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0fd1695766
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>
380 lines
9.9 KiB
C
380 lines
9.9 KiB
C
// SPDX-License-Identifier: MIT
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/*
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* VirtualBox Guest Shared Folders support: Regular file inode and file ops.
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*
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* Copyright (C) 2006-2018 Oracle Corporation
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*/
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#include <linux/mm.h>
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#include <linux/page-flags.h>
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/sizes.h>
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#include "vfsmod.h"
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struct vboxsf_handle {
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u64 handle;
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u32 root;
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u32 access_flags;
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struct kref refcount;
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struct list_head head;
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};
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static int vboxsf_file_open(struct inode *inode, struct file *file)
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{
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struct vboxsf_inode *sf_i = VBOXSF_I(inode);
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struct shfl_createparms params = {};
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struct vboxsf_handle *sf_handle;
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u32 access_flags = 0;
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int err;
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sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);
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if (!sf_handle)
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return -ENOMEM;
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/*
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* We check the value of params.handle afterwards to find out if
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* the call succeeded or failed, as the API does not seem to cleanly
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* distinguish error and informational messages.
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*
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* Furthermore, we must set params.handle to SHFL_HANDLE_NIL to
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* make the shared folders host service use our mode parameter.
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*/
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params.handle = SHFL_HANDLE_NIL;
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if (file->f_flags & O_CREAT) {
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params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;
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/*
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* We ignore O_EXCL, as the Linux kernel seems to call create
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* beforehand itself, so O_EXCL should always fail.
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*/
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if (file->f_flags & O_TRUNC)
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params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
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else
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params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
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} else {
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params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;
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if (file->f_flags & O_TRUNC)
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params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;
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}
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switch (file->f_flags & O_ACCMODE) {
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case O_RDONLY:
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access_flags |= SHFL_CF_ACCESS_READ;
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break;
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case O_WRONLY:
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access_flags |= SHFL_CF_ACCESS_WRITE;
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break;
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case O_RDWR:
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access_flags |= SHFL_CF_ACCESS_READWRITE;
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break;
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default:
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WARN_ON(1);
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}
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if (file->f_flags & O_APPEND)
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access_flags |= SHFL_CF_ACCESS_APPEND;
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params.create_flags |= access_flags;
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params.info.attr.mode = inode->i_mode;
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err = vboxsf_create_at_dentry(file_dentry(file), ¶ms);
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if (err == 0 && params.handle == SHFL_HANDLE_NIL)
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err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;
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if (err) {
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kfree(sf_handle);
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return err;
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}
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/* the host may have given us different attr then requested */
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sf_i->force_restat = 1;
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/* init our handle struct and add it to the inode's handles list */
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sf_handle->handle = params.handle;
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sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;
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sf_handle->access_flags = access_flags;
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kref_init(&sf_handle->refcount);
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mutex_lock(&sf_i->handle_list_mutex);
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list_add(&sf_handle->head, &sf_i->handle_list);
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mutex_unlock(&sf_i->handle_list_mutex);
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file->private_data = sf_handle;
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return 0;
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}
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static void vboxsf_handle_release(struct kref *refcount)
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{
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struct vboxsf_handle *sf_handle =
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container_of(refcount, struct vboxsf_handle, refcount);
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vboxsf_close(sf_handle->root, sf_handle->handle);
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kfree(sf_handle);
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}
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static int vboxsf_file_release(struct inode *inode, struct file *file)
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{
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struct vboxsf_inode *sf_i = VBOXSF_I(inode);
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struct vboxsf_handle *sf_handle = file->private_data;
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/*
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* When a file is closed on our (the guest) side, we want any subsequent
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* accesses done on the host side to see all changes done from our side.
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*/
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filemap_write_and_wait(inode->i_mapping);
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mutex_lock(&sf_i->handle_list_mutex);
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list_del(&sf_handle->head);
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mutex_unlock(&sf_i->handle_list_mutex);
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kref_put(&sf_handle->refcount, vboxsf_handle_release);
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return 0;
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}
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/*
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* Write back dirty pages now, because there may not be any suitable
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* open files later
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*/
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static void vboxsf_vma_close(struct vm_area_struct *vma)
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{
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filemap_write_and_wait(vma->vm_file->f_mapping);
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}
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static const struct vm_operations_struct vboxsf_file_vm_ops = {
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.close = vboxsf_vma_close,
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.fault = filemap_fault,
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.map_pages = filemap_map_pages,
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};
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static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)
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{
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int err;
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err = generic_file_mmap(file, vma);
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if (!err)
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vma->vm_ops = &vboxsf_file_vm_ops;
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return err;
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}
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/*
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* Note that since we are accessing files on the host's filesystem, files
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* may always be changed underneath us by the host!
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*
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* The vboxsf API between the guest and the host does not offer any functions
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* to deal with this. There is no inode-generation to check for changes, no
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* events / callback on changes and no way to lock files.
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*
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* To avoid returning stale data when a file gets *opened* on our (the guest)
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* side, we do a "stat" on the host side, then compare the mtime with the
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* last known mtime and invalidate the page-cache if they differ.
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* This is done from vboxsf_inode_revalidate().
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*
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* When reads are done through the read_iter fop, it is possible to do
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* further cache revalidation then, there are 3 options to deal with this:
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*
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* 1) Rely solely on the revalidation done at open time
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* 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf
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* host API does not allow stat on handles, so we would need to use
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* file->f_path.dentry and the stat will then fail if the file was unlinked
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* or renamed (and there is no thing like NFS' silly-rename). So we get:
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* 2a) "stat" and compare mtime, on stat failure invalidate the cache
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* 2b) "stat" and compare mtime, on stat failure do nothing
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* 3) Simply always call invalidate_inode_pages2_range on the range of the read
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*
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* Currently we are keeping things KISS and using option 1. this allows
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* directly using generic_file_read_iter without wrapping it.
