file.c

linux下的用户文件系统fuse-2.5.2

}
#else /* KERNEL_2_6 */
#define FUSE_BLOCK_SHIFT 16
#define FUSE_BLOCK_SIZE (1UL << FUSE_BLOCK_SHIFT)
#define FUSE_BLOCK_MASK (~(FUSE_BLOCK_SIZE-1))
#if (1UL << (FUSE_BLOCK_SHIFT - PAGE_CACHE_SHIFT)) > FUSE_MAX_PAGES_PER_REQ
#error FUSE_BLOCK_SHIFT too large
#endif

static int fuse_is_block_uptodate(struct inode *inode, unsigned start,
				  unsigned end)
{
	int index;

	for (index = start; index < end; index++) {
		struct page *page = find_get_page(inode->i_mapping, index);
		if (!page)
			return 0;
		if (!PageUptodate(page)) {
			page_cache_release(page);
			return 0;
		}
		page_cache_release(page);
	}
	return 1;
}

static int fuse_file_read_block(struct fuse_req *req, struct file *file,
				struct inode *inode, unsigned start,
				unsigned end)
{
	loff_t pos;
	size_t count;
	int index;
	int err = -EBUSY;
	int i;

	for (index = start; index < end; index++) {
		struct page *page = grab_cache_page(inode->i_mapping, index);
		if (!page)
			goto out;
		if (PageUptodate(page)) {
			unlock_page(page);
			page_cache_release(page);
			page = NULL;
		}
		req->pages[req->num_pages++] = page;
	}
	pos = (loff_t) start << PAGE_CACHE_SHIFT;
	count = req->num_pages << PAGE_CACHE_SHIFT;
	fuse_send_read(req, file, inode, pos, count);
	err = req->out.h.error;
 out:
	for (i = 0; i < req->num_pages; i++) {
		struct page *page = req->pages[i];
		if (page) {
			if (!err)
				SetPageUptodate(page);
			unlock_page(page);
			page_cache_release(page);
		}
	}
	return err;
}

static int fuse_file_bigread(struct file *file, struct inode *inode,
			     loff_t pos, size_t count)
{
	struct fuse_conn *fc = get_fuse_conn(inode);
	unsigned starti;
	unsigned endi;
	unsigned nexti;
	struct fuse_req *req;
	loff_t size = i_size_read(inode);
	loff_t end = (pos + count + FUSE_BLOCK_SIZE - 1) & FUSE_BLOCK_MASK;
	end = min(end, size);
	if (end <= pos)
		return 0;

	starti = (pos & FUSE_BLOCK_MASK) >> PAGE_CACHE_SHIFT;
	endi = (end + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	req = fuse_get_request(fc);
	if (!req)
		return -EINTR;

	for (; starti < endi; starti = nexti) {
		nexti = starti + (FUSE_BLOCK_SIZE >> PAGE_CACHE_SHIFT);
		nexti = min(nexti, endi);
		if (!fuse_is_block_uptodate(inode, starti, nexti)) {
			if (fuse_file_read_block(req, file, inode, starti, nexti))
				break;

			fuse_reset_request(req);
		}
	}
	fuse_put_request(fc, req);
	return 0;
}
#endif /* KERNEL_2_6 */

static size_t fuse_send_write(struct fuse_req *req, struct file *file,
			      struct inode *inode, loff_t pos, size_t count)
{
	struct fuse_conn *fc = get_fuse_conn(inode);
	struct fuse_file *ff = file->private_data;
	struct fuse_write_in inarg;
	struct fuse_write_out outarg;

	memset(&inarg, 0, sizeof(struct fuse_write_in));
	inarg.fh = ff->fh;
	inarg.offset = pos;
	inarg.size = count;
	req->in.h.opcode = FUSE_WRITE;
	req->in.h.nodeid = get_node_id(inode);
	req->inode = inode;
	req->file = file;
	req->in.argpages = 1;
	req->in.numargs = 2;
	req->in.args[0].size = sizeof(struct fuse_write_in);
	req->in.args[0].value = &inarg;
	req->in.args[1].size = count;
	req->out.numargs = 1;
	req->out.args[0].size = sizeof(struct fuse_write_out);
	req->out.args[0].value = &outarg;
	request_send(fc, req);
	return outarg.size;
}

