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authorHans de Goede <hdegoede@redhat.com>2019-12-12 15:09:14 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2020-02-08 17:34:58 -0500
commit0fd169576648452725fa2949bf391d10883d3991 (patch)
tree63818a8374ea0c88b010da5a8d5fa376ded42517 /fs/vboxsf/file.c
parentf35aa2bc809eacc44c3cee41b52cef1c451d4a89 (diff)
fs: Add VirtualBox guest shared folder (vboxsf) support
VirtualBox hosts can share folders with guests, this commit adds a VFS driver implementing the Linux-guest side of this, allowing folders exported by the host to be mounted under Linux. This driver depends on the guest <-> host IPC functions exported by the vboxguest driver. Acked-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Hans de Goede <hdegoede@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/vboxsf/file.c')
-rw-r--r--fs/vboxsf/file.c379
1 files changed, 379 insertions, 0 deletions
diff --git a/fs/vboxsf/file.c b/fs/vboxsf/file.c
new file mode 100644
index 000000000000..c4ab5996d97a
--- /dev/null
+++ b/fs/vboxsf/file.c
@@ -0,0 +1,379 @@
+// SPDX-License-Identifier: MIT
+/*
+ * VirtualBox Guest Shared Folders support: Regular file inode and file ops.
+ *
+ * Copyright (C) 2006-2018 Oracle Corporation
+ */
+
+#include <linux/mm.h>
+#include <linux/page-flags.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/sizes.h>
+#include "vfsmod.h"
+
+struct vboxsf_handle {
+ u64 handle;
+ u32 root;
+ u32 access_flags;
+ struct kref refcount;
+ struct list_head head;
+};
+
+static int vboxsf_file_open(struct inode *inode, struct file *file)
+{
+ struct vboxsf_inode *sf_i = VBOXSF_I(inode);
+ struct shfl_createparms params = {};
+ struct vboxsf_handle *sf_handle;
+ u32 access_flags = 0;
+ int err;
+
+ sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);
+ if (!sf_handle)
+ return -ENOMEM;
+
+ /*
+ * We check the value of params.handle afterwards to find out if
+ * the call succeeded or failed, as the API does not seem to cleanly
+ * distinguish error and informational messages.
+ *
+ * Furthermore, we must set params.handle to SHFL_HANDLE_NIL to
+ * make the shared folders host service use our mode parameter.
+ */
+ params.handle = SHFL_HANDLE_NIL;
+ if (file->f_flags & O_CREAT) {
+ params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;
+ /*
+ * We ignore O_EXCL, as the Linux kernel seems to call create
+ * beforehand itself, so O_EXCL should always fail.
+ */
+ if (file->f_flags & O_TRUNC)
+ params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
+ else
+ params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
+ } else {
+ params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;
+ if (file->f_flags & O_TRUNC)
+ params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
+ }
+
+ switch (file->f_flags & O_ACCMODE) {
+ case O_RDONLY:
+ access_flags |= SHFL_CF_ACCESS_READ;
+ break;
+
+ case O_WRONLY:
+ access_flags |= SHFL_CF_ACCESS_WRITE;
+ break;
+
+ case O_RDWR:
+ access_flags |= SHFL_CF_ACCESS_READWRITE;
+ break;
+
+ default:
+ WARN_ON(1);
+ }
+
+ if (file->f_flags & O_APPEND)
+ access_flags |= SHFL_CF_ACCESS_APPEND;
+
+ params.create_flags |= access_flags;
+ params.info.attr.mode = inode->i_mode;
+
+ err = vboxsf_create_at_dentry(file_dentry(file), &params);
+ if (err == 0 && params.handle == SHFL_HANDLE_NIL)
+ err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;
+ if (err) {
+ kfree(sf_handle);
+ return err;
+ }
+
+ /* the host may have given us different attr then requested */
+ sf_i->force_restat = 1;
+
+ /* init our handle struct and add it to the inode's handles list */
+ sf_handle->handle = params.handle;
+ sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;
+ sf_handle->access_flags = access_flags;
+ kref_init(&sf_handle->refcount);
+
+ mutex_lock(&sf_i->handle_list_mutex);
+ list_add(&sf_handle->head, &sf_i->handle_list);
+ mutex_unlock(&sf_i->handle_list_mutex);
+
+ file->private_data = sf_handle;
+ return 0;
+}
+
+static void vboxsf_handle_release(struct kref *refcount)
+{
+ struct vboxsf_handle *sf_handle =
+ container_of(refcount, struct vboxsf_handle, refcount);
+
+ vboxsf_close(sf_handle->root, sf_handle->handle);
+ kfree(sf_handle);
+}
+
+static int vboxsf_file_release(struct inode *inode, struct file *file)
+{
+ struct vboxsf_inode *sf_i = VBOXSF_I(inode);
+ struct vboxsf_handle *sf_handle = file->private_data;
+
+ /*
+ * When a file is closed on our (the guest) side, we want any subsequent
+ * accesses done on the host side to see all changes done from our side.
