drivers/block/ll_rw

/* */
This source file includes following definitions.
get_request
get_request_wait
is_read_only
set_device_ro
add_request
make_request
ll_rw_page
ll_rw_block
ll_rw_swap_file
blk_dev_init
   1 /*
   2  *  linux/kernel/blk_dev/ll_rw.c
   3  *
   4  * Copyright (C) 1991, 1992 Linus Torvalds
   5  */
   6 
   7 /*
   8  * This handles all read/write requests to block devices
   9  */
  10 #include <linux/sched.h>
  11 #include <linux/kernel.h>
  12 #include <linux/kernel_stat.h>
  13 #include <linux/errno.h>
  14 #include <linux/string.h>
  15 #include <linux/config.h>
  16 #include <linux/locks.h>
  17 
  18 #include <asm/system.h>
  19 
  20 #include "blk.h"
  21 
  22 /*
  23  * The request-struct contains all necessary data
  24  * to load a nr of sectors into memory
  25  */
  26 static struct request all_requests[NR_REQUEST];
  27 
  28 /*
  29  * used to wait on when there are no free requests
  30  */
  31 struct wait_queue * wait_for_request = NULL;
  32 
  33 /* This specifies how many sectors to read ahead on the disk.  */
  34 
  35 int read_ahead[MAX_BLKDEV] = {0, };
  36 
  37 /* blk_dev_struct is:
  38  *      do_request-address
  39  *      next-request
  40  */
  41 struct blk_dev_struct blk_dev[MAX_BLKDEV] = {
  42         { NULL, NULL },         /* no_dev */
  43         { NULL, NULL },         /* dev mem */
  44         { NULL, NULL },         /* dev fd */
  45         { NULL, NULL },         /* dev hd */
  46         { NULL, NULL },         /* dev ttyx */
  47         { NULL, NULL },         /* dev tty */
  48         { NULL, NULL },         /* dev lp */
  49         { NULL, NULL },         /* dev pipes */
  50         { NULL, NULL },         /* dev sd */
  51         { NULL, NULL }          /* dev st */
  52 };
  53 
  54 /*
  55  * blk_size contains the size of all block-devices in units of 1024 byte
  56  * sectors:
  57  *
  58  * blk_size[MAJOR][MINOR]
  59  *
  60  * if (!blk_size[MAJOR]) then no minor size checking is done.
  61  */
  62 int * blk_size[MAX_BLKDEV] = { NULL, NULL, };
  63 
  64 /*
  65  * blksize_size contains the size of all block-devices:
  66  *
  67  * blksize_size[MAJOR][MINOR]
  68  *
  69  * if (!blksize_size[MAJOR]) then 1024 bytes is assumed.
  70  */
  71 int * blksize_size[MAX_BLKDEV] = { NULL, NULL, };
  72 
  73 /*
  74  * look for a free request in the first N entries.
  75  * NOTE: interrupts must be disabled on the way in, and will still
  76  *       be disabled on the way out.
  77  */
  78 static inline struct request * get_request(int n, int dev)
     /*  */
  79 {
  80         static struct request *prev_found = NULL, *prev_limit = NULL;
  81         register struct request *req, *limit;
  82 
  83         if (n <= 0)
  84                 panic("get_request(%d): impossible!\n", n);
  85 
  86         limit = all_requests + n;
  87         if (limit != prev_limit) {
  88                 prev_limit = limit;
  89                 prev_found = all_requests;
  90         }
  91         req = prev_found;
  92         for (;;) {
  93                 req = ((req > all_requests) ? req : limit) - 1;
  94                 if (req->dev < 0)
  95                         break;
  96                 if (req == prev_found)
  97                         return NULL;
  98         }
  99         prev_found = req;
 100         req->dev = dev;
 101         return req;
 102 }
 103 
 104 /*
 105  * wait until a free request in the first N entries is available.
 106  * NOTE: interrupts must be disabled on the way in, and will still
 107  *       be disabled on the way out.