static int fuse_prepare_write(struct file *file, struct page *page,
			      unsigned offset, unsigned to)
{
	/* No op */
	return 0;
}

static int fuse_commit_write(struct file *file, struct page *page,
			     unsigned offset, unsigned to)
{
	int err;
	size_t nres;
	unsigned count = to - offset;
	struct inode *inode = page->mapping->host;
	struct fuse_conn *fc = get_fuse_conn(inode);
	loff_t pos = page_offset(page) + offset;
	struct fuse_req *req;

	if (is_bad_inode(inode))
		return -EIO;

	req = fuse_get_request(fc);
	if (!req)
		return -EINTR;

	req->num_pages = 1;
	req->pages[0] = page;
	req->page_offset = offset;
	nres = fuse_send_write(req, file, inode, pos, count);
	err = req->out.h.error;
	fuse_put_request(fc, req);
	if (!err && nres != count)
		err = -EIO;
	if (!err) {
		pos += count;
		if (pos > i_size_read(inode))
			i_size_write(inode, pos);

		if (offset == 0 && to == PAGE_CACHE_SIZE) {
			clear_page_dirty(page);
			SetPageUptodate(page);
		}
	}
	fuse_invalidate_attr(inode);
	return err;
}

static void fuse_release_user_pages(struct fuse_req *req, int write)
{
	unsigned i;

	for (i = 0; i < req->num_pages; i++) {
		struct page *page = req->pages[i];
		if (write)
			set_page_dirty_lock(page);
		put_page(page);
	}
}

static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,
			       unsigned nbytes, int write)
{
	unsigned long user_addr = (unsigned long) buf;
	unsigned offset = user_addr & ~PAGE_MASK;
	int npages;

	/* This doesn't work with nfsd */
	if (!current->mm)
		return -EPERM;

	nbytes = min(nbytes, (unsigned) FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);
	npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
	npages = max(npages, 1);
	npages = min(npages, FUSE_MAX_PAGES_PER_REQ);
	down_read(&current->mm->mmap_sem);
	npages = get_user_pages(current, current->mm, user_addr, npages, write,
				0, req->pages, NULL);
	up_read(&current->mm->mmap_sem);
	if (npages < 0)
		return npages;

	req->num_pages = npages;
	req->page_offset = offset;
	return 0;
}

static ssize_t fuse_direct_io(struct file *file, const char __user *buf,
			      size_t count, loff_t *ppos, int write)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct fuse_conn *fc = get_fuse_conn(inode);
	size_t nmax = write ? fc->max_write : fc->max_read;
	loff_t pos = *ppos;
	ssize_t res = 0;
	struct fuse_req *req;

	if (is_bad_inode(inode))
		return -EIO;

	req = fuse_get_request(fc);
	if (!req)
		return -EINTR;

	while (count) {
		size_t nres;
		size_t nbytes = min(count, nmax);
		int err = fuse_get_user_pages(req, buf, nbytes, !write);
		if (err) {
			res = err;
			break;
		}
		nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;
		nbytes = min(count, nbytes);
		if (write)
			nres = fuse_send_write(req, file, inode, pos, nbytes);
		else
			nres = fuse_send_read(req, file, inode, pos, nbytes);
		fuse_release_user_pages(req, !write);
		if (req->out.h.error) {
			if (!res)
				res = req->out.h.error;
			break;
		} else if (nres > nbytes) {
			res = -EIO;
			break;
		}
		count -= nres;
		res += nres;
		pos += nres;
		buf += nres;
		if (nres != nbytes)
			break;
		if (count)
			fuse_reset_request(req);
	}
	fuse_put_request(fc, req);
	if (res > 0) {
		if (write && pos > i_size_read(inode))
			i_size_write(inode, pos);
		*ppos = pos;
	}
	fuse_invalidate_attr(inode);

