diff options
Diffstat (limited to 'fs/kernfs/file.c')
| -rw-r--r-- | fs/kernfs/file.c | 1078 |
1 files changed, 1078 insertions, 0 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c new file mode 100644 index 000000000..9ab6c92e0 --- /dev/null +++ b/fs/kernfs/file.c @@ -0,0 +1,1078 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * fs/kernfs/file.c - kernfs file implementation + * + * Copyright (c) 2001-3 Patrick Mochel + * Copyright (c) 2007 SUSE Linux Products GmbH + * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org> + */ + +#include <linux/fs.h> +#include <linux/seq_file.h> +#include <linux/slab.h> +#include <linux/poll.h> +#include <linux/pagemap.h> +#include <linux/sched/mm.h> +#include <linux/fsnotify.h> +#include <linux/uio.h> + +#include "kernfs-internal.h" + +struct kernfs_open_node { + struct rcu_head rcu_head; + atomic_t event; + wait_queue_head_t poll; + struct list_head files; /* goes through kernfs_open_file.list */ + unsigned int nr_mmapped; + unsigned int nr_to_release; +}; + +/* + * kernfs_notify() may be called from any context and bounces notifications + * through a work item. To minimize space overhead in kernfs_node, the + * pending queue is implemented as a singly linked list of kernfs_nodes. + * The list is terminated with the self pointer so that whether a + * kernfs_node is on the list or not can be determined by testing the next + * pointer for NULL. + */ +#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list) + +static DEFINE_SPINLOCK(kernfs_notify_lock); +static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL; + +static inline struct mutex *kernfs_open_file_mutex_ptr(struct kernfs_node *kn) +{ + int idx = hash_ptr(kn, NR_KERNFS_LOCK_BITS); + + return &kernfs_locks->open_file_mutex[idx]; +} + +static inline struct mutex *kernfs_open_file_mutex_lock(struct kernfs_node *kn) +{ + struct mutex *lock; + + lock = kernfs_open_file_mutex_ptr(kn); + + mutex_lock(lock); + + return lock; +} + +/** + * of_on - Return the kernfs_open_node of the specified kernfs_open_file + * @of: taret kernfs_open_file + */ +static struct kernfs_open_node *of_on(struct kernfs_open_file *of) +{ + return rcu_dereference_protected(of->kn->attr.open, + !list_empty(&of->list)); +} + +/** + * kernfs_deref_open_node_locked - Get kernfs_open_node corresponding to @kn + * + * @kn: target kernfs_node. + * + * Fetch and return ->attr.open of @kn when caller holds the + * kernfs_open_file_mutex_ptr(kn). + * + * Update of ->attr.open happens under kernfs_open_file_mutex_ptr(kn). So when + * the caller guarantees that this mutex is being held, other updaters can't + * change ->attr.open and this means that we can safely deref ->attr.open + * outside RCU read-side critical section. + * + * The caller needs to make sure that kernfs_open_file_mutex is held. + */ +static struct kernfs_open_node * +kernfs_deref_open_node_locked(struct kernfs_node *kn) +{ + return rcu_dereference_protected(kn->attr.open, + lockdep_is_held(kernfs_open_file_mutex_ptr(kn))); +} + +static struct kernfs_open_file *kernfs_of(struct file *file) +{ + return ((struct seq_file *)file->private_data)->private; +} + +/* + * Determine the kernfs_ops for the given kernfs_node. This function must + * be called while holding an active reference. + */ +static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn) +{ + if (kn->flags & KERNFS_LOCKDEP) + lockdep_assert_held(kn); + return kn->attr.ops; +} + +/* + * As kernfs_seq_stop() is also called after kernfs_seq_start() or + * kernfs_seq_next() failure, it needs to distinguish whether it's stopping + * a seq_file iteration which is fully initialized with an active reference + * or an aborted kernfs_seq_start() due to get_active failure. The + * position pointer is the only context for each seq_file iteration and + * thus the stop condition should be encoded in it. As the return value is + * directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable + * choice to indicate get_active