 108  */
 109 static inline struct request * get_request_wait(int n, int dev)
     /*  */
 110 {
 111         register struct request *req;
 112 
 113         while ((req = get_request(n, dev)) == NULL)
 114                 sleep_on(&wait_for_request);
 115         return req;
 116 }
 117 
 118 /* RO fail safe mechanism */
 119 
 120 static long ro_bits[MAX_BLKDEV][8];
 121 
 122 int is_read_only(int dev)
     /*  */
 123 {
 124         int minor,major;
 125 
 126         major = MAJOR(dev);
 127         minor = MINOR(dev);
 128         if (major < 0 || major >= MAX_BLKDEV) return 0;
 129         return ro_bits[major][minor >> 5] & (1 << (minor & 31));
 130 }
 131 
 132 void set_device_ro(int dev,int flag)
     /*  */
 133 {
 134         int minor,major;
 135 
 136         major = MAJOR(dev);
 137         minor = MINOR(dev);
 138         if (major < 0 || major >= MAX_BLKDEV) return;
 139         if (flag) ro_bits[major][minor >> 5] |= 1 << (minor & 31);
 140         else ro_bits[major][minor >> 5] &= ~(1 << (minor & 31));
 141 }
 142 
 143 /*
 144  * add-request adds a request to the linked list.
 145  * It disables interrupts so that it can muck with the
 146  * request-lists in peace.
 147  */
 148 static void add_request(struct blk_dev_struct * dev, struct request * req)
     /*  */
 149 {
 150         struct request * tmp;
 151 
 152         req->next = NULL;
 153         cli();
 154         if (req->bh)
 155                 mark_buffer_clean(req->bh);
 156         if (!(tmp = dev->current_request)) {
 157                 dev->current_request = req;
 158                 (dev->request_fn)();
 159                 sti();
 160                 return;
 161         }
 162         for ( ; tmp->next ; tmp = tmp->next) {
 163                 if ((IN_ORDER(tmp,req) ||
 164                     !IN_ORDER(tmp,tmp->next)) &&
 165                     IN_ORDER(req,tmp->next))
 166                         break;
 167         }
 168         req->next = tmp->next;
 169         tmp->next = req;
 170 
 171 /* for SCSI devices, call request_fn unconditionally */
 172         if (scsi_major(MAJOR(req->dev)))
 173                 (dev->request_fn)();
 174 
 175         sti();
 176 }
 177 
 178 static void make_request(int major,int rw, struct buffer_head * bh)
     /*  */
 179 {
 180         unsigned int sector, count;
 181         struct request * req;
 182         int rw_ahead, max_req;
 183 
 184 /* WRITEA/READA is special case - it is not really needed, so if the */
 185 /* buffer is locked, we just forget about it, else it's a normal read */
 186         rw_ahead = (rw == READA || rw == WRITEA);
 187         if (rw_ahead) {
 188                 if (bh->b_lock)
 189                         return;
 190                 if (rw == READA)
 191                         rw = READ;
 192                 else
 193                         rw = WRITE;
 194         }
 195         if (rw!=READ && rw!=WRITE) {
 196                 printk("Bad block dev command, must be R/W/RA/WA\n");
 197                 return;
 198         }
 199         count = bh->b_size >> 9;
 200         sector = bh->b_blocknr * count;
 201         if (blk_size[major])
 202                 if (blk_size[major][MINOR(bh->b_dev)] < (sector + count)>>1) {
 203                         bh->b_dirt = bh->b_uptodate = 0;
 204                         return;
 205                 }
 206         lock_buffer(bh);
 207         if ((rw == WRITE && !bh->b_dirt) || (rw == READ && bh->b_uptodate)) {
 208                 unlock_buffer(bh);
 209                 return;
 210         }
 211 
 212 /* we don't allow the write-requests to fill up the queue completely:
 213  * we want some room for reads: they take precedence. The last third
 214  * of the requests are only for reads.
 215  */
 216         max_req = (rw == READ) ? NR_REQUEST : ((NR_REQUEST*2)/3);
 217 
 218 /* big loop: look for a free request. */
 219 
 220 repeat:
 221         cli();
 222 
 223 /* The scsi disk drivers completely remove the request from the queue when
 224  * they start processing an entry.  For this reason it is safe to continue
 225  * to add links to the top entry for scsi devices.