	return res;
}

static ssize_t fuse_direct_read(struct file *file, char __user *buf,
				     size_t count, loff_t *ppos)
{
	return fuse_direct_io(file, buf, count, ppos, 0);
}

static ssize_t fuse_direct_write(struct file *file, const char __user *buf,
				 size_t count, loff_t *ppos)
{
	struct inode *inode = file->f_dentry->d_inode;
	ssize_t res;
	/* Don't allow parallel writes to the same file */
#ifdef KERNEL_2_6_16_PLUS
	mutex_lock(&inode->i_mutex);
	res = fuse_direct_io(file, buf, count, ppos, 1);
	mutex_unlock(&inode->i_mutex);
#else
	down(&inode->i_sem);
	res = fuse_direct_io(file, buf, count, ppos, 1);
	up(&inode->i_sem);
#endif
	return res;
}

#ifndef KERNEL_2_6
static ssize_t fuse_file_read(struct file *file, char __user *buf,
			      size_t count, loff_t *ppos)
{
	struct inode *inode = file->f_dentry->d_inode;
	struct fuse_conn *fc = get_fuse_conn(inode);

	if (is_bad_inode(inode))
		return -EIO;

	if (fc->flags & FUSE_LARGE_READ) {
		int res;
		down(&inode->i_sem);
		res = fuse_file_bigread(file, inode, *ppos, count);
		up(&inode->i_sem);
		if (res)
			return res;
	}
	return generic_file_read(file, buf, count, ppos);
}
#endif
static int fuse_file_mmap(struct file *file, struct vm_area_struct *vma)
{
	if ((vma->vm_flags & VM_SHARED)) {
		if ((vma->vm_flags & VM_WRITE))
			return -ENODEV;
		else
			vma->vm_flags &= ~VM_MAYWRITE;
	}
	return generic_file_mmap(file, vma);
}

#ifdef KERNEL_2_6
static int fuse_set_page_dirty(struct page *page)
{
	printk("fuse_set_page_dirty: should not happen\n");
	dump_stack();
	return 0;
}
#endif

static struct file_operations fuse_file_operations = {
	.llseek		= generic_file_llseek,
#ifdef KERNEL_2_6
	.read		= do_sync_read,
	.write		= do_sync_write,
	.readv		= generic_file_readv,
	.writev		= generic_file_writev,
	.aio_read	= generic_file_aio_read,
	.aio_write	= generic_file_aio_write,
#else
	.read		= fuse_file_read,
	.write		= generic_file_write,
#endif
	.mmap		= fuse_file_mmap,
	.open		= fuse_open,
	.flush		= fuse_flush,
	.release	= fuse_release,
	.fsync		= fuse_fsync,
#ifdef KERNEL_2_6
	.sendfile	= generic_file_sendfile,
#endif
};

static struct file_operations fuse_direct_io_file_operations = {
	.llseek		= generic_file_llseek,
	.read		= fuse_direct_read,
	.write		= fuse_direct_write,
	.open		= fuse_open,
	.flush		= fuse_flush,
	.release	= fuse_release,
	.fsync		= fuse_fsync,
	/* no mmap and sendfile */
};

static struct address_space_operations fuse_file_aops  = {
	.readpage	= fuse_readpage,
	.prepare_write	= fuse_prepare_write,
	.commit_write	= fuse_commit_write,
#ifdef KERNEL_2_6
	.readpages	= fuse_readpages,
	.set_page_dirty	= fuse_set_page_dirty,
#endif
};

void fuse_init_file_inode(struct inode *inode)
{
	inode->i_fop = &fuse_file_operations;
	inode->i_data.a_ops = &fuse_file_aops;
}