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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /fs/kernfs/file.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/kernfs/file.c')
-rw-r--r--fs/kernfs/file.c1078
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;
+}