FreeBSD/Linux Kernel Cross Reference
sys/fs/pipe.c

     /*
      *  linux/fs/pipe.c
      *
      *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
      */
     
     #include <linux/mm.h>
     #include <linux/file.h>
     #include <linux/poll.h>
    #include <linux/slab.h>
    #include <linux/module.h>
    #include <linux/init.h>
    #include <linux/fs.h>
    #include <linux/log2.h>
    #include <linux/mount.h>
    #include <linux/magic.h>
    #include <linux/pipe_fs_i.h>
    #include <linux/uio.h>
    #include <linux/highmem.h>
    #include <linux/pagemap.h>
    #include <linux/audit.h>
    #include <linux/syscalls.h>
    #include <linux/fcntl.h>
    
    #include <asm/uaccess.h>
    #include <asm/ioctls.h>
    
    /*
     * The max size that a non-root user is allowed to grow the pipe. Can
     * be set by root in /proc/sys/fs/pipe-max-size
     */
    unsigned int pipe_max_size = 1048576;
    
    /*
     * Minimum pipe size, as required by POSIX
     */
    unsigned int pipe_min_size = PAGE_SIZE;
    
    /*
     * We use a start+len construction, which provides full use of the 
     * allocated memory.
     * -- Florian Coosmann (FGC)
     * 
     * Reads with count = 0 should always return 0.
     * -- Julian Bradfield 1999-06-07.
     *
     * FIFOs and Pipes now generate SIGIO for both readers and writers.
     * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
     *
     * pipe_read & write cleanup
     * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
     */
    
    static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
    {
            if (pipe->inode)
                    mutex_lock_nested(&pipe->inode->i_mutex, subclass);
    }
    
    void pipe_lock(struct pipe_inode_info *pipe)
    {
            /*
             * pipe_lock() nests non-pipe inode locks (for writing to a file)
             */
            pipe_lock_nested(pipe, I_MUTEX_PARENT);
    }
    EXPORT_SYMBOL(pipe_lock);
    
    void pipe_unlock(struct pipe_inode_info *pipe)
    {
            if (pipe->inode)
                    mutex_unlock(&pipe->inode->i_mutex);
    }
    EXPORT_SYMBOL(pipe_unlock);
    
    void pipe_double_lock(struct pipe_inode_info *pipe1,
                          struct pipe_inode_info *pipe2)
    {
            BUG_ON(pipe1 == pipe2);
    
            if (pipe1 < pipe2) {
                    pipe_lock_nested(pipe1, I_MUTEX_PARENT);
                    pipe_lock_nested(pipe2, I_MUTEX_CHILD);
            } else {
                    pipe_lock_nested(pipe2, I_MUTEX_PARENT);
                    pipe_lock_nested(pipe1, I_MUTEX_CHILD);
            }
    }
    
    /* Drop the inode semaphore and wait for a pipe event, atomically */
    void pipe_wait(struct pipe_inode_info *pipe)
    {
            DEFINE_WAIT(wait);
    
            /*
             * Pipes are system-local resources, so sleeping on them
             * is considered a noninteractive wait:
             */
            prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
           pipe_unlock(pipe);
           schedule();
           finish_wait(&pipe->wait, &wait);
           pipe_lock(pipe);
   }
   
   static int
   pipe_iov_copy_from_user(void *to, struct iovec *iov, unsigned long len,
                           int atomic)
   {
           unsigned long copy;
   
           while (len > 0) {
                   while (!iov->iov_len)
                           iov++;
                   copy = min_t(unsigned long, len, iov->iov_len);
   
                   if (atomic) {
                           if (__copy_from_user_inatomic(to, iov->iov_base, copy))
                                   return -EFAULT;
                   } else {
                           if (copy_from_user(to, iov->iov_base, copy))
                                   return -EFAULT;
                   }
                   to += copy;
                   len -= copy;
                   iov->iov_base += copy;
                   iov->iov_len -= copy;
           }
           return 0;
   }
   
   static int
   pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len,
                         int atomic)
   {
           unsigned long copy;
   
           while (len > 0) {
                   while (!iov->iov_len)
                           iov++;
                   copy = min_t(unsigned long, len, iov->iov_len);
   
                   if (atomic) {
                           if (__copy_to_user_inatomic(iov->iov_base, from, copy))
                                   return -EFAULT;
                   } else {
                           if (copy_to_user(iov->iov_base, from, copy))
                                   return -EFAULT;
                   }
                   from += copy;
                   len -= copy;
                   iov->iov_base += copy;
                   iov->iov_len -= copy;
           }
           return 0;
   }
   
