fs/ufs/ufs_file.c

/* */
This source file includes following definitions.
ufs_bmap
   1 /*
   2  *  linux/fs/ufs/ufs_file.c
   3  *
   4  * Copyright (C) 1996
   5  * Adrian Rodriguez (adrian@franklins-tower.rutgers.edu)
   6  * Laboratory for Computer Science Research Computing Facility
   7  * Rutgers, The State University of New Jersey
   8  *
   9  * $Id: ufs_file.c,v 1.3 1996/04/25 09:12:02 davem Exp $
  10  *
  11  */
  12 
  13 #include <linux/fs.h>
  14 
  15 /*
  16  * Return values:
  17  *   0:  bmap failed
  18  *  nonzero: absolute "block" number
  19  */
  20 int ufs_bmap (struct inode * inode, int block)
     /*  */
  21 {
  22         unsigned long int fsblkno, phys_block, lfsblkno;
  23         struct buffer_head * bh;
  24 
  25         /*
  26          * Note that contrary to what the BSD source calls these things,
  27          * blkno and lblkno are *frags* (1024), not UFS blocks (8192).
  28          * XXX - maybe I'm wrong, and ui_blocks is really 512-blocks...
  29          */
  30 
  31         /*
  32          * Ok, I think I figured out what is going on.  ui_blocks is the
  33          * number of 512-byte blocks that are allocated to the file.  The
  34          * elements in ui_db[UFS_NDADDR] are pointers to 1024-byte aligned
  35          * 8192 byte objects.  The entire 8192 bytes (16 512-blocks) may
  36          * not be allocated to the file in question - use ui_blocks to see
  37          * how many of the blocks are allocated.  Also, use ui_size to see
  38          * what fraction of the last block is allocated to the file, and
  39          * what fraction is unused.  I have not yet seen a file with a
  40          * hole in it, but I'd guess that a hole must be at least 8192
  41          * bytes of zeros, and it's represented by a zero in ui_db[X].
  42          *
  43          * Yes, this means that there is more than one way to name a given
  44          * 512-byte block on the disk. Because of the 1024-byte alignment
  45          * of 8192-byte filesystem blocks, a given 512-byte disk block
  46          * could be referred to in eight different ways.
  47          */
  48 
  49         /*
  50          * block is the logical 1024-block in the file
  51          * lfsblkno is the logical 8192-block in the file
  52          * fsblkno is the physical 8192-block
  53          * phys_block is the 1024-block
  54          */
  55         lfsblkno = block>>3;
  56 
  57         if (block < UFS_NDADDR) {
  58                 /* It's a direct block */
  59                 fsblkno = inode->u.ufs_i.ui_db[lfsblkno]; /* XXX */
  60 #if 0
  61                 phys_block = ufs_cgdmin(inode->i_sb, ufs_ino2cg(inode)) +
  62                         blkno%(inode->i_sb->u.ufs_sb.s_fpg);
  63 #endif
  64                 phys_block = fsblkno + ((block & 0x7)<<10); /* XXX */
  65                 if (inode->i_sb->u.ufs_sb.s_flags & UFS_DEBUG) {
  66                         printk("ufs_bmap: mapped ino %lu  logical %u to %lu (phys %lu)\n",
  67                                inode->i_ino, block, fsblkno, phys_block);
  68                 }
  69                 return(phys_block);
  70         } else {
  71                 /* Need to use indirect blocks */
  72                 /* XXX - bmap through indirect blocks not implemented */
  73                 block -= UFS_NDADDR;
  74                 if (block < (inode->i_sb->s_blocksize/sizeof(__u32))) {
  75                         bh = bread(inode->i_dev, inode->u.ufs_i.ui_ib[0],
  76                                    BLOCK_SIZE);
  77                         if (bh == NULL) {
  78                                 printk("ufs_bmap: can't map block %u, ino %lu\n",
  79                                        block + UFS_NDADDR, inode->i_ino);
  80                                 return(0);
  81                         }
  82                         phys_block = ((__u32 *)bh->b_data)[block];
  83                         brelse(bh);
  84                         printk("ufs_bmap: imap ino %lu block %u phys %lu\n",
  85                                inode->i_ino, block + UFS_NDADDR, phys_block);
  86                         return(phys_block);
  87                 } else {
  88                         printk("ufs_bmap: ino %lu: indirect blocks not implemented\n",
  89                                inode->i_ino);
  90                         return(0);
  91                 }
  92         }
  93 
  94         return(0);
  95 }
  96 
  97 static struct file_operations ufs_file_operations = {
  98         NULL,                   /* lseek */
  99         generic_file_read,      /* read */
 100         NULL,                   /* write */
 101         NULL,                   /* readdir */
 102         NULL,                   /* select */
 103         NULL,                   /* ioctl */
 104         generic_file_mmap,      /* mmap */
 105         NULL,                   /* open */
 106         NULL,                   /* release */
 107         file_fsync,             /* fsync */
 108         NULL,                   /* fasync */
 109         NULL,                   /* check_media_change */
 110         NULL,                   /* revalidate */
 111 };
 112 
 113 struct inode_operations ufs_file_inode_operations = {
 114         &ufs_file_operations,   /* default directory file operations */
 115         NULL,                   /* create */
 116         NULL,                   /* lookup */
 117         NULL,                   /* link */
 118         NULL,                   /* unlink */
 119         NULL,                   /* symlink */
 120         NULL,                   /* mkdir */
 121         NULL,                   /* rmdir */
 122         NULL,                   /* mknod */
 123         NULL,                   /* rename */
 124         NULL,                   /* readlink */
 125         NULL,                   /* follow_link */
 126         generic_readpage,       /* readpage */
 127         NULL,                   /* writepage */
 128         ufs_bmap,               /* bmap */
 129         NULL,                   /* truncate */
 130         NULL,                   /* permission */
 131         NULL,                   /* smap */
 132 };
 133 
 134 
 135 /*
 136  * Local Variables: ***
 137  * c-indent-level: 8 ***
 138  * c-continued-statement-offset: 8 ***
 139  * c-brace-offset: -8 ***
 140  * c-argdecl-indent: 0 ***
 141  * c-label-offset: -8 ***
 142  * End: ***
 143  */
/* */
root/fs/ufs/ufs_file.c

DEFINITIONS
