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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  fs/eventfd.c
  *
  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
  *
  */
 
 #include <linux/file.h>
 #include <linux/poll.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/sched/signal.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/anon_inodes.h>
 #include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/kref.h>
 #include <linux/eventfd.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/idr.h>
 #include <linux/uio.h>
 
 static DEFINE_IDA(eventfd_ida);
 
 struct eventfd_ctx {
     struct kref kref;
     wait_queue_head_t wqh;
     /*
      * Every time that a write(2) is performed on an eventfd, the
      * value of the __u64 being written is added to "count" and a
      * wakeup is performed on "wqh". A read(2) will return the "count"
      * value to userspace, and will reset "count" to zero. The kernel
      * side eventfd_signal() also, adds to the "count" counter and
      * issue a wakeup.
      */
     __u64 count;
     unsigned int flags;
     int id;
 };
 
 /**
  * eventfd_signal - Adds @n to the eventfd counter.
  * @ctx: [in] Pointer to the eventfd context.
  * @n: [in] Value of the counter to be added to the eventfd internal counter.
  *          The value cannot be negative.
  *
  * This function is supposed to be called by the kernel in paths that do not
  * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
  * value, and we signal this as overflow condition by returning a EPOLLERR
  * to poll(2).
  *
  * Returns the amount by which the counter was incremented.  This will be less
  * than @n if the counter has overflowed.
  */
 __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
 {
     unsigned long flags;
 
     /*
      * Deadlock or stack overflow issues can happen if we recurse here
      * through waitqueue wakeup handlers. If the caller users potentially
      * nested waitqueues with custom wakeup handlers, then it should
      * check eventfd_signal_allowed() before calling this function. If
      * it returns false, the eventfd_signal() call should be deferred to a
      * safe context.
      */
     if (WARN_ON_ONCE(current->in_eventfd_signal))
         return 0;
 
     spin_lock_irqsave(&ctx->wqh.lock, flags);
     current->in_eventfd_signal = 1;
     if (ULLONG_MAX - ctx->count < n)
         n = ULLONG_MAX - ctx->count;
     ctx->count += n;
     if (waitqueue_active(&ctx->wqh))
         wake_up_locked_poll(&ctx->wqh, EPOLLIN);
     current->in_eventfd_signal = 0;
     spin_unlock_irqrestore(&ctx->wqh.lock, flags);
 
     return n;
 }
 EXPORT_SYMBOL_GPL(eventfd_signal);
 
 static void eventfd_free_ctx(struct eventfd_ctx *ctx)
 {
     if (ctx->id >= 0)
         ida_simple_remove(&eventfd_ida, ctx->id);
     kfree(ctx);
 }
 
 static void eventfd_free(struct kref *kref)
 {
     struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
 
     eventfd_free_ctx(ctx);
 }
 
 /**
  * eventfd_ctx_put - Releases a reference to the internal eventfd context.
  * @ctx: [in] Pointer to eventfd context.
  *
  * The eventfd context reference must have been previously acquired either
  * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
  */
 void eventfd_ctx_put(struct eventfd_ctx *ctx)
 {
     kref_put(&ctx->kref, eventfd_free);
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_put);
 
 static int eventfd_release(struct inode *inode, struct file *file)
 {
     struct eventfd_ctx *ctx = file->private_data;
 
     wake_up_poll(&ctx->wqh, EPOLLHUP);
     eventfd_ctx_put(ctx);
     return 0;
 }
 
 static __poll_t eventfd_poll(struct file *file, poll_table *wait)
 {
     struct eventfd_ctx *ctx = file->private_data;
     __poll_t events = 0;
     u64 count;
 
     poll_wait(file, &ctx->wqh, wait);
 
     /*
      * All writes to ctx->count occur within ctx->wqh.lock.  This read
      * can be done outside ctx->wqh.lock because we know that poll_wait
      * takes that lock (through add_wait_queue) if our caller will sleep.
      *
      * The read _can_ therefore seep into add_wait_queue's critical
      * section, but cannot move above it!  add_wait_queue's spin_lock acts
      * as an acquire barrier and ensures that the read be ordered properly
      * against the writes.  The following CAN happen and is safe:
      *
      *     poll                               write
      *     -----------------                  ------------
      *     lock ctx->wqh.lock (in poll_wait)
      *     count = ctx->count
      *     __add_wait_queue
      *     unlock ctx->wqh.lock
      *                                        lock ctx->qwh.lock
      *                                        ctx->count += n
      *                                        if (waitqueue_active)
      *                                          wake_up_locked_poll
      *                                        unlock ctx->qwh.lock
      *     eventfd_poll returns 0
      *
      * but the following, which would miss a wakeup, cannot happen:
      *
      *     poll                               write
      *     -----------------                  ------------
      *     count = ctx->count (INVALID!)
      *                                        lock ctx->qwh.lock
      *                                        ctx->count += n
      *                                        **waitqueue_active is false**
      *                                        **no wake_up_locked_poll!**
      *                                        unlock ctx->qwh.lock
      *     lock ctx->wqh.lock (in poll_wait)
      *     __add_wait_queue
      *     unlock ctx->wqh.lock
      *     eventfd_poll returns 0
      */
     count = READ_ONCE(ctx->count);
 
