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/* file.c
read files on EFS filesystems
now replaced by generic functions of the kernel:
leaves only mapping of file block number -> disk block number in this file
(C)95,96 Christian Vogelgsang
*/
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/efs_fs.h>
#include <linux/efs_fs_i.h>
#include <linux/efs_fs_sb.h>
#include <linux/stat.h>
#include <asm/uaccess.h>
static struct file_operations efs_file_ops = {
NULL,
generic_file_read,
NULL,
NULL,
NULL,
NULL,
generic_file_mmap,
NULL,
NULL,
NULL
};
struct inode_operations efs_file_in_ops = {
&efs_file_ops,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
generic_readpage,
NULL,
efs_bmap,
NULL,
NULL
};
#define MIN(a,b) ((a)<(b)?(a):(b))
#define CHECK(num) \
eblk = ini->extents[num].ex_bytes[0]; \
epos = ini->extents[num].ex_bytes[1] & 0xffffff; \
elen = ini->extents[num].ex_bytes[1] >> 24; \
if((blk >= epos)&&(blk < (epos+elen))) \
result = (blk - epos) + eblk + sbi->fs_start;
/* ----- efs_getblknum -----
find the disc block number for a given logical file block number
in - inode of file
blk - logical file block number
return - 0 on error, or unmapped block number
*/
static __u32 efs_getblk(struct inode *in,__u32 blk)
{
struct efs_sb_info *sbi = &in->i_sb->u.efs_sb;
struct efs_inode_info *ini = &in->u.efs_i;
struct buffer_head *bh;
__u32 result = 0;
__u32 eblk,epos,elen;
int num,extnum,readahead;
__u32 extblk;
__u16 extoff,pos,cur,tot;
union efs_extent *ptr;
/* first check the current extend */
cur = ini->cur;
tot = ini->tot;
CHECK(cur)
if(result)
return result;
/* if only one extent exists and we are here the test failed */
if(tot==1) {
printk("efs: bmap failed on one extent!\n");
return 0;
}
/* check the stored extents in the inode */
num = MIN(tot,EFS_MAX_EXTENTS);
for(pos=0;pos<num;pos++) {
/* don't check the current again! */
if(pos==cur)
continue;
CHECK(pos)
if(result) {
ini->cur = pos;
return result;
}
}
/* If the inode has only direct extents,
the above tests must have found the block's extend! */
if(tot<=EFS_MAX_EXTENTS) {
printk("efs: bmap failed for direct extents!\n");
return 0;
}
/* --- search in the indirect extensions list blocks --- */
#ifdef DEBUG
printk("efs - indirect search for %lu\n",blk);
#endif
/* calculate block and offset for begin of extent descr and read it */
extblk = ini->extblk;
extoff = 0;
bh = bread(in->i_dev,extblk,EFS_BLOCK_SIZE);
if(!bh) {
printk("efs: read error in indirect extents\n");
return 0;
}
ptr = (union efs_extent *)bh->b_data;
pos = 0; /* number of extend store in the inode */
extnum = 0; /* count the extents in the indirect blocks */
readahead = 10; /* number of extents to read ahead */
while(1) {
/* skip last current extent store in the inode */
if(pos==cur) pos++;
/* read new extent in inode buffer */
ini->extents[pos].ex_bytes[0] = efs_swab32(ptr[pos].ex_bytes[0]);
ini->extents[pos].ex_bytes[1] = efs_swab32(ptr[pos].ex_bytes[1]);
/* we must still search */
if(!result) {
CHECK(pos)
if(result)
ini->cur = pos;
}
/* we found it already and read ahead */
else {
readahead--;
if(!readahead)
break;
}
/* next storage place */
pos++;
extnum++;
/* last extent checked -> finished */
if(extnum==tot) {
if(!result)
printk("efs: bmap on indirect failed!\n");
break;
}
extoff += 8;
/* need new block */
if(extoff==EFS_BLOCK_SIZE) {
extoff = 0;
extblk++;
brelse(bh);
bh = bread(in->i_dev,extblk,EFS_BLOCK_SIZE);
if(!bh) {
printk("efs: read error in indirect extents\n");
return 0;
}
ptr = (union efs_extent *)bh->b_data;
}
}
brelse(bh);
return result;
}
/* ----- efs_bmap -----
bmap: map a file block number to a device block number
in - inode owning the block
block - block number
return - disk block
*/
int efs_bmap(struct inode *in, int block)
{
/* quickly reject invalid block numbers */
if(block<0) {
#ifdef DEBUG
printk("efs_bmap: block < 0\n");
#endif
return 0;
}
/* since the kernel wants to read a full page of data, i.e. 8 blocks
we must check if the block number is not too large */
if(block>((in->i_size-1)>>EFS_BLOCK_SIZE_BITS)) {
#ifdef DEBUG
printk("efs_bmap: block %d > max %d == %d\n",
block,in->i_size>>EFS_BLOCK_SIZE_BITS,in->i_blocks);
#endif
return 0;
}
return efs_getblk(in,block);
}
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