   /*
    * Attempt to pre-fault in the user memory, so we can use atomic copies.
    * Returns the number of bytes not faulted in.
    */
   static int iov_fault_in_pages_write(struct iovec *iov, unsigned long len)
   {
           while (!iov->iov_len)
                   iov++;
   
           while (len > 0) {
                   unsigned long this_len;
   
                   this_len = min_t(unsigned long, len, iov->iov_len);
                   if (fault_in_pages_writeable(iov->iov_base, this_len))
                           break;
   
                   len -= this_len;
                   iov++;
           }
   
           return len;
   }
   
   /*
    * Pre-fault in the user memory, so we can use atomic copies.
    */
   static void iov_fault_in_pages_read(struct iovec *iov, unsigned long len)
   {
           while (!iov->iov_len)
                   iov++;
   
           while (len > 0) {
                   unsigned long this_len;
   
                   this_len = min_t(unsigned long, len, iov->iov_len);
                   fault_in_pages_readable(iov->iov_base, this_len);
                   len -= this_len;
                   iov++;
           }
   }
   
   static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
                                     struct pipe_buffer *buf)
   {
           struct page *page = buf->page;
   
           /*
            * If nobody else uses this page, and we don't already have a
            * temporary page, let's keep track of it as a one-deep
            * allocation cache. (Otherwise just release our reference to it)
            */
           if (page_count(page) == 1 && !pipe->tmp_page)
                   pipe->tmp_page = page;
           else
                   page_cache_release(page);
   }
   
   /**
    * generic_pipe_buf_map - virtually map a pipe buffer
    * @pipe:       the pipe that the buffer belongs to
    * @buf:        the buffer that should be mapped
    * @atomic:     whether to use an atomic map
    *
    * Description:
    *      This function returns a kernel virtual address mapping for the
    *      pipe_buffer passed in @buf. If @atomic is set, an atomic map is provided
    *      and the caller has to be careful not to fault before calling
    *      the unmap function.
    *
    *      Note that this function calls kmap_atomic() if @atomic != 0.
    */
   void *generic_pipe_buf_map(struct pipe_inode_info *pipe,
                              struct pipe_buffer *buf, int atomic)
   {
           if (atomic) {
                   buf->flags |= PIPE_BUF_FLAG_ATOMIC;
                   return kmap_atomic(buf->page);
           }
   
           return kmap(buf->page);
   }
   EXPORT_SYMBOL(generic_pipe_buf_map);
   
   /**
    * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
    * @pipe:       the pipe that the buffer belongs to
    * @buf:        the buffer that should be unmapped
    * @map_data:   the data that the mapping function returned
    *
    * Description:
    *      This function undoes the mapping that ->map() provided.
    */
   void generic_pipe_buf_unmap(struct pipe_inode_info *pipe,
                               struct pipe_buffer *buf, void *map_data)
   {
           if (buf->flags & PIPE_BUF_FLAG_ATOMIC) {
                   buf->flags &= ~PIPE_BUF_FLAG_ATOMIC;
                   kunmap_atomic(map_data);
           } else
                   kunmap(buf->page);
   }
   EXPORT_SYMBOL(generic_pipe_buf_unmap);
   
   /**
    * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
    * @pipe:       the pipe that the buffer belongs to
    * @buf:        the buffer to attempt to steal
    *
    * Description:
    *      This function attempts to steal the &struct page attached to
    *      @buf. If successful, this function returns 0 and returns with
    *      the page locked. The caller may then reuse the page for whatever
    *      he wishes; the typical use is insertion into a different file
    *      page cache.
    */
   int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
                              struct pipe_buffer *buf)
   {
           struct page *page = buf->page;
   
           /*
            * A reference of one is golden, that means that the owner of this
            * page is the only one holding a reference to it. lock the page
            * and return OK.
            */
           if (page_count(page) == 1) {
                   lock_page(page);
                   return 0;
           }
   
           return 1;
   }
   EXPORT_SYMBOL(generic_pipe_buf_steal);
   
