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 	strlcpy(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 	strlcpy(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 		dasd_eer_write_standard_trigger(device, NULL, id);
390 		break;
391 	case DASD_EER_STATECHANGE:
392 		dasd_eer_write_snss_trigger(device, cqr, id);
393 		break;
394 	default: /* unknown trigger, so we write it without any sense data */
395 		dasd_eer_write_standard_trigger(device, NULL, id);
396 		break;
397 	}
398 }
399 EXPORT_SYMBOL(dasd_eer_write);
400 
401 /*
402  * Start a sense subsystem status request.
403  * Needs to be called with the device held.
404  */
dasd_eer_snss(struct dasd_device * device)405 void dasd_eer_snss(struct dasd_device *device)
406 {
407 	struct dasd_ccw_req *cqr;
408 
409 	cqr = device->eer_cqr;
410 	if (!cqr)	/* Device not eer enabled. */
411 		return;
412 	if (test_and_set_bit(DASD_FLAG_EER_IN_USE, &device->flags)) {
413 		/* Sense subsystem status request in use. */
414 		set_bit(DASD_FLAG_EER_SNSS, &device->flags);
415 		return;
416 	}
417 	/* cdev is already locked, can't use dasd_add_request_head */
418 	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
419 	cqr->status = DASD_CQR_QUEUED;
420 	list_add(&cqr->devlist, &device->ccw_queue);
421 	dasd_schedule_device_bh(device);
422 }
423 
424 /*
425  * Callback function for use with sense subsystem status request.
426  */
dasd_eer_snss_cb(struct dasd_ccw_req * cqr,void * data)427 static void dasd_eer_snss_cb(struct dasd_ccw_req *cqr, void *data)
428 {
429 	struct dasd_device *device = cqr->startdev;
430 	unsigned long flags;
431 
432 	dasd_eer_write(device, cqr, DASD_EER_STATECHANGE);
433 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
434 	if (device->eer_cqr == cqr) {
435 		clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
436 		if (test_bit(DASD_FLAG_EER_SNSS, &device->flags))
437 			/* Another SNSS has been requested in the meantime. */
438 			dasd_eer_snss(device);
439 		cqr = NULL;
440 	}
441 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
442 	if (cqr)
443 		/*
444 		 * Extended error recovery has been switched off while
445 		 * the SNSS request was running. It could even have
446 		 * been switched off and on again in which case there
447 		 * is a new ccw in device->eer_cqr. Free the "old"
448 		 * snss request now.
449 		 */
450 		dasd_sfree_request(cqr, device);
451 }
452 
453 /*
454  * Enable error reporting on a given device.
455  */
dasd_eer_enable(struct dasd_device * device)456 int dasd_eer_enable(struct dasd_device *device)
457 {
458 	struct dasd_ccw_req *cqr = NULL;
459 	unsigned long flags;
460 	struct ccw1 *ccw;
461 	int rc = 0;
462 
463 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
464 	if (device->eer_cqr)
465 		goto out;
466 	else if (!device->discipline ||
467 		 strcmp(device->discipline->name, "ECKD"))
468 		rc = -EMEDIUMTYPE;
469 	else if (test_bit(DASD_FLAG_OFFLINE, &device->flags))
470 		rc = -EBUSY;
471 
472 	if (rc)
473 		goto out;
474 
475 	cqr = dasd_smalloc_request(DASD_ECKD_MAGIC, 1 /* SNSS */,
476 				   SNSS_DATA_SIZE, device, NULL);
477 	if (IS_ERR(cqr)) {
478 		rc = -ENOMEM;
479 		cqr = NULL;
480 		goto out;
481 	}
482 
483 	cqr->startdev = device;
484 	cqr->retries = 255;
485 	cqr->expires = 10 * HZ;
486 	clear_bit(DASD_CQR_FLAGS_USE_ERP, &cqr->flags);
487 	set_bit(DASD_CQR_ALLOW_SLOCK, &cqr->flags);
488 
489 	ccw = cqr->cpaddr;
490 	ccw->cmd_code = DASD_ECKD_CCW_SNSS;
491 	ccw->count = SNSS_DATA_SIZE;
492 	ccw->flags = 0;
493 	ccw->cda = (__u32)(addr_t) cqr->data;
494 
495 	cqr->buildclk = get_tod_clock();
496 	cqr->status = DASD_CQR_FILLED;
497 	cqr->callback = dasd_eer_snss_cb;
498 
499 	if (!device->eer_cqr) {
500 		device->eer_cqr = cqr;
501 		cqr = NULL;
502 	}
503 
504 out:
505 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
506 
507 	if (cqr)
508 		dasd_sfree_request(cqr, device);
509 
510 	return rc;
511 }
512 
513 /*
514  * Disable error reporting on a given device.
