C++ EXT4_SB函数代码示例

static ssize_t
ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
{
	struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
	int unaligned_aio = 0;
	int ret;

	/*
	 * If we have encountered a bitmap-format file, the size limit
	 * is smaller than s_maxbytes, which is for extent-mapped files.
	 */

	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
		size_t length = iov_length(iov, nr_segs);

		if ((pos > sbi->s_bitmap_maxbytes ||
		    (pos == sbi->s_bitmap_maxbytes && length > 0)))
			return -EFBIG;

		if (pos + length > sbi->s_bitmap_maxbytes) {
			nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
					      sbi->s_bitmap_maxbytes - pos);
		}
	} else if (unlikely((iocb->ki_filp->f_flags & O_DIRECT) &&
		   !is_sync_kiocb(iocb))) {
		unaligned_aio = ext4_unaligned_aio(inode, iov, nr_segs, pos);
	}

	/* Unaligned direct AIO must be serialized; see comment above */
	if (unaligned_aio) {
		static unsigned long unaligned_warn_time;

		/* Warn about this once per day */
		if (printk_timed_ratelimit(&unaligned_warn_time, 60*60*24*HZ))
			ext4_msg(inode->i_sb, KERN_WARNING,
				 "Unaligned AIO/DIO on inode %ld by %s; "
				 "performance will be poor.",
				 inode->i_ino, current->comm);
		mutex_lock(ext4_aio_mutex(inode));
		ext4_aiodio_wait(inode);
	}

	ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

	if (unaligned_aio)
		mutex_unlock(ext4_aio_mutex(inode));

	return ret;
}

static int ext4_file_open(struct inode * inode, struct file * filp)
{
	struct super_block *sb = inode->i_sb;
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct vfsmount *mnt = filp->f_path.mnt;
	struct path path;
	char buf[64], *cp;

	if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
		     !(sb->s_flags & MS_RDONLY))) {
		sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
		/*
		 * Sample where the filesystem has been mounted and
		 * store it in the superblock for sysadmin convenience
		 * when trying to sort through large numbers of block
		 * devices or filesystem images.
		 */
		memset(buf, 0, sizeof(buf));
		path.mnt = mnt;
		path.dentry = mnt->mnt_root;
		cp = d_path(&path, buf, sizeof(buf));
		if (!IS_ERR(cp)) {
			strlcpy(sbi->s_es->s_last_mounted, cp,
				sizeof(sbi->s_es->s_last_mounted));
			ext4_mark_super_dirty(sb);
		}
	}
	/*
	 * Set up the jbd2_inode if we are opening the inode for
	 * writing and the journal is present
	 */
	if (sbi->s_journal && !ei->jinode && (filp->f_mode & FMODE_WRITE)) {
		struct jbd2_inode *jinode = jbd2_alloc_inode(GFP_KERNEL);

		spin_lock(&inode->i_lock);
		if (!ei->jinode) {
			if (!jinode) {
				spin_unlock(&inode->i_lock);
				return -ENOMEM;
			}
			ei->jinode = jinode;
			jbd2_journal_init_jbd_inode(ei->jinode, inode);
			jinode = NULL;
		}
		spin_unlock(&inode->i_lock);
		if (unlikely(jinode != NULL))
			jbd2_free_inode(jinode);
	}
	return dquot_file_open(inode, filp);
}

/**
 * ext4_count_free_blocks() -- count filesystem free blocks
 * @sb:		superblock
 *
 * Adds up the number of free blocks from each block group.
 */
ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
{
	ext4_fsblk_t desc_count;
	struct ext4_group_desc *gdp;
	ext4_group_t i;
	ext4_group_t ngroups = ext4_get_groups_count(sb);
#ifdef EXT4FS_DEBUG
	struct ext4_super_block *es;
	ext4_fsblk_t bitmap_count;
	unsigned int x;
	struct buffer_head *bitmap_bh = NULL;

	es = EXT4_SB(sb)->s_es;
	desc_count = 0;
	bitmap_count = 0;
	gdp = NULL;

