tty, proc, kernfs, random: Use copy_splice_read()

Use copy_splice_read() for tty, procfs, kernfs and random files rather
than going through generic_file_splice_read() as they just copy the file
into the output buffer and don't splice pages.  This avoids the need for
them to have a ->read_folio() to satisfy filemap_splice_read().
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: John Hubbard <jhubbard@nvidia.com>
cc: David Hildenbrand <david@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: Miklos Szeredi <miklos@szeredi.hu>
cc: Arnd Bergmann <arnd@arndb.de>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/20230522135018.2742245-13-dhowells@redhat.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/char/random.c

@@ -1546,7 +1546,7 @@ const struct file_operations random_fops = {
 	.compat_ioctl = compat_ptr_ioctl,
 	.fasync = random_fasync,
 	.llseek = noop_llseek,
-	.splice_read = generic_file_splice_read,
+	.splice_read = copy_splice_read,
 	.splice_write = iter_file_splice_write,
 };
 
@@ -1557,7 +1557,7 @@ const struct file_operations urandom_fops = {
 	.compat_ioctl = compat_ptr_ioctl,
 	.fasync = random_fasync,
 	.llseek = noop_llseek,
-	.splice_read = generic_file_splice_read,
+	.splice_read = copy_splice_read,
 	.splice_write = iter_file_splice_write,
 };
 

drivers/tty/tty_io.c

@@ -466,7 +466,7 @@ static const struct file_operations tty_fops = {
 	.llseek		= no_llseek,
 	.read_iter	= tty_read,
 	.write_iter	= tty_write,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.poll		= tty_poll,
 	.unlocked_ioctl	= tty_ioctl,
@@ -481,7 +481,7 @@ static const struct file_operations console_fops = {
 	.llseek		= no_llseek,
 	.read_iter	= tty_read,
 	.write_iter	= redirected_tty_write,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.poll		= tty_poll,
 	.unlocked_ioctl	= tty_ioctl,

fs/kernfs/file.c

@@ -1011,7 +1011,7 @@ const struct file_operations kernfs_file_fops = {
 	.release	= kernfs_fop_release,
 	.poll		= kernfs_fop_poll,
 	.fsync		= noop_fsync,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 };
 

fs/proc/inode.c

@@ -591,7 +591,7 @@ static const struct file_operations proc_iter_file_ops = {
 	.llseek		= proc_reg_llseek,
 	.read_iter	= proc_reg_read_iter,
 	.write		= proc_reg_write,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,
 	.mmap		= proc_reg_mmap,
@@ -617,7 +617,7 @@ static const struct file_operations proc_reg_file_ops_compat = {
 static const struct file_operations proc_iter_file_ops_compat = {
 	.llseek		= proc_reg_llseek,
 	.read_iter	= proc_reg_read_iter,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.write		= proc_reg_write,
 	.poll		= proc_reg_poll,
 	.unlocked_ioctl	= proc_reg_unlocked_ioctl,

fs/proc/proc_sysctl.c

@@ -868,7 +868,7 @@ static const struct file_operations proc_sys_file_operations = {
 	.poll		= proc_sys_poll,
 	.read_iter	= proc_sys_read,
 	.write_iter	= proc_sys_write,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.llseek		= default_llseek,
 };

fs/proc_namespace.c

@@ -324,7 +324,7 @@ static int mountstats_open(struct inode *inode, struct file *file)
 const struct file_operations proc_mounts_operations = {
 	.open		= mounts_open,
 	.read_iter	= seq_read_iter,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -333,7 +333,7 @@ const struct file_operations proc_mounts_operations = {
 const struct file_operations proc_mountinfo_operations = {
 	.open		= mountinfo_open,
 	.read_iter	= seq_read_iter,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 	.poll		= mounts_poll,
@@ -342,7 +342,7 @@ const struct file_operations proc_mountinfo_operations = {
 const struct file_operations proc_mountstats_operations = {
 	.open		= mountstats_open,
 	.read_iter	= seq_read_iter,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= copy_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 };