C++ sb_bread函数代码示例

static inline Indirect *get_branch(struct inode *inode,
					int depth,
					int *offsets,
					Indirect chain[DEPTH],
					int *err)
{
	struct super_block *sb = inode->i_sb;
	Indirect *p = chain;
	struct buffer_head *bh;

	*err = 0;
	/* i_data is not going away, no lock needed */
	add_chain (chain, NULL, i_data(inode) + *offsets);
	if (!p->key)
		goto no_block;
	while (--depth) {
		bh = sb_bread(sb, block_to_cpu(p->key));
		if (!bh)
			goto failure;
		read_lock(&pointers_lock);
		if (!verify_chain(chain, p))
			goto changed;
		add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
		read_unlock(&pointers_lock);
		if (!p->key)
			goto no_block;
	}
	return NULL;

changed:
	read_unlock(&pointers_lock);
	brelse(bh);
	*err = -EAGAIN;
	goto no_block;
failure:
	*err = -EIO;
no_block:
	return p;
}

static int update_dind_extent_range(handle_t *handle, struct inode *inode,
				    ext4_fsblk_t pblock, ext4_lblk_t *blk_nump,
				    struct list_blocks_struct *lb)
{
	struct buffer_head *bh;
	__le32 *i_data;
	int i, retval = 0;
	ext4_lblk_t blk_count = *blk_nump;
	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;

	if (!pblock) {
		/* Only update the file block number */
		*blk_nump += max_entries * max_entries;
		return 0;
	}
	bh = sb_bread(inode->i_sb, pblock);
	if (!bh)
		return -EIO;

	i_data = (__le32 *)bh->b_data;
	for (i = 0; i < max_entries; i++) {
		if (i_data[i]) {
			retval = update_ind_extent_range(handle, inode,
						le32_to_cpu(i_data[i]),
						&blk_count, lb);
			if (retval)
				break;
		} else {
			/* Only update the file block number */
			blk_count += max_entries;
		}
	}

	/* Update the file block number */
	*blk_nump = blk_count;
	put_bh(bh);
	return retval;

}

/*
 * Read f2fs raw super block.
 * Because we have two copies of super block, so read the first one at first,
 * if the first one is invalid, move to read the second one.
 */
static int read_raw_super_block(struct super_block *sb,
			struct f2fs_super_block **raw_super,
			struct buffer_head **raw_super_buf)
{
	int block = 0;

retry:
	*raw_super_buf = sb_bread(sb, block);
	if (!*raw_super_buf) {
		f2fs_msg(sb, KERN_ERR, "Unable to read %dth superblock",
				block + 1);
		if (block == 0) {
			block++;
			goto retry;
		} else {
			return -EIO;
		}
	}

	*raw_super = (struct f2fs_super_block *)
		((char *)(*raw_super_buf)->b_data + F2FS_SUPER_OFFSET);

	/* sanity checking of raw super */
	if (sanity_check_raw_super(sb, *raw_super)) {
		brelse(*raw_super_buf);
		f2fs_msg(sb, KERN_ERR,
			"Can't find valid F2FS filesystem in %dth superblock",
								block + 1);
		if (block == 0) {
			block++;
			goto retry;
		} else {
			return -EINVAL;
		}
	}

	return 0;
}

int
ux_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
        unsigned long         pos;
        struct inode          *inode = filp->f_dentry->d_inode;
        struct ux_inode       *uip = (struct ux_inode *)
                                      &inode->i_private;
        struct ux_dirent      *udir;
        struct buffer_head    *bh;
        __u32                 blk;

start_again:
        pos = filp->f_pos;
        if (pos >= inode->i_size) {
                return 0;
        }
        blk = (pos + 1) / UX_BSIZE;
        blk = uip->i_addr[blk];
        bh = sb_bread(inode->i_sb, blk);
        udir = (struct ux_dirent *)(bh->b_data + pos % UX_BSIZE);

        /*
         * Skip over 'null' directory entries.
         */

        if (udir->d_ino == 0) {
                filp->f_pos += sizeof(struct ux_dirent);
                brelse(bh);
                goto start_again;
        } else {
                filldir(dirent, udir->d_name, 
                        sizeof(udir->d_name), pos, 
                        udir->d_ino, DT_UNKNOWN);
        }
        filp->f_pos += sizeof(struct ux_dirent);
        brelse(bh);
        return 0;        
}

/* Returns the inode number of the directory entry at offset pos. If bh is
   non-NULL, it is brelse'd before. Pos is incremented. The buffer header is
   returned in bh.
   AV. Most often we do it item-by-item. Makes sense to optimize.
   AV. OK, there we go: if both bh and de are non-NULL we assume that we just
   AV. want the next entry (took one explicit de=NULL in vfat/namei.c).
   AV. It's done in fat_get_entry() (inlined), here the slow case lives.
   AV. Additionally, when we return -1 (i.e. reached the end of directory)
   AV. we make bh NULL.
 */
static int fat__get_entry(struct inode *dir, loff_t *pos,
			  struct buffer_head **bh, struct msdos_dir_entry **de)
{
	struct super_block *sb = dir->i_sb;
	sector_t phys, iblock;
	unsigned long mapped_blocks;
	int err, offset;

next:
	if (*bh)
		brelse(*bh);