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*
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* This means that only data written on the host side before open() on
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* the guest side is guaranteed to be seen by the guest. If necessary
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* we may provide other read-cache strategies in the future and make this
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* configurable through a mount option.
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*/
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const struct file_operations vboxsf_reg_fops = {
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.llseek = generic_file_llseek,
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.read_iter = generic_file_read_iter,
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.write_iter = generic_file_write_iter,
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.mmap = vboxsf_file_mmap,
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.open = vboxsf_file_open,
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.release = vboxsf_file_release,
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.fsync = noop_fsync,
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.splice_read = generic_file_splice_read,
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};
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const struct inode_operations vboxsf_reg_iops = {
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.getattr = vboxsf_getattr,
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.setattr = vboxsf_setattr
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};
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static int vboxsf_readpage(struct file *file, struct page *page)
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{
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struct vboxsf_handle *sf_handle = file->private_data;
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loff_t off = page_offset(page);
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u32 nread = PAGE_SIZE;
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u8 *buf;
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int err;
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buf = kmap(page);
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err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);
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if (err == 0) {
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memset(&buf[nread], 0, PAGE_SIZE - nread);
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flush_dcache_page(page);
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SetPageUptodate(page);
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} else {
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SetPageError(page);
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}
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kunmap(page);
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unlock_page(page);
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return err;
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}
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static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)
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{
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struct vboxsf_handle *h, *sf_handle = NULL;
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mutex_lock(&sf_i->handle_list_mutex);
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list_for_each_entry(h, &sf_i->handle_list, head) {
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if (h->access_flags == SHFL_CF_ACCESS_WRITE ||
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h->access_flags == SHFL_CF_ACCESS_READWRITE) {
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kref_get(&h->refcount);
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sf_handle = h;
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break;
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}
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}
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mutex_unlock(&sf_i->handle_list_mutex);
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return sf_handle;
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}
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static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)
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{
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struct inode *inode = page->mapping->host;
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struct vboxsf_inode *sf_i = VBOXSF_I(inode);
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struct vboxsf_handle *sf_handle;
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loff_t off = page_offset(page);
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loff_t size = i_size_read(inode);
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u32 nwrite = PAGE_SIZE;
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u8 *buf;
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int err;
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if (off + PAGE_SIZE > size)
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nwrite = size & ~PAGE_MASK;
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sf_handle = vboxsf_get_write_handle(sf_i);
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if (!sf_handle)
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return -EBADF;
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buf = kmap(page);
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err = vboxsf_write(sf_handle->root, sf_handle->handle,
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off, &nwrite, buf);
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kunmap(page);
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kref_put(&sf_handle->refcount, vboxsf_handle_release);
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if (err == 0) {
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ClearPageError(page);
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/* mtime changed */
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sf_i->force_restat = 1;
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} else {
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ClearPageUptodate(page);
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}
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unlock_page(page);
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return err;
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}
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static int vboxsf_write_end(struct file *file, struct address_space *mapping,
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loff_t pos, unsigned int len, unsigned int copied,
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struct page *page, void *fsdata)
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{
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struct inode *inode = mapping->host;
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struct vboxsf_handle *sf_handle = file->private_data;
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unsigned int from = pos & ~PAGE_MASK;
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u32 nwritten = len;
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u8 *buf;
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int err;
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/* zero the stale part of the page if we did a short copy */
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if (!PageUptodate(page) && copied < len)
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zero_user(page, from + copied, len - copied);
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buf = kmap(page);
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err = vboxsf_write(sf_handle->root, sf_handle->handle,
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pos, &nwritten, buf + from);
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kunmap(page);
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if (err) {
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nwritten = 0;
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goto out;
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}
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/* mtime changed */
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VBOXSF_I(inode)->force_restat = 1;
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if (!PageUptodate(page) && nwritten == PAGE_SIZE)
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SetPageUptodate(page);
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pos += nwritten;
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if (pos > inode->i_size)
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i_size_write(inode, pos);
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out:
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unlock_page(page);
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put_page(page);
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return nwritten;
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}
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/*
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* Note simple_write_begin does not read the page from disk on partial writes
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* this is ok since vboxsf_write_end only writes the written parts of the
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* page and it does not call SetPageUptodate for partial writes.
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*/
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const struct address_space_operations vboxsf_reg_aops = {
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.readpage = vboxsf_readpage,
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.writepage = vboxsf_writepage,
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.set_page_dirty = __set_page_dirty_nobuffers,
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.write_begin = simple_write_begin,
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.write_end = vboxsf_write_end,
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};
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static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,
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struct delayed_call *done)
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{
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struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);
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struct shfl_string *path;
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char *link;
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int err;
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if (!dentry)
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return ERR_PTR(-ECHILD);
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path = vboxsf_path_from_dentry(sbi, dentry);
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if (IS_ERR(path))
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return ERR_CAST(path);
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link = kzalloc(PATH_MAX, GFP_KERNEL);
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if (!link) {
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__putname(path);
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return ERR_PTR(-ENOMEM);
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}
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err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);
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__putname(path);
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if (err) {
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kfree(link);
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return ERR_PTR(err);
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}
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set_delayed_call(done, kfree_link, link);
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return link;
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}
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const struct inode_operations vboxsf_lnk_iops = {
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.get_link = vboxsf_get_link
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};
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