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1// SPDX-License-Identifier: MIT2/*3 * VirtualBox Guest Shared Folders support: Regular file inode and file ops.4 *5 * Copyright (C) 2006-2018 Oracle Corporation6 */7 8#include <linux/mm.h>9#include <linux/page-flags.h>10#include <linux/pagemap.h>11#include <linux/highmem.h>12#include <linux/sizes.h>13#include "vfsmod.h"14 15struct vboxsf_handle {16 u64 handle;17 u32 root;18 u32 access_flags;19 struct kref refcount;20 struct list_head head;21};22 23struct vboxsf_handle *vboxsf_create_sf_handle(struct inode *inode,24 u64 handle, u32 access_flags)25{26 struct vboxsf_inode *sf_i = VBOXSF_I(inode);27 struct vboxsf_handle *sf_handle;28 29 sf_handle = kmalloc(sizeof(*sf_handle), GFP_KERNEL);30 if (!sf_handle)31 return ERR_PTR(-ENOMEM);32 33 /* the host may have given us different attr then requested */34 sf_i->force_restat = 1;35 36 /* init our handle struct and add it to the inode's handles list */37 sf_handle->handle = handle;38 sf_handle->root = VBOXSF_SBI(inode->i_sb)->root;39 sf_handle->access_flags = access_flags;40 kref_init(&sf_handle->refcount);41 42 mutex_lock(&sf_i->handle_list_mutex);43 list_add(&sf_handle->head, &sf_i->handle_list);44 mutex_unlock(&sf_i->handle_list_mutex);45 46 return sf_handle;47}48 49static int vboxsf_file_open(struct inode *inode, struct file *file)50{51 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);52 struct shfl_createparms params = {};53 struct vboxsf_handle *sf_handle;54 u32 access_flags = 0;55 int err;56 57 /*58 * We check the value of params.handle afterwards to find out if59 * the call succeeded or failed, as the API does not seem to cleanly60 * distinguish error and informational messages.61 *62 * Furthermore, we must set params.handle to SHFL_HANDLE_NIL to63 * make the shared folders host service use our mode parameter.64 */65 params.handle = SHFL_HANDLE_NIL;66 if (file->f_flags & O_CREAT) {67 params.create_flags |= SHFL_CF_ACT_CREATE_IF_NEW;68 /*69 * We ignore O_EXCL, as the Linux kernel seems to call create70 * beforehand itself, so O_EXCL should always fail.71 */72 if (file->f_flags & O_TRUNC)73 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;74 else75 params.create_flags |= SHFL_CF_ACT_OPEN_IF_EXISTS;76 } else {77 params.create_flags |= SHFL_CF_ACT_FAIL_IF_NEW;78 if (file->f_flags & O_TRUNC)79 params.create_flags |= SHFL_CF_ACT_OVERWRITE_IF_EXISTS;80 }81 82 switch (file->f_flags & O_ACCMODE) {83 case O_RDONLY:84 access_flags |= SHFL_CF_ACCESS_READ;85 break;86 87 case O_WRONLY:88 access_flags |= SHFL_CF_ACCESS_WRITE;89 break;90 91 case O_RDWR:92 access_flags |= SHFL_CF_ACCESS_READWRITE;93 break;94 95 default:96 WARN_ON(1);97 }98 99 if (file->f_flags & O_APPEND)100 access_flags |= SHFL_CF_ACCESS_APPEND;101 102 params.create_flags |= access_flags;103 params.info.attr.mode = inode->i_mode;104 105 err = vboxsf_create_at_dentry(file_dentry(file), ¶ms);106 if (err == 0 && params.handle == SHFL_HANDLE_NIL)107 err = (params.result == SHFL_FILE_EXISTS) ? -EEXIST : -ENOENT;108 if (err)109 return err;110 111 sf_handle = vboxsf_create_sf_handle(inode, params.handle, access_flags);112 if (IS_ERR(sf_handle)) {113 vboxsf_close(sbi->root, params.handle);114 return PTR_ERR(sf_handle);115 }116 117 file->private_data = sf_handle;118 return 0;119}120 121static void vboxsf_handle_release(struct kref *refcount)122{123 struct vboxsf_handle *sf_handle =124 container_of(refcount, struct vboxsf_handle, refcount);125 126 vboxsf_close(sf_handle->root, sf_handle->handle);127 kfree(sf_handle);128}129 130void vboxsf_release_sf_handle(struct inode *inode, struct vboxsf_handle *sf_handle)131{132 struct vboxsf_inode *sf_i = VBOXSF_I(inode);133 134 mutex_lock(&sf_i->handle_list_mutex);135 list_del(&sf_handle->head);136 