515  */
dasd_eer_disable(struct dasd_device * device)516 void dasd_eer_disable(struct dasd_device *device)
517 {
518 	struct dasd_ccw_req *cqr;
519 	unsigned long flags;
520 	int in_use;
521 
522 	if (!device->eer_cqr)
523 		return;
524 	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
525 	cqr = device->eer_cqr;
526 	device->eer_cqr = NULL;
527 	clear_bit(DASD_FLAG_EER_SNSS, &device->flags);
528 	in_use = test_and_clear_bit(DASD_FLAG_EER_IN_USE, &device->flags);
529 	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
530 	if (cqr && !in_use)
531 		dasd_sfree_request(cqr, device);
532 }
533 
534 /*
535  * SECTION: the device operations
536  */
537 
538 /*
539  * On the one side we need a lock to access our internal buffer, on the
540  * other side a copy_to_user can sleep. So we need to copy the data we have
541  * to transfer in a readbuffer, which is protected by the readbuffer_mutex.
542  */
543 static char readbuffer[PAGE_SIZE];
544 static DEFINE_MUTEX(readbuffer_mutex);
545 
dasd_eer_open(struct inode * inp,struct file * filp)546 static int dasd_eer_open(struct inode *inp, struct file *filp)
547 {
548 	struct eerbuffer *eerb;
549 	unsigned long flags;
550 
551 	eerb = kzalloc(sizeof(struct eerbuffer), GFP_KERNEL);
552 	if (!eerb)
553 		return -ENOMEM;
554 	eerb->buffer_page_count = eer_pages;
555 	if (eerb->buffer_page_count < 1 ||
556 	    eerb->buffer_page_count > INT_MAX / PAGE_SIZE) {
557 		kfree(eerb);
558 		DBF_EVENT(DBF_WARNING, "can't open device since module "
559 			"parameter eer_pages is smaller than 1 or"
560 			" bigger than %d", (int)(INT_MAX / PAGE_SIZE));
561 		return -EINVAL;
562 	}
563 	eerb->buffersize = eerb->buffer_page_count * PAGE_SIZE;
564 	eerb->buffer = kmalloc_array(eerb->buffer_page_count, sizeof(char *),
565 				     GFP_KERNEL);
566         if (!eerb->buffer) {
567 		kfree(eerb);
568                 return -ENOMEM;
569 	}
570 	if (dasd_eer_allocate_buffer_pages(eerb->buffer,
571 					   eerb->buffer_page_count)) {
572 		kfree(eerb->buffer);
573 		kfree(eerb);
574 		return -ENOMEM;
575 	}
576 	filp->private_data = eerb;
577 	spin_lock_irqsave(&bufferlock, flags);
578 	list_add(&eerb->list, &bufferlist);
579 	spin_unlock_irqrestore(&bufferlock, flags);
580 
581 	return nonseekable_open(inp,filp);
582 }
583 
dasd_eer_close(struct inode * inp,struct file * filp)584 static int dasd_eer_close(struct inode *inp, struct file *filp)
585 {
586 	struct eerbuffer *eerb;
587 	unsigned long flags;
588 
589 	eerb = (struct eerbuffer *) filp->private_data;
590 	spin_lock_irqsave(&bufferlock, flags);
591 	list_del(&eerb->list);
592 	spin_unlock_irqrestore(&bufferlock, flags);
593 	dasd_eer_free_buffer_pages(eerb->buffer, eerb->buffer_page_count);
594 	kfree(eerb->buffer);
595 	kfree(eerb);
596 
597 	return 0;
598 }
599 
dasd_eer_read(struct file * filp,char __user * buf,size_t count,loff_t * ppos)600 static ssize_t dasd_eer_read(struct file *filp, char __user *buf,
601 			     size_t count, loff_t *ppos)
602 {
603 	int tc,rc;
604 	int tailcount,effective_count;
605         unsigned long flags;
606 	struct eerbuffer *eerb;
607 
608 	eerb = (struct eerbuffer *) filp->private_data;
609 	if (mutex_lock_interruptible(&readbuffer_mutex))
610 		return -ERESTARTSYS;
611 
612 	spin_lock_irqsave(&bufferlock, flags);
