1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  Character device driver for extended error reporting.
4  *
5  *  Copyright IBM Corp. 2005
6  *  extended error reporting for DASD ECKD devices
7  *  Author(s): Stefan Weinhuber <wein@de.ibm.com>
8  */
9 
10 #define KMSG_COMPONENT "dasd-eckd"
11 
12 #include <linux/init.h>
13 #include <linux/fs.h>
14 #include <linux/kernel.h>
15 #include <linux/miscdevice.h>
16 #include <linux/module.h>
17 #include <linux/moduleparam.h>
18 #include <linux/device.h>
19 #include <linux/poll.h>
20 #include <linux/mutex.h>
21 #include <linux/err.h>
22 #include <linux/slab.h>
23 
24 #include <linux/uaccess.h>
25 #include <linux/atomic.h>
26 #include <asm/ebcdic.h>
27 
28 #include "dasd_int.h"
29 #include "dasd_eckd.h"
30 
31 #ifdef PRINTK_HEADER
32 #undef PRINTK_HEADER
33 #endif				/* PRINTK_HEADER */
34 #define PRINTK_HEADER "dasd(eer):"
35 
36 /*
37  * SECTION: the internal buffer
38  */
39 
40 /*
41  * The internal buffer is meant to store obaque blobs of data, so it does
42  * not know of higher level concepts like triggers.
43  * It consists of a number of pages that are used as a ringbuffer. Each data
44  * blob is stored in a simple record that consists of an integer, which
45  * contains the size of the following data, and the data bytes themselfes.
46  *
47  * To allow for multiple independent readers we create one internal buffer
48  * each time the device is opened and destroy the buffer when the file is
49  * closed again. The number of pages used for this buffer is determined by
50  * the module parmeter eer_pages.
51  *
52  * One record can be written to a buffer by using the functions
53  * - dasd_eer_start_record (one time per record to write the size to the
54  *                          buffer and reserve the space for the data)
55  * - dasd_eer_write_buffer (one or more times per record to write the data)
56  * The data can be written in several steps but you will have to compute
57  * the total size up front for the invocation of dasd_eer_start_record.
58  * If the ringbuffer is full, dasd_eer_start_record will remove the required
59  * number of old records.
60  *
61  * A record is typically read in two steps, first read the integer that
62  * specifies the size of the following data, then read the data.
63  * Both can be done by
64  * - dasd_eer_read_buffer
65  *
66  * For all mentioned functions you need to get the bufferlock first and keep
67  * it until a complete record is written or read.
68  *
69  * All information necessary to keep track of an internal buffer is kept in
70  * a struct eerbuffer. The buffer specific to a file pointer is strored in
71  * the private_data field of that file. To be able to write data to all
72  * existing buffers, each buffer is also added to the bufferlist.
73  * If the user does not want to read a complete record in one go, we have to
74  * keep track of the rest of the record. residual stores the number of bytes
75  * that are still to deliver. If the rest of the record is invalidated between
76  * two reads then residual will be set to -1 so that the next read will fail.
77  * All entries in the eerbuffer structure are protected with the bufferlock.
78  * To avoid races between writing to a buffer on the one side and creating
79  * and destroying buffers on the other side, the bufferlock must also be used
80  * to protect the bufferlist.
81  */
82 
83 static int eer_pages = 5;
84 module_param(eer_pages, int, S_IRUGO|S_IWUSR);
85 
86 struct eerbuffer {
87 	struct list_head list;
88 	char **buffer;
89 	int buffersize;
90 	int buffer_page_count;
91 	int head;
92         int tail;
93 	int residual;
94 };
95 
96 static LIST_HEAD(bufferlist);
97 static DEFINE_SPINLOCK(bufferlock);
98 static DECLARE_WAIT_QUEUE_HEAD(dasd_eer_read_wait_queue);
99 
100 /*
101  * How many free bytes are available on the buffer.
102  * Needs to be called with bufferlock held.