	for (i = 0; i < ngroups; i++) {
		gdp = ext4_get_group_desc(sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += ext4_free_blks_count(sb, gdp);
		brelse(bitmap_bh);
		bitmap_bh = ext4_read_block_bitmap(sb, i);
		if (bitmap_bh == NULL)
			continue;

		x = ext4_count_free(bitmap_bh->b_data,
				    EXT4_BLOCKS_PER_GROUP(sb) / 8);
		printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
			i, ext4_free_blks_count(sb, gdp), x);
		bitmap_count += x;
	}
	brelse(bitmap_bh);
	printk(KERN_DEBUG "ext4_count_free_blocks: stored = %llu"
		", computed = %llu, %llu\n", ext4_free_blocks_count(es),
	       desc_count, bitmap_count);
	return bitmap_count;
#else
	desc_count = 0;
	for (i = 0; i < ngroups; i++) {
		gdp = ext4_get_group_desc(sb, i, NULL);
		if (!gdp)
			continue;
		desc_count += ext4_free_blks_count(sb, gdp);
	}

	return desc_count;
#endif
}

int __ext4bf_handle_dirty_metadata(const char *where, unsigned int line,
				 handle_t *handle, struct inode *inode,
				 struct buffer_head *bh)
{
	int err = 0;

	if (ext4bf_handle_valid(handle)) {

#ifdef DCHECKSUM
        /* ext4bf: handle cases where it is a data block. */
        if (bh && bh->b_blocktype == B_BLOCKTYPE_DATA) {
#endif
#ifdef PARTJ
            if (!buffer_new(bh))
                err = jbdbf_journal_dirty_metadata(handle, bh);
            else
#endif
#ifdef DCHECKSUM

                jbdbf_journal_dirty_data(handle, bh);
        } else
#endif
            err = jbdbf_journal_dirty_metadata(handle, bh);
        if (err) {
            /* Errors can only happen if there is a bug */
            handle->h_err = err;
			__ext4bf_journal_stop(where, line, handle);
		}
	} else {
		if (inode)
			mark_buffer_dirty_inode(bh, inode);
		else
			mark_buffer_dirty(bh);
		if (inode && inode_needs_sync(inode)) {
			sync_dirty_buffer(bh);
			if (buffer_req(bh) && !buffer_uptodate(bh)) {
				struct ext4bf_super_block *es;

				es = EXT4_SB(inode->i_sb)->s_es;
				es->s_last_error_block =
					cpu_to_le64(bh->b_blocknr);
				ext4bf_error_inode(inode, where, line,
						 bh->b_blocknr,
					"IO error syncing itable block");
				err = -EIO;
			}
		}
	}
	return err;
}

static void reset_inode_seed(struct inode *inode)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
	__le32 inum = cpu_to_le32(inode->i_ino);
	__le32 gen = cpu_to_le32(inode->i_generation);
	__u32 csum;

	if (!ext4_has_metadata_csum(inode->i_sb))
		return;

	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)&inum, sizeof(inum));
	ei->i_csum_seed = ext4_chksum(sbi, csum, (__u8 *)&gen, sizeof(gen));
}

/*
 * Calculate the block group number and offset, given a block number
 */
void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
		ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
{
	struct ext4_super_block *es = EXT4_SB(sb)->s_es;
	ext4_grpblk_t offset;

	blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
	offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
	if (offsetp)
		*offsetp = offset;
	if (blockgrpp)
		*blockgrpp = blocknr;

}

static long ext4_ioctl_group_add(struct file *file,
				 struct ext4_new_group_data *input)
{
	struct super_block *sb = file_inode(file)->i_sb;
	int err, err2=0;

	err = ext4_resize_begin(sb);
	if (err)
		return err;

	if (ext4_has_feature_bigalloc(sb)) {
		ext4_msg(sb, KERN_ERR,
			 "Online resizing not supported with bigalloc");
		err = -EOPNOTSUPP;
		goto group_add_out;
	}

	err = mnt_want_write_file(file);
	if (err)
		goto group_add_out;

