slkern/diskio.c

// NEW CODE replacing old buffer management code with a more flexible system

#include "diskio.h"
#include "types.h"
#include "param.h"
#include "memlayout.h"
#include "riscv.h"
#include "defs.h"
#include "drives.h"
#include "fsinstance.h"
#include "vmrd.h"
#include "kprintf.h"

int strcmp(const char*, const char*);
void* memcpy(void*, void*, long);

diskio_buffer_t* diskio_buffer_alloc(diskio_cache_t* owner, unsigned long long blocksize) {
  if (blocksize > 4096ULL) { // TODO: Standardise page/block limits
    panic("diskio_buffer_alloc: Bad block size!");
  }
  diskio_buffer_t* result = kalloc();
  if (result) {
    if (blocksize == 0ULL) {
      result->data = NULL;
    } else {
      result->data = kalloc();
      if (!result->data) {
        kfree(result);
        return NULL;
      }
    }
    
    result->owner = owner;
    result->referencecount = 0;
    result->padding = 0; // unused
    result->isvalid = 0;
    result->isdisk = 0;
    result->device = 0;
    result->blocknumber = 0;
    
    result->previous = NULL;
    result->next = NULL;
    
    initsleeplock(&result->lock, "diskio_buffer_t");
  }
  return result;
}

void diskio_buffer_free(diskio_buffer_t* buffer) {
  if (buffer) {
    if (buffer->data) {
      kfree(buffer->data);
    }
    kfree(buffer->data);
  }
}

void diskio_buffer_reference(diskio_buffer_t* buffer) {
  acquire(&buffer->owner->spin);
  buffer->referencecount = buffer->referencecount + 1;
  release(&buffer->owner->spin);
}

void diskio_buffer_dereference(diskio_buffer_t* buffer) {
  acquire(&buffer->owner->spin);
  buffer->referencecount = buffer->referencecount - 1;
  release(&buffer->owner->spin);
}

// Checks that the buffer is already locked and writes it to the disk.
void diskio_buffer_write(diskio_buffer_t* buffer) {
  if (!holdingsleep(&buffer->lock)) {
    panic("diskio_buffer_write: Calling code is not holding the appropriate lock!");
  }
  
  diskio_performwrite(buffer);
}

// Performs a logical read of a buffer, returning it in locked form with the given block.
diskio_buffer_t* diskio_buffer_read(diskio_cache_t* cache, unsigned int device, unsigned int blocknumber) {
  diskio_buffer_t* buffer = diskio_buffer_get_noread(cache, device, blocknumber);
  
  if (!buffer->isvalid) {
    diskio_performread(buffer);
    buffer->isvalid = 1;
  }
  
  return buffer;
}

diskio_buffer_t* diskio_buffer_get_noread(diskio_cache_t* cache, unsigned int device, unsigned int blocknumber) {
  acquire(&cache->spin);
  
  diskio_buffer_t* list = cache->leastrecentlist;
  
  // Look for a matching cached entry if one exists and lock it.
  for (diskio_buffer_t* buffer = list->next; buffer != list; buffer = buffer->next) {
    if (buffer->device == device && buffer->blocknumber == blocknumber) {
      buffer->referencecount = buffer->referencecount + 1;
      release(&cache->spin);
      acquiresleep(&buffer->lock);
      return buffer;
    }
  }
  
  // Otherwise find an empty buffer to re-allocate.
  for (diskio_buffer_t* buffer = list->previous; buffer != list; buffer = buffer->previous) {
    if (buffer->referencecount == 0) {
      buffer->referencecount = 1;
      buffer->isvalid = 0;
      buffer->device = device;
      buffer->blocknumber = blocknumber;
      //printf("Set device to 0x%x (0x%x)\n", buffer->device, device);
      
      release(&cache->spin);
      
      acquiresleep(&buffer->lock);
      
      return buffer;
    }
  }
  
  panic("diskio_buffer_get_noread: TODO: Better handling when running out of buffers!");
  
  return NULL;
}

void diskio_buffer_release(diskio_buffer_t* buffer) {
  diskio_cache_t* cache = buffer->owner;
  
  if (!holdingsleep(&buffer->lock)) {
    panic("diskio_buffer_release: Calling code is not holding the appropriate lock!");
  }
  
  releasesleep(&buffer->lock);
  
  acquire(&cache->spin);
  
  diskio_buffer_t* list = cache->leastrecentlist;
  
  buffer->referencecount = buffer->referencecount - 1;
  
  if (buffer->referencecount == 0) {
    buffer->next->previous = buffer->previous;
    buffer->previous->next = buffer->next;
    
    buffer->next = list->next;
    buffer->previous = list;
    
    list->next->previous = buffer;
    list->next = buffer;
  }
  
  release(&cache->spin);
}

diskio_cache_t* diskio_cache_alloc(unsigned long long buffercount, unsigned long long blocksize) {
  if (buffercount > DISKIO_CACHE_MAXBUFFERS) {
    panic("diskio_cache_alloc: buffercount is out of range!");
  }
  diskio_cache_t* result = kalloc();
  if (result) {
    initlock(&result->spin, "diskio_cache_t");
    