103  */
dasd_eer_get_free_bytes(struct eerbuffer * eerb)104 static int dasd_eer_get_free_bytes(struct eerbuffer *eerb)
105 {
106 	if (eerb->head < eerb->tail)
107 		return eerb->tail - eerb->head - 1;
108 	return eerb->buffersize - eerb->head + eerb->tail -1;
109 }
110 
111 /*
112  * How many bytes of buffer space are used.
113  * Needs to be called with bufferlock held.
114  */
dasd_eer_get_filled_bytes(struct eerbuffer * eerb)115 static int dasd_eer_get_filled_bytes(struct eerbuffer *eerb)
116 {
117 
118 	if (eerb->head >= eerb->tail)
119 		return eerb->head - eerb->tail;
120 	return eerb->buffersize - eerb->tail + eerb->head;
121 }
122 
123 /*
124  * The dasd_eer_write_buffer function just copies count bytes of data
125  * to the buffer. Make sure to call dasd_eer_start_record first, to
126  * make sure that enough free space is available.
127  * Needs to be called with bufferlock held.
128  */
dasd_eer_write_buffer(struct eerbuffer * eerb,char * data,int count)129 static void dasd_eer_write_buffer(struct eerbuffer *eerb,
130 				  char *data, int count)
131 {
132 
133 	unsigned long headindex,localhead;
134 	unsigned long rest, len;
135 	char *nextdata;
136 
137 	nextdata = data;
138 	rest = count;
139 	while (rest > 0) {
140  		headindex = eerb->head / PAGE_SIZE;
141  		localhead = eerb->head % PAGE_SIZE;
142 		len = min(rest, PAGE_SIZE - localhead);
143 		memcpy(eerb->buffer[headindex]+localhead, nextdata, len);
144 		nextdata += len;
145 		rest -= len;
146 		eerb->head += len;
147 		if (eerb->head == eerb->buffersize)
148 			eerb->head = 0; /* wrap around */
149 		BUG_ON(eerb->head > eerb->buffersize);
150 	}
151 }
152 
153 /*
154  * Needs to be called with bufferlock held.
155  */
dasd_eer_read_buffer(struct eerbuffer * eerb,char * data,int count)156 static int dasd_eer_read_buffer(struct eerbuffer *eerb, char *data, int count)
157 {
158 
159 	unsigned long tailindex,localtail;
160 	unsigned long rest, len, finalcount;
161 	char *nextdata;
162 
163 	finalcount = min(count, dasd_eer_get_filled_bytes(eerb));
164 	nextdata = data;
165 	rest = finalcount;
166 	while (rest > 0) {
167  		tailindex = eerb->tail / PAGE_SIZE;
168  		localtail = eerb->tail % PAGE_SIZE;
169 		len = min(rest, PAGE_SIZE - localtail);
170 		memcpy(nextdata, eerb->buffer[tailindex] + localtail, len);
171 		nextdata += len;
172 		rest -= len;
173 		eerb->tail += len;
174 		if (eerb->tail == eerb->buffersize)
175 			eerb->tail = 0; /* wrap around */
176 		BUG_ON(eerb->tail > eerb->buffersize);
177 	}
178 	return finalcount;
179 }
180 
181 /*
182  * Whenever you want to write a blob of data to the internal buffer you
183  * have to start by using this function first. It will write the number
184  * of bytes that will be written to the buffer. If necessary it will remove
185  * old records to make room for the new one.
186  * Needs to be called with bufferlock held.
187  */
dasd_eer_start_record(struct eerbuffer * eerb,int count)188 static int dasd_eer_start_record(struct eerbuffer *eerb, int count)
189 {
190 	int tailcount;
191 
192 	if (count + sizeof(count) > eerb->buffersize)
193 		return -ENOMEM;
194 	while (dasd_eer_get_free_bytes(eerb) < count + sizeof(count)) {
195 		if (eerb->residual > 0) {
196 			eerb->tail += eerb->residual;
197 			if (eerb->tail >= eerb->buffersize)
198 				eerb->tail -= eerb->buffersize;
199 			eerb->residual = -1;
200 		}
201 		dasd_eer_read_buffer(eerb, (char *) &tailcount,
202 				     sizeof(tailcount));
203 		eerb->tail += tailcount;
204 		if (eerb->tail >= eerb->buffersize)
205 			eerb->tail -= eerb->buffersize;
206 	}
207 	dasd_eer_write_buffer(eerb, (char*) &count, sizeof(count));
208 
209 	return 0;
210 };
211 
212 /*
213  * Release pages that are not used anymore.
