journal_ext2.c

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

/*
 * Intermezzo. (C) 1998 Peter J. Braam
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/locks.h>
#include <asm/segment.h>
#include <asm/uaccess.h>
#include <linux/string.h>
#include <linux/ext2_fs.h> 

#include <linux/intermezzo_fs.h>
#include <linux/intermezzo_upcall.h>
#include <linux/intermezzo_psdev.h>
#include <linux/intermezzo_kml.h>

#if defined(CONFIG_EXT2_FS)

/* EXT2 has no journalling, so these functions do nothing */
static loff_t presto_e2_freespace(struct presto_cache *cache,
                                         struct super_block *sb)
{
        unsigned long freebl = le32_to_cpu(sb->u.ext2_sb.s_es->s_free_blocks_count);
        unsigned long avail =   freebl - le32_to_cpu(sb->u.ext2_sb.s_es->s_r_blocks_count);
	return (avail <<  EXT2_BLOCK_SIZE_BITS(sb));
}

/* start the filesystem journal operations */
static void *presto_e2_trans_start(struct presto_file_set *fset, struct inode *inode, int op)
{
        __u32 avail_kmlblocks;

        if ( presto_no_journal(fset) ||
             strcmp(fset->fset_cache->cache_type, "ext2"))
                return NULL;

        avail_kmlblocks = inode->i_sb->u.ext2_sb.s_es->s_free_blocks_count;
        
        if ( avail_kmlblocks < 3 ) {
                return ERR_PTR(-ENOSPC);
        }
        
        if (  (op != PRESTO_OP_UNLINK && op != PRESTO_OP_RMDIR)
              && avail_kmlblocks < 6 ) {
                return ERR_PTR(-ENOSPC);
        }            
	return (void *) 1;
}

static void presto_e2_trans_commit(struct presto_file_set *fset, void *handle)
{
  do {} while (0);
}

struct journal_ops presto_ext2_journal_ops = {
        tr_avail: presto_e2_freespace,
        tr_start: presto_e2_trans_start,
        tr_commit: presto_e2_trans_commit,
        tr_journal_data: NULL
};

#endif /* CONFIG_EXT2_FS */