+ */
+ filemap_write_and_wait(inode->i_mapping);
+
+ mutex_lock(&sf_i->handle_list_mutex);
+ list_del(&sf_handle->head);
+ mutex_unlock(&sf_i->handle_list_mutex);
+
+ kref_put(&sf_handle->refcount, vboxsf_handle_release);
+ return 0;
+}
+
+/*
+ * Write back dirty pages now, because there may not be any suitable
+ * open files later
+ */
+static void vboxsf_vma_close(struct vm_area_struct *vma)
+{
+ filemap_write_and_wait(vma->vm_file->f_mapping);
+}
+
+static const struct vm_operations_struct vboxsf_file_vm_ops = {
+ .close = vboxsf_vma_close,
+ .fault = filemap_fault,
+ .map_pages = filemap_map_pages,
+};
+
+static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int err;
+
+ err = generic_file_mmap(file, vma);
+ if (!err)
+ vma->vm_ops = &vboxsf_file_vm_ops;
+
+ return err;
+}
+
+/*
+ * Note that since we are accessing files on the host's filesystem, files
+ * may always be changed underneath us by the host!
+ *
+ * The vboxsf API between the guest and the host does not offer any functions
+ * to deal with this. There is no inode-generation to check for changes, no
+ * events / callback on changes and no way to lock files.
+ *
+ * To avoid returning stale data when a file gets *opened* on our (the guest)
+ * side, we do a "stat" on the host side, then compare the mtime with the
+ * last known mtime and invalidate the page-cache if they differ.
+ * This is done from vboxsf_inode_revalidate().
+ *
+ * When reads are done through the read_iter fop, it is possible to do
+ * further cache revalidation then, there are 3 options to deal with this:
+ *
+ * 1) Rely solely on the revalidation done at open time
+ * 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf
+ * host API does not allow stat on handles, so we would need to use
+ * file->f_path.dentry and the stat will then fail if the file was unlinked
+ * or renamed (and there is no thing like NFS' silly-rename). So we get:
+ * 2a) "stat" and compare mtime, on stat failure invalidate the cache
+ * 2b) "stat" and compare mtime, on stat failure do nothing
+ * 3) Simply always call invalidate_inode_pages2_range on the range of the read
+ *
+ * Currently we are keeping things KISS and using option 1. this allows
+ * directly using generic_file_read_iter without wrapping it.
+ *
+ * This means that only data written on the host side before open() on
+ * the guest side is guaranteed to be seen by the guest. If necessary
+ * we may provide other read-cache strategies in the future and make this
+ * configurable through a mount option.