     if (count > 0)
         events |= EPOLLIN;
     if (count == ULLONG_MAX)
         events |= EPOLLERR;
     if (ULLONG_MAX - 1 > count)
         events |= EPOLLOUT;
 
     return events;
 }
 
 void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
 {
     lockdep_assert_held(&ctx->wqh.lock);
 
     *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
     ctx->count -= *cnt;
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_do_read);
 
 /**
  * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
  * @ctx: [in] Pointer to eventfd context.
  * @wait: [in] Wait queue to be removed.
  * @cnt: [out] Pointer to the 64-bit counter value.
  *
  * Returns %0 if successful, or the following error codes:
  *
  * -EAGAIN      : The operation would have blocked.
  *
  * This is used to atomically remove a wait queue entry from the eventfd wait
  * queue head, and read/reset the counter value.
  */
 int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
                   __u64 *cnt)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&ctx->wqh.lock, flags);
     eventfd_ctx_do_read(ctx, cnt);
     __remove_wait_queue(&ctx->wqh, wait);
     if (*cnt != 0 && waitqueue_active(&ctx->wqh))
         wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
     spin_unlock_irqrestore(&ctx->wqh.lock, flags);
 
     return *cnt != 0 ? 0 : -EAGAIN;
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
 
 static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
 {
     struct file *file = iocb->ki_filp;
     struct eventfd_ctx *ctx = file->private_data;
     __u64 ucnt = 0;
     DECLARE_WAITQUEUE(wait, current);
 
     if (iov_iter_count(to) < sizeof(ucnt))
         return -EINVAL;
     spin_lock_irq(&ctx->wqh.lock);
     if (!ctx->count) {
         if ((file->f_flags & O_NONBLOCK) ||
             (iocb->ki_flags & IOCB_NOWAIT)) {
             spin_unlock_irq(&ctx->wqh.lock);
             return -EAGAIN;
         }
         __add_wait_queue(&ctx->wqh, &wait);
         for (;;) {
             set_current_state(TASK_INTERRUPTIBLE);
             if (ctx->count)
                 break;
             if (signal_pending(current)) {
                 __remove_wait_queue(&ctx->wqh, &wait);
                 __set_current_state(TASK_RUNNING);
                 spin_unlock_irq(&ctx->wqh.lock);
                 return -ERESTARTSYS;
             }
             spin_unlock_irq(&ctx->wqh.lock);
             schedule();
             spin_lock_irq(&ctx->wqh.lock);
         }
         __remove_wait_queue(&ctx->wqh, &wait);
         __set_current_state(TASK_RUNNING);
     }
     eventfd_ctx_do_read(ctx, &ucnt);
     if (waitqueue_active(&ctx->wqh))
         wake_up_locked_poll(&ctx->wqh, EPOLLOUT);
     spin_unlock_irq(&ctx->wqh.lock);
     if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt)))
         return -EFAULT;
 
     return sizeof(ucnt);
 }
 
 static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
                  loff_t *ppos)
 {
     struct eventfd_ctx *ctx = file->private_data;
     ssize_t res;
     __u64 ucnt;
     DECLARE_WAITQUEUE(wait, current);
 
     if (count < sizeof(ucnt))
         return -EINVAL;
     if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
         return -EFAULT;
     if (ucnt == ULLONG_MAX)
         return -EINVAL;
     spin_lock_irq(&ctx->wqh.lock);
     res = -EAGAIN;
     if (ULLONG_MAX - ctx->count > ucnt)
         res = sizeof(ucnt);
     else if (!(file->f_flags & O_NONBLOCK)) {
         __add_wait_queue(&ctx->wqh, &wait);
         for (res = 0;;) {
             set_current_state(TASK_INTERRUPTIBLE);
             if (ULLONG_MAX - ctx->count > ucnt) {
                 res = sizeof(ucnt);
                 break;
             }
             if (signal_pending(current)) {
                 res = -ERESTARTSYS;
                 break;
             }
             spin_unlock_irq(&ctx->wqh.lock);
             schedule();
             spin_lock_irq(&ctx->wqh.lock);
         }
         __remove_wait_queue(&ctx->wqh, &wait);
         __set_current_state(TASK_RUNNING);
     }
     if (likely(res > 0)) {
         ctx->count += ucnt;
         if (waitqueue_active(&ctx->wqh))
             wake_up_locked_poll(&ctx->wqh, EPOLLIN);
     }
     spin_unlock_irq(&ctx->wqh.lock);
 
