diff options
Diffstat (limited to 'fs/kernfs/file.c')
| -rw-r--r-- | fs/kernfs/file.c | 805 |
1 files changed, 805 insertions, 0 deletions
diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c index 90b1e88..fa172e8 100644 --- a/fs/kernfs/file.c +++ b/fs/kernfs/file.c @@ -7,3 +7,808 @@ * * This file is released under the GPLv2. */ + +#include <linux/fs.h> +#include <linux/seq_file.h> +#include <linux/slab.h> +#include <linux/poll.h> +#include <linux/pagemap.h> +#include <linux/poll.h> +#include <linux/sched.h> + +#include "kernfs-internal.h" + +/* + * There's one sysfs_open_file for each open file and one sysfs_open_dirent + * for each sysfs_dirent with one or more open files. + * + * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open is + * protected by sysfs_open_dirent_lock. + * + * filp->private_data points to seq_file whose ->private points to + * sysfs_open_file. sysfs_open_files are chained at + * sysfs_open_dirent->files, which is protected by sysfs_open_file_mutex. + */ +static DEFINE_SPINLOCK(sysfs_open_dirent_lock); +static DEFINE_MUTEX(sysfs_open_file_mutex); + +struct sysfs_open_dirent { + atomic_t refcnt; + atomic_t event; + wait_queue_head_t poll; + struct list_head files; /* goes through sysfs_open_file.list */ +}; + +static struct sysfs_open_file *sysfs_of(struct file *file) +{ + return ((struct seq_file *)file->private_data)->private; +} + +/* + * Determine the kernfs_ops for the given sysfs_dirent. This function must + * be called while holding an active reference. + */ +static const struct kernfs_ops *kernfs_ops(struct sysfs_dirent *sd) +{ + if (sd->s_flags & SYSFS_FLAG_LOCKDEP) + lockdep_assert_held(sd); + return sd->s_attr.ops; +} + +static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos) +{ + struct sysfs_open_file *of = sf->private; + const struct kernfs_ops *ops; + + /* + * @of->mutex nests outside active ref and is just to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!sysfs_get_active(of->sd)) + return ERR_PTR(-ENODEV); + + ops = kernfs_ops(of->sd); + if (ops->seq_start) { + return ops->seq_start(sf, ppos); + } else { + /* + * The same behavior and code as single_open(). Returns + * !NULL if pos is at the beginning; otherwise, NULL. + */ + return NULL + !*ppos; + } +} + +static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos) +{ + struct sysfs_open_file *of = sf->private; + const struct kernfs_ops *ops = kernfs_ops(of->sd); + + if (ops->seq_next) { + return ops->seq_next(sf, v, ppos); + } 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 sysfs_open_file *of = sf->private; + const struct kernfs_ops *ops = kernfs_ops(of->sd); + + if (ops->seq_stop) + ops->seq_stop(sf, v); + + sysfs_put_active(of->sd); + mutex_unlock(&of->mutex); +} + +static int kernfs_seq_show(struct seq_file *sf, void *v) +{ + struct sysfs_open_file *of = sf->private; + + of->event = atomic_read(&of->sd->s_attr.open->event); + + return of->sd->s_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_direct_read(struct sysfs_open_file *of, + char __user *user_buf, size_t count, + loff_t *ppos) +{ + ssize_t len = min_t(size_t, count, PAGE_SIZE); + const struct kernfs_ops *ops; + char *buf; + + buf = kmalloc(len, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + /* + * @of->mutex nests outside active ref and is just to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!sysfs_get_active(of->sd)) { + len = -ENODEV; + mutex_unlock(&of->mutex); + goto out_free; + } + + ops = kernfs_ops(of->sd); + if (ops->read) + len = ops->read(of, buf, len, *ppos); + else + len = -EINVAL; + + sysfs_put_active(of->sd); + mutex_unlock(&of->mutex); + + if (len < 0) + goto out_free; + + if (copy_to_user(user_buf, buf, len)) { + len = -EFAULT; + goto out_free; + } + + *ppos += len; + + out_free: + kfree(buf); + return len; +} + +/** + * kernfs_file_read - kernfs vfs read callback + * @file: file pointer + * @user_buf: data to write + * @count: number of bytes + * @ppos: starting offset + */ +static ssize_t