    result->buffercount = buffercount;
    
    diskio_buffer_t* listhead = diskio_buffer_alloc(result, 0);
    if (listhead == NULL) {
      kfree(result);
      return NULL;
    }
    listhead->previous = listhead;
    listhead->next = listhead;
    result->leastrecentlist = listhead;
    
    for (int bufnum = 0; bufnum < buffercount; bufnum++) {
      diskio_buffer_t* buffer = diskio_buffer_alloc(result, blocksize);
      if (buffer == NULL) {
        while (--bufnum > 0) {
          diskio_buffer_free(result->buffers[bufnum]);
          diskio_buffer_free(listhead);
          kfree(result);
        }
        return NULL;
      }
      
      buffer->next = listhead->next;
      buffer->previous = listhead;
      listhead->next->previous = buffer;
      listhead->next = buffer;
      
      result->buffers[bufnum] = buffer;
    }
    
    result->blocksize = blocksize;
  }
  return result;
}

void diskio_cache_free(diskio_cache_t* cache) {
  if (cache) {
    // TODO: Free block cache structure
  }
}

void diskio_performread(diskio_buffer_t* buffer) {
  if ((buffer->device & 0xFF00) == 0x0900) {
    diskio_ramdisk_rw(buffer, 0);
  } else {
    if (vmrd_present()) {
      vmrd_rw(buffer, 0);
    } else {
      virtio_disk_rw(buffer, 0);
    }
  }
}

void diskio_performwrite(diskio_buffer_t* buffer) {
  if ((buffer->device & 0xFF00) == 0x0900) {
    diskio_ramdisk_rw(buffer, 1);
  } else {
    if (vmrd_present()) {
      vmrd_rw(buffer, 0);
    } else {
      virtio_disk_rw(buffer, 1);
    }
  }
}

#define RESOURCES_MAX 256

typedef struct resource resource_t;
struct resource {
  const char* type;
  const char* name;
  unsigned long size;
  unsigned char* data;
};

resource_t resources[RESOURCES_MAX];

int nresources = -1;

void resources_checkinit() {
  if (nresources == -1) {
    printf("Initialising resources...\n");
    nresources = 0;
  }
}

void resources_register(const char* type, const char* name, unsigned char* data, unsigned long size) {
  resources_checkinit();
  if (strcmp(type, "RAMDISK") == 0) {
    resources[nresources].type = type;
    resources[nresources].name = name;
    resources[nresources].data = data;
    resources[nresources].size = size;
    nresources++;
  } else {
    printf("TODO: resources_register(\"%s\", \"%s\", %p, %d);\n", type, name, data, (int) size);
  }
}

void diskio_ramdisk_rw(diskio_buffer_t* buffer, int wr) {
  resource_t* ramdisk = &resources[buffer->device & 0xFF];
  if ((buffer->blocknumber + 1)*DISKIO_BLOCK_SIZE > ramdisk->size) {
    panic("diskio_ramdisk_rw: block number out of range");
  }
  unsigned long offset = buffer->blocknumber * DISKIO_BLOCK_SIZE;
  unsigned char* ramdiskptr = ramdisk->data + offset;
  if (wr) {
    memcpy(ramdiskptr, buffer->data, DISKIO_BLOCK_SIZE);
  } else {
    memcpy(buffer->data, ramdiskptr, DISKIO_BLOCK_SIZE);
  }
}

void diskio_mountramdisk(struct drives* drives, const char* mountname, unsigned int device) {
  printf("TODO: mount ramdisk '%s' on device %x\n", mountname, device);
  
  printf("  diskio_cache_alloc()...\n");
  diskio_cache_t* cache = diskio_cache_alloc(NBUF, DISKIO_BLOCK_SIZE);
  printf("  diskio_cache_alloc() returned %p\n", cache);
  
  printf("  fsinstance_alloc()...\n");
  fsinstance_t* instance = fsinstance_alloc();
  printf("  fsinstance_alloc() returned %p\n", instance);
  
  instance->cache = cache;
  
  printf("  drives_setup()...\n");
  int dn = drives_setup(drives, DRIVES_HANDLER_FS, instance, mountname);
  printf("  drives_setup() returned %d\n", dn);
  
  printf("  fsinstance_init()...\n");
  void * fsp = fsinstance_init(instance, device);
  printf("  fsinstance_init() returned %p\n", fsp);
  
  printf("device=%x\n", (int)((long)instance->fslog_device));
}

void diskio_mountallramdisks(struct drives* drives) {
  for (int i = 0; i < nresources; i++) {
    resource_t* r = &resources[i];
    if (!strcmp(r->type, "RAMDISK")) {
      diskio_mountramdisk(drives, r->name, 0x0900 + i);
    }
  }
}