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, 47 insertions, 0 deletions

diff --git a/drivers/crypto/ccp/dbc.h b/drivers/crypto/ccp/dbc.h
new file mode 100644
index 000000000..e0fecbe92
--- /dev/null
+++ b/drivers/crypto/ccp/dbc.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * AMD Platform Security Processor (PSP) Dynamic Boost Control support
+ *
+ * Copyright (C) 2023 Advanced Micro Devices, Inc.
+ *
+ * Author: Mario Limonciello <mario.limonciello@amd.com>
+ */
+
+#ifndef __DBC_H__
+#define __DBC_H__
+
+#include <uapi/linux/psp-dbc.h>
+
+#include <linux/device.h>
+#include <linux/miscdevice.h>
+#include <linux/psp-platform-access.h>
+
+#include "psp-dev.h"
+
+struct psp_dbc_device {
+	struct device *dev;
+	struct psp_device *psp;
+
+	union dbc_buffer *mbox;
+
+	struct mutex ioctl_mutex;
+
+	struct miscdevice char_dev;
+
+	/* used to abstract communication path */
+	bool	use_ext;
+	u32	header_size;
+	u32	*payload_size;
+	u32	*result;
+	void	*payload;
+};
+
+union dbc_buffer {
+	struct psp_request		pa_req;
+	struct psp_ext_request		ext_req;
+};
+
+void dbc_dev_destroy(struct psp_device *psp);
+int dbc_dev_init(struct psp_device *psp);
+
+#endif /* __DBC_H */