214  */
dasd_eer_free_buffer_pages(char ** buf,int no_pages)215 static void dasd_eer_free_buffer_pages(char **buf, int no_pages)
216 {
217 	int i;
218 
219 	for (i = 0; i < no_pages; i++)
220 		free_page((unsigned long) buf[i]);
221 }
222 
223 /*
224  * Allocate a new set of memory pages.
225  */
dasd_eer_allocate_buffer_pages(char ** buf,int no_pages)226 static int dasd_eer_allocate_buffer_pages(char **buf, int no_pages)
227 {
228 	int i;
229 
230 	for (i = 0; i < no_pages; i++) {
231 		buf[i] = (char *) get_zeroed_page(GFP_KERNEL);
232 		if (!buf[i]) {
233 			dasd_eer_free_buffer_pages(buf, i);
234 			return -ENOMEM;
235 		}
236 	}
237 	return 0;
238 }
239 
240 /*
241  * SECTION: The extended error reporting functionality
242  */
243 
244 /*
245  * When a DASD device driver wants to report an error, it calls the
246  * function dasd_eer_write and gives the respective trigger ID as
247  * parameter. Currently there are four kinds of triggers:
248  *
249  * DASD_EER_FATALERROR:  all kinds of unrecoverable I/O problems
250  * DASD_EER_PPRCSUSPEND: PPRC was suspended
251  * DASD_EER_NOPATH:      There is no path to the device left.
252  * DASD_EER_STATECHANGE: The state of the device has changed.
253  *
254  * For the first three triggers all required information can be supplied by
255  * the caller. For these triggers a record is written by the function
256  * dasd_eer_write_standard_trigger.
257  *
258  * The DASD_EER_STATECHANGE trigger is special since a sense subsystem
259  * status ccw need to be executed to gather the necessary sense data first.
260  * The dasd_eer_snss function will queue the SNSS request and the request
261  * callback will then call dasd_eer_write with the DASD_EER_STATCHANGE
262  * trigger.
263  *
264  * To avoid memory allocations at runtime, the necessary memory is allocated
265  * when the extended error reporting is enabled for a device (by
266  * dasd_eer_probe). There is one sense subsystem status request for each
267  * eer enabled DASD device. The presence of the cqr in device->eer_cqr
268  * indicates that eer is enable for the device. The use of the snss request
269  * is protected by the DASD_FLAG_EER_IN_USE bit. When this flag indicates
270  * that the cqr is currently in use, dasd_eer_snss cannot start a second
271  * request but sets the DASD_FLAG_EER_SNSS flag instead. The callback of
272  * the SNSS request will check the bit and call dasd_eer_snss again.
273  */
274 
275 #define SNSS_DATA_SIZE 44
276 
277 #define DASD_EER_BUSID_SIZE 10
278 struct dasd_eer_header {
279 	__u32 total_size;
280 	__u32 trigger;
281 	__u64 tv_sec;
282 	__u64 tv_usec;
283 	char busid[DASD_EER_BUSID_SIZE];
284 } __attribute__ ((packed));
285 
286 /*
287  * The following function can be used for those triggers that have
288  * all necessary data available when the function is called.
289  * If the parameter cqr is not NULL, the chain of requests will be searched
290  * for valid sense data, and all valid sense data sets will be added to
291  * the triggers data.