   /**
    * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
    * @pipe:       the pipe that the buffer belongs to
    * @buf:        the buffer to get a reference to
    *
    * Description:
    *      This function grabs an extra reference to @buf. It's used in
    *      in the tee() system call, when we duplicate the buffers in one
    *      pipe into another.
    */
   void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
   {
           page_cache_get(buf->page);
   }
   EXPORT_SYMBOL(generic_pipe_buf_get);
   
   /**
    * generic_pipe_buf_confirm - verify contents of the pipe buffer
    * @info:       the pipe that the buffer belongs to
    * @buf:        the buffer to confirm
    *
    * Description:
    *      This function does nothing, because the generic pipe code uses
    *      pages that are always good when inserted into the pipe.
    */
   int generic_pipe_buf_confirm(struct pipe_inode_info *info,
                                struct pipe_buffer *buf)
   {
           return 0;
   }
   EXPORT_SYMBOL(generic_pipe_buf_confirm);
   
   /**
    * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
    * @pipe:       the pipe that the buffer belongs to
    * @buf:        the buffer to put a reference to
    *
    * Description:
    *      This function releases a reference to @buf.
    */
   void generic_pipe_buf_release(struct pipe_inode_info *pipe,
                                 struct pipe_buffer *buf)
   {
           page_cache_release(buf->page);
   }
   EXPORT_SYMBOL(generic_pipe_buf_release);
   
   static const struct pipe_buf_operations anon_pipe_buf_ops = {
           .can_merge = 1,
           .map = generic_pipe_buf_map,
           .unmap = generic_pipe_buf_unmap,
           .confirm = generic_pipe_buf_confirm,
           .release = anon_pipe_buf_release,
           .steal = generic_pipe_buf_steal,
           .get = generic_pipe_buf_get,
   };
   
   static const struct pipe_buf_operations packet_pipe_buf_ops = {
           .can_merge = 0,
           .map = generic_pipe_buf_map,
           .unmap = generic_pipe_buf_unmap,
           .confirm = generic_pipe_buf_confirm,
           .release = anon_pipe_buf_release,
           .steal = generic_pipe_buf_steal,
           .get = generic_pipe_buf_get,
   };
   
   static ssize_t
   pipe_read(struct kiocb *iocb, const struct iovec *_iov,
              unsigned long nr_segs, loff_t pos)
   {
           struct file *filp = iocb->ki_filp;
           struct inode *inode = filp->f_path.dentry->d_inode;
           struct pipe_inode_info *pipe;
           int do_wakeup;
           ssize_t ret;
           struct iovec *iov = (struct iovec *)_iov;
           size_t total_len;
   
           total_len = iov_length(iov, nr_segs);
           /* Null read succeeds. */
           if (unlikely(total_len == 0))
                   return 0;
   
           do_wakeup = 0;
           ret = 0;
           mutex_lock(&inode->i_mutex);
           pipe = inode->i_pipe;
           for (;;) {
                   int bufs = pipe->nrbufs;
                   if (bufs) {
                           int curbuf = pipe->curbuf;
                           struct pipe_buffer *buf = pipe->bufs + curbuf;
                           const struct pipe_buf_operations *ops = buf->ops;
                           void *addr;
                           size_t chars = buf->len;
                           int error, atomic;
   
                           if (chars > total_len)
                                   chars = total_len;
   
                           error = ops->confirm(pipe, buf);
                           if (error) {
                                   if (!ret)
                                           ret = error;
                                   break;
                           }
   
                           atomic = !iov_fault_in_pages_write(iov, chars);
   redo:
                           addr = ops->map(pipe, buf, atomic);
                           error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars, atomic);
                           ops->unmap(pipe, buf, addr);
                           if (unlikely(error)) {
                                   /*
                                    * Just retry with the slow path if we failed.
                                    */
                                   if (atomic) {
                                           atomic = 0;
                                           goto redo;
                                   }
                                   if (!ret)
                                           ret = error;
                                   break;
                           }
                           ret += chars;
                           buf->offset += chars;
                           buf->len -= chars;
   
                           /* Was it a packet buffer? Clean up and exit */
                           if (buf->flags & PIPE_BUF_FLAG_PACKET) {
                                   total_len = chars;
                                   buf->len = 0;
                           }
   
