linux-2.6.33/__blockdev_direct_IO の履歴(No.1)

• 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/__blockdev_direct_IO へ行く。
  • 1 (2010-09-30 (木) 08:59:02)

参照元†

• linux-2.6.33/blockdev_direct_IO_no_locking()

説明†

• パス: linux-2.6.33/fs/direct-io.c

• FIXME: これは何？
  • 説明

引数†

返り値†

参考†

実装†

/*
 * This is a library function for use by filesystem drivers.
 *
 * The locking rules are governed by the flags parameter:
 *  - if the flags value contains DIO_LOCKING we use a fancy locking
 *    scheme for dumb filesystems.
 *    For writes this function is called under i_mutex and returns with
 *    i_mutex held, for reads, i_mutex is not held on entry, but it is
 *    taken and dropped again before returning.
 *    For reads and writes i_alloc_sem is taken in shared mode and released
 *    on I/O completion (which may happen asynchronously after returning to
 *    the caller).
 *
 *  - if the flags value does NOT contain DIO_LOCKING we don't use any
 *    internal locking but rather rely on the filesystem to synchronize
 *    direct I/O reads/writes versus each other and truncate.
 *    For reads and writes both i_mutex and i_alloc_sem are not held on
 *    entry and are never taken.
 */
ssize_t
__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
	struct block_device *bdev, const struct iovec *iov, loff_t offset, 
	unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
	int flags)
{
	int seg;
	size_t size;
	unsigned long addr;
	unsigned blkbits = inode->i_blkbits;
	unsigned bdev_blkbits = 0;
	unsigned blocksize_mask = (1 << blkbits) - 1;
	ssize_t retval = -EINVAL;
	loff_t end = offset;
	struct dio *dio;

	if (rw & WRITE)
		rw = WRITE_ODIRECT_PLUG;

	if (bdev)
		bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev));

	if (offset & blocksize_mask) {
		if (bdev)
			 blkbits = bdev_blkbits;
		blocksize_mask = (1 << blkbits) - 1;
		if (offset & blocksize_mask)
			goto out;
	}

	/* Check the memory alignment.  Blocks cannot straddle pages */
	for (seg = 0; seg < nr_segs; seg++) {
		addr = (unsigned long)iov[seg].iov_base;
		size = iov[seg].iov_len;
		end += size;
		if ((addr & blocksize_mask) || (size & blocksize_mask))  {
			if (bdev)
				 blkbits = bdev_blkbits;
			blocksize_mask = (1 << blkbits) - 1;
			if ((addr & blocksize_mask) || (size & blocksize_mask))  
				goto out;
		}
	}

	dio = kmalloc(sizeof(*dio), GFP_KERNEL);
	retval = -ENOMEM;
	if (!dio)
		goto out;
	/*
	 * Believe it or not, zeroing out the page array caused a .5%
	 * performance regression in a database benchmark.  So, we take
	 * care to only zero out what's needed.
	 */
	memset(dio, 0, offsetof(struct dio, pages));

	dio->flags = flags;
	if (dio->flags & DIO_LOCKING) {
		/* watch out for a 0 len io from a tricksy fs */
		if (rw == READ && end > offset) {
			struct address_space *mapping =
					iocb->ki_filp->f_mapping;

			/* will be released by direct_io_worker */
			mutex_lock(&inode->i_mutex);

			retval = filemap_write_and_wait_range(mapping, offset,
							      end - 1);
			if (retval) {
				mutex_unlock(&inode->i_mutex);
				kfree(dio);
				goto out;
			}
		}

		/*
		 * Will be released at I/O completion, possibly in a
		 * different thread.
		 */
		down_read_non_owner(&inode->i_alloc_sem);
	}

	/*
	 * For file extending writes updating i_size before data
	 * writeouts complete can expose uninitialized blocks. So
	 * even for AIO, we need to wait for i/o to complete before
	 * returning in this case.
	 */
	dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) &&
		(end > i_size_read(inode)));

	retval = direct_io_worker(rw, iocb, inode, iov, offset,
				nr_segs, blkbits, get_block, end_io, dio);

	/*
	 * In case of error extending write may have instantiated a few
	 * blocks outside i_size. Trim these off again for DIO_LOCKING.
	 *
	 * NOTE: filesystems with their own locking have to handle this
	 * on their own.
	 */
	if (flags & DIO_LOCKING) {
		if (unlikely((rw & WRITE) && retval < 0)) {
			loff_t isize = i_size_read(inode);
			if (end > isize)
				vmtruncate(inode, isize);
		}
	}

out:
	return retval;
}
EXPORT_SYMBOL(__blockdev_direct_IO);

• 特にライセンスを区別せず関数をエクスポートする。
  • linux-2.6.33/EXPORT_SYMBOL()

コメント†