292  */
dasd_eer_write_standard_trigger(struct dasd_device * device,struct dasd_ccw_req * cqr,int trigger)293 static void dasd_eer_write_standard_trigger(struct dasd_device *device,
294 					    struct dasd_ccw_req *cqr,
295 					    int trigger)
296 {
297 	struct dasd_ccw_req *temp_cqr;
298 	int data_size;
299 	struct timespec64 ts;
300 	struct dasd_eer_header header;
301 	unsigned long flags;
302 	struct eerbuffer *eerb;
303 	char *sense;
304 
305 	/* go through cqr chain and count the valid sense data sets */
306 	data_size = 0;
307 	for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers)
308 		if (dasd_get_sense(&temp_cqr->irb))
309 			data_size += 32;
310 
311 	header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
312 	header.trigger = trigger;
313 	ktime_get_real_ts64(&ts);
314 	header.tv_sec = ts.tv_sec;
315 	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
316 	strscpy(header.busid, dev_name(&device->cdev->dev),
317 		DASD_EER_BUSID_SIZE);
318 
319 	spin_lock_irqsave(&bufferlock, flags);
320 	list_for_each_entry(eerb, &bufferlist, list) {
321 		dasd_eer_start_record(eerb, header.total_size);
322 		dasd_eer_write_buffer(eerb, (char *) &header, sizeof(header));
323 		for (temp_cqr = cqr; temp_cqr; temp_cqr = temp_cqr->refers) {
324 			sense = dasd_get_sense(&temp_cqr->irb);
325 			if (sense)
326 				dasd_eer_write_buffer(eerb, sense, 32);
327 		}
328 		dasd_eer_write_buffer(eerb, "EOR", 4);
329 	}
330 	spin_unlock_irqrestore(&bufferlock, flags);
331 	wake_up_interruptible(&dasd_eer_read_wait_queue);
332 }
333 
334 /*
335  * This function writes a DASD_EER_STATECHANGE trigger.
336  */
dasd_eer_write_snss_trigger(struct dasd_device * device,struct dasd_ccw_req * cqr,int trigger)337 static void dasd_eer_write_snss_trigger(struct dasd_device *device,
338 					struct dasd_ccw_req *cqr,
339 					int trigger)
340 {
341 	int data_size;
342 	int snss_rc;
343 	struct timespec64 ts;
344 	struct dasd_eer_header header;
345 	unsigned long flags;
346 	struct eerbuffer *eerb;
347 
348 	snss_rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
349 	if (snss_rc)
350 		data_size = 0;
351 	else
352 		data_size = SNSS_DATA_SIZE;
353 
354 	header.total_size = sizeof(header) + data_size + 4; /* "EOR" */
355 	header.trigger = DASD_EER_STATECHANGE;
356 	ktime_get_real_ts64(&ts);
357 	header.tv_sec = ts.tv_sec;
358 	header.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
359 	strscpy(header.busid, dev_name(&device->cdev->dev),
360 		DASD_EER_BUSID_SIZE);
361 
362 	spin_lock_irqsave(&bufferlock, flags);
363 	list_for_each_entry(eerb, &bufferlist, list) {
364 		dasd_eer_start_record(eerb, header.total_size);
365 		dasd_eer_write_buffer(eerb, (char *) &header , sizeof(header));
366 		if (!snss_rc)
367 			dasd_eer_write_buffer(eerb, cqr->data, SNSS_DATA_SIZE);
368 		dasd_eer_write_buffer(eerb, "EOR", 4);
369 	}
370 	spin_unlock_irqrestore(&bufferlock, flags);
371 	wake_up_interruptible(&dasd_eer_read_wait_queue);
372 }
373 
374 /*
375  * This function is called for all triggers. It calls the appropriate
376  * function that writes the actual trigger records.