                           if (!buf->len) {
                                   buf->ops = NULL;
                                   ops->release(pipe, buf);
                                   curbuf = (curbuf + 1) & (pipe->buffers - 1);
                                   pipe->curbuf = curbuf;
                                   pipe->nrbufs = --bufs;
                                   do_wakeup = 1;
                           }
                           total_len -= chars;
                           if (!total_len)
                                   break;  /* common path: read succeeded */
                   }
                   if (bufs)       /* More to do? */
                           continue;
                   if (!pipe->writers)
                           break;
                   if (!pipe->waiting_writers) {
                           /* syscall merging: Usually we must not sleep
                            * if O_NONBLOCK is set, or if we got some data.
                            * But if a writer sleeps in kernel space, then
                            * we can wait for that data without violating POSIX.
                            */
                           if (ret)
                                   break;
                           if (filp->f_flags & O_NONBLOCK) {
                                   ret = -EAGAIN;
                                   break;
                           }
                   }
                   if (signal_pending(current)) {
                           if (!ret)
                                   ret = -ERESTARTSYS;
                           break;
                   }
                   if (do_wakeup) {
                           wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
                           kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
                   }
                   pipe_wait(pipe);
           }
           mutex_unlock(&inode->i_mutex);
   
           /* Signal writers asynchronously that there is more room. */
           if (do_wakeup) {
                   wake_up_interruptible_sync_poll(&pipe->wait, POLLOUT | POLLWRNORM);
                   kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
           }
           if (ret > 0)
                   file_accessed(filp);
           return ret;
   }
   
   static inline int is_packetized(struct file *file)
   {
           return (file->f_flags & O_DIRECT) != 0;
   }
   
   static ssize_t
   pipe_write(struct kiocb *iocb, const struct iovec *_iov,
               unsigned long nr_segs, loff_t ppos)
   {
           struct file *filp = iocb->ki_filp;
           struct inode *inode = filp->f_path.dentry->d_inode;
           struct pipe_inode_info *pipe;
           ssize_t ret;
           int do_wakeup;
           struct iovec *iov = (struct iovec *)_iov;
           size_t total_len;
           ssize_t chars;
   
           total_len = iov_length(iov, nr_segs);
           /* Null write succeeds. */
           if (unlikely(total_len == 0))
                   return 0;
   
           do_wakeup = 0;
           ret = 0;
           mutex_lock(&inode->i_mutex);
           pipe = inode->i_pipe;
   
           if (!pipe->readers) {
                   send_sig(SIGPIPE, current, 0);
                   ret = -EPIPE;
                   goto out;
           }
   
           /* We try to merge small writes */
           chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
           if (pipe->nrbufs && chars != 0) {
                   int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
                                                           (pipe->buffers - 1);
                   struct pipe_buffer *buf = pipe->bufs + lastbuf;
                   const struct pipe_buf_operations *ops = buf->ops;
                   int offset = buf->offset + buf->len;
   
                   if (ops->can_merge && offset + chars <= PAGE_SIZE) {
                           int error, atomic = 1;
                           void *addr;
   
                           error = ops->confirm(pipe, buf);
                           if (error)
                                   goto out;
   
                           iov_fault_in_pages_read(iov, chars);
   redo1:
                           addr = ops->map(pipe, buf, atomic);
                           error = pipe_iov_copy_from_user(offset + addr, iov,
                                                           chars, atomic);
                           ops->unmap(pipe, buf, addr);
                           ret = error;
                           do_wakeup = 1;
                           if (error) {
                                   if (atomic) {
                                           atomic = 0;
                                           goto redo1;
                                   }
                                   goto out;
                           }
                           buf->len += chars;
                           total_len -= chars;
                           ret = chars;
                           if (!total_len)
                                   goto out;
                   }
           }
   
           for (;;) {
                   int bufs;
   
                   if (!pipe->readers) {
                           send_sig(SIGPIPE, current, 0);
                           if (!ret)
                                   ret = -EPIPE;
                           break;
                   }
                   bufs = pipe->nrbufs;
                   if (bufs < pipe->buffers) {
                           int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
                           struct pipe_buffer *buf = pipe->bufs + newbuf;
                           struct page *page = pipe->tmp_page;
                           char *src;
                           int error, atomic = 1;
   