kernfs_file_read(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct sysfs_open_file *of = sysfs_of(file); + + if (of->sd->s_flags & SYSFS_FLAG_HAS_SEQ_SHOW) + return seq_read(file, user_buf, count, ppos); + else + return kernfs_file_direct_read(of, user_buf, count, ppos); +} + +/** + * kernfs_file_write - kernfs vfs write callback + * @file: file pointer + * @user_buf: data to write + * @count: number of bytes + * @ppos: starting offset + * + * 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 the value you're changing, then write entire buffer + * back. + */ +static ssize_t kernfs_file_write(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + struct sysfs_open_file *of = sysfs_of(file); + ssize_t len = min_t(size_t, count, PAGE_SIZE); + const struct kernfs_ops *ops; + char *buf; + + buf = kmalloc(len + 1, GFP_KERNEL); + if (!buf) + return -ENOMEM; + + if (copy_from_user(buf, user_buf, len)) { + len = -EFAULT; + goto out_free; + } + buf[len] = '\0'; /* guarantee string termination */ + + /* + * @of->mutex nests outside active ref and is just to ensure that + * the ops aren't called concurrently for the same open file. + */ + mutex_lock(&of->mutex); + if (!sysfs_get_active(of->sd)) { + mutex_unlock(&of->mutex); + len = -ENODEV; + goto out_free; + } + + ops = kernfs_ops(of->sd); + if (ops->write) + len = ops->write(of, buf, len, *ppos); + else + len = -EINVAL; + + sysfs_put_active(of->sd); + mutex_unlock(&of->mutex); + + if (len > 0) + *ppos += len; +out_free: + kfree(buf); + return len; +} + +static void kernfs_vma_open(struct vm_area_struct *vma) +{ + struct file *file = vma->vm_file; + struct sysfs_open_file *of = sysfs_of(file); + + if (!of->vm_ops) + return; + + if (!sysfs_get_active(of->sd)) + return; + + if (of->vm_ops->open) + of->vm_ops->open(vma); + + sysfs_put_active(of->sd); +} + +static int kernfs_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct file *file = vma->vm_file; + struct sysfs_open_file *of = sysfs_of(file); + int ret; + + if (!of->vm_ops) + return VM_FAULT_SIGBUS; + + if (!sysfs_get_active(of->sd)) + return VM_FAULT_SIGBUS; + + ret = VM_FAULT_SIGBUS; + if (of->vm_ops->fault) + ret = of->vm_ops->fault(vma, vmf); + + sysfs_put_active(of->sd); + return ret; +} + +static int kernfs_vma_page_mkwrite(struct vm_area_struct *vma, + struct vm_fault *vmf) +{ + struct file *file = vma->vm_file; + struct sysfs_open_file *of = sysfs_of(file); + int ret; + + if (!of->vm_ops) + return VM_FAULT_SIGBUS; + + if (!sysfs_get_active(of->sd)) + return VM_FAULT_SIGBUS; + + ret = 0; + if (of->vm_ops->page_mkwrite) + ret = of->vm_ops->page_mkwrite(vma, vmf); + else + file_update_time(file); + + sysfs_put_active(of->sd); + 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 sysfs_open_file *of = sysfs_of(file); + int ret; + + if (!of->vm_ops) + return -EINVAL; + + if (!sysfs_get_active(of->sd)) + return -EINVAL; + + ret = -EINVAL; + if (of->vm_ops->access) + ret = of->vm_ops->access(vma, addr, buf, len, write); + + sysfs_put_active(of->sd); + 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 sysfs_open_file *of = sysfs_of(file); + int ret; + + if (!of->vm_ops) + return 0; + + if (!sysfs_get_active(of->sd)) + return -EINVAL; + + ret = 0; + if (of->vm_ops->set_policy) + ret = of->vm_ops->set_policy(vma, new); + + sysfs_put_active(of->sd); + return ret; +} + +static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma, + unsigned long addr) +{ + struct file *file = vma->vm_file; + struct sysfs_open_file *of = sysfs_of(file); + struct mempolicy *pol; + + if (!of->vm_ops) + return vma->vm_policy; + + if (!sysfs_get_active(of->sd)) + return vma->vm_policy; + + pol = vma->vm_policy; + if (of->vm_ops->get_policy) + pol = of->vm_ops->get_policy(vma, addr); + + sysfs_put_active(of->sd); + return pol; +} + +static int kernfs_vma_migrate(struct vm_area_struct *vma, + const nodemask_t *from, const nodemask_t *to, + unsigned long flags) +{ + struct file *file = vma->vm_file; + struct sysfs_open_file *of = sysfs_of(file); + int ret; + + if (!of->vm_ops) + return 0; + + if (!sysfs_get_active(of->sd)) + return 0; + + ret = 0; + if (of->vm_ops->migrate) + ret = of->vm_ops->migrate(vma, from, to, flags); + + sysfs_put_active(of->sd); + return ret; +} +#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, + .migrate = kernfs_vma_migrate, +#endif +}; + +static int kernfs_file_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct sysfs_open_file *of = sysfs_of(file); + const struct kernfs_ops *ops; + int rc; + + mutex_lock(&of->mutex); + + rc = -ENODEV; + if (!sysfs_get_active(of->sd)) + goto out_unlock; + + ops = kernfs_ops(of->sd); + if (ops->mmap) + 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. + */ + rc = -EINVAL; + if (vma->vm_ops && vma->vm_ops->close) + goto out_put; + + rc = 0; + of->mmapped = 1; + of->vm_ops = vma->vm_ops; + vma->vm_ops = &kernfs_vm_ops; +out_put: + sysfs_put_active(of->sd); +out_unlock: + mutex_unlock(&of->mutex); + + return rc; +} + +/** + * sysfs_get_open_dirent - get or create sysfs_open_dirent + * @sd: target sysfs_dirent + * @of: sysfs_open_file for this instance of open + * + * If @sd->s_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 sysfs_get_open_dirent(struct sysfs_dirent *sd, + struct sysfs_open_file *of) +{ + struct sysfs_open_dirent *od, *new_od = NULL; + + retry: + mutex_lock(&sysfs_open_file_mutex); + spin_lock_irq(&sysfs_open_dirent_lock); + + if (!sd->s_attr.open && new_od) { + sd->s_attr.open = new_od; + new_od = NULL; + } + + od = sd->s_attr.open; + if (od) { + atomic_inc(&od->refcnt); + list_add_tail(&of->list, &od->files); + } + + spin_unlock_irq(&sysfs_open_dirent_lock); + mutex_unlock(&sysfs_open_file_mutex); + + if (od) { + kfree(new_od); + return 0; + } + + /* not there, initialize a new one and retry */ + new_od = kmalloc(sizeof(*new_od), GFP_KERNEL); + if (!new_od) + return -ENOMEM; + + atomic_set(&new_od->refcnt, 0); + atomic_set(&new_od->event, 1); + init_waitqueue_head(&new_od->poll); + INIT_LIST_HEAD(&new_od->files); + goto retry; +} + +/** + * sysfs_put_open_dirent - put sysfs_open_dirent + * @sd: target sysfs_dirent + * @of: associated sysfs_open_file + * + * Put @sd->s_attr.open and unlink @of from the files list. If + * reference count reaches zero, disassociate and free it. + * + * LOCKING: + * None. + */ +static void sysfs_put_open_dirent(struct sysfs_dirent *sd, + struct sysfs_open_file *of) +{ + struct sysfs_open_dirent *od = sd->s_attr.open; + unsigned long flags; + + mutex_lock(&sysfs_open_file_mutex); + spin_lock_irqsave(&sysfs_open_dirent_lock, flags); + + if (of) + list_del(&of->list); + + if (atomic_dec_and_test(&od->refcnt)) + sd->s_attr.open = NULL; + else + od = NULL; + + spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags); + mutex_unlock(&sysfs_open_file_mutex); + + kfree(od); +} + +static int kernfs_file_open(struct inode *inode, struct file *file) +{ + struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata; + const struct kernfs_ops *ops; + struct sysfs_open_file *of; + bool has_read, has_write, has_mmap; + int error = -EACCES; + + if (!sysfs_get_active(attr_sd)) + return -ENODEV; + + ops = kernfs_ops(attr_sd); + + has_read = ops->seq_show || ops->read || ops->mmap; + has_write = ops->write || ops->mmap; + has_mmap = ops->mmap; + + /* check perms and supported operations */ + 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 sysfs_open_file for the file */ + error = -ENOMEM; + of = kzalloc(sizeof(struct sysfs_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_sem - mmap nests @of->mutex under mm->mmap_sem and + * reading /sys/block/sda/trace/act_mask grabs sr_mutex, under + * which mm->mmap_sem 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. + */ + if (has_mmap) + mutex_init(&of->mutex); + else + mutex_init(&of->mutex); + + of->sd = attr_sd; + of->file = file; + + /* + * 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; + + ((struct seq_file *)file->private_data)->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 