377  */
dasd_eer_write(struct dasd_device * device,struct dasd_ccw_req * cqr,unsigned int id)378 void dasd_eer_write(struct dasd_device *device, struct dasd_ccw_req *cqr,
379 		    unsigned int id)
380 {
381 	if (!device->eer_cqr)
382 		return;
383 	switch (id) {
384 	case DASD_EER_FATALERROR:
385 	case DASD_EER_PPRCSUSPEND:
386 		dasd_eer_write_standard_trigger(device, cqr, id);
387 		break;
388 	case DASD_EER_NOPATH:
389 	case DASD_EER_NOSPC:
390 	case DASD_EER_AUTOQUIESCE:
391 		dasd_eer_write_standard_trigger(device, NULL, id);
392 		break;
393 	case DASD_EER_STATECHANGE:
394 		dasd_eer_write_snss_trigger(device, cqr, id);
395 		break;
396 	default: /* unknown trigger, so we write it without any sense data */
397 		dasd_eer_write_standard_trigger(device, NULL, id);
398 		break;
399 	}
400 }
401 EXPORT_SYMBOL(dasd_eer_write);
402 
403 /*
404  * Start a sense subsystem status request.
405  * Needs to be called with the device held.
406  */
dasd_eer_snss(struct dasd_device * device)407 void dasd_eer_snss(struct dasd_device *device)
408 {
409 	struct dasd_ccw_req *cqr;
410 
411 	cqr = device->eer_cqr;
412 	if (!cqr)	/* Device not eer enabled. */
413 		return;
414 	if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
415 		/* Sense subsystem status request in use. */
416 		set_bit(DASD_FLAG_EER_SNSS, &device->flags);
417 		return;
418 	}
419 	/* cdev is already locked, can't use dasd_add_request_head */
420 	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
421 	cqr->status = DASD_CQR_QUEUED;
422 	list_add(&cqr->devlist, &device->ccw_queue);
423 	dasd_schedule_device_bh(device);
424 }
425 
426 /*
427  * Callback function for use with sense subsystem status request.
428  */
dasd_eer_snss_cb(struct dasd_ccw_req * cqr,void * data)429 static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
430 {
431 	struct dasd_device *device = cqr->startdev;
432 	unsigned long flags;
433 
434 	dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
435 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
436 	if (device->eer_cqr == cqr) {
437 		clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
438 		if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
439 			/* Another SNSS has been requested in the meantime. */
440 			dasd_eer_snss(device);
441 		cqr = NULL;
442 	}
443 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
444 	if (cqr)
445 		/*
446 		 * Extended error recovery has been switched off while
447 		 * the SNSS request was running. It could even have
448 		 * been switched off and on again in which case there
449 		 * is a new ccw in device->eer_cqr. Free the "old"
450 		 * snss request now.
451 		 */
452 		dasd_sfree_request(cqr, device);
453 }
454 
455 /*
456  * Enable error reporting on a given device.
457  */
dasd_eer_enable(struct dasd_device * device)458 int dasd_eer_enable(struct dasd_device *device)
459 {
460 	struct dasd_ccw_req *cqr = NULL;
461 	unsigned long flags;
462 	struct ccw1 *ccw;
463 	int rc = 0;
464 
465 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
466 	if (device->eer_cqr)
467 		goto out;
468 	else if (!device->discipline ||
469 		 strcmp(device->discipline->name, "ECKD"))
470 		rc = -EMEDIUMTYPE;
471 	else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
472 		rc = -EBUSY;
473 
474 	if (rc)
475 		goto out;
476 
477 	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
478 				   SNSS_DATA_SIZE, device, NULL);
479 	if (IS_ERR(cqr)) {
480 		rc = -ENOMEM;
481 		cqr = NULL;
482 		goto out;
483 	}
484 
485 	cqr->startdev = device;
486 	cqr->retries = 255;
487 	cqr->expires = 10 * HZ;
488 	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
489 	set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
490 
491 	ccw = cqr->cpaddr;
492 	ccw->cmd_code = DASD_ECKD_CCW_SNSS;
493 	ccw->count = SNSS_DATA_SIZE;
494 	ccw->flags = 0;
495 	ccw->cda = (__u32)virt_to_phys(cqr->data);
496 
497 	cqr->buildclk = get_tod_clock();
498 	cqr->status = DASD_CQR_FILLED;
499 	cqr->callback = dasd_eer_snss_cb;
500 
501 	if (!device->eer_cqr) {
502 		device->eer_cqr = cqr;
503 		cqr = NULL;
504 	}
505 
506 out:
507 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
508 
509 	if (cqr)
510 		dasd_sfree_request(cqr, device);
511 
512 	return rc;
513 }
514 
515 /*
516  * Disable error reporting on a given device.