mutex_unlock(&sf_i->handle_list_mutex);137 138 kref_put(&sf_handle->refcount, vboxsf_handle_release);139}140 141static int vboxsf_file_release(struct inode *inode, struct file *file)142{143 /*144 * When a file is closed on our (the guest) side, we want any subsequent145 * accesses done on the host side to see all changes done from our side.146 */147 filemap_write_and_wait(inode->i_mapping);148 149 vboxsf_release_sf_handle(inode, file->private_data);150 return 0;151}152 153/*154 * Write back dirty pages now, because there may not be any suitable155 * open files later156 */157static void vboxsf_vma_close(struct vm_area_struct *vma)158{159 filemap_write_and_wait(vma->vm_file->f_mapping);160}161 162static const struct vm_operations_struct vboxsf_file_vm_ops = {163 .close = vboxsf_vma_close,164 .fault = filemap_fault,165 .map_pages = filemap_map_pages,166};167 168static int vboxsf_file_mmap(struct file *file, struct vm_area_struct *vma)169{170 int err;171 172 err = generic_file_mmap(file, vma);173 if (!err)174 vma->vm_ops = &vboxsf_file_vm_ops;175 176 return err;177}178 179/*180 * Note that since we are accessing files on the host's filesystem, files181 * may always be changed underneath us by the host!182 *183 * The vboxsf API between the guest and the host does not offer any functions184 * to deal with this. There is no inode-generation to check for changes, no185 * events / callback on changes and no way to lock files.186 *187 * To avoid returning stale data when a file gets *opened* on our (the guest)188 * side, we do a "stat" on the host side, then compare the mtime with the189 * last known mtime and invalidate the page-cache if they differ.190 * This is done from vboxsf_inode_revalidate().191 *192 * When reads are done through the read_iter fop, it is possible to do193 * further cache revalidation then, there are 3 options to deal with this:194 *195 * 1) Rely solely on the revalidation done at open time196 * 2) Do another "stat" and compare mtime again. Unfortunately the vboxsf197 * host API does not allow stat on handles, so we would need to use198 * file->f_path.dentry and the stat will then fail if the file was unlinked199 * or renamed (and there is no thing like NFS' silly-rename). So we get:200 * 2a) "stat" and compare mtime, on stat failure invalidate the cache201 * 2b) "stat" and compare mtime, on stat failure do nothing202 * 3) Simply always call invalidate_inode_pages2_range on the range of the read203 *204 * Currently we are keeping things KISS and using option 1. this allows205 * directly using generic_file_read_iter without wrapping it.206 *207 * This means that only data written on the host side before open() on208 * the guest side is guaranteed to be seen by the guest. If necessary209 * we may provide other read-cache strategies in the future and make this210 * configurable through a mount option.211 */212const struct file_operations vboxsf_reg_fops = {213 .llseek = generic_file_llseek,214 .read_iter = generic_file_read_iter,215 .write_iter = generic_file_write_iter,216 .mmap = vboxsf_file_mmap,217 .open = vboxsf_file_open,218 .release = vboxsf_file_release,219 .fsync = noop_fsync,220 .splice_read = filemap_splice_read,221 .setlease = simple_nosetlease,222};223 224const struct inode_operations vboxsf_reg_iops = {225 .getattr = vboxsf_getattr,226 .setattr = vboxsf_setattr227};228 229static int vboxsf_read_folio(struct file *file, struct folio *folio)230{231 struct vboxsf_handle *sf_handle = file->private_data;232 loff_t off = folio_pos(folio);233 u32 nread = PAGE_SIZE;234 u8 *buf;235 int err;236 237 buf = kmap_local_folio(folio, 0);238 239 err = vboxsf_read(sf_handle->root, sf_handle->handle, off, &nread, buf);240 buf = folio_zero_tail(folio, nread, buf + nread);241 242 