failure. + * + * Unfortunately, this is complicated due to the optional custom seq_file + * operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop() + * can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or + * custom seq_file operations and thus can't decide whether put_active + * should be performed or not only on ERR_PTR(-ENODEV). + * + * This is worked around by factoring out the custom seq_stop() and + * put_active part into kernfs_seq_stop_active(), skipping it from + * kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after + * custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures + * that kernfs_seq_stop_active() is skipped only after get_active failure. + */ +static void kernfs_seq_stop_active(struct seq_file *sf, void *v) +{ + struct kernfs_open_file *of = sf->private; + const struct kernfs_ops *ops = kernfs_ops(of->kn); + + if (ops->seq_stop) + ops->seq_stop(sf, v); + kernfs_put_active(of->kn); +} + +static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) +{ + struct kernfs_open_file *of = sf->private; + const struct kernfs_ops *ops; + + /* + * @of->mutex nests outside active ref and is primarily to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!kernfs_get_active(of->kn)) + return ERR_PTR(-ENODEV); + + ops = kernfs_ops(of->kn); + if (ops->seq_start) { + void *next = ops->seq_start(sf, ppos); + /* see the comment above kernfs_seq_stop_active() */ + if (next == ERR_PTR(-ENODEV)) + kernfs_seq_stop_active(sf, next); + return next; + } + return single_start(sf, ppos); +} + +static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos) +{ + struct kernfs_open_file *of = sf->private; + const struct kernfs_ops *ops = kernfs_ops(of->kn); + + if (ops->seq_next) { + void *next = ops->seq_next(sf, v, ppos); + /* see the comment above kernfs_seq_stop_active() */ + if (next == ERR_PTR(-ENODEV)) + kernfs_seq_stop_active(sf, next); + return next; + } else { + /* + * The same behavior and code as single_open(), always + * terminate after the initial read. + */ + ++*ppos; + return NULL; + } +} + +static void kernfs_seq_stop(struct seq_file *sf, void *v) +{ + struct kernfs_open_file *of = sf->private; + + if (v != ERR_PTR(-ENODEV)) + kernfs_seq_stop_active(sf, v); + mutex_unlock(&of->mutex); +} + +static int kernfs_seq_show(struct seq_file *sf, void *v) +{ + struct kernfs_open_file *of = sf->private; + + of->event = atomic_read(&of_on(of)->event); + + return of->kn->attr.ops->seq_show(sf, v); +} + +static const struct seq_operations kernfs_seq_ops = { + .start = kernfs_seq_start, + .next = kernfs_seq_next, + .stop = kernfs_seq_stop, + .show = kernfs_seq_show, +}; + +/* + * As reading a bin file can have side-effects, the exact offset and bytes + * specified in read(2) call should be passed to the read callback making + * it difficult to use seq_file. Implement simplistic custom buffering for + * bin files. + */ +static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + struct kernfs_open_file *of = kernfs_of(iocb->ki_filp); + ssize_t len = min_t(size_t, iov_iter_count(iter), PAGE_SIZE); + const struct kernfs_ops *ops; + char *buf; + + buf = of->prealloc_buf; + if (buf) + mutex_lock(&of->prealloc_mutex); + else + buf = kmalloc(len, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + /* + * @of->mutex nests outside active ref and is used both to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!kernfs_get_active(of->kn)) { + len = -ENODEV; + mutex_unlock(&of->mutex); + goto out_free; + } + + of->event = atomic_read(&of_on(of)->event); + + ops = kernfs_ops(of->kn); + if (ops->read) + len = ops->read(of, buf, len, iocb->ki_pos); + else + len = -EINVAL; + + kernfs_put_active(of->kn); + mutex_unlock(&of->mutex); + + if (len < 0) + goto out_free; + + if (copy_to_iter(buf, len, iter) != len) { + len = -EFAULT; + goto out_free; + } + + iocb->ki_pos += len; + + out_free: + if (buf == of->prealloc_buf) + mutex_unlock(&of->prealloc_mutex); + else + kfree(buf); + return len; +} + +static ssize_t