	err = ext4_group_add(sb, input);
	if (EXT4_SB(sb)->s_journal) {
		jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
		err2 = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
		jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
	}
	if (err == 0)
		err = err2;
	mnt_drop_write_file(file);
	if (!err && ext4_has_group_desc_csum(sb) &&
	    test_opt(sb, INIT_INODE_TABLE))
		err = ext4_register_li_request(sb, input->group);
group_add_out:
	ext4_resize_end(sb);
	return err;
}

int ext4_sync_file(struct file *file, struct dentry *dentry, int datasync)
{
	struct inode *inode = dentry->d_inode;
	struct ext4_inode_info *ei = EXT4_I(inode);
	journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
	int ret;
	tid_t commit_tid;
	bool needs_barrier = false;

	J_ASSERT(ext4_journal_current_handle() == NULL);

	trace_ext4_sync_file(file, dentry, datasync);

	if (inode->i_sb->s_flags & MS_RDONLY)
		return 0;

	ret = flush_aio_dio_completed_IO(inode);
	if (ret < 0)
		return ret;

	if (!journal)
		return simple_fsync(file, dentry, datasync);

	/*
	 * data=writeback,ordered:
	 *  The caller's filemap_fdatawrite()/wait will sync the data.
	 *  Metadata is in the journal, we wait for proper transaction to
	 *  commit here.
	 *
	 * data=journal:
	 *  filemap_fdatawrite won't do anything (the buffers are clean).
	 *  ext4_force_commit will write the file data into the journal and
	 *  will wait on that.
	 *  filemap_fdatawait() will encounter a ton of newly-dirtied pages
	 *  (they were dirtied by commit).  But that's OK - the blocks are
	 *  safe in-journal, which is all fsync() needs to ensure.
	 */
	if (ext4_should_journal_data(inode))
		return ext4_force_commit(inode->i_sb);

	commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid;
	if (journal->j_flags & JBD2_BARRIER &&
	    !jbd2_trans_will_send_data_barrier(journal, commit_tid))
		needs_barrier = true;
	ret = jbd2_complete_transaction(journal, commit_tid);
	if (needs_barrier)
		blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
	return ret;
}

void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
				struct ext4_group_desc *gdp,
				struct buffer_head *bh, int sz)
{
	__u32 csum;
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	if (!ext4_has_metadata_csum(sb))
		return;

	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
	gdp->bg_inode_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
	if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END)
		gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
}

int __ext4bf_handle_dirty_super(const char *where, unsigned int line,
			      handle_t *handle, struct super_block *sb)
{
	struct buffer_head *bh = EXT4_SB(sb)->s_sbh;
	int err = 0;

	if (ext4bf_handle_valid(handle)) {
		err = jbdbf_journal_dirty_metadata(handle, bh);
		if (err)
			ext4bf_journal_abort_handle(where, line, __func__,
						  bh, handle, err);
	} else
		sb->s_dirt = 1;
	return err;
}

int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
				 handle_t *handle, struct inode *inode,
				 struct buffer_head *bh)
{
	int err = 0;

	might_sleep();

	set_buffer_meta(bh);
	set_buffer_prio(bh);
	if (ext4_handle_valid(handle)) {
		err = jbd2_journal_dirty_metadata(handle, bh);
		/* Errors can only happen if there is a bug */
		if (WARN_ON_ONCE(err)) {
			ext4_journal_abort_handle(where, line, __func__, bh,
						  handle, err);
			ext4_error_inode(inode, where, line,
					 bh->b_blocknr,
					 "journal_dirty_metadata failed: "
					 "handle type %u started at line %u, "
					 "credits %u/%u, errcode %d",
					 handle->h_type,
					 handle->h_line_no,
					 handle->h_requested_credits,
					 handle->h_buffer_credits, err);
		}
	} else {
		if (inode)
			mark_buffer_dirty_inode(bh, inode);
		else
			mark_buffer_dirty(bh);
		if (inode && inode_needs_sync(inode)) {
			sync_dirty_buffer(bh);
			if (buffer_req(bh) && !buffer_uptodate(bh)) {
				struct ext4_super_block *es;