	*bh = NULL;
	iblock = *pos >> sb->s_blocksize_bits;
	err = fat_bmap(dir, iblock, &phys, &mapped_blocks, 0);
	if (err || !phys)
		return -1;	/* beyond EOF or error */

	fat_dir_readahead(dir, iblock, phys);

	*bh = sb_bread(sb, phys);
	if (*bh == NULL) {
/* [email protected] remove error message at pulling sd card without unmount */
#ifdef LGE_REMOVE_ERROR
		printk(KERN_ERR "FAT: Directory bread(block %llu) failed\n",
		       (llu)phys);
#endif
		/* skip this block */
		*pos = (iblock + 1) << sb->s_blocksize_bits;
		goto next;
	}

	offset = *pos & (sb->s_blocksize - 1);
	*pos += sizeof(struct msdos_dir_entry);
	*de = (struct msdos_dir_entry *)((*bh)->b_data + offset);

	return 0;
}

static int udf_symlink_filler(struct file *file, struct page *page)
{
	struct inode *inode = page->mapping->host;
	struct buffer_head *bh = NULL;
	char *symlink;
	int err = -EIO;
	char *p = kmap(page);
	struct udf_inode_info *iinfo;

	lock_kernel();
	iinfo = UDF_I(inode);
	if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
		symlink = iinfo->i_ext.i_data + iinfo->i_lenEAttr;
	} else {
		bh = sb_bread(inode->i_sb, udf_block_map(inode, 0));

		if (!bh)
			goto out;

		symlink = bh->b_data;
	}

	udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p);
	brelse(bh);

	unlock_kernel();
	SetPageUptodate(page);
	kunmap(page);
	unlock_page(page);
	return 0;

out:
	unlock_kernel();
	SetPageError(page);
	kunmap(page);
	unlock_page(page);
	return err;
}

ssize_t hellofs_read(struct file *filp, char __user *buf, size_t len,
                     loff_t *ppos) {
    struct super_block *sb;
    struct inode *inode;
    struct hellofs_inode *hellofs_inode;
    struct buffer_head *bh;
    char *buffer;
    int nbytes;

    inode = filp->f_path.dentry->d_inode;
    sb = inode->i_sb;
    hellofs_inode = HELLOFS_INODE(inode);
    
    if (*ppos >= hellofs_inode->file_size) {
        return 0;
    }

    bh = sb_bread(sb, hellofs_inode->data_block_no);
    if (!bh) {
        printk(KERN_ERR "Failed to read data block %llu\n",
               hellofs_inode->data_block_no);
        return 0;
    }

    buffer = (char *)bh->b_data + *ppos;
    nbytes = min((size_t)(hellofs_inode->file_size - *ppos), len);

    if (copy_to_user(buf, buffer, nbytes)) {
        brelse(bh);
        printk(KERN_ERR
               "Error copying file content to userspace buffer\n");
        return -EFAULT;
    }

    brelse(bh);
    *ppos += nbytes;
    return nbytes;
}

static int read_from_real_sfs(sfs_info_t *info, byte4_t block, byte4_t offset, void *buf, byte4_t len)
{
	byte4_t block_size = info->sb.block_size;
	byte4_t bd_block_size = info->vfs_sb->s_bdev->bd_block_size;
	byte4_t abs;
	struct buffer_head *bh;

	// Translating the real SFS block numbering to underlying block device block numbering, for sb_bread()
	abs = block * block_size + offset;
	block = abs / bd_block_size;
	offset = abs % bd_block_size;
	if (offset + len > bd_block_size) // Should never happen
	{
		return -EINVAL;
	}
	if (!(bh = sb_bread(info->vfs_sb, block)))
	{
		return -EIO;
	}
	memcpy(buf, bh->b_data + offset, len);
	brelse(bh);
	return 0;
}

struct buffer_head *
befs_bread(struct super_block *sb, befs_blocknr_t block)
{
	struct buffer_head *bh = NULL;

	befs_debug(sb, "---> Enter %s %lu", __func__, (unsigned long)block);

	bh = sb_bread(sb, block);

	if (bh == NULL) {
		befs_error(sb, "Failed to read block %lu",
			   (unsigned long)block);
		goto error;
	}

	befs_debug(sb, "<--- %s", __func__);

	return bh;

      error:
	befs_debug(sb, "<--- %s ERROR", __func__);
	return NULL;
}

struct ufs_buffer_head * ubh_bread_uspi (struct ufs_sb_private_info * uspi,
	struct super_block *sb, u64 fragment, u64 size)
{
	unsigned i, j;
	u64 count = 0;
	if (size & ~uspi->s_fmask)
		return NULL;
	count = size >> uspi->s_fshift;
	if (count <= 0 || count > UFS_MAXFRAG)
		return NULL;
	USPI_UBH(uspi)->fragment = fragment;
	USPI_UBH(uspi)->count = count;
	for (i = 0; i < count; i++)
		if (!(USPI_UBH(uspi)->bh[i] = sb_bread(sb, fragment + i)))
			goto failed;
	for (; i < UFS_MAXFRAG; i++)
		USPI_UBH(uspi)->bh[i] = NULL;
	return USPI_UBH(uspi);
failed:
	for (j = 0; j < i; j++)
		brelse (USPI_UBH(uspi)->bh[j]);
	return NULL;
}

