root/fs/ext2/file.c

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DEFINITIONS

This source file includes following definitions.
  1. ext2_file_read
  2. ext2_file_write
  3. ext2_release_file

   1 /*
   2  *  linux/fs/ext2/file.c
   3  *
   4  *  Copyright (C) 1992, 1993, 1994  Remy Card (card@masi.ibp.fr)
   5  *                                  Laboratoire MASI - Institut Blaise Pascal
   6  *                                  Universite Pierre et Marie Curie (Paris VI)
   7  *
   8  *  from
   9  *
  10  *  linux/fs/minix/file.c
  11  *
  12  *  Copyright (C) 1991, 1992  Linus Torvalds
  13  *
  14  *  ext2 fs regular file handling primitives
  15  */
  16 
  17 #include <asm/segment.h>
  18 #include <asm/system.h>
  19 
  20 #include <linux/errno.h>
  21 #include <linux/fs.h>
  22 #include <linux/ext2_fs.h>
  23 #include <linux/fcntl.h>
  24 #include <linux/sched.h>
  25 #include <linux/stat.h>
  26 #include <linux/locks.h>
  27 
  28 #define NBUF    32
  29 
  30 #define MIN(a,b) (((a)<(b))?(a):(b))
  31 #define MAX(a,b) (((a)>(b))?(a):(b))
  32 
  33 #include <linux/fs.h>
  34 #include <linux/ext2_fs.h>
  35 
  36 static int ext2_file_read (struct inode *, struct file *, char *, int);
  37 static int ext2_file_write (struct inode *, struct file *, char *, int);
  38 static void ext2_release_file (struct inode *, struct file *);
  39 
  40 /*
  41  * We have mostly NULL's here: the current defaults are ok for
  42  * the ext2 filesystem.
  43  */
  44 static struct file_operations ext2_file_operations = {
  45         NULL,                   /* lseek - default */
  46         ext2_file_read,         /* read */
  47         ext2_file_write,        /* write */
  48         NULL,                   /* readdir - bad */
  49         NULL,                   /* select - default */
  50         ext2_ioctl,             /* ioctl */
  51         generic_mmap,           /* mmap */
  52         NULL,                   /* no special open is needed */
  53         ext2_release_file,      /* release */
  54         ext2_sync_file          /* fsync */
  55 };
  56 
  57 struct inode_operations ext2_file_inode_operations = {
  58         &ext2_file_operations,/* default file operations */
  59         NULL,                   /* create */
  60         NULL,                   /* lookup */
  61         NULL,                   /* link */
  62         NULL,                   /* unlink */
  63         NULL,                   /* symlink */
  64         NULL,                   /* mkdir */
  65         NULL,                   /* rmdir */
  66         NULL,                   /* mknod */
  67         NULL,                   /* rename */
  68         NULL,                   /* readlink */
  69         NULL,                   /* follow_link */
  70         ext2_bmap,              /* bmap */
  71         ext2_truncate,          /* truncate */
  72         ext2_permission         /* permission */
  73 };
  74 
  75 static int ext2_file_read (struct inode * inode, struct file * filp,
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  76                     char * buf, int count)
  77 {
  78         int read, left, chars;
  79         int block, blocks, offset;
  80         int bhrequest, uptodate;
  81         struct buffer_head ** bhb, ** bhe;
  82         struct buffer_head * bhreq[NBUF];
  83         struct buffer_head * buflist[NBUF];
  84         struct super_block * sb;
  85         unsigned int size;
  86         int err;
  87 
  88         if (!inode) {
  89                 printk ("ext2_file_read: inode = NULL\n");
  90                 return -EINVAL;
  91         }
  92         sb = inode->i_sb;
  93         if (!S_ISREG(inode->i_mode)) {
  94                 ext2_warning (sb, "ext2_file_read", "mode = %07o",
  95                               inode->i_mode);
  96                 return -EINVAL;
  97         }
  98         offset = filp->f_pos;
  99         size = inode->i_size;
 100         if (offset > size)
 101                 left = 0;
 102         else
 103                 left = size - offset;
 104         if (left > count)
 105                 left = count;
 106         if (left <= 0)
 107                 return 0;
 108         read = 0;
 109         block = offset >> EXT2_BLOCK_SIZE_BITS(sb);
 110         offset &= (sb->s_blocksize - 1);
 111         size = (size + sb->s_blocksize - 1) >> EXT2_BLOCK_SIZE_BITS(sb);
 112         blocks = (left + offset + sb->s_blocksize - 1) >> EXT2_BLOCK_SIZE_BITS(sb);
 113         bhb = bhe = buflist;
 114         if (filp->f_reada) {
 115                 blocks += read_ahead[MAJOR(inode->i_dev)] >>
 116                         (EXT2_BLOCK_SIZE_BITS(sb) - 9);
 117                 if (block + blocks > size)
 118                         blocks = size - block;
 119         }
 120 
 121         /*
 122          * We do this in a two stage process.  We first try and request
 123          * as many blocks as we can, then we wait for the first one to
 124          * complete, and then we try and wrap up as many as are actually
 125          * done.  This routine is rather generic, in that it can be used
 126          * in a filesystem by substituting the appropriate function in
 127          * for getblk
 128          *
 129          * This routine is optimized to make maximum use of the various
 130          * buffers and caches.
 131          */
 132 
 133         do {
 134                 bhrequest = 0;
 135                 uptodate = 1;
 136                 while (blocks) {
 137                         --blocks;
 138                         *bhb = ext2_getblk (inode, block++, 0, &err);
 139                         if (*bhb && !(*bhb)->b_uptodate) {
 140                                 uptodate = 0;
 141                                 bhreq[bhrequest++] = *bhb;
 142                         }
 143 
 144                         if (++bhb == &buflist[NBUF])
 145                                 bhb = buflist;
 146 
 147                         /*
 148                          * If the block we have on hand is uptodate, go ahead
 149                          * and complete processing
 150                          */
 151                         if (uptodate)