     return res;
 }
 
 #ifdef CONFIG_PROC_FS
 static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
 {
     struct eventfd_ctx *ctx = f->private_data;
 
     spin_lock_irq(&ctx->wqh.lock);
     seq_printf(m, "eventfd-count: %16llx\n",
            (unsigned long long)ctx->count);
     spin_unlock_irq(&ctx->wqh.lock);
     seq_printf(m, "eventfd-id: %d\n", ctx->id);
 }
 #endif
 
 static const struct file_operations eventfd_fops = {
 #ifdef CONFIG_PROC_FS
     .show_fdinfo    = eventfd_show_fdinfo,
 #endif
     .release    = eventfd_release,
     .poll       = eventfd_poll,
     .read_iter  = eventfd_read,
     .write      = eventfd_write,
     .llseek     = noop_llseek,
 };
 
 /**
  * eventfd_fget - Acquire a reference of an eventfd file descriptor.
  * @fd: [in] Eventfd file descriptor.
  *
  * Returns a pointer to the eventfd file structure in case of success, or the
  * following error pointer:
  *
  * -EBADF    : Invalid @fd file descriptor.
  * -EINVAL   : The @fd file descriptor is not an eventfd file.
  */
 struct file *eventfd_fget(int fd)
 {
     struct file *file;
 
     file = fget(fd);
     if (!file)
         return ERR_PTR(-EBADF);
     if (file->f_op != &eventfd_fops) {
         fput(file);
         return ERR_PTR(-EINVAL);
     }
 
     return file;
 }
 EXPORT_SYMBOL_GPL(eventfd_fget);
 
 /**
  * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
  * @fd: [in] Eventfd file descriptor.
  *
  * Returns a pointer to the internal eventfd context, otherwise the error
  * pointers returned by the following functions:
  *
  * eventfd_fget
  */
 struct eventfd_ctx *eventfd_ctx_fdget(int fd)
 {
     struct eventfd_ctx *ctx;
     struct fd f = fdget(fd);
     if (!f.file)
         return ERR_PTR(-EBADF);
     ctx = eventfd_ctx_fileget(f.file);
     fdput(f);
     return ctx;
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
 
 /**
  * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
  * @file: [in] Eventfd file pointer.
  *
  * Returns a pointer to the internal eventfd context, otherwise the error
  * pointer:
  *
  * -EINVAL   : The @fd file descriptor is not an eventfd file.
  */
 struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
 {
     struct eventfd_ctx *ctx;
 
     if (file->f_op != &eventfd_fops)
         return ERR_PTR(-EINVAL);
 
     ctx = file->private_data;
     kref_get(&ctx->kref);
     return ctx;
 }
 EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
 
 static int do_eventfd(unsigned int count, int flags)
 {
     struct eventfd_ctx *ctx;
     struct file *file;
     int fd;
 
     /* Check the EFD_* constants for consistency.  */
     BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
     BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
 
     if (flags & ~EFD_FLAGS_SET)
         return -EINVAL;
 
     ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
     if (!ctx)
         return -ENOMEM;
 
     kref_init(&ctx->kref);
     init_waitqueue_head(&ctx->wqh);
     ctx->count = count;
     ctx->flags = flags;
     ctx->id = ida_simple_get(&eventfd_ida, 0, 0, GFP_KERNEL);
 
     flags &= EFD_SHARED_FCNTL_FLAGS;
     flags |= O_RDWR;
     fd = get_unused_fd_flags(flags);
     if (fd < 0)
         goto err;
 
     file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
     if (IS_ERR(file)) {
         put_unused_fd(fd);
         fd = PTR_ERR(file);
         goto err;
     }
 
     file->f_mode |= FMODE_NOWAIT;
     fd_install(fd, file);
     return fd;
 err:
     eventfd_free_ctx(ctx);
     return fd;
 }
 
 SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
 {
     return do_eventfd(count, flags);
 }
 
 SYSCALL_DEFINE1(eventfd, unsigned int, count)
 {
     return do_eventfd(count, 0);
 }
 

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