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From:   Christoph Hellwig <hch@lst.de>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Miklos Szeredi <miklos@szeredi.hu>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Howells <dhowells@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        ceph-devel@vger.kernel.org, linux-ext4@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
        linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH 14/17] block: open code __generic_file_write_iter for blkdev writes
Date:   Mon, 24 Apr 2023 07:49:23 +0200
Message-Id: <20230424054926.26927-15-hch@lst.de>
In-Reply-To: <20230424054926.26927-1-hch@lst.de>
References: <20230424054926.26927-1-hch@lst.de>
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Open code __generic_file_write_iter to remove the indirect call into
->direct_IO and to prepare using the iomap based write code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/fops.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/block/fops.c b/block/fops.c
index b670aa7c5bb745..fd510b6142bd57 100644
--- a/block/fops.c
+++ b/block/fops.c
@@ -508,6 +508,29 @@ static int blkdev_close(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+static ssize_t
+blkdev_direct_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	size_t count = iov_iter_count(from);
+	ssize_t written;
+
+	written = kiocb_invalidate_pages(iocb, count);
+	if (written) {
+		if (written == -EBUSY)
+			return 0;
+		return written;
+	}
+
+	written = blkdev_direct_IO(iocb, from);
+	if (written > 0) {
+		kiocb_invalidate_post_write(iocb, count);
+		iocb->ki_pos += written;
+	}
+	if (written != -EIOCBQUEUED)
+		iov_iter_revert(from, count - written - iov_iter_count(from));
+	return written;
+}
+
 /*
  * Write data to the block device.  Only intended for the block device itself
  * and the raw driver which basically is a fake block device.
@@ -517,7 +540,8 @@ static int blkdev_close(struct inode *inode, struct file *filp)
  */
 static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 {
-	struct block_device *bdev = iocb->ki_filp->private_data;
+	struct file *file = iocb->ki_filp;
+	struct block_device *bdev = file->private_data;
 	struct inode *bd_inode = bdev->bd_inode;
 	loff_t size = bdev_nr_bytes(bdev);
 	size_t shorted = 0;
@@ -538,13 +562,31 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
 		return -EOPNOTSUPP;
 
+	ret = file_remove_privs(file);
+	if (ret)
+		return ret;
+
+	ret = file_update_time(file);
+	if (ret)
+		return ret;
+
 	size -= iocb->ki_pos;
 	if (iov_iter_count(from) > size) {
 		shorted = iov_iter_count(from) - size;
 		iov_iter_truncate(from, size);
 	}
 
-	ret = __generic_file_write_iter(iocb, from);
+	current->backing_dev_info = bdev->bd_disk->bdi;
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		ret = blkdev_direct_write(iocb, from);
+		if (ret >= 0 && iov_iter_count(from))
+			ret = direct_write_fallback(iocb, from, ret,
+					generic_perform_write(iocb, from));
+	} else {
+		ret = generic_perform_write(iocb, from);
+	}
+	current->backing_dev_info = NULL;
+
 	if (ret > 0)
 		ret = generic_write_sync(iocb, ret);
 	iov_iter_reexpand(from, iov_iter_count(from) + shorted);
-- 
2.39.2