Commit f4975c67 authored by Miklos Szeredi's avatar Miklos Szeredi
Browse files

fuse: allow kernel to access "direct_io" files 



Allow the kernel read and write on "direct_io" files.  This is
necessary for nfs export and execute support.

The implementation is simple: if an access from the kernel is
detected, don't perform get_user_pages(), just use the kernel address
provided by the requester to copy from/to the userspace filesystem.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 833bb304

fs/fuse/dir.c

+1 −0
Original line number Diff line number Diff line
@@ -1032,6 +1032,7 @@ static int fuse_readdir(struct file *file, void *dstbuf, filldir_t filldir) 
		fuse_put_request(fc, req);

		return -ENOMEM;

	}

	req->out.argpages = 1;

	req->num_pages = 1;

	req->pages[0] = page;

	fuse_read_fill(req, file, inode, file->f_pos, PAGE_SIZE, FUSE_READDIR);

fs/fuse/file.c

+30 −12
Original line number Diff line number Diff line
@@ -386,7 +386,6 @@ void fuse_read_fill(struct fuse_req *req, struct file *file, 
	req->in.numargs = 1;

	req->in.args[0].size = sizeof(struct fuse_read_in);

	req->in.args[0].value = inarg;

	req->out.argpages = 1;

	req->out.argvar = 1;

	req->out.numargs = 1;

	req->out.args[0].size = count;
@@ -453,6 +452,7 @@ static int fuse_readpage(struct file *file, struct page *page) 
	attr_ver = fuse_get_attr_version(fc);



	req->out.page_zeroing = 1;

	req->out.argpages = 1;

	req->num_pages = 1;

	req->pages[0] = page;

	num_read = fuse_send_read(req, file, inode, pos, count, NULL);
@@ -510,6 +510,8 @@ static void fuse_send_readpages(struct fuse_req *req, struct file *file, 
	struct fuse_conn *fc = get_fuse_conn(inode);

	loff_t pos = page_offset(req->pages[0]);

	size_t count = req->num_pages << PAGE_CACHE_SHIFT;



	req->out.argpages = 1;

	req->out.page_zeroing = 1;

	fuse_read_fill(req, file, inode, pos, count, FUSE_READ);

	req->misc.read.attr_ver = fuse_get_attr_version(fc);
@@ -621,7 +623,6 @@ static void fuse_write_fill(struct fuse_req *req, struct file *file, 
	inarg->flags = file ? file->f_flags : 0;

	req->in.h.opcode = FUSE_WRITE;

	req->in.h.nodeid = get_node_id(inode);

	req->in.argpages = 1;

	req->in.numargs = 2;

	if (fc->minor < 9)

		req->in.args[0].size = FUSE_COMPAT_WRITE_IN_SIZE;
@@ -695,6 +696,7 @@ static int fuse_buffered_write(struct file *file, struct inode *inode, 
	if (IS_ERR(req))

		return PTR_ERR(req);



	req->in.argpages = 1;

	req->num_pages = 1;

	req->pages[0] = page;

	req->page_offset = offset;
@@ -771,6 +773,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req, 
	size_t count = 0;

	int err;



	req->in.argpages = 1;

	req->page_offset = offset;



	do {
@@ -935,21 +938,28 @@ static void fuse_release_user_pages(struct fuse_req *req, int write) 
}



static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf,

			       unsigned nbytes, int write)

			       unsigned *nbytesp, int write)

{

	unsigned nbytes = *nbytesp;

	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;

	/* Special case for kernel I/O: can copy directly into the buffer */

	if (segment_eq(get_fs(), KERNEL_DS)) {

		if (write)

			req->in.args[1].value = (void *) user_addr;

		else

			req->out.args[0].value = (void *) user_addr;



		return 0;

	}



	nbytes = min(nbytes, (unsigned) FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT);

	npages = (nbytes + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;

	npages = clamp(npages, 1, FUSE_MAX_PAGES_PER_REQ);

	down_read(&current->mm->mmap_sem);

	npages = get_user_pages(current, current->mm, user_addr, npages, write,

	npages = get_user_pages(current, current->mm, user_addr, npages, !write,

				0, req->pages, NULL);

	up_read(&current->mm->mmap_sem);

	if (npages < 0)
@@ -957,6 +967,15 @@ static int fuse_get_user_pages(struct fuse_req *req, const char __user *buf, 


	req->num_pages = npages;

	req->page_offset = offset;



	if (write)

		req->in.argpages = 1;

	else

		req->out.argpages = 1;



	nbytes = (req->num_pages << PAGE_SHIFT) - req->page_offset;

	*nbytesp = min(*nbytesp, nbytes);



	return 0;

}
@@ -979,15 +998,13 @@ static ssize_t fuse_direct_io(struct file *file, const char __user *buf, 


	while (count) {

		size_t nres;

		size_t nbytes_limit = min(count, nmax);

		size_t nbytes;

		int err = fuse_get_user_pages(req, buf, nbytes_limit, !write);

		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(nbytes_limit, nbytes);



		if (write)

			nres = fuse_send_write(req, file, inode, pos, nbytes,

					       current->files);
@@ -1163,6 +1180,7 @@ static int fuse_writepage_locked(struct page *page) 
	fuse_write_fill(req, NULL, ff, inode, page_offset(page), 0, 1);



	copy_highpage(tmp_page, page);

	req->in.argpages = 1;

	req->num_pages = 1;

	req->pages[0] = tmp_page;

	req->page_offset = 0;

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