517  */
dasd_eer_disable(struct dasd_device * device)518 void dasd_eer_disable(struct dasd_device *device)
519 {
520 	struct dasd_ccw_req *cqr;
521 	unsigned long flags;
522 	int in_use;
523 
524 	if (!device->eer_cqr)
525 		return;
526 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
527 	cqr = device->eer_cqr;
528 	device->eer_cqr = NULL;
529 	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
530 	in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
531 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
532 	if (cqr && !in_use)
533 		dasd_sfree_request(cqr, device);
534 }
535 
536 /*
537  * SECTION: the device operations
538  */
539 
540 /*
541  * On the one side we need a lock to access our internal buffer, on the
542  * other side a copy_to_user can sleep. So we need to copy the data we have
543  * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
544  */
545 static char readbuffer[PAGE_SIZE];
546 static DEFINE_MUTEX(readbuffer_mutex);
547 
dasd_eer_open(struct inode * inp,struct file * filp)548 static int dasd_eer_open(struct inode *inp, struct file *filp)
549 {
550 	struct eerbuffer *eerb;
551 	unsigned long flags;
552 
553 	eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
554 	if (!eerb)
555 		return -ENOMEM;
556 	eerb->buffer_page_count = eer_pages;
557 	if (eerb->buffer_page_count < 1 ||
558 	    eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
559 		kfree(eerb);
560 		DBF_EVENT(DBF_WARNING, "can't open device since module "
561 			"parameter eer_pages is smaller than 1 or"
562 			" bigger than %d", (int)(INT_MAX / PAGE_SIZE));
563 		return -EINVAL;
564 	}
565 	eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
566 	eerb->buffer = kmalloc_array(eerb->buffer_page_count, sizeof(char *),
567 				     GFP_KERNEL);
568         if (!eerb->buffer) {
569 		kfree(eerb);
570                 return -ENOMEM;
571 	}
572 	if (dasd_eer_allocate_buffer_pages(eerb->buffer,
573 					   eerb->buffer_page_count)) {
574 		kfree(eerb->buffer);
575 		kfree(eerb);
576 		return -ENOMEM;
577 	}
578 	filp->private_data = eerb;
579 	spin_lock_irqsave(&bufferlock, flags);
580 	list_add(&eerb->list, &bufferlist);
581 	spin_unlock_irqrestore(&bufferlock, flags);
582 
583 	return nonseekable_open(inp,filp);
584 }
585 
dasd_eer_close(struct inode * inp,struct file * filp)586 static int dasd_eer_close(struct inode *inp, struct file *filp)
587 {
588 	struct eerbuffer *eerb;
589 	unsigned long flags;
590 
591 	eerb = (struct eerbuffer *) filp->private_data;
592 	spin_lock_irqsave(&bufferlock, flags);
593 	list_del(&eerb->list);
594 	spin_unlock_irqrestore(&bufferlock, flags);
595 	dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
596 	kfree(eerb->buffer);
597 	kfree(eerb);
598 
599 	return 0;
600 }
601 
dasd_eer_read(struct file * filp,char __user * buf,size_t count,loff_t * ppos)602 static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
603 			     size_t count, loff_t *ppos)
604 {
605 	int tc,rc;
606 	int tailcount,effective_count;
607         unsigned long flags;
608 	struct eerbuffer *eerb;
609 
610 	eerb = (struct eerbuffer *) filp->private_data;
611 	if (mutex_lock_interruptible(&readbuffer_mutex))
612 		return -ERESTARTSYS;
613 
614 	spin_lock_irqsave(&bufferlock, flags);
615 
