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 static int do_backing_file_read_iter(struct file *file, struct iov_iter *iter, 161 struct kiocb *iocb, int flags) 162 { 163 struct backing_aio *aio = NULL; 164 int ret; 165 166 if (is_sync_kiocb(iocb)) { 167 rwf_t rwf = iocb_to_rw_flags(flags); 168 169 return vfs_iter_read(file, iter, &iocb->ki_pos, rwf); 170 } 171 172 aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); 173 if (!aio) 174 return -ENOMEM; 175 176 aio->orig_iocb = iocb; 177 kiocb_clone(&aio->iocb, iocb, get_file(file)); 178 aio->iocb.ki_complete = backing_aio_rw_complete; 179 refcount_set(&aio->ref, 2); 180 ret = vfs_iocb_iter_read(file, &aio->iocb, iter); 181 backing_aio_put(aio); 182 if (ret != -EIOCBQUEUED) 183 backing_aio_cleanup(aio, ret); 184 return ret; 185 } 186 187 ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter, 188 struct kiocb *iocb, int flags, 189 struct backing_file_ctx *ctx) 190 { 191 ssize_t ret; 192 193 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 194 return -EIO; 195 196 if (!iov_iter_count(iter)) 197 return 0; 198 199 if (iocb->ki_flags & IOCB_DIRECT && 200 !(file->f_mode & FMODE_CAN_ODIRECT)) 201 return -EINVAL; 202 203 scoped_with_creds(ctx->cred) 204 ret = do_backing_file_read_iter(file, iter, iocb, flags); 205 206 if (ctx->accessed) 207 ctx->accessed(iocb->ki_filp); 208 209 return ret; 210 } 211 EXPORT_SYMBOL_GPL(backing_file_read_iter); 212 213 static int do_backing_file_write_iter(struct file *file, struct iov_iter *iter, 214 struct kiocb *iocb, int flags, 215 void (*end_write)(struct kiocb *, ssize_t)) 216 { 217 struct backing_aio *aio; 218 int ret; 219 220 if (is_sync_kiocb(iocb)) { 221 rwf_t rwf = iocb_to_rw_flags(flags); 222 223 ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf); 224 if (end_write) 225 end_write(iocb, ret); 226 return ret; 227 } 228 229 ret = backing_aio_init_wq(iocb); 230 if (ret) 231 return ret; 232 233 aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL); 234 if (!aio) 235 return -ENOMEM; 236 237 aio->orig_iocb = iocb; 238 aio->end_write = end_write; 239 kiocb_clone(&aio->iocb, iocb, get_file(file)); 240 aio->iocb.ki_flags = flags; 241 aio->iocb.ki_complete = backing_aio_queue_completion; 242 refcount_set(&aio->ref, 2); 243 ret = vfs_iocb_iter_write(file, &aio->iocb, iter); 244 backing_aio_put(aio); 245 if (ret != -EIOCBQUEUED) 246 backing_aio_cleanup(aio, ret); 247 return ret; 248 } 249 250 ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter, 251 struct kiocb *iocb, int flags, 252 struct backing_file_ctx *ctx) 253 { 254 ssize_t ret; 255 256 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 257 return -EIO; 258 259 if (!iov_iter_count(iter)) 260 return 0; 261 262 ret = file_remove_privs(iocb->ki_filp); 263 if (ret) 264 return ret; 265 266 if (iocb->ki_flags & IOCB_DIRECT && 267 !(file->f_mode & FMODE_CAN_ODIRECT)) 268 return -EINVAL; 269 270 scoped_with_creds(ctx->cred) 271 return do_backing_file_write_iter(file, iter, iocb, flags, ctx->end_write); 272 } 273 EXPORT_SYMBOL_GPL(backing_file_write_iter); 274 275 ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb, 276 struct pipe_inode_info *pipe, size_t len, 277 unsigned int flags, 278 struct backing_file_ctx *ctx) 279 { 280 ssize_t ret; 281 282 if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING))) 283 return -EIO; 284 285 scoped_with_creds(ctx->cred) 286 ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags); 287 288 if (ctx->accessed) 289 ctx->accessed(iocb->ki_filp); 290 291 return ret; 292 } 293 EXPORT_SYMBOL_GPL(backing_file_splice_read); 294 295 ssize_t backing_file_splice_write(struct pipe_inode_info *pipe, 296 struct file *out, struct kiocb *iocb, 297 size_t len, unsigned int flags, 298 struct backing_file_ctx *ctx) 299 { 300 ssize_t ret; 301 302 if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING))) 303 return -EIO; 304 305 if (!out->f_op->splice_write) 306 return -EINVAL; 307 308 ret = file_remove_privs(iocb->ki_filp); 309 if (ret) 310 return ret; 311 312 scoped_with_creds(ctx->cred) { 313 file_start_write(out); 314 ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags); 315 file_end_write(out); 316 } 317 318 if (ctx->end_write) 319 ctx->end_write(iocb, ret); 320 321 return ret; 322 } 323 EXPORT_SYMBOL_GPL(backing_file_splice_write); 324 325 int backing_file_mmap(struct file *file, struct vm_area_struct *vma, 326 struct backing_file_ctx *ctx) 327 { 328 struct file *user_file = vma->vm_file; 329 int ret; 330 331 if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) 332 return -EIO; 333 334 if (!can_mmap_file(file)) 335 return -ENODEV; 336 337 vma_set_file(vma, file); 338 339 scoped_with_creds(ctx->cred) 340 ret = vfs_mmap(vma->vm_file, vma); 341 342 if (ctx->accessed) 343 ctx->accessed(user_file); 344 345 return ret; 346 } 347 EXPORT_SYMBOL_GPL(backing_file_mmap); 348 349 static int __init backing_aio_init(void) 350 { 351 backing_aio_cachep = KMEM_CACHE(backing_aio, SLAB_HWCACHE_ALIGN); 352 if (!backing_aio_cachep) 353 return -ENOMEM; 354 355 return 0; 356 } 357 fs_initcall(backing_aio_init); 358