/* FUSE: Filesystem in Userspace Copyright (C) 2001-2005 Miklos Szeredi <miklos@szeredi.hu> This program can be distributed under the terms of the GNU GPL. See the file COPYING. */ #include "fuse_i.h" #include <linux/init.h> #include <linux/module.h> #include <linux/poll.h> #include <linux/uio.h> #include <linux/miscdevice.h> #include <linux/pagemap.h> #include <linux/file.h> #include <linux/slab.h> MODULE_ALIAS_MISCDEV(FUSE_MINOR); static kmem_cache_t *fuse_req_cachep; static struct fuse_conn *fuse_get_conn(struct file *file) { struct fuse_conn *fc; spin_lock(&fuse_lock); fc = file->private_data; if (fc && !fc->connected) fc = NULL; spin_unlock(&fuse_lock); return fc; } static void fuse_request_init(struct fuse_req *req) { memset(req, 0, sizeof(*req)); INIT_LIST_HEAD(&req->list); init_waitqueue_head(&req->waitq); atomic_set(&req->count, 1); } struct fuse_req *fuse_request_alloc(void) { struct fuse_req *req = kmem_cache_alloc(fuse_req_cachep, SLAB_KERNEL); if (req) fuse_request_init(req); return req; } void fuse_request_free(struct fuse_req *req) { kmem_cache_free(fuse_req_cachep, req); } static void block_sigs(sigset_t *oldset) { sigset_t mask; siginitsetinv(&mask, sigmask(SIGKILL)); sigprocmask(SIG_BLOCK, &mask, oldset); } static void restore_sigs(sigset_t *oldset) { sigprocmask(SIG_SETMASK, oldset, NULL); } /* * Reset request, so that it can be reused * * The caller must be _very_ careful to make sure, that it is holding * the only reference to req */ void fuse_reset_request(struct fuse_req *req) { int preallocated = req->preallocated; BUG_ON(atomic_read(&req->count) != 1); fuse_request_init(req); req->preallocated = preallocated; } static void __fuse_get_request(struct fuse_req *req) { atomic_inc(&req->count); } /* Must be called with > 1 refcount */ static void __fuse_put_request(struct fuse_req *req) { BUG_ON(atomic_read(&req->count) < 2); atomic_dec(&req->count); } static struct fuse_req *do_get_request(struct fuse_conn *fc) { struct fuse_req *req; spin_lock(&fuse_lock); BUG_ON(list_empty(&fc->unused_list)); req = list_entry(fc->unused_list.next, struct fuse_req, list); list_del_init(&req->list); spin_unlock(&fuse_lock); fuse_request_init(req); req->preallocated = 1; req->in.h.uid = current->fsuid; req->in.h.gid = current->fsgid; req->in.h.pid = current->pid; return req; } /* This can return NULL, but only in case it's interrupted by a SIGKILL */ struct fuse_req *fuse_get_request(struct fuse_conn *fc) { int intr; sigset_t oldset; atomic_inc(&fc->num_waiting); block_sigs(&oldset); intr = down_interruptible(&fc->outstanding_sem); restore_sigs(&oldset); if (intr) { atomic_dec(&fc->num_waiting); return NULL; } return do_get_request(fc); } /* Must be called with fuse_lock held */ static void fuse_putback_request(struct fuse_conn *fc, struct fuse_req *req) { if (req->preallocated) { atomic_dec(&fc->num_waiting); list_add(&req->list, &fc->unused_list); } else fuse_request_free(req); /* If we are in debt decrease that first */ if (fc->outstanding_debt) fc->outstanding_debt--; else up(&fc->outstanding_sem); } void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req) { if (atomic_dec_and_test(&req->count)) { spin_lock(&fuse_lock); fuse_putback_request(fc, req); spin_unlock(&fuse_lock); } } static void fuse_put_request_locked(struct fuse_conn *fc, struct fuse_req *req) { if (atomic_dec_and_test(&req->count)) fuse_putback_request(fc, req); } void fuse_release_background(struct fuse_req *req) { iput(req->inode); iput(req->inode2); if (req->file) fput(req->file); spin_lock(&fuse_lock); list_del(&req->bg_entry); spin_unlock(&fuse_lock); } /* * This function is called when a request is finished. Either a reply * has arrived or it was interrupted (and not yet sent) or some error * occurred during communication with userspace, or the device file * was closed. In case of a background request the reference to the * stored