613 
614 	if (eerb->residual < 0) { /* the remainder of this record */
615 		                  /* has been deleted             */
616 		eerb->residual = 0;
617 		spin_unlock_irqrestore(&bufferlock, flags);
618 		mutex_unlock(&readbuffer_mutex);
619 		return -EIO;
620 	} else if (eerb->residual > 0) {
621 		/* OK we still have a second half of a record to deliver */
622 		effective_count = min(eerb->residual, (int) count);
623 		eerb->residual -= effective_count;
624 	} else {
625 		tc = 0;
626 		while (!tc) {
627 			tc = dasd_eer_read_buffer(eerb, (char *) &tailcount,
628 						  sizeof(tailcount));
629 			if (!tc) {
630 				/* no data available */
631 				spin_unlock_irqrestore(&bufferlock, flags);
632 				mutex_unlock(&readbuffer_mutex);
633 				if (filp->f_flags & O_NONBLOCK)
634 					return -EAGAIN;
635 				rc = wait_event_interruptible(
636 					dasd_eer_read_wait_queue,
637 					eerb->head != eerb->tail);
638 				if (rc)
639 					return rc;
640 				if (mutex_lock_interruptible(&readbuffer_mutex))
641 					return -ERESTARTSYS;
642 				spin_lock_irqsave(&bufferlock, flags);
643 			}
644 		}
645 		WARN_ON(tc != sizeof(tailcount));
646 		effective_count = min(tailcount,(int)count);
647 		eerb->residual = tailcount - effective_count;
648 	}
649 
650 	tc = dasd_eer_read_buffer(eerb, readbuffer, effective_count);
651 	WARN_ON(tc != effective_count);
652 
653 	spin_unlock_irqrestore(&bufferlock, flags);
654 
655 	if (copy_to_user(buf, readbuffer, effective_count)) {
656 		mutex_unlock(&readbuffer_mutex);
657 		return -EFAULT;
658 	}
659 
660 	mutex_unlock(&readbuffer_mutex);
661 	return effective_count;
662 }
663 
dasd_eer_poll(struct file * filp,poll_table * ptable)664 static __poll_t dasd_eer_poll(struct file *filp, poll_table *ptable)
665 {
666 	__poll_t mask;
667 	unsigned long flags;
668 	struct eerbuffer *eerb;
669 
670 	eerb = (struct eerbuffer *) filp->private_data;
671 	poll_wait(filp, &dasd_eer_read_wait_queue, ptable);
672 	spin_lock_irqsave(&bufferlock, flags);
673 	if (eerb->head != eerb->tail)
674 		mask = EPOLLIN | EPOLLRDNORM ;
675 	else
676 		mask = 0;
677 	spin_unlock_irqrestore(&bufferlock, flags);
678 	return mask;
679 }
680 
681 static const struct file_operations dasd_eer_fops = {
682 	.open		= &dasd_eer_open,
683 	.release	= &dasd_eer_close,
684 	.read		= &dasd_eer_read,
685 	.poll		= &dasd_eer_poll,
686 	.owner		= THIS_MODULE,
687 	.llseek		= noop_llseek,
688 };
689 
690 static struct miscdevice *dasd_eer_dev = NULL;
691 
dasd_eer_init(void)692 int __init dasd_eer_init(void)
693 {
694 	int rc;
695 
696 	dasd_eer_dev = kzalloc(sizeof(*dasd_eer_dev), GFP_KERNEL);
697 	if (!dasd_eer_dev)
698 		return -ENOMEM;
699 
700 	dasd_eer_dev->minor = MISC_DYNAMIC_MINOR;
701 	dasd_eer_dev->name  = "dasd_eer";
702 	dasd_eer_dev->fops  = &dasd_eer_fops;
703 
704 	rc = misc_register(dasd_eer_dev);
705 	if (rc) {
706 		kfree(dasd_eer_dev);
707 		dasd_eer_dev = NULL;
708 		DBF_EVENT(DBF_ERR, "%s", "dasd_eer_init could not "
709 		       "register misc device");
710 		return rc;
711 	}
712 
713 	return 0;
714 }
715 
dasd_eer_exit(void)716 void dasd_eer_exit(void)
717 {
718 	if (dasd_eer_dev) {
719 		misc_deregister(dasd_eer_dev);
720 		kfree(dasd_eer_dev);
721 		dasd_eer_dev = NULL;
722 	}
723 }
724