 152                                 break;
 153 
 154                         if (bhb == bhe)
 155                                 break;
 156                 }
 157 
 158                 /*
 159                  * Now request them all
 160                  */
 161                 if (bhrequest)
 162                         ll_rw_block (READ, bhrequest, bhreq);
 163 
 164                 do {
 165                         /*
 166                          * Finish off all I/O that has actually completed
 167                          */
 168                         if (*bhe) {
 169                                 wait_on_buffer (*bhe);
 170                                 if (!(*bhe)->b_uptodate) { /* read error? */
 171                                         brelse(*bhe);
 172                                         if (++bhe == &buflist[NBUF])
 173                                           bhe = buflist;
 174                                         left = 0;
 175                                         break;
 176                                 }
 177                         }
 178                         if (left < sb->s_blocksize - offset)
 179                                 chars = left;
 180                         else
 181                                 chars = sb->s_blocksize - offset;
 182                         filp->f_pos += chars;
 183                         left -= chars;
 184                         read += chars;
 185                         if (*bhe) {
 186                                 memcpy_tofs (buf, offset + (*bhe)->b_data,
 187                                              chars);
 188                                 brelse (*bhe);
 189                                 buf += chars;
 190                         } else {
 191                                 while (chars-- > 0)
 192                                         put_fs_byte (0, buf++);
 193                         }
 194                         offset = 0;
 195                         if (++bhe == &buflist[NBUF])
 196                                 bhe = buflist;
 197                 } while (left > 0 && bhe != bhb && (!*bhe || !(*bhe)->b_lock));
 198         } while (left > 0);
 199 
 200         /*
 201          * Release the read-ahead blocks
 202          */
 203         while (bhe != bhb) {
 204                 brelse (*bhe);
 205                 if (++bhe == &buflist[NBUF])
 206                         bhe = buflist;
 207         }
 208         if (!read)
 209                 return -EIO;
 210         filp->f_reada = 1;
 211         if (!IS_RDONLY(inode)) {
 212                 inode->i_atime = CURRENT_TIME;
 213                 inode->i_dirt = 1;
 214         }
 215         return read;
 216 }
 217 
 218 static int ext2_file_write (struct inode * inode, struct file * filp,
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 219                             char * buf, int count)
 220 {
 221         off_t pos;
 222         int written, c;
 223         struct buffer_head * bh;
 224         char * p;
 225         struct super_block * sb;
 226         int err;
 227 
 228         if (!inode) {
 229                 printk("ext2_file_write: inode = NULL\n");
 230                 return -EINVAL;
 231         }
 232         sb = inode->i_sb;
 233         if (sb->s_flags & MS_RDONLY)
 234                 /*
 235                  * This fs has been automatically remounted ro because of errors
 236                  */
 237                 return -ENOSPC;
 238 
 239         if (!S_ISREG(inode->i_mode)) {
 240                 ext2_warning (sb, "ext2_file_write", "mode = %07o\n",
 241                               inode->i_mode);
 242                 return -EINVAL;
 243         }
 244 /*
 245  * ok, append may not work when many processes are writing at the same time
 246  * but so what. That way leads to madness anyway.
 247  */
 248         if (filp->f_flags & O_APPEND)
 249                 pos = inode->i_size;
 250         else
 251                 pos = filp->f_pos;
 252         written = 0;
 253         while (written < count) {
 254                 bh = ext2_getblk (inode, pos / sb->s_blocksize, 1, &err);
 255                 if (!bh) {
 256                         if (!written)
 257                                 written = err;
 258                         break;
 259                 }
 260                 c = sb->s_blocksize - (pos % sb->s_blocksize);
 261                 if (c > count-written)
 262                         c = count - written;
 263                 if (c != sb->s_blocksize && !bh->b_uptodate) {
 264                         ll_rw_block (READ, 1, &bh);
 265                         wait_on_buffer (bh);
 266                         if (!bh->b_uptodate) {
 267                                 brelse (bh);
 268                                 if (!written)
 269                                         written = -EIO;
 270                                 break;
 271                         }
 272                 }
 273                 p = (pos % sb->s_blocksize) + bh->b_data;
 274                 pos += c;
 275                 if (pos > inode->i_size) {
 276                         inode->i_size = pos;
 277                         inode->i_dirt = 1;
 278                 }
 279                 written += c;
 280                 memcpy_fromfs (p, buf, c);
 281                 buf += c;
 282                 bh->b_uptodate = 1;
 283                 bh->b_dirt = 1;
 284                 brelse (bh);
 285         }
 286         inode->i_ctime = inode->i_mtime = CURRENT_TIME;
 287         filp->f_pos = pos;
 288         inode->i_dirt = 1;
 289         return written;
 290 }
 291 
 292 /*
 293  * Called when a inode is released. Note that this is different
 294  * from ext2_open: open gets called at every open, but release
 295  * gets called only when /all/ the files are closed.
 296  */
 297 static void ext2_release_file (struct inode * inode, struct file * filp)
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 298 {
 299         if (filp->f_mode & 2)
 300                 ext2_discard_prealloc (inode);
 301 }

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