objects are released. The requester thread is woken up (if * still waiting), the 'end' callback is called if given, else the * reference to the request is released * * Releasing extra reference for foreground requests must be done * within the same locked region as setting state to finished. This * is because fuse_reset_request() may be called after request is * finished and it must be the sole possessor. If request is * interrupted and put in the background, it will return with an error * and hence never be reset and reused. * * Called with fuse_lock, unlocks it */ static void request_end(struct fuse_conn *fc, struct fuse_req *req) { list_del(&req->list); req->state = FUSE_REQ_FINISHED; if (!req->background) { wake_up(&req->waitq); fuse_put_request_locked(fc, req); spin_unlock(&fuse_lock); } else { void (*end) (struct fuse_conn *, struct fuse_req *) = req->end; req->end = NULL; spin_unlock(&fuse_lock); down_read(&fc->sbput_sem); if (fc->mounted) fuse_release_background(req); up_read(&fc->sbput_sem); if (end) end(fc, req); else fuse_put_request(fc, req); } } /* * Unfortunately request interruption not just solves the deadlock * problem, it causes problems too. These stem from the fact, that an * interrupted request is continued to be processed in userspace, * while all the locks and object references (inode and file) held * during the operation are released. * * To release the locks is exactly why there's a need to interrupt the * request, so there's not a lot that can be done about this, except * introduce additional locking in userspace. * * More important is to keep inode and file references until userspace * has replied, otherwise FORGET and RELEASE could be sent while the * inode/file is still used by the filesystem. * * For this reason the concept of "background" request is introduced. * An interrupted request is backgrounded if it has been already sent * to userspace. Backgrounding involves getting an extra reference to * inode(s) or file used in the request, and adding the request to * fc->background list. When a reply is received for a background * request, the object references are released, and the request is * removed from the list. If the filesystem is unmounted while there * are still background requests, the list is walked and references * are released as if a reply was received. * * There's one more use for a background request. The RELEASE message is * always sent as background, since it doesn't return an error or * data. */ static void background_request(struct fuse_conn *fc, struct fuse_req *req) { req->background = 1; list_add(&req->bg_entry, &fc->background); if (req->inode) req->inode = igrab(req->inode); if (req->inode2) req->inode2 = igrab(req->inode2); if (req->file) get_file(req->file); } /* Called with fuse_lock held. Releases, and then reacquires it. */ static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req) { sigset_t oldset; spin_unlock(&fuse_lock); block_sigs(&oldset); wait_event_interruptible(req->waitq, req->state == FUSE_REQ_FINISHED); restore_sigs(&oldset); spin_lock(&fuse_lock); if (req->state == FUSE_REQ_FINISHED && !req->interrupted) return; if (!req->interrupted) { req->out.h.error = -EINTR; req->interrupted = 1; } if (req->locked) { /* This is uninterruptible sleep, because data is being copied to/from the buffers of req. During locked state, there mustn't be any filesystem operation (e.g. page fault), since that could lead to deadlock */ spin_unlock(&fuse_lock); wait_event(req->waitq, !req->locked); spin_lock(&fuse_lock); } if (req->state == FUSE_REQ_PENDING) { list_del(&req->list); __fuse_put_request(req); } else if (req->state == FUSE_REQ_SENT) background_request(fc, req); } static unsigned len_args(unsigned numargs, struct fuse_arg *args) { unsigned nbytes = 0; unsigned i; for (i = 0; i < numargs; i++) nbytes += args[i].size; return nbytes; } static void