kernfs_fop_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + if (kernfs_of(iocb->ki_filp)->kn->flags & KERNFS_HAS_SEQ_SHOW) + return seq_read_iter(iocb, iter); + return kernfs_file_read_iter(iocb, iter); +} + +/* + * Copy data in from userland and pass it to the matching kernfs write + * operation. + * + * There is no easy way for us to know if userspace is only doing a partial + * write, so we don't support them. We expect the entire buffer to come on + * the first write. Hint: if you're writing a value, first read the file, + * modify only the value you're changing, then write entire buffer + * back. + */ +static ssize_t kernfs_fop_write_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + struct kernfs_open_file *of = kernfs_of(iocb->ki_filp); + ssize_t len = iov_iter_count(iter); + const struct kernfs_ops *ops; + char *buf; + + if (of->atomic_write_len) { + if (len > of->atomic_write_len) + return -E2BIG; + } else { + len = min_t(size_t, len, PAGE_SIZE); + } + + buf = of->prealloc_buf; + if (buf) + mutex_lock(&of->prealloc_mutex); + else + buf = kmalloc(len + 1, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + if (copy_from_iter(buf, len, iter) != len) { + len = -EFAULT; + goto out_free; + } + buf[len] = '\0'; /* guarantee string termination */ + + /* + * @of->mutex nests outside active ref and is used both to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!kernfs_get_active(of->kn)) { + mutex_unlock(&of->mutex); + len = -ENODEV; + goto out_free; + } + + ops = kernfs_ops(of->kn); + if (ops->write) + len = ops->write(of, buf, len, iocb->ki_pos); + else + len = -EINVAL; + + kernfs_put_active(of->kn); + mutex_unlock(&of->mutex); + + if (len > 0) + iocb->ki_pos += len; + +out_free: + if (buf == of->prealloc_buf) + mutex_unlock(&of->prealloc_mutex); + else + kfree(buf); + return len; +} + +static void kernfs_vma_open(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + + if (!of->vm_ops) + return; + + if (!kernfs_get_active(of->kn)) + return; + + if (of->vm_ops->open) + of->vm_ops->open(vma); + + kernfs_put_active(of->kn); +} + +static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf) +{ + struct file *file = vmf->vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + vm_fault_t ret; + + if (!of->vm_ops) + return VM_FAULT_SIGBUS; + + if (!kernfs_get_active(of->kn)) + return VM_FAULT_SIGBUS; + + ret = VM_FAULT_SIGBUS; + if (of->vm_ops->fault) + ret = of->vm_ops->fault(vmf); + + kernfs_put_active(of->kn); + return ret; +} + +static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf) +{ + struct file *file = vmf->vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + vm_fault_t ret; + + if (!of->vm_ops) + return VM_FAULT_SIGBUS; + + if (!kernfs_get_active(of->kn)) + return VM_FAULT_SIGBUS; + + ret = 0; + if (of->vm_ops->page_mkwrite) + ret = of->vm_ops->page_mkwrite(vmf); + else + file_update_time(file); + + kernfs_put_active(of->kn); + return ret; +} + +static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr, + void *buf, int len, int write) +{ + struct file *file = vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + int ret; + + if (!of->vm_ops) + return -EINVAL; + + if (!kernfs_get_active(of->kn)) + return -EINVAL; + + ret = -EINVAL; + if (of->vm_ops->access) + ret = of->vm_ops->access(vma, addr, buf, len, write); + + kernfs_put_active(of->kn); + return ret; +} + +#ifdef CONFIG_NUMA +static int kernfs_vma_set_policy(struct vm_area_struct *vma, + struct mempolicy *new) +{ + struct file *file = vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + int ret; + + if (!of->vm_ops) + return 0; + + if (!kernfs_get_active(of->kn)) + return -EINVAL; + + ret = 0; + if (of->vm_ops->set_policy) + ret = of->vm_ops->set_policy(vma, new); + + kernfs_put_active(of->kn); + return ret; +} + +static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma, + unsigned long addr) +{ + struct file *file = vma->vm_file; + struct kernfs_open_file *of = kernfs_of(file); + struct mempolicy *pol; + + if (!of->vm_ops) + return vma->vm_policy; + + if (!kernfs_get_active(of->kn)) + return vma->vm_policy; + + pol = vma->vm_policy; + if (of->vm_ops->get_policy) + pol = of->vm_ops->get_policy(vma, addr); + + kernfs_put_active(of->kn); + return pol; +} + +#endif + +static const struct vm_operations_struct kernfs_vm_ops = { + .open = kernfs_vma_open, + .fault = kernfs_vma_fault, + .page_mkwrite = kernfs_vma_page_mkwrite, + .access = kernfs_vma_access, +#ifdef CONFIG_NUMA + .set_policy = kernfs_vma_set_policy, + .get_policy = kernfs_vma_get_policy, +#endif +}; + +static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct kernfs_open_file *of = kernfs_of(file); + const struct kernfs_ops *ops; + int rc; + + /* + * mmap path and of->mutex are prone to triggering spurious lockdep + * warnings and we don't want to add spurious locking dependency + * between the two. Check whether mmap is actually implemented + * without grabbing @of->mutex by testing HAS_MMAP flag. See the + * comment in kernfs_file_open() for more details. + */ + if (!(of->kn->flags & KERNFS_HAS_MMAP)) + return -ENODEV; + + mutex_lock(&of->mutex); + + rc = -ENODEV; + if (!kernfs_get_active(of->kn)) + goto out_unlock; + + ops = kernfs_ops(of->kn); + rc = ops->mmap(of, vma); + if (rc) + goto out_put; + + /* + * PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup() + * to satisfy versions of X which crash if the mmap fails: that + * substitutes a new vm_file, and we don't then want bin_vm_ops. + */ + if (vma->vm_file != file) + goto out_put; + + rc = -EINVAL; + if (of->mmapped && of->vm_ops != vma->vm_ops) + goto out_put; + + /* + * It is not possible to successfully wrap close. + * So error if someone is trying to use close. + */ + if (vma->vm_ops && vma->vm_ops->close) + goto out_put; + + rc = 0; + of->mmapped = true; + of_on(of)->nr_mmapped++; + of->vm_ops = vma->vm_ops; + vma->vm_ops = &kernfs_vm_ops; +out_put: + kernfs_put_active(of->kn); +out_unlock: + mutex_unlock(&of->mutex); + + return rc; +} + +/** + * kernfs_get_open_node - get or create kernfs_open_node + * @kn: target kernfs_node + * @of: kernfs_open_file for this instance of open + * + * If @kn->attr.open exists, increment its reference count; otherwise, + * create one. @of is chained to the files list. + * + * LOCKING: + * Kernel thread context (may sleep). + * + * RETURNS: + * 0 on success, -errno on failure. + */ +static int kernfs_get_open_node(struct kernfs_node *kn, + struct kernfs_open_file *of) +{ + struct kernfs_open_node *on; + struct mutex *mutex; + + mutex = kernfs_open_file_mutex_lock(kn); + on = kernfs_deref_open_node_locked(kn); + + if (!on) { + /* not there, initialize a new one */ + on = kzalloc(sizeof(*on), GFP_KERNEL); + if (!on) { + mutex_unlock(mutex); + return -ENOMEM; + } + atomic_set(&on->event, 1); + init_waitqueue_head(&on->poll); + INIT_LIST_HEAD(&on->files); + rcu_assign_pointer(kn->attr.open, on); + } + + list_add_tail(&of->list, &on->files); + if (kn->flags & KERNFS_HAS_RELEASE) + on->nr_to_release++; + + mutex_unlock(mutex); + return 0; +} + +/** + * kernfs_unlink_open_file - Unlink @of from @kn. + * + * @kn: target kernfs_node + * @of: associated kernfs_open_file + * @open_failed: ->open() failed, cancel ->release() + * + * Unlink @of from list of @kn's associated open files. If list of + * associated open files becomes empty, disassociate and free + * kernfs_open_node. + * + * LOCKING: + * None. + */ +static void kernfs_unlink_open_file(struct kernfs_node *kn, + struct kernfs_open_file *of, + bool open_failed) +{ + struct kernfs_open_node *on; + struct mutex *mutex; + + mutex = kernfs_open_file_mutex_lock(kn); + + on = kernfs_deref_open_node_locked(kn); + if (!on) { + mutex_unlock(mutex); + return; + } + + if (of) { + if (kn->flags & KERNFS_HAS_RELEASE) { + WARN_ON_ONCE(of->released == open_failed); + if (open_failed) + on->nr_to_release--; + } + if (of->mmapped) + on->nr_mmapped--; + list_del(&of->list); + } + + if (list_empty(&on->files)) { + rcu_assign_pointer(kn->attr.open, NULL); + kfree_rcu(on, rcu_head); + } + + mutex_unlock(mutex); +} + +static