				es = EXT4_SB(inode->i_sb)->s_es;
				es->s_last_error_block =
					cpu_to_le64(bh->b_blocknr);
				ext4_error_inode(inode, where, line,
						 bh->b_blocknr,
					"IO error syncing itable block");
				err = -EIO;
			}
		}
	}
	return err;
}

static ssize_t
ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
                unsigned long nr_segs, loff_t pos)
{
    struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
    int unaligned_aio = 0;
    int ret;

    trace_ext4_file_write(iocb->ki_filp->f_path.dentry, iocb->ki_left);

    if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
        size_t length = iov_length(iov, nr_segs);

        if ((pos > sbi->s_bitmap_maxbytes ||
                (pos == sbi->s_bitmap_maxbytes && length > 0)))
            return -EFBIG;

        if (pos + length > sbi->s_bitmap_maxbytes) {
            nr_segs = iov_shorten((struct iovec *)iov, nr_segs,
                                  sbi->s_bitmap_maxbytes - pos);
        }
    } else if (unlikely((iocb->ki_filp->f_flags & O_DIRECT) &&
                        !is_sync_kiocb(iocb))) {
        unaligned_aio = ext4_unaligned_aio(inode, iov, nr_segs, pos);
    }


    if (unaligned_aio) {
        static unsigned long unaligned_warn_time;


        if (printk_timed_ratelimit(&unaligned_warn_time, 60*60*24*HZ))
            ext4_msg(inode->i_sb, KERN_WARNING,
                     "Unaligned AIO/DIO on inode %ld by %s; "
                     "performance will be poor.",
                     inode->i_ino, current->comm);
        mutex_lock(ext4_aio_mutex(inode));
        ext4_aiodio_wait(inode);
    }

    ret = generic_file_aio_write(iocb, iov, nr_segs, pos);

    if (unaligned_aio)
        mutex_unlock(ext4_aio_mutex(inode));

    return ret;
}

void ext4_block_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
				struct ext4_group_desc *gdp,
				struct buffer_head *bh, int sz)
{
	__u32 csum;
	struct ext4_sb_info *sbi = EXT4_SB(sb);

	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
			EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
		return;

	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
	gdp->bg_block_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
	if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END)
		gdp->bg_block_bitmap_csum_hi = cpu_to_le16(csum >> 16);
}

handle_t *__ext4_journal_start_sb(struct super_block *sb, unsigned int line,
				  int type, int blocks, int rsv_blocks)
{
	journal_t *journal;
	int err;

	trace_ext4_journal_start(sb, blocks, rsv_blocks, _RET_IP_);
	err = ext4_journal_check_start(sb);
	if (err < 0)
		return ERR_PTR(err);

	journal = EXT4_SB(sb)->s_journal;
	if (!journal)
		return ext4_get_nojournal();
	return jbd2__journal_start(journal, blocks, rsv_blocks, GFP_NOFS,
				   type, line);
}

static int ext4_shutdown(struct super_block *sb, unsigned long arg)
{
	struct ext4_sb_info *sbi = EXT4_SB(sb);
	__u32 flags;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (get_user(flags, (__u32 __user *)arg))
		return -EFAULT;

	if (flags > EXT4_GOING_FLAGS_NOLOGFLUSH)
		return -EINVAL;

	if (ext4_forced_shutdown(sbi))
		return 0;

	ext4_msg(sb, KERN_ALERT, "shut down requested (%d)", flags);

	switch (flags) {
	case EXT4_GOING_FLAGS_DEFAULT:
		freeze_bdev(sb->s_bdev);
		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
		thaw_bdev(sb->s_bdev, sb);
		break;
	case EXT4_GOING_FLAGS_LOGFLUSH:
		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal)) {
			(void) ext4_force_commit(sb);
			jbd2_journal_abort(sbi->s_journal, 0);
		}
		break;
	case EXT4_GOING_FLAGS_NOLOGFLUSH:
		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal)) {
			msleep(100);
			jbd2_journal_abort(sbi->s_journal, 0);
		}
		break;
	default:
		return -EINVAL;
	}
	clear_opt(sb, DISCARD);
	return 0;
}