queue_request(struct fuse_conn *fc, struct fuse_req *req) { fc->reqctr++; /* zero is special */ if (fc->reqctr == 0) fc->reqctr = 1; req->in.h.unique = fc->reqctr; req->in.h.len = sizeof(struct fuse_in_header) + len_args(req->in.numargs, (struct fuse_arg *) req->in.args); if (!req->preallocated) { /* If request is not preallocated (either FORGET or RELEASE), then still decrease outstanding_sem, so user can't open infinite number of files while not processing the RELEASE requests. However for efficiency do it without blocking, so if down() would block, just increase the debt instead */ if (down_trylock(&fc->outstanding_sem)) fc->outstanding_debt++; } list_add_tail(&req->list, &fc->pending); req->state = FUSE_REQ_PENDING; wake_up(&fc->waitq); } /* * This can only be interrupted by a SIGKILL */ void request_send(struct fuse_conn *fc, struct fuse_req *req) { req->isreply = 1; spin_lock(&fuse_lock); if (!fc->connected) req->out.h.error = -ENOTCONN; else if (fc->conn_error) req->out.h.error = -ECONNREFUSED; else { queue_request(fc, req); /* acquire extra reference, since request is still needed after request_end() */ __fuse_get_request(req); request_wait_answer(fc, req); } spin_unlock(&fuse_lock); } static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req) { spin_lock(&fuse_lock); if (fc->connected) { queue_request(fc, req); spin_unlock(&fuse_lock); } else { req->out.h.error = -ENOTCONN; request_end(fc, req); } } void request_send_noreply(struct fuse_conn *fc, struct fuse_req *req) { req->isreply = 0; request_send_nowait(fc, req); } void request_send_background(struct fuse_conn *fc, struct fuse_req *req) { req->isreply = 1; spin_lock(&fuse_lock); background_request(fc, req); spin_unlock(&fuse_lock); request_send_nowait(fc, req); } /* * Lock the request. Up to the next unlock_request() there mustn't be * anything that could cause a page-fault. If the request was already * interrupted bail out. */ static int lock_request(struct fuse_req *req) { int err = 0; if (req) { spin_lock(&fuse_lock); if (req->interrupted) err = -ENOENT; else req->locked = 1; spin_unlock(&fuse_lock); } return err; } /* * Unlock request. If it was interrupted during being locked, the * requester thread is currently waiting for it to be unlocked, so * wake it up. */ static void unlock_request(struct fuse_req *req) { if (req) { spin_lock(&fuse_lock); req->locked = 0; if (req->interrupted) wake_up(&req->waitq); spin_unlock(&fuse_lock); } } struct fuse_copy_state { int write; struct fuse_req *req; const struct iovec *iov; unsigned long nr_segs; unsigned long seglen; unsigned long addr; struct page *pg; void *mapaddr; void *buf; unsigned len; }; static void fuse_copy_init(struct fuse_copy_state *cs, int write, struct fuse_req *req, const struct iovec *iov, unsigned long nr_segs) { memset(cs, 0, sizeof(*cs)); cs->write = write; cs->req = req; cs->iov = iov; cs->nr_segs = nr_segs; } /* Unmap and put previous page of userspace buffer */ static void fuse_copy_finish(struct fuse_copy_state *cs) { if (cs->mapaddr) { kunmap_atomic(cs->mapaddr, KM_USER0); if (cs->write) { flush_dcache_page(cs->pg); set_page_dirty_lock(cs->pg); } put_page(cs->pg); cs->mapaddr = NULL; } } /* * Get another pagefull of userspace buffer, and map it to kernel * address space, and lock request */ static int fuse_copy_fill(struct fuse_copy_state *cs) { unsigned long offset; int err; unlock_request(cs->req); fuse_copy_finish(cs); if (!cs->seglen) { BUG_ON(!cs->nr_segs); cs->seglen = cs->iov[0].iov_len; cs->addr = (unsigned long) cs->iov[0].iov_base; cs->iov ++; cs->nr_segs --; } down_read(¤t->mm->mmap_sem); err = get_user_pages(current, current->mm, cs->addr, 1, cs->write, 0, &cs->pg, NULL); up_read(¤t->mm->mmap_sem); if (err < 0) return err; BUG_ON(err != 1); offset = cs->addr % PAGE_SIZE; cs->mapaddr = kmap_atomic(cs->pg, KM_USER0); cs->buf = cs->mapaddr + offset; cs->len = min(PAGE_SIZE - offset, cs->seglen); cs->seglen -= cs->len; cs->addr += cs->len; return lock_request(cs->req); } /* Do as much copy to/from userspace buffer as we can */ static int fuse_copy_do(struct fuse_copy_state *cs, void **val, unsigned *size) { unsigned ncpy = min(*size, cs->len); if (val) { if (cs->write) memcpy(cs->buf, *val, ncpy); else memcpy(*val, cs->buf, ncpy); *val += ncpy; } *size -= ncpy; cs->len -= ncpy; cs->buf += ncpy; return ncpy; } /* * Copy a page in the request to/from the userspace buffer. Must be * done atomically */ static int fuse_copy_page(struct fuse_copy_state *cs, struct page *page, unsigned offset, unsigned count, int zeroing) { if (page && zeroing && count < PAGE_SIZE) { void *mapaddr = kmap_atomic(page, KM_USER1); memset(mapaddr, 0, PAGE_SIZE); kunmap_atomic(mapaddr, KM_USER1); } while (count) { int err; if (!cs->len && (err = fuse_copy_fill(cs))) return err; if (page) { void *mapaddr = kmap_atomic(page, KM_USER1); void *buf = mapaddr + offset; offset += fuse_copy_do(cs, &buf, &count); kunmap_atomic(mapaddr, KM_USER1); } else offset += fuse_copy_do(cs, NULL, &count); } if (page && !cs->write) flush_dcache_page(page); return 0; } /* Copy pages in the request to/from userspace buffer */ static int fuse_copy_pages(struct fuse_copy_state *cs, unsigned nbytes, int zeroing) { unsigned i; struct fuse_req *req = cs->req; unsigned offset = req->page_offset; unsigned count = min(nbytes, (unsigned) PAGE_SIZE - offset); for (i = 0; i < req->num_pages && (nbytes || zeroing); i++) { struct page *page = req->pages[i]; int err = fuse_copy_page(cs, page, offset, count, zeroing); if (err) return err; nbytes -= count; count = min(nbytes, (unsigned) PAGE_SIZE); offset = 0; } return 0; } /* Copy a single argument in the request to/from userspace buffer */ static int fuse_copy_one(struct fuse_copy_state *cs, void *val, unsigned size) { while (size) { int err; if (!cs->len && (err = fuse_copy_fill(cs))) return err; fuse_copy_do(cs, &val, &size); } return 0; } /* Copy request arguments to/from userspace buffer */ static int fuse_copy_args(struct fuse_copy_state *cs, unsigned numargs, unsigned argpages, struct fuse_arg *args, int zeroing) { int err = 0; unsigned i; for (i = 0; !err && i < numargs; i++) { struct fuse_arg *arg = &args[i]; if (i == numargs - 1 && argpages) err = fuse_copy_pages(cs, arg->size, zeroing); else err = fuse_copy_one(cs, arg->value, arg->size); } return err; } /* Wait until a request is available on the pending list */ static void request_wait(struct fuse_conn *fc) { DECLARE_WAITQUEUE(wait, current); add_wait_queue_exclusive(&fc->waitq, &wait); while (fc->connected && list_empty(&fc->pending)) { set_current_state(TASK_INTERRUPTIBLE); if (signal_pending(current)) break; spin_unlock(&fuse_lock); schedule(); spin_lock(&fuse_lock); } set_current_state(TASK_RUNNING); remove_wait_queue(&fc->waitq, &wait); } /* * Read a single request into the userspace filesystem's buffer. This * function waits until a request is available, then removes it from * the pending list and copies request data to userspace buffer. If * no reply is needed (FORGET) or request has been interrupted or * there was an error during the copying then it's finished by calling * request_end(). Otherwise add it to the processing list, and set * the 'sent' flag. */ static ssize_t fuse_dev_readv(struct file *file, const struct iovec *iov, unsigned long nr_segs, loff_t *off) { int err; struct fuse_conn *fc; struct fuse_req *req; struct fuse_in *in; struct fuse_copy_state cs; unsigned reqsize; restart: spin_lock(&fuse_lock); fc = file->private_data; err = -EPERM; if (!fc) goto err_unlock; request_wait(fc); err = -ENODEV; if (!fc->connected) goto err_unlock; err = -ERESTARTSYS; if (list_empty(&fc->pending)) goto err_unlock; req = list_entry(fc->pending.next, struct fuse_req, list); req->state = FUSE_REQ_READING; list_move(&req->list, &fc->io); in = &req->in; reqsize = in->h.len; /* If request is too large, reply with an error and restart the read */ if (iov_length(iov, nr_segs) < reqsize) { req->out.h.error = -EIO; /* SETXATTR is special, since it may contain too large data */ if (in->h.opcode == FUSE_SETXATTR) req->out.h.error = -E2BIG; request_end(fc, req); goto restart; } spin_unlock(&fuse_lock); fuse_copy_init(&cs, 1, req, iov, nr_segs); err = fuse_copy_one(&cs, &in->h, sizeof(in->h)); if (!err) err = fuse_copy_args(&cs, in->numargs, in->argpages, (struct fuse_arg *) in->args, 0); fuse_copy_finish(&cs); spin_lock(&fuse_lock); req->locked = 0; if (!err && req->interrupted) err = -ENOENT; if (err) { if (!req->interrupted) req->out.h.error = -EIO; request_end(fc, req); return err; } if (!req->isreply) request_end(fc, req); else { req->state = FUSE_REQ_SENT; list_move_tail(&req->list, &fc->processing); spin_unlock(&fuse_lock); } return reqsize; err_unlock: spin_unlock(&fuse_lock); return err; } static ssize_t fuse_dev_read(struct file *file, char __user *buf, size_t nbytes, loff_t *off) { struct iovec iov; iov.iov_len = nbytes; iov.iov_base = buf; return fuse_dev_readv(file, &iov, 1, off); } /* Look up request on processing list by unique ID */ static struct fuse_req *request_find(struct fuse_conn *fc, u64 unique) { struct list_head *entry; list_for_each(entry, &fc->processing) { struct fuse_req *req; req = list_entry(entry, struct fuse_req, list); if (req->in.h.unique == unique) return req; } return NULL; } static int copy_out_args(struct fuse_copy_state *cs, struct fuse_out *out, unsigned nbytes) { unsigned reqsize = sizeof(struct fuse_out_header); if (out->h.error) return nbytes != reqsize ? -EINVAL : 0; reqsize += len_args(out->numargs, out->args); if (reqsize < nbytes || (reqsize > nbytes && !out->argvar)) return -EINVAL; else if (reqsize > nbytes) { struct fuse_arg *lastarg = &out->args[out->numargs-1]; unsigned diffsize = reqsize - nbytes; if (diffsize > lastarg->size) return -EINVAL; lastarg->size -= diffsize; } return fuse_copy_args(cs, out->numargs, out->argpages, out->args, out->page_zeroing); } /* * Write a single reply to a request. First the header is copied from * the write buffer. The request is then searched on the processing * list by the unique ID found in the header. If found, then remove * it from the list and copy the rest of the buffer to the request. * The request is finished by calling request_end() */ static ssize_t fuse_dev_writev(struct file *file, const struct iovec *iov, unsigned long nr_segs, loff_t *off) { int err; unsigned nbytes = iov_length(iov, nr_segs); struct fuse_req *req; struct fuse_out_header oh; struct fuse_copy_state cs; struct fuse_conn *fc = fuse_get_conn(file); if (!fc) return -ENODEV; fuse_copy_init(&cs, 0, NULL, iov, nr_segs); if (nbytes < sizeof(struct fuse_out_header)) return -EINVAL; err = fuse_copy_one(&cs, &oh, sizeof(oh)); if (err) goto err_finish; err = -EINVAL; if (!oh.unique || oh.error <= -1000 || oh.error > 0 || oh.len != nbytes) goto err_finish; spin_lock(&fuse_lock); err = -ENOENT; if (!fc->connected) goto err_unlock; req = request_find(fc, oh.unique); err = -EINVAL; if (!req) goto err_unlock; if (req->interrupted) { spin_unlock(&fuse_lock); fuse_copy_finish(&cs); spin_lock(&fuse_lock); request_end(fc, req); return -ENOENT; } list_move(&req->list, &fc->io); req->out.h = oh; req->locked = 1; cs.req = req; spin_unlock(&fuse_lock); err = copy_out_args(&cs, &req->out, nbytes); fuse_copy_finish(&cs); spin_lock(&fuse_lock); req->locked = 0; if (!err) { if (req->interrupted) err = -ENOENT; } else if (!req->interrupted) req->out.h.error = -EIO; request_end(fc, req); return err ? err : nbytes; err_unlock: spin_unlock(&fuse_lock); err_finish: fuse_copy_finish(&cs); return err; } static ssize_t fuse_dev_write(struct file *file, const char __user *buf, size_t nbytes, loff_t *off) { struct iovec