+ */
+const struct file_operations vboxsf_reg_fops = {
+ .llseek = generic_file_llseek,
+ .read_iter = generic_file_read_iter,
+ .write_iter = generic_file_write_iter,
+ .mmap = vboxsf_file_mmap,
+ .open = vboxsf_file_open,
+ .release = vboxsf_file_release,
+ .fsync = noop_fsync,
+ .splice_read = generic_file_splice_read,
+};
+
+const struct inode_operations vboxsf_reg_iops = {
+ .getattr = vboxsf_getattr,
+ .setattr = vboxsf_setattr
+};
+
+static int vboxsf_readpage(struct file *file, struct page *page)
+{
+ struct vboxsf_handle *sf_handle = file->private_data;
+ loff_t off = page_offset(page);
+ u32 nread = PAGE_SIZE;
+ u8 *buf;
+ int err;
+
+ buf = kmap(page);
+
+ err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);
+ if (err == 0) {
+ memset(&buf[nread], 0, PAGE_SIZE - nread);
+ flush_dcache_page(page);
+ SetPageUptodate(page);
+ } else {
+ SetPageError(page);
+ }
+
+ kunmap(page);
+ unlock_page(page);
+ return err;
+}
+
+static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)
+{
+ struct vboxsf_handle *h, *sf_handle = NULL;
+
+ mutex_lock(&sf_i->handle_list_mutex);
+ list_for_each_entry(h, &sf_i->handle_list, head) {
+ if (h->access_flags == SHFL_CF_ACCESS_WRITE ||
+ h->access_flags == SHFL_CF_ACCESS_READWRITE) {
+ kref_get(&h->refcount);
+ sf_handle = h;
+ break;
+ }
+ }
+ mutex_unlock(&sf_i->handle_list_mutex);
+
+ return sf_handle;
+}
+
+static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)
+{
+ struct inode *inode = page->mapping->host;
+ struct vboxsf_inode *sf_i = VBOXSF_I(inode);
+ struct vboxsf_handle *sf_handle;
+ loff_t off = page_offset(page);
+ loff_t size = i_size_read(inode);
+ u32 nwrite = PAGE_SIZE;
+ u8 *buf;
+ int err;
+
+ if (off + PAGE_SIZE > size)
+ nwrite = size & ~PAGE_MASK;
+
+ sf_handle = vboxsf_get_write_handle(sf_i);
+ if (!sf_handle)
+ return -EBADF;
+
+ buf = kmap(page);
+ err = vboxsf_write(sf_handle->root, sf_handle->handle,
+ off, &nwrite, buf);
+ kunmap(page);
+
+ kref_put(&sf_handle->refcount, vboxsf_handle_release);
+
+ if (err == 0) {
+ ClearPageError(page);
+ /* mtime changed */
+ sf_i->force_restat = 1;
+ } else {
+ ClearPageUptodate(page);
+ }
+
+ unlock_page(page);
+ return err;
+}
+
+static int vboxsf_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned int len, unsigned int copied,
+ struct page *page, void *fsdata)
+{
+ struct inode *inode = mapping->host;
+ struct vboxsf_handle *sf_handle = file->private_data;
+ unsigned int from = pos & ~PAGE_MASK;
+ u32 nwritten = len;
+ u8 *buf;
+ int err;
+
+ /* zero the stale part of the page if we did a short copy */
+ if (!PageUptodate(page) && copied < len)
+ zero_user(page, from + copied, len - copied);
+
+ buf = kmap(page);
+ err = vboxsf_write(sf_handle->root, sf_handle->handle,
+ pos, &nwritten, buf + from);
+ kunmap(page);
+
+ if (err) {
+ nwritten = 0;
+ goto out;
+ }
+
+ /* mtime changed */
+ VBOXSF_I(inode)->force_restat = 1;
+
+ if (!PageUptodate(page) && nwritten == PAGE_SIZE)
+ SetPageUptodate(page);
+
+ pos += nwritten;
+ if (pos > inode->i_size)
+ i_size_write(inode, pos);
+
+out:
+ unlock_page(page);
+ put_page(page);
+
+ return nwritten;
+}
+
+/*
+ * Note simple_write_begin does not read the page from disk on partial writes
+ * this is ok since vboxsf_write_end only writes the written parts of the
+ * page and it does not call SetPageUptodate for partial writes.
+ */
+const struct address_space_operations vboxsf_reg_aops = {
+ .readpage = vboxsf_readpage,
+ .writepage = vboxsf_writepage,
+ .set_page_dirty = __set_page_dirty_nobuffers,
+ .write_begin = simple_write_begin,
+ .write_end = vboxsf_write_end,
+};
+
+static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
+ struct delayed_call *done)
+{
+ struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
+ struct shfl_string *path;
+ char *link;
+ int err;
+
+ if (!dentry)
+ return ERR_PTR(-ECHILD);
+
+ path = vboxsf_path_from_dentry(sbi, dentry);
+ if (IS_ERR(path))
+ return ERR_CAST(path);
+
+ link = kzalloc(PATH_MAX, GFP_KERNEL);
+ if (!link) {
+ __putname(path);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);
+ __putname(path);
+ if (err) {
+ kfree(link);
+ return ERR_PTR(err);
+ }
+
+ set_delayed_call(done, kfree_link, link);
+ return link;
+}
+
+const struct inode_operations vboxsf_lnk_iops = {
+ .get_link = vboxsf_get_link
+};