f_op->write(file, p, count, pos);
-	else if (file->f_op->write_iter)
-		ret = new_sync_write(file, p, count, pos);
-	else
+	if (file->f_op->write_iter) {
+		struct kvec iov = { .iov_base = (void *)buf, .iov_len = count };
+		struct kiocb kiocb;
+		struct iov_iter iter;
+
+		init_sync_kiocb(&kiocb, file);
+		kiocb.ki_pos = *pos;
+		iov_iter_kvec(&iter, WRITE, &iov, 1, count);
+		ret = file->f_op->write_iter(&kiocb, &iter);
+		if (ret > 0)
+			*pos = kiocb.ki_pos;
+	} else if (file->f_op->write) {
+		mm_segment_t old_fs = get_fs();
+
+		set_fs(KERNEL_DS);
+		ret = file->f_op->write(file, (__force const char __user *)buf,
+				count, pos);
+		set_fs(old_fs);
+	} else {
 		ret = -EINVAL;
-	set_fs(old_fs);
+	}
 	if (ret > 0) {
 		fsnotify_modify(file);
 		add_wchar(current, ret);
-- 
2.26.2


  parent reply	other threads:[~2020-05-08  9:23 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-08  9:22 clean up kernel_{read,write} & friends Christoph Hellwig
2020-05-08  9:22 ` [PATCH 01/11] fs: call file_{start,end}_write from __kernel_write Christoph Hellwig
2020-05-08  9:22 ` [PATCH 02/11] fs: check FMODE_WRITE in __kernel_write Christoph Hellwig
2020-05-08  9:22 ` [PATCH 03/11] fs: remove the call_{read,write}_iter functions Christoph Hellwig
2020-05-08  9:22 ` [PATCH 04/11] fs: implement kernel_write using __kernel_write Christoph Hellwig
2020-05-08  9:22 ` [PATCH 05/11] fs: remove __vfs_write Christoph Hellwig
2020-05-08  9:22 ` Christoph Hellwig [this message]
2020-05-08  9:22 ` [PATCH 07/11] fs: add a __kernel_read helper Christoph Hellwig
2020-05-08  9:22 ` [PATCH 08/11] integrity/ima: switch to using __kernel_read Christoph Hellwig
2020-05-08  9:22 ` [PATCH 09/11] fs: implement kernel_read " Christoph Hellwig
2020-05-08  9:22 ` [PATCH 10/11] fs: remove __vfs_read Christoph Hellwig
2020-05-08 15:45   ` Ira Weiny
2020-05-08 15:46     ` Christoph Hellwig
2020-05-08  9:22 ` [PATCH 11/11] fs: don't change the address limit for ->read_iter in __kernel_read Christoph Hellwig

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