struct minix_inode *
minix_V1_raw_inode(struct super_block *sb, ino_t ino, struct buffer_head **bh)
{
	int block;
	struct minix_sb_info *sbi = minix_sb(sb);
	struct minix_inode *p;

	if (!ino || ino > sbi->s_ninodes) {
		printk("Bad inode number on dev %s: %ld is out of range\n",
		       sb->s_id, (long)ino);
		return NULL;
	}
	ino--;
	block = 2 + sbi->s_imap_blocks + sbi->s_zmap_blocks +
		 ino / MINIX_INODES_PER_BLOCK;
	*bh = sb_bread(sb, block);
	if (!*bh) {
		printk("Unable to read inode block\n");
		return NULL;
	}
	p = (void *)(*bh)->b_data;
	return p + ino % MINIX_INODES_PER_BLOCK;
}

/*
 * Initialize a data index block for specified inode at specified block number
 *
 */
int lab5fs_inode_init_block_index(struct inode *ino, int bi_block_num)
{
	int err = 0;
	struct super_block *sb = ino->i_sb;
	struct buffer_head *bibh = NULL;
	struct lab5fs_inode_data_index *lab5fs_data_index = NULL;

	/* read the inode's block index. */
	if (!(bibh = sb_bread(sb, bi_block_num))) {
		printk("unable to read inode block index, block %d.\n",
				bi_block_num);
		err = -ENOMEM;
		goto ret;
	}
	lab5fs_data_index = (struct lab5fs_inode_data_index *)(bibh->b_data);
	memset(lab5fs_data_index->blocks, 0, sizeof(*lab5fs_data_index));
	mark_buffer_dirty(bibh);

ret:
	if (bibh)
		brelse(bibh);
	return err;
}

/*Clear out data and data index blocks of given inode*/
void lab5fs_inode_clear_blocks(struct inode *ino){
	struct super_block *sb = ino->i_sb;
	struct lab5fs_inode_info *inode_info = LAB5FS_INODE_INFO(ino);
	int bi_block_num = inode_info->i_bi_block_num;
	struct buffer_head *bibh = NULL;
	struct lab5fs_inode_data_index *block_index_table = NULL;
	int i, block_num;
	printk("inode_clear_blocks:: freeing data blocks \n");

	/* read the inode's block index. */
	if (!(bibh = sb_bread(sb, bi_block_num))) {
		printk("unable to read block index, block %d.\n",bi_block_num);
	}
	block_index_table = (struct lab5fs_inode_data_index *) bibh->b_data;
	for (i=0;i < LAB5FS_MAX_BLOCK_INDEX; i++) {
		block_num = le32_to_cpu(block_index_table->blocks[i]);
		if (block_num != 0) { //block is in used
			printk("freeing block %u\n",block_num);
			lab5fs_release_block_num(sb, block_num);
		}
	}
	ino->i_blocks=0;
}

static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
{
	struct buffer_head * bh;
	unsigned long nr;

	if (depth--) {
		for ( ; p < q ; p++) {
			nr = block_to_cpu(*p);
			if (!nr)
				continue;
			*p = 0;
			bh = sb_bread(inode->i_sb, nr);
			if (!bh)
				continue;
			free_branches(inode, (block_t*)bh->b_data,
				      block_end(bh), depth);
			bforget(bh);
			xiafs_free_block(inode, nr);
			mark_inode_dirty(inode);
		}
	} else
		free_data(inode, p, q);
}

void dedupfs_inode_add(struct super_block *vsb, 
						struct dedupfs_inode *inode)
{
	struct dedupfs_super_block *sb = DEDUPFS_SB(vsb);
	struct buffer_head *bh;
	struct dedupfs_inode *inode_iterator;

	if(mutex_lock_interruptible(&dedupfs_inodes_mgmt_lock)) {
		printk(KERN_ERR "Failed to acquire mutex lock %s +%d\n",
					__FILE__, __LINE__);
		return;
	}

	bh = (struct buffer_head *)sb_bread(vsb,
									DEDUPFS_INODESTORE_BLOCK_NUMBER);

	inode_iterator = (struct dedupfs_inode *)bh->b_data;

	if(mutex_lock_interruptible(&dedupfs_sb_lock)) {
		printk(KERN_ERR "Failed to acquire mutex lock %s +%d\n",
							__FILE__, __LINE__);	
		return;
	}

	/* Append the new inode in the end in the inode store */
	inode_iterator += sb->inodes_count;

	memcpy(inode_iterator, inode, sizeof(struct dedupfs_inode));
	sb->inodes_count++;

	mark_buffer_dirty(bh);
	dedupfs_sb_sync(vsb);

	mutex_unlock(&dedupfs_sb_lock);
	mutex_unlock(&dedupfs_inodes_mgmt_lock);

}