1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Common helpers for stackable filesystems and backing files. 4 * 5 * Forked from fs/overlayfs/file.c. 6 * 7 * Copyright (C) 2017 Red Hat, Inc. 8 * Copyright (C) 2023 CTERA Networks. 9 */ 10 11 #include <linux/fs.h> 12 #include <linux/backing-file.h> 13 #include <linux/splice.h> 14 #include <linux/mm.h> 15 16 #include "internal.h" 17 18 /** 19 * backing_file_open - open a backing file for kernel internal use 20 * @user_path: path that the user reuqested to open 21 * @flags: open flags 22 * @real_path: path of the backing file 23 * @cred: credentials for open 24 * 25 * Open a backing file for a stackable filesystem (e.g., overlayfs). 26 * @user_path may be on the stackable filesystem and @real_path on the 27 * underlying filesystem. In this case, we want to be able to return the 28 * @user_path of the stackable filesystem. This is done by embedding the 29 * returned file into a container structure that also stores the stacked 30 * file's path, which can be retrieved using backing_file_user_path(). 31 */ 32 struct file *backing_file_open(const struct path *user_path, int flags, 33 const struct path *real_path, 34 const struct cred *cred) 35 { 36 struct file *f; 37 int error; 38 39 f = alloc_empty_backing_file(flags, cred); 40 if (IS_ERR(f)) 41 return f; 42 43 path_get(user_path); 44 backing_file_set_user_path(f, user_path); 45 error = vfs_open(real_path, f); 46 if (error) { 47 fput(f); 48 f = ERR_PTR(error); 49 } 50 51 return f; 52 } 53 EXPORT_SYMBOL_GPL(backing_file_open); 54 55 struct file *backing_tmpfile_open(const struct path *user_path, int flags, 56 const struct path *real_parentpath, 57 umode_t mode, const struct cred *cred) 58 { 59 struct mnt_idmap *real_idmap = mnt_idmap(real_parentpath->mnt); 60 struct file *f; 61 int error; 62 63 f = alloc_empty_backing_file(flags, cred); 64 if (IS_ERR(f)) 65 return f; 66 67 path_get(user_path); 68 backing_file_set_user_path(f, user_path); 69 error = vfs_tmpfile(real_idmap, real_parentpath, f, mode); 70 if (error) { 71 fput(f); 72 f = ERR_PTR(error); 73 } 74 return f; 75 } 76 EXPORT_SYMBOL(backing_tmpfile_open); 77 78 struct backing_aio { 79 struct kiocb iocb; 80 refcount_t ref; 81 struct kiocb *orig_iocb; 82 /* used for aio completion */ 83 void (*end_write)(struct kiocb *iocb, ssize_t); 84 struct work_struct work; 85 long res; 86 }; 87 88 static struct kmem_cache *backing_aio_cachep; 89 90 #define BACKING_IOCB_MASK \ 91 (IOCB_NOWAIT | IOCB_HIPRI | IOCB_DSYNC | IOCB_SYNC | IOCB_APPEND) 92 93 static rwf_t iocb_to_rw_flags(int flags) 94 { 95 return (__force rwf_t)(flags & BACKING_IOCB_MASK); 96 } 97 98 static void backing_aio_put(struct backing_aio *aio) 99 { 100 if (refcount_dec_and_test(&aio->ref)) { 101 fput(aio->iocb.ki_filp); 102 kmem_cache_free(backing_aio_cachep, aio); 103 } 104 } 105 106 static void backing_aio_cleanup(struct backing_aio *aio, long res) 107 { 108 struct kiocb *iocb = &aio->iocb; 109 struct kiocb *orig_iocb = aio->orig_iocb; 110 111 orig_iocb->ki_pos = iocb->ki_pos; 112 if (aio->end_write) 113 aio->end_write(orig_iocb, res); 114 115 backing_aio_put(aio); 116 } 117 118 static void backing_aio_rw_complete(struct kiocb *iocb, long res) 119 { 120 struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb); 121 struct kiocb *orig_iocb = aio->orig_iocb; 122 123 if (iocb->ki_flags & IOCB_WRITE) 124 kiocb_end_write(iocb); 125 126 backing_aio_cleanup(aio, res); 127 orig_iocb->ki_complete(orig_iocb, res); 128 } 129 130 static void backing_aio_complete_work(struct work_struct *work) 131 { 132 struct backing_aio *aio = container_of(work, struct backing_aio, work); 133 134 backing_aio_rw_complete(&aio->iocb, aio->res); 135 } 136 137 static void backing_aio_queue_completion(struct kiocb *iocb, long res) 138 { 139 struct backing_aio *aio = container_of(iocb, struct backing_aio, iocb); 140 141 /* 142 * Punt to a work queue to serialize updates of mtime/size. 143 */ 144 aio->res = res; 145 INIT_WORK(&aio->work, backing_aio_complete_work); 146 queue_work(file_inode(aio->orig_iocb->ki_filp)->i_sb->s_dio_done_wq, 147 &aio->work); 148 } 149 150 static int backing_aio_init_wq(struct kiocb *iocb) 151 { 152 struct super_block *sb = file_inode(iocb->ki_filp)->i_sb; 153 154 if (sb->s_dio_done_wq) 155 return 0; 156 157 return sb_init_dio_done_wq(sb); 158 } 159 160 161 ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, 162 struct kiocb *iocb, int flags, 163 struct backing_file_ctx *ctx) 164 { 165 struct backing_aio *aio = NULL; 166 const struct cred *old_cred; 167 ssize_t ret; 168 169 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 170 return -EIO; 171 172 if (!iov_iter_count(iter)) 173 return 0; 174 175 if (iocb->ki_flags & IOCB_DIRECT && 176 !