main.c

一个简单的操作系统minix的核心代码

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				src/fs/main.c	 	 
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22500	/* This file contains the main program of the File System.  It consists of
22501	 * a loop that gets messages requesting work, carries out the work, and sends
22502	 * replies.
22503	 *
22504	 * The entry points into this file are
22505	 *   main:      main program of the File System
22506	 *   reply:     send a reply to a process after the requested work is done
22507	 */
22508	
22509	struct super_block;             /* proto.h needs to know this */
22510	
22511	#include "fs.h"
22512	#include <fcntl.h>
22513	#include <string.h>
22514	#include <sys/ioctl.h>
22515	#include <minix/callnr.h>
22516	#include <minix/com.h>
22517	#include <minix/boot.h>
22518	#include "buf.h"
22519	#include "dev.h"
22520	#include "file.h"
22521	#include "fproc.h"
22522	#include "inode.h"
22523	#include "param.h"
22524	#include "super.h"
22525	
22526	FORWARD _PROTOTYPE( void buf_pool, (void)                               );
22527	FORWARD _PROTOTYPE( void fs_init, (void)                                );
22528	FORWARD _PROTOTYPE( void get_boot_parameters, (void)                    );
22529	FORWARD _PROTOTYPE( void get_work, (void)                               );
22530	FORWARD _PROTOTYPE( void load_ram, (void)                               );
22531	FORWARD _PROTOTYPE( void load_super, (Dev_t super_dev)                  );
22532	
22533	
22534	/*===========================================================================*
22535	 *                              main                                         *
22536	 *===========================================================================*/
22537	PUBLIC void main()
22538	{
22539	/* This is the main program of the file system.  The main loop consists of
22540	 * three major activities: getting new work, processing the work, and sending
22541	 * the reply.  This loop never terminates as long as the file system runs.
22542	 */
22543	  int error;
22544	
22545	  fs_init();
22546	
22547	  /* This is the main loop that gets work, processes it, and sends replies. */
22548	  while (TRUE) {
22549	        get_work();             /* sets who and fs_call */
22550	
22551	        fp = &fproc[who];       /* pointer to proc table struct */
22552	        super_user = (fp->fp_effuid == SU_UID ? TRUE : FALSE);   /* su? */
22553	        dont_reply = FALSE;     /* in other words, do reply is default */
22554	
22555	        /* Call the internal function that does the work. */
22556	        if (fs_call < 0 || fs_call >= NCALLS)
22557	                error = EBADCALL;
22558	        else
22559	                error = (*call_vector[fs_call])();
22560	
22561	        /* Copy the results back to the user and send reply. */
22562	        if (dont_reply) continue;
22563	        reply(who, error);
22564	        if (rdahed_inode != NIL_INODE) read_ahead(); /* do block read ahead */
22565	  }
22566	}
	
	
22569	/*===========================================================================*
22570	 *                              get_work                                     *
22571	 *===========================================================================*/
22572	PRIVATE void get_work()
22573	{  
22574	  /* Normally wait for new input.  However, if 'reviving' is
22575	   * nonzero, a suspended process must be awakened.
22576	   */
22577	
22578	  register struct fproc *rp;
22579	
22580	  if (reviving != 0) {
22581	        /* Revive a suspended process. */
22582	        for (rp = &fproc[0]; rp < &fproc[NR_PROCS]; rp++) 
22583	                if (rp->fp_revived == REVIVING) {
22584	                        who = (int)(rp - fproc);
22585	                        fs_call = rp->fp_fd & BYTE;
22586	                        fd = (rp->fp_fd >>8) & BYTE;
22587	                        buffer = rp->fp_buffer;
22588	                        nbytes = rp->fp_nbytes;
22589	                        rp->fp_suspended = NOT_SUSPENDED; /*no longer hanging*/
22590	                        rp->fp_revived = NOT_REVIVING;
22591	                        reviving--;
22592	                        return;
22593	                }
22594	        panic("get_work couldn't revive anyone", NO_NUM);
22595	  }
22596	
22597	  /* Normal case.  No one to revive. */
22598	  if (receive(ANY, &m) != OK) panic("fs receive error", NO_NUM);
22599	
22600	  who = m.m_source;
22601	  fs_call = m.m_type;
22602	}
	