iov; iov.iov_len = nbytes; iov.iov_base = (char __user *) buf; return fuse_dev_writev(file, &iov, 1, off); } static unsigned fuse_dev_poll(struct file *file, poll_table *wait) { struct fuse_conn *fc = fuse_get_conn(file); unsigned mask = POLLOUT | POLLWRNORM; if (!fc) return -ENODEV; poll_wait(file, &fc->waitq, wait); spin_lock(&fuse_lock); if (!list_empty(&fc->pending)) mask |= POLLIN | POLLRDNORM; spin_unlock(&fuse_lock); return mask; } /* * Abort all requests on the given list (pending or processing) * * This function releases and reacquires fuse_lock */ static void end_requests(struct fuse_conn *fc, struct list_head *head) { while (!list_empty(head)) { struct fuse_req *req; req = list_entry(head->next, struct fuse_req, list); req->out.h.error = -ECONNABORTED; request_end(fc, req); spin_lock(&fuse_lock); } } /* * Abort requests under I/O * * The requests are set to interrupted and finished, and the request * waiter is woken up. This will make request_wait_answer() wait * until the request is unlocked and then return. * * If the request is asynchronous, then the end function needs to be * called after waiting for the request to be unlocked (if it was * locked). */ static void end_io_requests(struct fuse_conn *fc) { while (!list_empty(&fc->io)) { struct fuse_req *req = list_entry(fc->io.next, struct fuse_req, list); void (*end) (struct fuse_conn *, struct fuse_req *) = req->end; req->interrupted = 1; req->out.h.error = -ECONNABORTED; req->state = FUSE_REQ_FINISHED; list_del_init(&req->list); wake_up(&req->waitq); if (end) { req->end = NULL; /* The end function will consume this reference */ __fuse_get_request(req); spin_unlock(&fuse_lock); wait_event(req->waitq, !req->locked); end(fc, req); spin_lock(&fuse_lock); } } } /* * Abort all requests. * * Emergency exit in case of a malicious or accidental deadlock, or * just a hung filesystem. * * The same effect is usually achievable through killing the * filesystem daemon and all users of the filesystem. The exception * is the combination of an asynchronous request and the tricky * deadlock (see Documentation/filesystems/fuse.txt). * * During the aborting, progression of requests from the pending and * processing lists onto the io list, and progression of new requests * onto the pending list is prevented by req->connected being false. * * Progression of requests under I/O to the processing list is * prevented by the req->interrupted flag being true for these * requests. For this reason requests on the io list must be aborted * first. */ void fuse_abort_conn(struct fuse_conn *fc) { spin_lock(&fuse_lock); if (fc->connected) { fc->connected = 0; end_io_requests(fc); end_requests(fc, &fc->pending); end_requests(fc, &fc->processing); wake_up_all(&fc->waitq); } spin_unlock(&fuse_lock); } static int fuse_dev_release(struct inode *inode, struct file *file) { struct fuse_conn *fc; spin_lock(&fuse_lock); fc = file->private_data; if (fc) { fc->connected = 0; end_requests(fc, &fc->pending); end_requests(fc, &fc->processing); } spin_unlock(&fuse_lock); if (fc) kobject_put(&fc->kobj); return 0; } struct file_operations fuse_dev_operations = { .owner = THIS_MODULE, .llseek = no_llseek, .read = fuse_dev_read, .readv = fuse_dev_readv, .write = fuse_dev_write, .writev = fuse_dev_writev, .poll = fuse_dev_poll, .release = fuse_dev_release, }; static struct miscdevice fuse_miscdevice = { .minor = FUSE_MINOR, .name = "fuse", .fops = &fuse_dev_operations, }; int __init fuse_dev_init(void) { int err = -ENOMEM; fuse_req_cachep = kmem_cache_create("fuse_request", sizeof(struct fuse_req), 0, 0, NULL, NULL); if (!fuse_req_cachep) goto out; err = misc_register(&fuse_miscdevice); if (err) goto out_cache_clean; return 0; out_cache_clean: kmem_cache_destroy(fuse_req_cachep); out: return err; } void fuse_dev_cleanup(void) { misc_deregister(&fuse_miscdevice); kmem_cache_destroy(fuse_req_cachep); }