servers/pfs/read.c

   1 #include "fs.h"
   2 #include "buf.h"
   3 #include <minix/com.h>
   4 #include <string.h>
   5 #include <minix/u64.h>
   6 #include "inode.h"
   7
   8
   9 /*===========================================================================*
  10  *                              fs_readwrite                                 *
  11  *===========================================================================*/
  12 PUBLIC int fs_readwrite(void)
  13 {
  14   int r, rw_flag;
  15   struct buf *bp;
  16   cp_grant_id_t gid;
  17   off_t position, f_size;
  18   unsigned int nrbytes, cum_io;
  19   mode_t mode_word;
  20   struct inode *rip;
  21   ino_t inumb;
  22
  23   r = OK;
  24   cum_io = 0;
  25   inumb = fs_m_in.REQ_INODE_NR;
  26   rw_flag = (fs_m_in.m_type == REQ_READ ? READING : WRITING);
  27
  28   /* Find the inode referred */
  29   if ((rip = find_inode(inumb)) == NIL_INODE) return(EINVAL);
  30
  31   mode_word = rip->i_mode & I_TYPE;
  32   if (mode_word != I_NAMED_PIPE) return(EIO);
  33   f_size = rip->i_size;
  34
  35   /* Get the values from the request message */
  36   rw_flag = (fs_m_in.m_type == REQ_READ ? READING : WRITING);
  37   gid = fs_m_in.REQ_GRANT;
  38   position = fs_m_in.REQ_SEEK_POS_LO;
  39   nrbytes = (unsigned) fs_m_in.REQ_NBYTES;
  40
  41   if (rw_flag == WRITING) {
  42           /* Check in advance to see if file will grow too big. */
  43           if (position > PIPE_BUF - nrbytes) return(EFBIG);
  44   }
  45
  46   /* Mark inode in use */
  47   if ((get_inode(rip->i_dev, rip->i_num)) == NIL_INODE) return(err_code);
  48   if ((bp = get_block(rip->i_dev, rip->i_num)) == NIL_BUF) return(err_code);
  49
  50   if (rw_flag == READING) {
  51         /* Copy a chunk from the block buffer to user space. */
  52         r = sys_safecopyto(FS_PROC_NR, gid, 0,
  53                 (vir_bytes) (bp->b_data+position), (phys_bytes) nrbytes, D);
  54   } else {
  55         /* Copy a chunk from user space to the block buffer. */
  56         r = sys_safecopyfrom(FS_PROC_NR, gid, 0,
  57                 (vir_bytes) (bp->b_data+position), (phys_bytes) nrbytes, D);
  58   }
  59
  60   if (r == OK) {
  61         position += nrbytes; /* Update position */
  62         cum_io += nrbytes;
  63   }
  64
  65   fs_m_out.RES_SEEK_POS_LO = position; /* It might change later and the VFS
  66                                            has to know this value */
  67
  68   /* On write, update file size and access time. */
  69   if (rw_flag == WRITING) {
  70           if (position > f_size) rip->i_size = position;
  71   } else {
  72         if(position >= rip->i_size) {
  73                 /* All data in the pipe is read, so reset pipe pointers */
  74                 rip->i_size = 0;        /* no data left */
  75                 position = 0;           /* reset reader(s) */
  76         }
  77   }
  78
  79   bp->b_bytes = position;
  80   if (rw_flag == READING) rip->i_update |= ATIME;
  81   if (rw_flag == WRITING) rip->i_update |= CTIME | MTIME;
  82   fs_m_out.RES_NBYTES = cum_io;
  83   put_inode(rip);
  84   put_block(rip->i_dev, rip->i_num);
  85
  86   return(r);
  87 }
  88