                           if (!page) {
                                   page = alloc_page(GFP_HIGHUSER);
                                   if (unlikely(!page)) {
                                           ret = ret ? : -ENOMEM;
                                           break;
                                   }
                                   pipe->tmp_page = page;
                           }
                           /* Always wake up, even if the copy fails. Otherwise
                            * we lock up (O_NONBLOCK-)readers that sleep due to
                            * syscall merging.
                            * FIXME! Is this really true?
                            */
                           do_wakeup = 1;
                           chars = PAGE_SIZE;
                           if (chars > total_len)
                                   chars = total_len;
   
                           iov_fault_in_pages_read(iov, chars);
   redo2:
                           if (atomic)
                                   src = kmap_atomic(page);
                           else
                                   src = kmap(page);
   
                           error = pipe_iov_copy_from_user(src, iov, chars,
                                                           atomic);
                           if (atomic)
                                   kunmap_atomic(src);
                           else
                                   kunmap(page);
   
                           if (unlikely(error)) {
                                   if (atomic) {
                                           atomic = 0;
                                           goto redo2;
                                   }
                                   if (!ret)
                                           ret = error;
                                   break;
                           }
                           ret += chars;
   
                           /* Insert it into the buffer array */
                           buf->page = page;
                           buf->ops = &anon_pipe_buf_ops;
                           buf->offset = 0;
                           buf->len = chars;
                           buf->flags = 0;
                           if (is_packetized(filp)) {
                                   buf->ops = &packet_pipe_buf_ops;
                                   buf->flags = PIPE_BUF_FLAG_PACKET;
                           }
                           pipe->nrbufs = ++bufs;
                           pipe->tmp_page = NULL;
   
                           total_len -= chars;
                           if (!total_len)
                                   break;
                   }
                   if (bufs < pipe->buffers)
                           continue;
                   if (filp->f_flags & O_NONBLOCK) {
                           if (!ret)
                                   ret = -EAGAIN;
                           break;
                   }
                   if (signal_pending(current)) {
                           if (!ret)
                                   ret = -ERESTARTSYS;
                           break;
                   }
                   if (do_wakeup) {
                           wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
                           kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
                           do_wakeup = 0;
                   }
                   pipe->waiting_writers++;
                   pipe_wait(pipe);
                   pipe->waiting_writers--;
           }
   out:
           mutex_unlock(&inode->i_mutex);
           if (do_wakeup) {
                   wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
                   kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
           }
           if (ret > 0) {
                   int err = file_update_time(filp);
                   if (err)
                           ret = err;
           }
           return ret;
   }
   
   static ssize_t
   bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
   {
           return -EBADF;
   }
   
   static ssize_t
   bad_pipe_w(struct file *filp, const char __user *buf, size_t count,
              loff_t *ppos)
   {
           return -EBADF;
   }
   
   static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
   {
           struct inode *inode = filp->f_path.dentry->d_inode;
           struct pipe_inode_info *pipe;
           int count, buf, nrbufs;
   
           switch (cmd) {
                   case FIONREAD:
                           mutex_lock(&inode->i_mutex);
                           pipe = inode->i_pipe;
                           count = 0;
                           buf = pipe->curbuf;
                           nrbufs = pipe->nrbufs;
                           while (--nrbufs >= 0) {
                                   count += pipe->bufs[buf].len;
                                   buf = (buf+1) & (pipe->buffers - 1);
                           }
                           mutex_unlock(&inode->i_mutex);
   
                           return put_user(count, (int __user *)arg);
                   default:
                           return -ENOIOCTLCMD;
           }
   }
   
   /* No kernel lock held - fine */
   static unsigned int
   pipe_poll(struct file *filp, poll_table *wait)
   {
           unsigned int mask;
           struct inode *inode = filp->f_path.dentry->d_inode;
           struct pipe_inode_info *pipe = inode->i_pipe;
           int nrbufs;
   
           poll_wait(filp, &pipe->wait, wait);
   
