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, 94 insertions, 0 deletions

diff --git a/drivers/cdx/cdx.h b/drivers/cdx/cdx.h
new file mode 100644
index 000000000..9c60c04dc
--- /dev/null
+++ b/drivers/cdx/cdx.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Header file for the CDX Bus
+ *
+ * Copyright (C) 2022-2023, Advanced Micro Devices, Inc.
+ */
+
+#ifndef _CDX_H_
+#define _CDX_H_
+
+#include <linux/cdx/cdx_bus.h>
+
+/**
+ * struct cdx_dev_params - CDX device parameters
+ * @cdx: CDX controller associated with the device
+ * @parent: Associated CDX Bus device
+ * @vendor: Vendor ID for CDX device
+ * @device: Device ID for CDX device
+ * @subsys_vendor: Sub vendor ID for CDX device
+ * @subsys_device: Sub device ID for CDX device
+ * @bus_num: Bus number for this CDX device
+ * @dev_num: Device number for this device
+ * @res: array of MMIO region entries
+ * @res_count: number of valid MMIO regions
+ * @req_id: Requestor ID associated with CDX device
+ * @class: Class of the CDX Device
+ * @revision: Revision of the CDX device
+ * @msi_dev_id: MSI device ID associated with CDX device
+ * @num_msi: Number of MSI's supported by the device
+ */
+struct cdx_dev_params {
+	struct cdx_controller *cdx;
+	struct device *parent;
+	u16 vendor;
+	u16 device;
+	u16 subsys_vendor;
+	u16 subsys_device;
+	u8 bus_num;
+	u8 dev_num;
+	struct resource res[MAX_CDX_DEV_RESOURCES];
+	u8 res_count;
+	u32 req_id;
+	u32 class;
+	u8 revision;
+	u32 msi_dev_id;
+	u32 num_msi;
+};
+
+/**
+ * cdx_register_controller - Register a CDX controller and its ports
+ *		on the CDX bus.
+ * @cdx: The CDX controller to register
+ *
+ * Return: -errno on failure, 0 on success.
+ */
+int cdx_register_controller(struct cdx_controller *cdx);
+
+/**
+ * cdx_unregister_controller - Unregister a CDX controller
+ * @cdx: The CDX controller to unregister
+ */
+void cdx_unregister_controller(struct cdx_controller *cdx);
+
+/**
+ * cdx_device_add - Add a CDX device. This function adds a CDX device
+ *		on the CDX bus as per the device parameters provided
+ *		by caller. It also creates and registers an associated
+ *		Linux generic device.
+ * @dev_params: device parameters associated with the device to be created.
+ *
+ * Return: -errno on failure, 0 on success.
+ */
+int cdx_device_add(struct cdx_dev_params *dev_params);
+
+/**
+ * cdx_bus_add - Add a CDX bus. This function adds a bus on the CDX bus
+ *		subsystem. It creates a CDX device for the corresponding bus and
+ *		also registers an associated Linux generic device.
+ * @cdx: Associated CDX controller
+ * @us_num: Bus number
+ *
+ * Return: associated Linux generic device pointer on success or NULL on failure.
+ */
+struct device *cdx_bus_add(struct cdx_controller *cdx, u8 bus_num);
+
+/**
+ * cdx_msi_domain_init - Init the CDX bus MSI domain.
+ * @dev: Device of the CDX bus controller
+ *
+ * Return: CDX MSI domain, NULL on failure
+ */
+struct irq_domain *cdx_msi_domain_init(struct device *dev);
+
+#endif /* _CDX_H_ */