 226  */
 227         if ((major == HD_MAJOR
 228              || major == SCSI_DISK_MAJOR
 229              || major == SCSI_CDROM_MAJOR)
 230             && (req = blk_dev[major].current_request))
 231         {
 232                 if (major == HD_MAJOR)
 233                         req = req->next;
 234                 while (req) {
 235                         if (req->dev == bh->b_dev &&
 236                             !req->sem &&
 237                             req->cmd == rw &&
 238                             req->sector + req->nr_sectors == sector &&
 239                             req->nr_sectors < 244)
 240                         {
 241                                 req->bhtail->b_reqnext = bh;
 242                                 req->bhtail = bh;
 243                                 req->nr_sectors += count;
 244                                 mark_buffer_clean(bh);
 245                                 sti();
 246                                 return;
 247                         }
 248 
 249                         if (req->dev == bh->b_dev &&
 250                             !req->sem &&
 251                             req->cmd == rw &&
 252                             req->sector - count == sector &&
 253                             req->nr_sectors < 244)
 254                         {
 255                                 req->nr_sectors += count;
 256                                 bh->b_reqnext = req->bh;
 257                                 req->buffer = bh->b_data;
 258                                 req->current_nr_sectors = count;
 259                                 req->sector = sector;
 260                                 mark_buffer_clean(bh);
 261                                 req->bh = bh;
 262                                 sti();
 263                                 return;
 264                         }    
 265 
 266                         req = req->next;
 267                 }
 268         }
 269 
 270 /* find an unused request. */
 271         req = get_request(max_req, bh->b_dev);
 272 
 273 /* if no request available: if rw_ahead, forget it; otherwise try again. */
 274         if (! req) {
 275                 if (rw_ahead) {
 276                         sti();
 277                         unlock_buffer(bh);
 278                         return;
 279                 }
 280                 sleep_on(&wait_for_request);
 281                 sti();
 282                 goto repeat;
 283         }
 284 
 285 /* we found a request. */
 286         sti();
 287 
 288 /* fill up the request-info, and add it to the queue */
 289         req->cmd = rw;
 290         req->errors = 0;
 291         req->sector = sector;
 292         req->nr_sectors = count;
 293         req->current_nr_sectors = count;
 294         req->buffer = bh->b_data;
 295         req->sem = NULL;
 296         req->bh = bh;
 297         req->bhtail = bh;
 298         req->next = NULL;
 299         add_request(major+blk_dev,req);
 300 }
 301 
 302 void ll_rw_page(int rw, int dev, int page, char * buffer)
     /*  */
 303 {
 304         struct request * req;
 305         unsigned int major = MAJOR(dev);
 306         struct semaphore sem = MUTEX_LOCKED;
 307 
 308         if (major >= MAX_BLKDEV || !(blk_dev[major].request_fn)) {
 309                 printk("Trying to read nonexistent block-device %04x (%d)\n",dev,page*8);
 310                 return;
 311         }
 312         if (rw!=READ && rw!=WRITE)
 313                 panic("Bad block dev command, must be R/W");
 314         if (rw == WRITE && is_read_only(dev)) {
 315                 printk("Can't page to read-only device 0x%X\n",dev);
 316                 return;
 317         }
 318         cli();
 319         req = get_request_wait(NR_REQUEST, dev);
 320         sti();
 321 /* fill up the request-info, and add it to the queue */
 322         req->cmd = rw;
 323         req->errors = 0;
 324         req->sector = page<<3;
 325         req->nr_sectors = 8;
 326         req->current_nr_sectors = 8;
 327         req->buffer = buffer;
 328         req->sem = &sem;
 329         req->bh = NULL;
 330         req->next = NULL;
 331         add_request(major+blk_dev,req);
 332         down(&sem);
 333 }
 334 
 335 /* This function can be used to request a number of buffers from a block
 336    device. Currently the only restriction is that all buffers must belong to
 337    the same device */
 338 
 339 void ll_rw_block(int rw, int nr, struct buffer_head * bh[])
     /*  */
 340 {
 341         unsigned int major;
 342         struct request plug;
 343         int plugged;
 344         int correct_size;
 345         struct blk_dev_struct * dev;
 346         int i;
 347 
 348         /* Make sure that the first block contains something reasonable */
 349         while (!*bh) {
 350                 bh++;
 351                 if (--nr <= 0)
 352                         return;
 353         };
 354 
 355         dev = NULL;
 356         if ((major = MAJOR(bh[0]->b_dev)) < MAX_BLKDEV)
 357                 dev = blk_dev + major;
 358         if (!dev || !dev->request_fn) {
 359                 printk(
