96 lines
2.6 KiB
C
96 lines
2.6 KiB
C
#include "fs.h"
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#include "buf.h"
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#include "inode.h"
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#include <minix/com.h>
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#include <string.h>
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/*===========================================================================*
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* fs_readwrite *
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*===========================================================================*/
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int fs_readwrite(message *fs_m_in, message *fs_m_out)
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{
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int r, rw_flag;
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struct buf *bp;
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cp_grant_id_t gid;
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off_t position, f_size;
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unsigned int nrbytes, cum_io;
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pmode_t mode_word;
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struct inode *rip;
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pino_t inumb;
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r = OK;
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cum_io = 0;
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inumb = (pino_t) fs_m_in->REQ_INODE_NR;
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/* Find the inode referred */
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if ((rip = find_inode(inumb)) == NULL) return(EINVAL);
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mode_word = rip->i_mode & I_TYPE;
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if (mode_word != I_NAMED_PIPE) return(EIO);
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f_size = rip->i_size;
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/* Get the values from the request message */
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rw_flag = (fs_m_in->m_type == REQ_READ ? READING : WRITING);
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gid = (cp_grant_id_t) fs_m_in->REQ_GRANT;
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nrbytes = (unsigned) fs_m_in->REQ_NBYTES;
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/* We can't read beyond the max file position */
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if (nrbytes > PIPE_BUF) return(EFBIG);
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/* Mark inode in use */
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if ((get_inode(rip->i_dev, rip->i_num)) == NULL) return(err_code);
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if ((bp = get_block(rip->i_dev, rip->i_num)) == NULL) return(err_code);
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if (rw_flag == WRITING) {
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/* Check in advance to see if file will grow too big. */
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/* Casting nrbytes to signed is safe, because it's guaranteed not to
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* be beyond max signed value (i.e., MAX_FILE_POS).
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*/
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position = rip->i_size;
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if ((unsigned) position + nrbytes > PIPE_BUF) {
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put_inode(rip);
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put_block(rip->i_dev, rip->i_num);
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return(EFBIG);
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}
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} else {
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position = 0;
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if (nrbytes > rip->i_size) {
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/* There aren't that many bytes to read */
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nrbytes = rip->i_size;
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}
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}
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if (rw_flag == READING) {
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/* Copy a chunk from the block buffer to user space. */
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r = sys_safecopyto(VFS_PROC_NR, gid, (vir_bytes) 0,
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(vir_bytes) (bp->b_data+position), (size_t) nrbytes);
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} else {
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/* Copy a chunk from user space to the block buffer. */
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r = sys_safecopyfrom(VFS_PROC_NR, gid, (vir_bytes) 0,
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(vir_bytes) (bp->b_data+position), (size_t) nrbytes);
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}
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if (r == OK) {
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position += (signed) nrbytes; /* Update position */
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cum_io += nrbytes;
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}
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/* On write, update file size and access time. */
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if (rw_flag == WRITING) {
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rip->i_size = position;
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} else {
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memmove(bp->b_data, bp->b_data+nrbytes, rip->i_size - nrbytes);
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rip->i_size -= nrbytes;
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}
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if (rw_flag == READING) rip->i_update |= ATIME;
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if (rw_flag == WRITING) rip->i_update |= CTIME | MTIME;
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fs_m_out->RES_NBYTES = (size_t) cum_io;
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fs_m_out->RES_SEEK_POS_LO = rip->i_size;
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put_inode(rip);
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put_block(rip->i_dev, rip->i_num);
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return(r);
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}
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