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From:   David Howells <dhowells@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>, Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>
Cc:     David Howells <dhowells@redhat.com>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Hillf Danton <hdanton@sina.com>,
        Christian Brauner <brauner@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Christoph Hellwig <hch@lst.de>,
        Christian Brauner <christian@brauner.io>
Subject: [RFC PATCH 02/11] vfs: Set IOCB_WRITE in iocbs that we're going to write from
Date:   Fri, 30 Jun 2023 16:25:15 +0100
Message-ID: <20230630152524.661208-3-dhowells@redhat.com>
In-Reply-To: <20230630152524.661208-1-dhowells@redhat.com>
References: <20230630152524.661208-1-dhowells@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
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IOCB_WRITE is set by aio, io_uring and cachefiles before submitting a write
operation to the VFS, but it isn't set by, say, the write() system call.

Fix this by adding an extra argument to init_sync_kiocb() to indicate the
direction and setting that to READ or WRITE, which will cause IOCB_WRITE to
be set as appropriate.

Whilst we're at it, rename init_sync_kiocb() to init_kiocb().

This will allow drivers to use IOCB_WRITE instead of the iterator data
source to determine the I/O direction.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christian Brauner <christian@brauner.io>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
---
 fs/btrfs/ioctl.c   |  4 ++--
 fs/read_write.c    | 10 +++++-----
 fs/seq_file.c      |  2 +-
 fs/splice.c        |  2 +-
 include/linux/fs.h |  6 +++++-
 mm/filemap.c       |  2 +-
 mm/page_io.c       |  4 ++--
 7 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a895d105464b..15870337dd26 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4422,7 +4422,7 @@ static int btrfs_ioctl_encoded_read(struct file *file, void __user *argp,
 	if (ret < 0)
 		goto out_iov;
 
-	init_sync_kiocb(&kiocb, file);
+	init_kiocb(&kiocb, file, READ);
 	kiocb.ki_pos = pos;
 
 	ret = btrfs_encoded_read(&kiocb, &iter, &args);
@@ -4523,7 +4523,7 @@ static int btrfs_ioctl_encoded_write(struct file *file, void __user *argp, bool
 	if (ret < 0)
 		goto out_end_write;
 
-	init_sync_kiocb(&kiocb, file);
+	init_kiocb(&kiocb, file, WRITE);
 	ret = kiocb_set_rw_flags(&kiocb, 0);
 	if (ret)
 		goto out_end_write;
diff --git a/fs/read_write.c b/fs/read_write.c
index b07de77ef126..6fe517047095 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -382,7 +382,7 @@ static ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, lo
 	struct iov_iter iter;
 	ssize_t ret;
 
-	init_sync_kiocb(&kiocb, filp);
+	init_kiocb(&kiocb, filp, READ);
 	kiocb.ki_pos = (ppos ? *ppos : 0);
 	iov_iter_ubuf(&iter, ITER_DEST, buf, len);
 
@@ -422,7 +422,7 @@ ssize_t __kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 	if (unlikely(!file->f_op->read_iter || file->f_op->read))
 		return warn_unsupported(file, "read");
 
-	init_sync_kiocb(&kiocb, file);
+	init_kiocb(&kiocb, file, READ);
 	kiocb.ki_pos = pos ? *pos : 0;
 	iov_iter_kvec(&iter, ITER_DEST, &iov, 1, iov.iov_len);
 	ret = file->f_op->read_iter(&kiocb, &iter);
@@ -484,7 +484,7 @@ static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t
 	struct iov_iter iter;
 	ssize_t ret;
 
-	init_sync_kiocb(&kiocb, filp);
+	init_kiocb(&kiocb, filp, WRITE);
 	kiocb.ki_pos = (ppos ? *ppos : 0);
 	iov_iter_ubuf(&iter, ITER_SOURCE, (void __user *)buf, len);
 
@@ -512,7 +512,7 @@ ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *po
 	if (unlikely(!file->f_op->write_iter || file->f_op->write))
 		return warn_unsupported(file, "write");
 
