Commit 7e418833 authored by Benjamin Block's avatar Benjamin Block Committed by Martin K. Petersen
Browse files

scsi: zfcp: diagnostics buffer caching and use for exchange port data 

The FCP channel exposes two central interfaces to receive information about
the local FCP-Adapter/-Port: Exchange Port and Exchange Config Data. Using
these commands can negatively impact the adapter if we allow them to be
sent at a very high rate.

The later parts of this patchset will introduce new user-interfaces to
receive more diagnostics from the adapter. To prevent any negative impact
from using those, this patch adds a simple caching-mechanism that will
prevent a malicious/faulty userspace-application from generating an
abnormal high amount of Exchange Port/Config Data traffic.

Relevant diagnostic data that is received via Exchange Config/Port Data is
cached in buffers associated with the corresponding adapter-struct.  Each
buffer is associated with a timestamp that signals how old the data is,
and, added via a following patch in this series, lets userspace-interfaces
determine when the data is too old and needs to be updated.

Buffer-updates are made during the normal response path of the
corresponding command. With this patch only the output of the Exchange Port
Data command is captured.

Link: https://lore.kernel.org/r/054ca020ce0a53dc0d9176428bea373898944e6a.1572018130.git.bblock@linux.ibm.com


Reviewed-by: default avatarSteffen Maier <maier@linux.ibm.com>
Signed-off-by: default avatarBenjamin Block <bblock@linux.ibm.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 92953c6e

drivers/s390/scsi/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -5,6 +5,6 @@ 


zfcp-objs := zfcp_aux.o zfcp_ccw.o zfcp_dbf.o zfcp_erp.o \

	     zfcp_fc.o zfcp_fsf.o zfcp_qdio.o zfcp_scsi.o zfcp_sysfs.o \

	     zfcp_unit.o

	     zfcp_unit.o zfcp_diag.o



obj-$(CONFIG_ZFCP) += zfcp.o

drivers/s390/scsi/zfcp_aux.c

+7 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 
 *

 * Module interface and handling of zfcp data structures.

 *

 * Copyright IBM Corp. 2002, 2017

 * Copyright IBM Corp. 2002, 2018

 */



/*
@@ -25,6 +25,7 @@ 
 *            Martin Petermann

 *            Sven Schuetz

 *            Steffen Maier

 *	      Benjamin Block

 */



#define KMSG_COMPONENT "zfcp"
@@ -36,6 +37,7 @@ 
#include "zfcp_ext.h"

#include "zfcp_fc.h"

#include "zfcp_reqlist.h"

#include "zfcp_diag.h"



#define ZFCP_BUS_ID_SIZE	20
@@ -356,6 +358,9 @@ struct zfcp_adapter *zfcp_adapter_enqueue(struct ccw_device *ccw_device) 


	adapter->erp_action.adapter = adapter;



	if (zfcp_diag_adapter_setup(adapter))

		goto failed;



	if (zfcp_qdio_setup(adapter))

		goto failed;
@@ -449,6 +454,7 @@ void zfcp_adapter_release(struct kref *ref) 
	dev_set_drvdata(&adapter->ccw_device->dev, NULL);

	zfcp_fc_gs_destroy(adapter);

	zfcp_free_low_mem_buffers(adapter);

	zfcp_diag_adapter_free(adapter);

	kfree(adapter->req_list);

	kfree(adapter->fc_stats);

	kfree(adapter->stats_reset_data);

drivers/s390/scsi/zfcp_def.h

+2 −1
Original line number Diff line number Diff line
@@ -4,7 +4,7 @@ 
 *

 * Global definitions for the zfcp device driver.

 *

 * Copyright IBM Corp. 2002, 2017

 * Copyright IBM Corp. 2002, 2018

 */



#ifndef ZFCP_DEF_H
@@ -198,6 +198,7 @@ struct zfcp_adapter { 
	struct device_dma_parameters dma_parms;

	struct zfcp_fc_events events;

	unsigned long		next_port_scan;

	struct zfcp_diag_adapter	*diagnostics;

};



struct zfcp_port {

drivers/s390/scsi/zfcp_diag.c

0 → 100644
+93 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * zfcp device driver

 *

 * Functions to handle diagnostics.

 *

 * Copyright IBM Corp. 2018

 */



#include <linux/spinlock.h>

#include <linux/jiffies.h>

#include <linux/string.h>

#include <linux/errno.h>

#include <linux/slab.h>



#include "zfcp_diag.h"

#include "zfcp_ext.h"

#include "zfcp_def.h"



/* Max age of data in a diagnostics buffer before it needs a refresh (in ms). */

#define ZFCP_DIAG_MAX_AGE (5 * 1000)



/**

 * zfcp_diag_adapter_setup() - Setup storage for adapter diagnostics.