 360         "ll_rw_block: Trying to read nonexistent block-device %04lX (%ld)\n",
 361                        (unsigned long) bh[0]->b_dev, bh[0]->b_blocknr);
 362                 goto sorry;
 363         }
 364 
 365         /* Determine correct block size for this device.  */
 366         correct_size = BLOCK_SIZE;
 367         if (blksize_size[major]) {
 368                 i = blksize_size[major][MINOR(bh[0]->b_dev)];
 369                 if (i)
 370                         correct_size = i;
 371         }
 372 
 373         /* Verify requested block sizees.  */
 374         for (i = 0; i < nr; i++) {
 375                 if (bh[i] && bh[i]->b_size != correct_size) {
 376                         printk(
 377                         "ll_rw_block: only %d-char blocks implemented (%lu)\n",
 378                                correct_size, bh[i]->b_size);
 379                         goto sorry;
 380                 }
 381         }
 382 
 383         if ((rw == WRITE || rw == WRITEA) && is_read_only(bh[0]->b_dev)) {
 384                 printk("Can't write to read-only device 0x%X\n",bh[0]->b_dev);
 385                 goto sorry;
 386         }
 387 
 388         /* If there are no pending requests for this device, then we insert
 389            a dummy request for that device.  This will prevent the request
 390            from starting until we have shoved all of the blocks into the
 391            queue, and then we let it rip.  */
 392 
 393         plugged = 0;
 394         cli();
 395         if (!dev->current_request && nr > 1) {
 396                 dev->current_request = &plug;
 397                 plug.dev = -1;
 398                 plug.next = NULL;
 399                 plugged = 1;
 400         }
 401         sti();
 402         for (i = 0; i < nr; i++) {
 403                 if (bh[i]) {
 404                         bh[i]->b_req = 1;
 405                         make_request(major, rw, bh[i]);
 406                         if (rw == READ || rw == READA)
 407                                 kstat.pgpgin++;
 408                         else
 409                                 kstat.pgpgout++;
 410                 }
 411         }
 412         if (plugged) {
 413                 cli();
 414                 dev->current_request = plug.next;
 415                 (dev->request_fn)();
 416                 sti();
 417         }
 418         return;
 419 
 420       sorry:
 421         for (i = 0; i < nr; i++) {
 422                 if (bh[i])
 423                         bh[i]->b_dirt = bh[i]->b_uptodate = 0;
 424         }
 425         return;
 426 }
 427 
 428 void ll_rw_swap_file(int rw, int dev, unsigned int *b, int nb, char *buf)
     /*  */
 429 {
 430         int i;
 431         int buffersize;
 432         struct request * req;
 433         unsigned int major = MAJOR(dev);
 434         struct semaphore sem = MUTEX_LOCKED;
 435 
 436         if (major >= MAX_BLKDEV || !(blk_dev[major].request_fn)) {
 437                 printk("ll_rw_swap_file: trying to swap nonexistent block-device\n");
 438                 return;
 439         }
 440 
 441         if (rw!=READ && rw!=WRITE) {
 442                 printk("ll_rw_swap: bad block dev command, must be R/W");
 443                 return;
 444         }
 445         if (rw == WRITE && is_read_only(dev)) {
 446                 printk("Can't swap to read-only device 0x%X\n",dev);
 447                 return;
 448         }
 449         
 450         buffersize = PAGE_SIZE / nb;
 451 
 452         for (i=0; i<nb; i++, buf += buffersize)
 453         {
 454                 cli();
 455                 req = get_request_wait(NR_REQUEST, dev);
 456                 sti();
 457                 req->cmd = rw;
 458                 req->errors = 0;
 459                 req->sector = (b[i] * buffersize) >> 9;
 460                 req->nr_sectors = buffersize >> 9;
 461                 req->current_nr_sectors = buffersize >> 9;
 462                 req->buffer = buf;
 463                 req->sem = &sem;
 464                 req->bh = NULL;
 465                 req->next = NULL;
 466                 add_request(major+blk_dev,req);
 467                 down(&sem);
 468         }
 469 }
 470 
 471 long blk_dev_init(long mem_start, long mem_end)
     /*  */
 472 {
 473         struct request * req;
 474 
 475         req = all_requests + NR_REQUEST;
 476         while (--req >= all_requests) {
 477                 req->dev = -1;
 478                 req->next = NULL;
 479         }
 480         memset(ro_bits,0,sizeof(ro_bits));
 481 #ifdef CONFIG_BLK_DEV_HD
 482         mem_start = hd_init(mem_start,mem_end);
 483 #endif
 484 #ifdef CONFIG_BLK_DEV_XD
 485         mem_start = xd_init(mem_start,mem_end);
 486 #endif
 487 #ifdef CONFIG_CDU31A
 488         mem_start = cdu31a_init(mem_start,mem_end);
 489 #endif
 490 #ifdef CONFIG_MCD
 491         mem_start = mcd_init(mem_start,mem_end);
 492 #endif
 493 #ifdef CONFIG_SBPCD
 494         mem_start = sbpcd_init(mem_start, mem_end);
 495 #endif CONFIG_SBPCD
 496         if (ramdisk_size)
 497                 mem_start += rd_init(mem_start, ramdisk_size*1024);
 498         return mem_start;
 499 }
/* */
root/drivers/block/ll_rw_blk.c

DEFINITIONS