           /* Reading only -- no need for acquiring the semaphore.  */
           nrbufs = pipe->nrbufs;
           mask = 0;
           if (filp->f_mode & FMODE_READ) {
                   mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0;
                   if (!pipe->writers && filp->f_version != pipe->w_counter)
                           mask |= POLLHUP;
           }
   
           if (filp->f_mode & FMODE_WRITE) {
                   mask |= (nrbufs < pipe->buffers) ? POLLOUT | POLLWRNORM : 0;
                   /*
                    * Most Unices do not set POLLERR for FIFOs but on Linux they
                    * behave exactly like pipes for poll().
                    */
                   if (!pipe->readers)
                           mask |= POLLERR;
           }
   
           return mask;
   }
   
   static int
   pipe_release(struct inode *inode, int decr, int decw)
   {
           struct pipe_inode_info *pipe;
   
           mutex_lock(&inode->i_mutex);
           pipe = inode->i_pipe;
           pipe->readers -= decr;
           pipe->writers -= decw;
   
           if (!pipe->readers && !pipe->writers) {
                   free_pipe_info(inode);
           } else {
                   wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM | POLLERR | POLLHUP);
                   kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
                   kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
           }
           mutex_unlock(&inode->i_mutex);
   
           return 0;
   }
   
   static int
   pipe_read_fasync(int fd, struct file *filp, int on)
   {
           struct inode *inode = filp->f_path.dentry->d_inode;
           int retval;
   
           mutex_lock(&inode->i_mutex);
           retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers);
           mutex_unlock(&inode->i_mutex);
   
           return retval;
   }
   
   
   static int
   pipe_write_fasync(int fd, struct file *filp, int on)
   {
           struct inode *inode = filp->f_path.dentry->d_inode;
           int retval;
   
           mutex_lock(&inode->i_mutex);
           retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers);
           mutex_unlock(&inode->i_mutex);
   
           return retval;
   }
   
   
   static int
   pipe_rdwr_fasync(int fd, struct file *filp, int on)
   {
           struct inode *inode = filp->f_path.dentry->d_inode;
           struct pipe_inode_info *pipe = inode->i_pipe;
           int retval;
   
           mutex_lock(&inode->i_mutex);
           retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
           if (retval >= 0) {
                   retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
                   if (retval < 0) /* this can happen only if on == T */
                           fasync_helper(-1, filp, 0, &pipe->fasync_readers);
           }
           mutex_unlock(&inode->i_mutex);
           return retval;
   }
   
   
   static int
   pipe_read_release(struct inode *inode, struct file *filp)
   {
           return pipe_release(inode, 1, 0);
   }
   
   static int
   pipe_write_release(struct inode *inode, struct file *filp)
   {
           return pipe_release(inode, 0, 1);
   }
   
   static int
   pipe_rdwr_release(struct inode *inode, struct file *filp)
   {
           int decr, decw;
   
           decr = (filp->f_mode & FMODE_READ) != 0;
           decw = (filp->f_mode & FMODE_WRITE) != 0;
           return pipe_release(inode, decr, decw);
   }
   
   static int
   pipe_read_open(struct inode *inode, struct file *filp)
   {
           int ret = -ENOENT;
   
           mutex_lock(&inode->i_mutex);
   
           if (inode->i_pipe) {
                   ret = 0;
                   inode->i_pipe->readers++;
           }
   
           mutex_unlock(&inode->i_mutex);
   
           return ret;
   }
   
   static int
   pipe_write_open(struct inode *inode, struct file *filp)
   {
           int ret = -ENOENT;
   
           mutex_lock(&inode->i_mutex);
   
           if (inode->i_pipe) {
                   ret = 0;
                   inode->i_pipe->writers++;
           }
   
           mutex_unlock(&inode->i_mutex);
   
           return ret;
   }
   
   static int
   pipe_rdwr_open(struct inode *inode, struct file *filp)
   {
           int ret = -ENOENT;
   
           mutex_lock(&inode->i_mutex);
   
           if (inode->i_pipe) {
                   ret = 0;
                   if (filp->f_mode & FMODE_READ)
                           inode->i_pipe->readers++;
                   if (filp->f_mode & FMODE_WRITE)
                           inode->i_pipe->writers++;
           }
   
           mutex_unlock(&inode->i_mutex);
   
           return ret;
   }
   
   /*
    * The file_operations structs are not static because they
    * are also used in linux/fs/fifo.c to do operations on FIFOs.
    *
    * Pipes reuse fifos' file_operations structs.
    */
   const struct file_operations read_pipefifo_fops = {
           .llseek         = no_llseek,
           .read           = do_sync_read,
           .aio_read       = pipe_read,
           .write          = bad_pipe_w,
           .poll           = pipe_poll,
           .unlocked_ioctl = pipe_ioctl,
           .open           = pipe_read_open,
           .release        = pipe_read_release,
           .fasync         = pipe_read_fasync,
   };
   