	
22605	/*===========================================================================*
22606	 *                              reply                                        *
22607	 *===========================================================================*/
22608	PUBLIC void reply(whom, result)
22609	int whom;                       /* process to reply to */
22610	int result;                     /* result of the call (usually OK or error #) */
22611	{
22612	/* Send a reply to a user process. It may fail (if the process has just
22613	 * been killed by a signal), so don't check the return code.  If the send
22614	 * fails, just ignore it.
22615	 */
22616	
22617	  reply_type = result;
22618	  send(whom, &m1);
22619	}
	
	
22622	/*===========================================================================*
22623	 *                              fs_init                                      *
22624	 *===========================================================================*/
22625	PRIVATE void fs_init()
22626	{
22627	/* Initialize global variables, tables, etc. */
22628	
22629	  register struct inode *rip;
22630	  int i;
22631	  message mess;
22632	  
22633	  /* The following initializations are needed to let dev_opcl succeed .*/
22634	  fp = (struct fproc *) NULL;
22635	  who = FS_PROC_NR;
22636	
22637	  buf_pool();                   /* initialize buffer pool */
22638	  get_boot_parameters();        /* get the parameters from the menu */
22639	  load_ram();                   /* init RAM disk, load if it is root */
22640	  load_super(ROOT_DEV);         /* load super block for root device */
22641	
22642	  /* Initialize the 'fproc' fields for process 0 .. INIT. */
22643	  for (i = 0; i <= LOW_USER; i+= 1) {
22644	        if (i == FS_PROC_NR) continue;  /* do not initialize FS */
22645	        fp = &fproc[i];
22646	        rip = get_inode(ROOT_DEV, ROOT_INODE);
22647	        fp->fp_rootdir = rip;
22648	        dup_inode(rip);
22649	        fp->fp_workdir = rip;
22650	        fp->fp_realuid = (uid_t) SYS_UID;
22651	        fp->fp_effuid = (uid_t) SYS_UID;
22652	        fp->fp_realgid = (gid_t) SYS_GID;
22653	        fp->fp_effgid = (gid_t) SYS_GID;
22654	        fp->fp_umask = ~0;
22655	  }
22656	
22657	  /* Certain relations must hold for the file system to work at all. */
22658	  if (SUPER_SIZE > BLOCK_SIZE) panic("SUPER_SIZE > BLOCK_SIZE", NO_NUM);
22659	  if (BLOCK_SIZE % V2_INODE_SIZE != 0)  /* this checks V1_INODE_SIZE too */
22660	        panic("BLOCK_SIZE % V2_INODE_SIZE != 0", NO_NUM);
22661	  if (OPEN_MAX > 127) panic("OPEN_MAX > 127", NO_NUM);
22662	  if (NR_BUFS < 6) panic("NR_BUFS < 6", NO_NUM);
22663	  if (V1_INODE_SIZE != 32) panic("V1 inode size != 32", NO_NUM);
22664	  if (V2_INODE_SIZE != 64) panic("V2 inode size != 64", NO_NUM);
22665	  if (OPEN_MAX > 8 * sizeof(long)) panic("Too few bits in fp_cloexec", NO_NUM);
22666	
22667	  /* Tell the memory task where my process table is for the sake of ps(1). */
22668	  mess.m_type = DEV_IOCTL;
22669	  mess.PROC_NR = FS_PROC_NR;
22670	  mess.REQUEST = MIOCSPSINFO;
22671	  mess.ADDRESS = (void *) fproc;
22672	  (void) sendrec(MEM, &mess);
22673	}
	
	
22676	/*===========================================================================*
22677	 *                              buf_pool                                     *
22678	 *===========================================================================*/