linux-2.6.33/generic_file_aio_read() の履歴(No.4)

• 履歴一覧
• 差分 を表示
• 現在との差分 を表示
• ソース を表示
• linux-2.6.33/generic_file_aio_read() へ行く。
  • 1 (2010-06-22 (火) 14:03:43)
  • 2 (2010-06-22 (火) 14:22:37)
  • 3 (2010-07-01 (木) 12:17:05)
  • 4 (2010-09-30 (木) 08:42:24)

---

参照元†

• linux-2.6.33/do_sync_read()

説明†

• パス: linux-2.6.33/mm/filemap.c

• FIXME: これは何？
  • 説明

引数†

• struct kiocb *iocb
  • linux-2.6.33/kiocb
• const struct iovec *iov
  • linux-2.6.33/iovec
• unsigned long nr_segs
• loff_t pos

返り値†

• ssize_t

参考†

• writepages に設定される関数
• 検索方法

  $ egrep -nr '\.direct_IO[\s]*' fs

• 結果

  fs/block_dev.c:1472:    .direct_IO      = blkdev_direct_IO,
  fs/btrfs/inode.c:6008:  .direct_IO      = btrfs_direct_IO,
  fs/cifs/file.c:2355:    /* .direct_IO = */
  fs/cifs/file.c:2371:    /* .direct_IO = */
  fs/ext2/inode.c:820:    .direct_IO              = ext2_direct_IO,
  fs/ext2/inode.c:840:    .direct_IO              = ext2_direct_IO,
  fs/ext3/inode.c:1847:   .direct_IO              = ext3_direct_IO,
  fs/ext3/inode.c:1863:   .direct_IO              = ext3_direct_IO,
  fs/ext4/inode.c:3853:   .direct_IO              = ext4_direct_IO,
  fs/ext4/inode.c:3869:   .direct_IO              = ext4_direct_IO,
  fs/ext4/inode.c:3901:   .direct_IO              = ext4_direct_IO,
  fs/fat/inode.c:220:     .direct_IO      = fat_direct_IO,
  fs/gfs2/aops.c:1127:    .direct_IO = gfs2_direct_IO,
  fs/gfs2/aops.c:1144:    .direct_IO = gfs2_direct_IO,
  fs/hfs/inode.c:143:     .direct_IO      = hfs_direct_IO,
  fs/hfsplus/inode.c:136: .direct_IO      = hfsplus_direct_IO,
  fs/jfs/inode.c:328:     .direct_IO      = jfs_direct_IO,
  fs/nfs/file.c:527:      .direct_IO = nfs_direct_IO,
  fs/nilfs2/inode.c:253:  .direct_IO              = nilfs_direct_IO,
  fs/ocfs2/aops.c:1994:   .direct_IO              = ocfs2_direct_IO,
  fs/reiserfs/inode.c:3189:       .direct_IO = reiserfs_direct_IO,
  fs/xfs/linux-2.6/xfs_aops.c:1558:       .direct_IO              = xfs_vm_direct_IO,

実装†

/**
 * generic_file_aio_read - generic filesystem read routine
 * @iocb:	kernel I/O control block
 * @iov:	io vector request
 * @nr_segs:	number of segments in the iovec
 * @pos:	current file position
 *
 * This is the "read()" routine for all filesystems
 * that can use the page cache directly.
 */
ssize_t
generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
		unsigned long nr_segs, loff_t pos)
{
	struct file *filp = iocb->ki_filp;
	ssize_t retval;
	unsigned long seg;
	size_t count;
	loff_t *ppos = &iocb->ki_pos;

• • linux-2.6.33/file

	count = 0;
	retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
	if (retval)
		return retval;

• • linux-2.6.33/generic_segment_checks()

	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
	if (filp->f_flags & O_DIRECT) {
		loff_t size;
		struct address_space *mapping;
		struct inode *inode;

• • linux-2.6.33/address_space

• linux-2.6.33/inode

		mapping = filp->f_mapping;
		inode = mapping->host;
		if (!count)
			goto out; /* skip atime */
		size = i_size_read(inode);

• • linux-2.6.33/i_size_read()

		if (pos < size) {
			retval = filemap_write_and_wait_range(mapping, pos,
					pos + iov_length(iov, nr_segs) - 1);

• • linux-2.6.33/filemap_write_and_wait_range()

			if (!retval) {
				retval = mapping->a_ops->direct_IO(READ, iocb,
							iov, pos, nr_segs);

• mapping->a_ops は address_space_operations 型
  • linux-2.6.33/address_space_operations

			}
			if (retval > 0)
				*ppos = pos + retval;
			if (retval) {
				file_accessed(filp);
				goto out;
			}

• • linux-2.6.33/file_accessed()

		}
	}

	for (seg = 0; seg < nr_segs; seg++) {
		read_descriptor_t desc;

• • linux-2.6.33/read_descriptor_t

		desc.written = 0;
		desc.arg.buf = iov[seg].iov_base;
		desc.count = iov[seg].iov_len;
		if (desc.count == 0)
			continue;
		desc.error = 0;
		do_generic_file_read(filp, ppos, &desc, file_read_actor);

• • linux-2.6.33/do_generic_file_read()
  • linux-2.6.33/file_read_actor()

		retval += desc.written;
		if (desc.error) {
			retval = retval ?: desc.error;
			break;
		}
		if (desc.count > 0)
			break;
	}
out:
	return retval;
}
EXPORT_SYMBOL(generic_file_aio_read);

• 特にライセンスを区別せずシンボルを公開する。
  • linux-2.6.33/EXPORT_SYMBOL()

コメント†