(file->f_mode & FMODE_CAN_ODIRECT)) 177 return -EINVAL; 178 179 old_cred = override_creds(ctx->cred); 180 if (is_sync_kiocb(iocb)) { 181 rwf_t rwf = iocb_to_rw_flags(flags); 182 183 ret = vfs_iter_read(file, iter, &iocb->ki_pos, rwf); 184 } else { 185 ret = -ENOMEM; 186 aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); 187 if (!aio) 188 goto out; 189 190 aio->orig_iocb = iocb; 191 kiocb_clone(&aio->iocb, iocb, get_file(file)); 192 aio->iocb.ki_complete = backing_aio_rw_complete; 193 refcount_set(&aio->ref, 2); 194 ret = vfs_iocb_iter_read(file, &aio->iocb, iter); 195 backing_aio_put(aio); 196 if (ret != -EIOCBQUEUED) 197 backing_aio_cleanup(aio, ret); 198 } 199 out: 200 revert_creds(old_cred); 201 202 if (ctx->accessed) 203 ctx->accessed(iocb->ki_filp); 204 205 return ret; 206 } 207 EXPORT_SYMBOL_GPL(backing_file_read_iter); 208 209 ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, 210 struct kiocb *iocb, int flags, 211 struct backing_file_ctx *ctx) 212 { 213 const struct cred *old_cred; 214 ssize_t ret; 215 216 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 217 return -EIO; 218 219 if (!iov_iter_count(iter)) 220 return 0; 221 222 ret = file_remove_privs(iocb->ki_filp); 223 if (ret) 224 return ret; 225 226 if (iocb->ki_flags & IOCB_DIRECT && 227 !(file->f_mode & FMODE_CAN_ODIRECT)) 228 return -EINVAL; 229 230 old_cred = override_creds(ctx->cred); 231 if (is_sync_kiocb(iocb)) { 232 rwf_t rwf = iocb_to_rw_flags(flags); 233 234 ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); 235 if (ctx->end_write) 236 ctx->end_write(iocb, ret); 237 } else { 238 struct backing_aio *aio; 239 240 ret = backing_aio_init_wq(iocb); 241 if (ret) 242 goto out; 243 244 ret = -ENOMEM; 245 aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); 246 if (!aio) 247 goto out; 248 249 aio->orig_iocb = iocb; 250 aio->end_write = ctx->end_write; 251 kiocb_clone(&aio->iocb, iocb, get_file(file)); 252 aio->iocb.ki_flags = flags; 253 aio->iocb.ki_complete = backing_aio_queue_completion; 254 refcount_set(&aio->ref, 2); 255 ret = vfs_iocb_iter_write(file, &aio->iocb, iter); 256 backing_aio_put(aio); 257 if (ret != -EIOCBQUEUED) 258 backing_aio_cleanup(aio, ret); 259 } 260 out: 261 revert_creds(old_cred); 262 263 return ret; 264 } 265 EXPORT_SYMBOL_GPL(backing_file_write_iter); 266 267 ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb, 268 struct pipe_inode_info *pipe, size_t len, 269 unsigned int flags, 270 struct backing_file_ctx *ctx) 271 { 272 const struct cred *old_cred; 273 ssize_t ret; 274 275 if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING))) 276 return -EIO; 277 278 old_cred = override_creds(ctx->cred); 279 ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags); 280 revert_creds(old_cred); 281 282 if (ctx->accessed) 283 ctx->accessed(iocb->ki_filp); 284 285 return ret; 286 } 287 EXPORT_SYMBOL_GPL(backing_file_splice_read); 288 289 ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, 290 struct file *out, struct kiocb *iocb, 291 size_t len, unsigned int flags, 292 struct backing_file_ctx *ctx) 293 { 294 const struct cred *old_cred; 295 ssize_t ret; 296 297 if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) 298 return -EIO; 299 300 if (!out->f_op->splice_write) 301 return -EINVAL; 302 303 ret = file_remove_privs(iocb->ki_filp); 304 if (ret) 305 return ret; 306 307 old_cred = override_creds(ctx->cred); 308 file_start_write(out); 309 ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags); 310 file_end_write(out); 311 revert_creds(old_cred); 312 313 if (ctx->end_write) 314 ctx->end_write(iocb, ret); 315 316 return ret; 317 } 318 EXPORT_SYMBOL_GPL(backing_file_splice_write); 319 320 int backing_file_mmap(struct file *file, struct vm_area_struct *vma, 321 struct backing_file_ctx *ctx) 322 { 323 const struct cred *old_cred; 324 struct file *user_file = vma->vm_file; 325 int ret; 326 327 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 328 return -EIO; 329 330 if (!can_mmap_file(file)) 331 return -ENODEV; 332 333 vma_set_file(vma, file); 334 335 old_cred = override_creds(ctx->cred); 336 ret = vfs_mmap(vma->vm_file, vma); 337 revert_creds(old_cred); 338 339 if (ctx->accessed) 340 ctx->accessed(user_file); 341 342 return ret; 343 } 344 EXPORT_SYMBOL_GPL(backing_file_mmap); 345 346 static int __init backing_aio_init(void) 347 { 348 backing_aio_cachep = KMEM_CACHE(backing_aio, SLAB_HWCACHE_ALIGN); 349 if (!backing_aio_cachep) 350 return -ENOMEM; 351 352 return 0; 353 } 354 fs_initcall(backing_aio_init); 355