dirent struct */ + error = sysfs_get_open_dirent(attr_sd, of); + if (error) + goto err_close; + + /* open succeeded, put active references */ + sysfs_put_active(attr_sd); + return 0; + +err_close: + seq_release(inode, file); +err_free: + kfree(of); +err_out: + sysfs_put_active(attr_sd); + return error; +} + +static int kernfs_file_release(struct inode *inode, struct file *filp) +{ + struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata; + struct sysfs_open_file *of = sysfs_of(filp); + + sysfs_put_open_dirent(sd, of); + seq_release(inode, filp); + kfree(of); + + return 0; +} + +void sysfs_unmap_bin_file(struct sysfs_dirent *sd) +{ + struct sysfs_open_dirent *od; + struct sysfs_open_file *of; + + if (!(sd->s_flags & SYSFS_FLAG_HAS_MMAP)) + return; + + spin_lock_irq(&sysfs_open_dirent_lock); + od = sd->s_attr.open; + if (od) + atomic_inc(&od->refcnt); + spin_unlock_irq(&sysfs_open_dirent_lock); + if (!od) + return; + + mutex_lock(&sysfs_open_file_mutex); + list_for_each_entry(of, &od->files, list) { + struct inode *inode = file_inode(of->file); + unmap_mapping_range(inode->i_mapping, 0, 0, 1); + } + mutex_unlock(&sysfs_open_file_mutex); + + sysfs_put_open_dirent(sd, NULL); +} + +/* Sysfs 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 POLLERR|POLLPRI, 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. + */ +static unsigned int kernfs_file_poll(struct file *filp, poll_table *wait) +{ + struct sysfs_open_file *of = sysfs_of(filp); + struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata; + struct sysfs_open_dirent *od = attr_sd->s_attr.open; + + /* need parent for the kobj, grab both */ + if (!sysfs_get_active(attr_sd)) + goto trigger; + + poll_wait(filp, &od->poll, wait); + + sysfs_put_active(attr_sd); + + if (of->event != atomic_read(&od->event)) + goto trigger; + + return DEFAULT_POLLMASK; + + trigger: + return DEFAULT_POLLMASK|POLLERR|POLLPRI; +} + +/** + * kernfs_notify - notify a kernfs file + * @sd: file to notify + * + * Notify @sd such that poll(2) on @sd wakes up. + */ +void kernfs_notify(struct sysfs_dirent *sd) +{ + struct sysfs_open_dirent *od; + unsigned long flags; + + spin_lock_irqsave(&sysfs_open_dirent_lock, flags); + + if (!WARN_ON(sysfs_type(sd) != SYSFS_KOBJ_ATTR)) { + od = sd->s_attr.open; + if (od) { + atomic_inc(&od->event); + wake_up_interruptible(&od->poll); + } + } + + spin_unlock_irqrestore(&sysfs_open_dirent_lock, flags); +} +EXPORT_SYMBOL_GPL(kernfs_notify); + +const struct file_operations kernfs_file_operations = { + .read = kernfs_file_read, + .write = kernfs_file_write, + .llseek = generic_file_llseek, + .mmap = kernfs_file_mmap, + .open = kernfs_file_open, + .release = kernfs_file_release, + .poll = kernfs_file_poll, +}; + +/** + * kernfs_create_file_ns_key - create a file + * @parent: directory to create the file in + * @name: name of the file + * @mode: mode 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 sysfs_dirent *kernfs_create_file_ns_key(struct sysfs_dirent *parent, + const char *name, + umode_t mode, loff_t size, + const struct kernfs_ops *ops, + void *priv, const void *ns, + struct lock_class_key *key) +{ + struct sysfs_addrm_cxt acxt; + struct sysfs_dirent *sd; + int rc; + + sd = sysfs_new_dirent(name, (mode & S_IALLUGO) | S_IFREG, + SYSFS_KOBJ_ATTR); + if (!sd) + return ERR_PTR(-ENOMEM); + + sd->s_attr.ops = ops; + sd->s_attr.size = size; + sd->s_ns = ns; + sd->priv = priv; + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + if (key) { + lockdep_init_map(&sd->dep_map, "s_active", key, 0); + sd->s_flags |= SYSFS_FLAG_LOCKDEP; + } +#endif + + /* + * sd->s_attr.ops is accesible 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) + sd->s_flags |= SYSFS_FLAG_HAS_SEQ_SHOW; + if (ops->mmap) + sd->s_flags |= SYSFS_FLAG_HAS_MMAP; + + sysfs_addrm_start(&acxt); + rc = sysfs_add_one(&acxt, sd, parent); + sysfs_addrm_finish(&acxt); + + if (rc) { + kernfs_put(sd); + return ERR_PTR(rc); + } + return sd; +} |
