| // 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; |
| }; |
| |
| struct vboxsf_handle *vboxsf_create_sf_handle(struct inode *inode, |
| u64 handle, u32 access_flags) |
| { |
| struct vboxsf_inode *sf_i = VBOXSF_I(inode); |
| struct vboxsf_handle *sf_handle; |
| |
| sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL); |
| if (!sf_handle) |
| return ERR_PTR(-ENOMEM); |
| |
| /* 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 = 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); |
| |
| return sf_handle; |
| } |
| |
| static int vboxsf_file_open(struct inode *inode, struct file *file) |
| { |
| struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb); |
| struct shfl_createparms params = {}; |
| struct vboxsf_handle *sf_handle; |
| u32 access_flags = 0; |
| int err; |
| |
| /* |
| * 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), ¶ms); |
| if (err == 0 && params.handle == SHFL_HANDLE_NIL) |
| err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT; |
| if (err) |
| return err; |
| |
| sf_handle = vboxsf_create_sf_handle(inode, params.handle, access_flags); |
| if (IS_ERR(sf_handle)) { |
| vboxsf_close(sbi->root, params.handle); |
| return PTR_ERR(sf_handle); |
| } |
| |
| 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); |
| } |
| |
| void vboxsf_release_sf_handle(struct inode *inode, struct vboxsf_handle *sf_handle) |
| { |
| struct vboxsf_inode *sf_i = VBOXSF_I(inode); |
| |
| 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); |
| } |
| |
| static int vboxsf_file_release(struct inode *inode, struct file *file) |
| { |
| /* |
| * 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); |
| |
| vboxsf_release_sf_handle(inode, file->private_data); |
| 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 = filemap_splice_read, |
| .setlease = simple_nosetlease, |
| }; |
| |
| const struct inode_operations vboxsf_reg_iops = { |
| .getattr = vboxsf_getattr, |
| .setattr = vboxsf_setattr |
| }; |
| |
| static int vboxsf_read_folio(struct file *file, struct folio *folio) |
| { |
| struct vboxsf_handle *sf_handle = file->private_data; |
| loff_t off = folio_pos(folio); |
| u32 nread = PAGE_SIZE; |
| u8 *buf; |
| int err; |
| |
| buf = kmap_local_folio(folio, 0); |
| |
| err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf); |
| buf = folio_zero_tail(folio, nread, buf + nread); |
| |
| kunmap_local(buf); |
| folio_end_read(folio, err == 0); |
| 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) { |
| /* 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 = { |
| .read_folio = vboxsf_read_folio, |
| .writepage = vboxsf_writepage, |
| .dirty_folio = filemap_dirty_folio, |
| .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 |
| }; |