kunmap_local(buf);243 folio_end_read(folio, err == 0);244 return err;245}246 247static struct vboxsf_handle *vboxsf_get_write_handle(struct vboxsf_inode *sf_i)248{249 struct vboxsf_handle *h, *sf_handle = NULL;250 251 mutex_lock(&sf_i->handle_list_mutex);252 list_for_each_entry(h, &sf_i->handle_list, head) {253 if (h->access_flags == SHFL_CF_ACCESS_WRITE ||254 h->access_flags == SHFL_CF_ACCESS_READWRITE) {255 kref_get(&h->refcount);256 sf_handle = h;257 break;258 }259 }260 mutex_unlock(&sf_i->handle_list_mutex);261 262 return sf_handle;263}264 265static int vboxsf_writepage(struct page *page, struct writeback_control *wbc)266{267 struct inode *inode = page->mapping->host;268 struct vboxsf_inode *sf_i = VBOXSF_I(inode);269 struct vboxsf_handle *sf_handle;270 loff_t off = page_offset(page);271 loff_t size = i_size_read(inode);272 u32 nwrite = PAGE_SIZE;273 u8 *buf;274 int err;275 276 if (off + PAGE_SIZE > size)277 nwrite = size & ~PAGE_MASK;278 279 sf_handle = vboxsf_get_write_handle(sf_i);280 if (!sf_handle)281 return -EBADF;282 283 buf = kmap(page);284 err = vboxsf_write(sf_handle->root, sf_handle->handle,285 off, &nwrite, buf);286 kunmap(page);287 288 kref_put(&sf_handle->refcount, vboxsf_handle_release);289 290 if (err == 0) {291 /* mtime changed */292 sf_i->force_restat = 1;293 } else {294 ClearPageUptodate(page);295 }296 297 unlock_page(page);298 return err;299}300 301static int vboxsf_write_end(struct file *file, struct address_space *mapping,302 loff_t pos, unsigned int len, unsigned int copied,303 struct folio *folio, void *fsdata)304{305 struct inode *inode = mapping->host;306 struct vboxsf_handle *sf_handle = file->private_data;307 size_t from = offset_in_folio(folio, pos);308 u32 nwritten = len;309 u8 *buf;310 int err;311 312 /* zero the stale part of the folio if we did a short copy */313 if (!folio_test_uptodate(folio) && copied < len)314 folio_zero_range(folio, from + copied, len - copied);315 316 buf = kmap(&folio->page);317 err = vboxsf_write(sf_handle->root, sf_handle->handle,318 pos, &nwritten, buf + from);319 kunmap(&folio->page);320 321 if (err) {322 nwritten = 0;323 goto out;324 }325 326 /* mtime changed */327 VBOXSF_I(inode)->force_restat = 1;328 329 if (!folio_test_uptodate(folio) && nwritten == folio_size(folio))330 folio_mark_uptodate(folio);331 332 pos += nwritten;333 if (pos > inode->i_size)334 i_size_write(inode, pos);335 336out:337 folio_unlock(folio);338 folio_put(folio);339 340 return nwritten;341}342 343/*344 * Note simple_write_begin does not read the page from disk on partial writes345 * this is ok since vboxsf_write_end only writes the written parts of the346 * page and it does not call folio_mark_uptodate for partial writes.347 */348const struct address_space_operations vboxsf_reg_aops = {349 .read_folio = vboxsf_read_folio,350 .writepage = vboxsf_writepage,351 .dirty_folio = filemap_dirty_folio,352 .write_begin = simple_write_begin,353 .write_end = vboxsf_write_end,354};355 356static const char *vboxsf_get_link(struct dentry *dentry, struct inode *inode,357 struct delayed_call *done)358{359 struct vboxsf_sbi *sbi = VBOXSF_SBI(inode->i_sb);360 struct shfl_string *path;361 char *link;362 int err;363 364 if (!dentry)365 return ERR_PTR(-ECHILD);366 367 path = vboxsf_path_from_dentry(sbi, dentry);368 if (IS_ERR(path))369 return ERR_CAST(path);370 371 link = kzalloc(PATH_MAX, GFP_KERNEL);372 if (!link) {373 __putname(path);374 return ERR_PTR(-ENOMEM);375 }376 377 err = vboxsf_readlink(sbi->root, path, PATH_MAX, link);378 __putname(path);379 if (err) {380 kfree(link);381 return ERR_PTR(err);382 }383 384 set_delayed_call(done, kfree_link, link);385 return link;386}387 388const struct inode_operations vboxsf_lnk_iops = {389 .get_link = vboxsf_get_link390};391