 * @adapter: the adapter to setup diagnostics for.

 *

 * Creates the data-structures to store the diagnostics for an adapter. This

 * overwrites whatever was stored before at &zfcp_adapter->diagnostics!

 *

 * Return:

 * * 0	     - Everyting is OK

 * * -ENOMEM - Could not allocate all/parts of the data-structures;

 *	       &zfcp_adapter->diagnostics remains unchanged

 */

int zfcp_diag_adapter_setup(struct zfcp_adapter *const adapter)

{

	struct zfcp_diag_adapter *diag;

	struct zfcp_diag_header *hdr;



	diag = kzalloc(sizeof(*diag), GFP_KERNEL);

	if (diag == NULL)

		return -ENOMEM;



	/* setup header for port_data */

	hdr = &diag->port_data.header;



	spin_lock_init(&hdr->access_lock);

	hdr->buffer = &diag->port_data.data;

	hdr->buffer_size = sizeof(diag->port_data.data);

	/* set the timestamp so that the first test on age will always fail */

	hdr->timestamp = jiffies - msecs_to_jiffies(ZFCP_DIAG_MAX_AGE);



	adapter->diagnostics = diag;

	return 0;

}



/**

 * zfcp_diag_adapter_free() - Frees all adapter diagnostics allocations.

 * @adapter: the adapter whose diagnostic structures should be freed.

 *

 * Frees all data-structures in the given adapter that store diagnostics

 * information. Can savely be called with partially setup diagnostics.

 */

void zfcp_diag_adapter_free(struct zfcp_adapter *const adapter)

{

	kfree(adapter->diagnostics);

	adapter->diagnostics = NULL;

}



/**

 * zfcp_diag_update_xdata() - Update a diagnostics buffer.

 * @hdr: the meta data to update.

 * @data: data to use for the update.

 * @incomplete: flag stating whether the data in @data is incomplete.

 */

void zfcp_diag_update_xdata(struct zfcp_diag_header *const hdr,

			    const void *const data, const bool incomplete)

{

	const unsigned long capture_timestamp = jiffies;

	unsigned long flags;



	spin_lock_irqsave(&hdr->access_lock, flags);



	/* make sure we never go into the past with an update */

	if (!time_after_eq(capture_timestamp, hdr->timestamp))

		goto out;



	hdr->timestamp = capture_timestamp;

	hdr->incomplete = incomplete;

	memcpy(hdr->buffer, data, hdr->buffer_size);

out:

	spin_unlock_irqrestore(&hdr->access_lock, flags);

}

drivers/s390/scsi/zfcp_diag.h

0 → 100644
+60 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

/*

 * zfcp device driver

 *

 * Definitions for handling diagnostics in the the zfcp device driver.

 *

 * Copyright IBM Corp. 2018

 */



#ifndef ZFCP_DIAG_H

#define ZFCP_DIAG_H



#include <linux/spinlock.h>



#include "zfcp_fsf.h"

#include "zfcp_def.h"



/**

 * struct zfcp_diag_header - general part of a diagnostic buffer.

 * @access_lock: lock protecting all the data in this buffer.

 * @updating: flag showing that an update for this buffer is currently running.

 * @incomplete: flag showing that the data in @buffer is incomplete.

 * @timestamp: time in jiffies when the data of this buffer was last captured.

 * @buffer: implementation-depending data of this buffer

 * @buffer_size: size of @buffer

 */

struct zfcp_diag_header {

	spinlock_t	access_lock;



	/* Flags */

	u64		updating	:1;

	u64		incomplete	:1;



	unsigned long	timestamp;



	void		*buffer;

	size_t		buffer_size;

};



/**

 * struct zfcp_diag_adapter - central storage for all diagnostics concerning an

 *			      adapter.

 * @port_data: data retrieved using exchange port data.

 * @port_data.header: header with metadata for the cache in @port_data.data.

 * @port_data.data: cached QTCB Bottom of command exchange port data.

 */

struct zfcp_diag_adapter {

	struct {

		struct zfcp_diag_header		header;

		struct fsf_qtcb_bottom_port	data;

	} port_data;

};



int zfcp_diag_adapter_setup(struct zfcp_adapter *const adapter);

void zfcp_diag_adapter_free(struct zfcp_adapter *const adapter);



void zfcp_diag_update_xdata(struct zfcp_diag_header *const hdr,

			    const void *const data, const bool incomplete);



#endif /* ZFCP_DIAG_H */

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