netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 212 insertions, 0 deletions

diff --git a/drivers/hid/hid-wiimote-debug.c b/drivers/hid/hid-wiimote-debug.c
new file mode 100644
index 000000000..5f7491778
--- /dev/null
+++ b/drivers/hid/hid-wiimote-debug.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Debug support for HID Nintendo Wii / Wii U peripherals
+ * Copyright (c) 2011-2013 David Herrmann <dh.herrmann@gmail.com>
+ */
+
+/*
+ */
+
+#include <linux/debugfs.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include "hid-wiimote.h"
+
+struct wiimote_debug {
+	struct wiimote_data *wdata;
+	struct dentry *eeprom;
+	struct dentry *drm;
+};
+
+static ssize_t wiidebug_eeprom_read(struct file *f, char __user *u, size_t s,
+								loff_t *off)
+{
+	struct wiimote_debug *dbg = f->private_data;
+	struct wiimote_data *wdata = dbg->wdata;
+	unsigned long flags;
+	ssize_t ret;
+	char buf[16];
+	__u16 size = 0;
+
+	if (s == 0)
+		return -EINVAL;
+	if (*off > 0xffffff)
+		return 0;
+	if (s > 16)
+		s = 16;
+
+	ret = wiimote_cmd_acquire(wdata);
+	if (ret)
+		return ret;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->state.cmd_read_size = s;
+	wdata->state.cmd_read_buf = buf;
+	wiimote_cmd_set(wdata, WIIPROTO_REQ_RMEM, *off & 0xffff);
+	wiiproto_req_reeprom(wdata, *off, s);
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	ret = wiimote_cmd_wait(wdata);
+	if (!ret)
+		size = wdata->state.cmd_read_size;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->state.cmd_read_buf = NULL;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	wiimote_cmd_release(wdata);
+
+	if (ret)
+		return ret;
+	else if (size == 0)
+		return -EIO;
+
+	if (copy_to_user(u, buf, size))
+		return -EFAULT;
+
+	*off += size;
+	ret = size;
+
+	return ret;
+}
+
+static const struct file_operations wiidebug_eeprom_fops = {
+	.owner = THIS_MODULE,
+	.open = simple_open,
+	.read = wiidebug_eeprom_read,
+	.llseek = generic_file_llseek,
+};
+
+static const char *wiidebug_drmmap[] = {
+	[WIIPROTO_REQ_NULL] = "NULL",
+	[WIIPROTO_REQ_DRM_K] = "K",
+	[WIIPROTO_REQ_DRM_KA] = "KA",
+	[WIIPROTO_REQ_DRM_KE] = "KE",
+	[WIIPROTO_REQ_DRM_KAI] = "KAI",
+	[WIIPROTO_REQ_DRM_KEE] = "KEE",
+	[WIIPROTO_REQ_DRM_KAE] = "KAE",
+	[WIIPROTO_REQ_DRM_KIE] = "KIE",
+	[WIIPROTO_REQ_DRM_KAIE] = "KAIE",
+	[WIIPROTO_REQ_DRM_E] = "E",
+	[WIIPROTO_REQ_DRM_SKAI1] = "SKAI1",
+	[WIIPROTO_REQ_DRM_SKAI2] = "SKAI2",
+	[WIIPROTO_REQ_MAX] = NULL
+};
+
+static int wiidebug_drm_show(struct seq_file *f, void *p)
+{
+	struct wiimote_debug *dbg = f->private;
+	const char *str = NULL;
+	unsigned long flags;
+	__u8 drm;
+
+	spin_lock_irqsave(&dbg->wdata->state.lock, flags);
+	drm = dbg->wdata->state.drm;
+	spin_unlock_irqrestore(&dbg->wdata->state.lock, flags);
+
+	if (drm < WIIPROTO_REQ_MAX)
+		str = wiidebug_drmmap[drm];
+	if (!str)
+		str = "unknown";
+
+	seq_printf(f, "%s\n", str);
+
+	return 0;
+}
+
+static int wiidebug_drm_open(struct inode *i, struct file *f)
+{
+	return single_open(f, wiidebug_drm_show, i->i_private);
+}
+
+static ssize_t wiidebug_drm_write(struct file *f, const char __user *u,
+							size_t s, loff_t *off)
+{
+	struct seq_file *sf = f->private_data;
+	struct wiimote_debug *dbg = sf->private;
+	unsigned long flags;
+	char buf[16];
+	ssize_t len;
+	int i;
+
+	if (s == 0)
+		return -EINVAL;
+
+	len = min((size_t) 15, s);
+	if (copy_from_user(buf, u, len))
+		return -EFAULT;
+
+	buf[len] = 0;
+
+	for (i = 0; i < WIIPROTO_REQ_MAX; ++i) {
+		if (!wiidebug_drmmap[i])
+			continue;
+		if (!strcasecmp(buf, wiidebug_drmmap[i]))
+			break;
+	}
+
+	if (i == WIIPROTO_REQ_MAX)
+		i = simple_strtoul(buf, NULL, 16);
+
+	spin_lock_irqsave(&dbg->wdata->state.lock, flags);
+	dbg->wdata->state.flags &= ~WIIPROTO_FLAG_DRM_LOCKED;
+	wiiproto_req_drm(dbg->wdata, (__u8) i);
+	if (i != WIIPROTO_REQ_NULL)
+		dbg->wdata->state.flags |= WIIPROTO_FLAG_DRM_LOCKED;
+	spin_unlock_irqrestore(&dbg->wdata->state.lock, flags);
+
+	return len;
+}
+
+static const struct file_operations wiidebug_drm_fops = {
+	.owner = THIS_MODULE,
+	.open = wiidebug_drm_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.write = wiidebug_drm_write,
+	.release = single_release,
+};
+
+int wiidebug_init(struct wiimote_data *wdata)
+{
+	struct wiimote_debug *dbg;
+	unsigned long flags;
+
+	dbg = kzalloc_obj(*dbg);
+	if (!dbg)
+		return -ENOMEM;
+
+	dbg->wdata = wdata;
+
+	dbg->eeprom = debugfs_create_file("eeprom", S_IRUSR,
+		dbg->wdata->hdev->debug_dir, dbg, &wiidebug_eeprom_fops);
+
+	dbg->drm = debugfs_create_file("drm", S_IRUSR,
+			dbg->wdata->hdev->debug_dir, dbg, &wiidebug_drm_fops);
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->debug = dbg;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	return 0;
+
+}
+
+void wiidebug_deinit(struct wiimote_data *wdata)
+{
+	struct wiimote_debug *dbg = wdata->debug;
+	unsigned long flags;
+
+	if (!dbg)
+		return;
+
+	spin_lock_irqsave(&wdata->state.lock, flags);
+	wdata->debug = NULL;
+	spin_unlock_irqrestore(&wdata->state.lock, flags);
+
+	debugfs_remove(dbg->drm);
+	debugfs_remove(dbg->eeprom);
+	kfree(dbg);
+}