-	init_sync_kiocb(&kiocb, file);
+	init_kiocb(&kiocb, file, WRITE);
 	kiocb.ki_pos = pos ? *pos : 0;
 	ret = file->f_op->write_iter(&kiocb, from);
 	if (ret > 0) {
@@ -723,7 +723,7 @@ static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
 	struct kiocb kiocb;
 	ssize_t ret;
 
-	init_sync_kiocb(&kiocb, filp);
+	init_kiocb(&kiocb, filp, type);
 	ret = kiocb_set_rw_flags(&kiocb, flags);
 	if (ret)
 		return ret;
diff --git a/fs/seq_file.c b/fs/seq_file.c
index f5fdaf3b1572..1ee6ffc630da 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -155,7 +155,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
 	struct iov_iter iter;
 	ssize_t ret;
 
-	init_sync_kiocb(&kiocb, file);
+	init_kiocb(&kiocb, file, READ);
 	iov_iter_init(&iter, ITER_DEST, &iov, 1, size);
 
 	kiocb.ki_pos = *ppos;
diff --git a/fs/splice.c b/fs/splice.c
index 004eb1c4ce31..867357ebb2c3 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -362,7 +362,7 @@ ssize_t copy_splice_read(struct file *in, loff_t *ppos,
 
 	/* Do the I/O */
 	iov_iter_bvec(&to, ITER_DEST, bv, npages, len);
-	init_sync_kiocb(&kiocb, in);
+	init_kiocb(&kiocb, in, READ);
 	kiocb.ki_pos = *ppos;
 	ret = call_read_iter(in, &kiocb, &to);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d4b67bdeb53e..466eba253502 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2017,13 +2017,17 @@ static inline bool HAS_UNMAPPED_ID(struct mnt_idmap *idmap,
 	       !vfsgid_valid(i_gid_into_vfsgid(idmap, inode));
 }
 
-static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
+static inline void init_kiocb(struct kiocb *kiocb, struct file *filp,
+			      unsigned int rw)
 {
 	*kiocb = (struct kiocb) {
 		.ki_filp = filp,
 		.ki_flags = filp->f_iocb_flags,
 		.ki_ioprio = get_current_ioprio(),
 	};
+
+	if (rw == WRITE)
+		kiocb->ki_flags |= IOCB_WRITE;
 }
 
 static inline void kiocb_clone(struct kiocb *kiocb, struct kiocb *kiocb_src,
diff --git a/mm/filemap.c b/mm/filemap.c
index 9e44a49bbd74..cd763122d2a2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2905,7 +2905,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
 	if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
 		return 0;
 
-	init_sync_kiocb(&iocb, in);
+	init_kiocb(&iocb, in, READ);
 	iocb.ki_pos = *ppos;
 
 	/* Work out how much data we can actually add into the pipe */
diff --git a/mm/page_io.c b/mm/page_io.c
index 684cd3c7b59b..85cbadaf7395 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -312,7 +312,7 @@ static void swap_writepage_fs(struct page *page, struct writeback_control *wbc)
 	}
 	if (!sio) {
 		sio = mempool_alloc(sio_pool, GFP_NOIO);
-		init_sync_kiocb(&sio->iocb, swap_file);
+		init_kiocb(&sio->iocb, swap_file, WRITE);
 		sio->iocb.ki_complete = sio_write_complete;
 		sio->iocb.ki_pos = pos;
 		sio->pages = 0;
@@ -443,7 +443,7 @@ static void swap_readpage_fs(struct page *page,
 	}
 	if (!sio) {
 		sio = mempool_alloc(sio_pool, GFP_KERNEL);
-		init_sync_kiocb(&sio->iocb, sis->swap_file);
+		init_kiocb(&sio->iocb, sis->swap_file, READ);
 		sio->iocb.ki_pos = pos;
 		sio->iocb.ki_complete = sio_read_complete;
 		sio->pages = 0;