int kernfs_fop_open(struct inode *inode, struct file *file) +{ + struct kernfs_node *kn = inode->i_private; + struct kernfs_root *root = kernfs_root(kn); + const struct kernfs_ops *ops; + struct kernfs_open_file *of; + bool has_read, has_write, has_mmap; + int error = -EACCES; + + if (!kernfs_get_active(kn)) + return -ENODEV; + + ops = kernfs_ops(kn); + + has_read = ops->seq_show || ops->read || ops->mmap; + has_write = ops->write || ops->mmap; + has_mmap = ops->mmap; + + /* see the flag definition for details */ + if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) { + if ((file->f_mode & FMODE_WRITE) && + (!(inode->i_mode & S_IWUGO) || !has_write)) + goto err_out; + + if ((file->f_mode & FMODE_READ) && + (!(inode->i_mode & S_IRUGO) || !has_read)) + goto err_out; + } + + /* allocate a kernfs_open_file for the file */ + error = -ENOMEM; + of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL); + if (!of) + goto err_out; + + /* + * The following is done to give a different lockdep key to + * @of->mutex for files which implement mmap. This is a rather + * crude way to avoid false positive lockdep warning around + * mm->mmap_lock - mmap nests @of->mutex under mm->mmap_lock and + * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under + * which mm->mmap_lock nests, while holding @of->mutex. As each + * open file has a separate mutex, it's okay as long as those don't + * happen on the same file. At this point, we can't easily give + * each file a separate locking class. Let's differentiate on + * whether the file has mmap or not for now. + * + * Both paths of the branch look the same. They're supposed to + * look that way and give @of->mutex different static lockdep keys. + */ + if (has_mmap) + mutex_init(&of->mutex); + else + mutex_init(&of->mutex); + + of->kn = kn; + of->file = file; + + /* + * Write path needs to atomic_write_len outside active reference. + * Cache it in open_file. See kernfs_fop_write_iter() for details. + */ + of->atomic_write_len = ops->atomic_write_len; + + error = -EINVAL; + /* + * ->seq_show is incompatible with ->prealloc, + * as seq_read does its own allocation. + * ->read must be used instead. + */ + if (ops->prealloc && ops->seq_show) + goto err_free; + if (ops->prealloc) { + int len = of->atomic_write_len ?: PAGE_SIZE; + of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL); + error = -ENOMEM; + if (!of->prealloc_buf) + goto err_free; + mutex_init(&of->prealloc_mutex); + } + + /* + * Always instantiate seq_file even if read access doesn't use + * seq_file or is not requested. This unifies private data access + * and readable regular files are the vast majority anyway. + */ + if (ops->seq_show) + error = seq_open(file, &kernfs_seq_ops); + else + error = seq_open(file, NULL); + if (error) + goto err_free; + + of->seq_file = file->private_data; + of->seq_file->private = of; + + /* seq_file clears PWRITE unconditionally, restore it if WRITE */ + if (file->f_mode & FMODE_WRITE) + file->f_mode |= FMODE_PWRITE; + + /* make sure we have open node struct */ + error = kernfs_get_open_node(kn, of); + if (error) + goto err_seq_release; + + if (ops->open) { + /* nobody has access to @of yet, skip @of->mutex */ + error = ops->open(of); + if (error) + goto err_put_node; + } + + /* open succeeded, put active references */ + kernfs_put_active(kn); + return 0; + +err_put_node: + kernfs_unlink_open_file(kn, of, true); +err_seq_release: + seq_release(inode, file); +err_free: + kfree(of->prealloc_buf); + kfree(of); +err_out: + kernfs_put_active(kn); + return error; +} + +/* used from release/drain to ensure that ->release() is called exactly once */ +static void kernfs_release_file(struct kernfs_node *kn, + struct kernfs_open_file *of) +{ + /* + * @of is guaranteed to have no other file operations in flight and + * we just want to synchronize release and drain paths. + * @kernfs_open_file_mutex_ptr(kn) is enough. @of->mutex can't be used + * here because