616 	if (eerb->residual < 0) { /* the remainder of this record */
617 		                  /* has been deleted             */
618 		eerb->residual = 0;
619 		spin_unlock_irqrestore(&bufferlock, flags);
620 		mutex_unlock(&readbuffer_mutex);
621 		return -EIO;
622 	} else if (eerb->residual > 0) {
623 		/* OK we still have a second half of a record to deliver */
624 		effective_count = min(eerb->residual, (int) count);
625 		eerb->residual -= effective_count;
626 	} else {
627 		tc = 0;
628 		while (!tc) {
629 			tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
630 						  sizeof(tailcount));
631 			if (!tc) {
632 				/* no data available */
633 				spin_unlock_irqrestore(&bufferlock, flags);
634 				mutex_unlock(&readbuffer_mutex);
635 				if (filp->f_flags & O_NONBLOCK)
636 					return -EAGAIN;
637 				rc = wait_event_interruptible(
638 					dasd_eer_read_wait_queue,
639 					eerb->head != eerb->tail);
640 				if (rc)
641 					return rc;
642 				if (mutex_lock_interruptible(&readbuffer_mutex))
643 					return -ERESTARTSYS;
644 				spin_lock_irqsave(&bufferlock, flags);
645 			}
646 		}
647 		WARN_ON(tc != sizeof(tailcount));
648 		effective_count = min(tailcount,(int)count);
649 		eerb->residual = tailcount - effective_count;
650 	}
651 
652 	tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
653 	WARN_ON(tc != effective_count);
654 
655 	spin_unlock_irqrestore(&bufferlock, flags);
656 
657 	if (copy_to_user(buf, readbuffer, effective_count)) {
658 		mutex_unlock(&readbuffer_mutex);
659 		return -EFAULT;
660 	}
661 
662 	mutex_unlock(&readbuffer_mutex);
663 	return effective_count;
664 }
665 
dasd_eer_poll(struct file * filp,poll_table * ptable)666 static __poll_t dasd_eer_poll(struct file *filp, poll_table *ptable)
667 {
668 	__poll_t mask;
669 	unsigned long flags;
670 	struct eerbuffer *eerb;
671 
672 	eerb = (struct eerbuffer *) filp->private_data;
673 	poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
674 	spin_lock_irqsave(&bufferlock, flags);
675 	if (eerb->head != eerb->tail)
676 		mask = EPOLLIN | EPOLLRDNORM ;
677 	else
678 		mask = 0;
679 	spin_unlock_irqrestore(&bufferlock, flags);
680 	return mask;
681 }
682 
683 static const struct file_operations dasd_eer_fops = {
684 	.open		= &dasd_eer_open,
685 	.release	= &dasd_eer_close,
686 	.read		= &dasd_eer_read,
687 	.poll		= &dasd_eer_poll,
688 	.owner		= THIS_MODULE,
689 	.llseek		= noop_llseek,
690 };
691 
692 static struct miscdevice *dasd_eer_dev = NULL;
693 
dasd_eer_init(void)694 int __init dasd_eer_init(void)
695 {
696 	int rc;
697 
698 	dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
699 	if (!dasd_eer_dev)
700 		return -ENOMEM;
701 
702 	dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
703 	dasd_eer_dev->name  = "dasd_eer";
704 	dasd_eer_dev->fops  = &dasd_eer_fops;
705 
706 	rc = misc_register(dasd_eer_dev);
707 	if (rc) {
708 		kfree(dasd_eer_dev);
709 		dasd_eer_dev = NULL;
710 		DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
711 		       "register misc device");
712 		return rc;
713 	}
714 
715 	return 0;
716 }
717 
dasd_eer_exit(void)718 void dasd_eer_exit(void)
719 {
720 	if (dasd_eer_dev) {
721 		misc_deregister(dasd_eer_dev);
722 		kfree(dasd_eer_dev);
723 		dasd_eer_dev = NULL;
724 	}
725 }
726