drain path may be called from places which can + * cause circular dependency. + */ + lockdep_assert_held(kernfs_open_file_mutex_ptr(kn)); + + if (!of->released) { + /* + * A file is never detached without being released and we + * need to be able to release files which are deactivated + * and being drained. Don't use kernfs_ops(). + */ + kn->attr.ops->release(of); + of->released = true; + of_on(of)->nr_to_release--; + } +} + +static int kernfs_fop_release(struct inode *inode, struct file *filp) +{ + struct kernfs_node *kn = inode->i_private; + struct kernfs_open_file *of = kernfs_of(filp); + + if (kn->flags & KERNFS_HAS_RELEASE) { + struct mutex *mutex; + + mutex = kernfs_open_file_mutex_lock(kn); + kernfs_release_file(kn, of); + mutex_unlock(mutex); + } + + kernfs_unlink_open_file(kn, of, false); + seq_release(inode, filp); + kfree(of->prealloc_buf); + kfree(of); + + return 0; +} + +bool kernfs_should_drain_open_files(struct kernfs_node *kn) +{ + struct kernfs_open_node *on; + bool ret; + + /* + * @kn being deactivated guarantees that @kn->attr.open can't change + * beneath us making the lockless test below safe. + */ + WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS); + + rcu_read_lock(); + on = rcu_dereference(kn->attr.open); + ret = on && (on->nr_mmapped || on->nr_to_release); + rcu_read_unlock(); + + return ret; +} + +void kernfs_drain_open_files(struct kernfs_node *kn) +{ + struct kernfs_open_node *on; + struct kernfs_open_file *of; + struct mutex *mutex; + + mutex = kernfs_open_file_mutex_lock(kn); + on = kernfs_deref_open_node_locked(kn); + if (!on) { + mutex_unlock(mutex); + return; + } + + list_for_each_entry(of, &on->files, list) { + struct inode *inode = file_inode(of->file); + + if (of->mmapped) { + unmap_mapping_range(inode->i_mapping, 0, 0, 1); + of->mmapped = false; + on->nr_mmapped--; + } + + if (kn->flags & KERNFS_HAS_RELEASE) + kernfs_release_file(kn, of); + } + + WARN_ON_ONCE(on->nr_mmapped || on->nr_to_release); + mutex_unlock(mutex); +} + +/* + * Kernfs attribute files are pollable. The idea is that you read + * the content and then you use 'poll' or 'select' to wait for + * the content to change. When the content changes (assuming the + * manager for the kobject supports notification), poll will + * return EPOLLERR|EPOLLPRI, and select will return the fd whether + * it is waiting for read, write, or exceptions. + * Once poll/select indicates that the value has changed, you + * need to close and re-open the file, or seek to 0 and read again. + * Reminder: this only works for attributes which actively support + * it, and it is not possible to test an attribute from userspace + * to see if it supports poll (Neither 'poll' nor 'select' return + * an appropriate error code). When in doubt, set a suitable timeout value. + */ +__poll_t kernfs_generic_poll(struct kernfs_open_file *of, poll_table *wait) +{ + struct kernfs_open_node *on = of_on(of); + + poll_wait(of->file, &on->poll, wait); + + if (of->event != atomic_read(&on->event)) + return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI; + + return DEFAULT_POLLMASK; +} + +static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait) +{ + struct kernfs_open_file *of = kernfs_of(filp); + struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry); + __poll_t ret; + + if (!kernfs_get_active(kn)) + return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI; + + if (kn->attr.ops->poll) + ret = kn->attr.ops->poll(of, wait); + else + ret = kernfs_generic_poll(of, wait); + + kernfs_put_active(kn); + return ret; +} + +static void kernfs_notify_workfn(struct work_struct *work) +{ + struct kernfs_node *kn; + struct kernfs_super_info *info; + struct kernfs_root *root; +repeat: + /* pop one off the notify_list */ + spin_lock_irq(&kernfs_notify_lock); + kn = kernfs_notify_list; + if (kn == KERNFS_NOTIFY_EOL) { + spin_unlock_irq(&kernfs_notify_lock); + return; + } + kernfs_notify_list = kn->attr.notify_next; + kn->attr.notify_next = NULL; + spin_unlock_irq(&kernfs_notify_lock); + + root = kernfs_root(kn); + /* kick fsnotify */ + down_write(&root->kernfs_rwsem); + + list_for_each_entry(info, &kernfs_root(kn)->supers, node) { + struct kernfs_node *parent; + struct inode *p_inode = NULL; + struct inode *inode; + struct qstr name; + + /* + * We want fsnotify_modify() on @kn but as the + * modifications aren't originating from userland don't + * have the matching @file available. Look up the inodes + * and generate the events manually. + */ + inode = ilookup(info->sb, kernfs_ino(kn)); + if (!inode) + continue; + + name = (struct qstr)QSTR_INIT(kn->name, strlen(kn->name)); + parent = kernfs_get_parent(kn); + if (parent) { + p_inode = ilookup(info->sb, kernfs_ino(parent)); + if (p_inode) { + fsnotify(FS_MODIFY | FS_EVENT_ON_CHILD, + inode, FSNOTIFY_EVENT_INODE, + p_inode, &name, inode, 0); + iput(p_inode); + } + + kernfs_put(parent); + } + + if (!p_inode) + fsnotify_inode(inode, FS_MODIFY); + + iput(inode); + } + + up_write(&root->kernfs_rwsem); + kernfs_put(kn); + goto repeat; +} + +/** + * kernfs_notify - notify a kernfs file + * @kn: file to notify + * + * Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any + * context. + */ +void kernfs_notify(struct kernfs_node *kn) +{ + static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn); + unsigned long flags; + struct kernfs_open_node *on; + + if (WARN_ON(kernfs_type(kn) != KERNFS_FILE)) + return; + + /* kick poll immediately */ + rcu_read_lock(); + on = rcu_dereference(kn->attr.open); + if (on) { + atomic_inc(&on->event); + wake_up_interruptible(&on->poll); + } + rcu_read_unlock(); + + /* schedule work to kick fsnotify */ + spin_lock_irqsave(&kernfs_notify_lock, flags); + if (!kn->attr.notify_next) { + kernfs_get(kn); + kn->attr.notify_next = kernfs_notify_list; + kernfs_notify_list = kn; + schedule_work(&kernfs_notify_work); + } + spin_unlock_irqrestore(&kernfs_notify_lock, flags); +} +EXPORT_SYMBOL_GPL(kernfs_notify); + +const struct file_operations kernfs_file_fops = { + .read_iter = kernfs_fop_read_iter, + .write_iter = kernfs_fop_write_iter, + .llseek = generic_file_llseek, + .mmap = kernfs_fop_mmap, + .open = kernfs_fop_open, + .release = kernfs_fop_release, + .poll = kernfs_fop_poll, + .fsync = noop_fsync, + .splice_read = generic_file_splice_read, + .splice_write = iter_file_splice_write, +}; + +/** + * __kernfs_create_file - kernfs internal function to create a file + * @parent: directory to create the file in + * @name: name of the file + * @mode: mode of the file + * @uid: uid of the file + * @gid: gid of the file + * @size: size of the file + * @ops: kernfs operations for the file + * @priv: private data for the file + * @ns: optional namespace tag of the file + * @key: lockdep key for the file's active_ref, %NULL to disable lockdep + * + * Returns the created node on success, ERR_PTR() value on error. + */ +struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent, + const char *name, + umode_t mode, kuid_t uid, kgid_t gid, + loff_t size, + const struct kernfs_ops *ops, + void *priv, const void *ns, + struct lock_class_key *key) +{ + struct kernfs_node *kn; + unsigned flags; + int rc; + + flags = KERNFS_FILE; + + kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG, + uid, gid, flags); + if (!kn) + return ERR_PTR(-ENOMEM); + + kn->attr.ops = ops; + kn->attr.size = size; + kn->ns = ns; + kn->priv = priv; + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + if (key) { + lockdep_init_map(&kn->dep_map, "kn->active", key, 0); + kn->flags |= KERNFS_LOCKDEP; + } +#endif + + /* + * kn->attr.ops is accessible only while holding active ref. We + * need to know whether some ops are implemented outside active + * ref. Cache their existence in flags. + */ + if (ops->seq_show) + kn->flags |= KERNFS_HAS_SEQ_SHOW; + if (ops->mmap) + kn->flags |= KERNFS_HAS_MMAP; + if (ops->release) + kn->flags |= KERNFS_HAS_RELEASE; + + rc = kernfs_add_one(kn); + if (rc) { + kernfs_put(kn); + return ERR_PTR(rc); + } + return kn; +} |