   const struct file_operations write_pipefifo_fops = {
           .llseek         = no_llseek,
           .read           = bad_pipe_r,
           .write          = do_sync_write,
           .aio_write      = pipe_write,
           .poll           = pipe_poll,
           .unlocked_ioctl = pipe_ioctl,
           .open           = pipe_write_open,
           .release        = pipe_write_release,
           .fasync         = pipe_write_fasync,
   };
   
   const struct file_operations rdwr_pipefifo_fops = {
           .llseek         = no_llseek,
           .read           = do_sync_read,
           .aio_read       = pipe_read,
           .write          = do_sync_write,
           .aio_write      = pipe_write,
           .poll           = pipe_poll,
           .unlocked_ioctl = pipe_ioctl,
           .open           = pipe_rdwr_open,
           .release        = pipe_rdwr_release,
           .fasync         = pipe_rdwr_fasync,
   };
   
   struct pipe_inode_info * alloc_pipe_info(struct inode *inode)
   {
           struct pipe_inode_info *pipe;
   
           pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
           if (pipe) {
                   pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
                   if (pipe->bufs) {
                           init_waitqueue_head(&pipe->wait);
                           pipe->r_counter = pipe->w_counter = 1;
                           pipe->inode = inode;
                           pipe->buffers = PIPE_DEF_BUFFERS;
                           return pipe;
                   }
                   kfree(pipe);
           }
   
           return NULL;
   }
   
   void __free_pipe_info(struct pipe_inode_info *pipe)
   {
           int i;
   
           for (i = 0; i < pipe->buffers; i++) {
                   struct pipe_buffer *buf = pipe->bufs + i;
                   if (buf->ops)
                           buf->ops->release(pipe, buf);
           }
           if (pipe->tmp_page)
                   __free_page(pipe->tmp_page);
           kfree(pipe->bufs);
           kfree(pipe);
   }
   
   void free_pipe_info(struct inode *inode)
   {
           __free_pipe_info(inode->i_pipe);
           inode->i_pipe = NULL;
   }
   
   static struct vfsmount *pipe_mnt __read_mostly;
   
   /*
    * pipefs_dname() is called from d_path().
    */
   static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
   {
           return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
                                   dentry->d_inode->i_ino);
   }
   
   static const struct dentry_operations pipefs_dentry_operations = {
           .d_dname        = pipefs_dname,
   };
   
   static struct inode * get_pipe_inode(void)
   {
           struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
           struct pipe_inode_info *pipe;
   
           if (!inode)
                   goto fail_inode;
   
           inode->i_ino = get_next_ino();
   
           pipe = alloc_pipe_info(inode);
           if (!pipe)
                   goto fail_iput;
           inode->i_pipe = pipe;
   
           pipe->readers = pipe->writers = 1;
           inode->i_fop = &rdwr_pipefifo_fops;
   
           /*
            * Mark the inode dirty from the very beginning,
           * that way it will never be moved to the dirty
           * list because "mark_inode_dirty()" will think
           * that it already _is_ on the dirty list.
           */
          inode->i_state = I_DIRTY;
          inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
          inode->i_uid = current_fsuid();
          inode->i_gid = current_fsgid();
          inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
  
          return inode;
  
  fail_iput:
          iput(inode);
  
  fail_inode:
          return NULL;
  }
  
  int create_pipe_files(struct file **res, int flags)
  {
          int err;
          struct inode *inode = get_pipe_inode();
          struct file *f;
          struct path path;
          static struct qstr name = { .name = "" };
  
          if (!inode)
                  return -ENFILE;
  
          err = -ENOMEM;
          path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);
          if (!path.dentry)
                  goto err_inode;
          path.mnt = mntget(pipe_mnt);
  
          d_instantiate(path.dentry, inode);
  
          err = -ENFILE;
          f = alloc_file(&path, FMODE_WRITE, &write_pipefifo_fops);
          if (!f)
                  goto err_dentry;
  
          f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
  
          res[0] = alloc_file(&path, FMODE_READ, &read_pipefifo_fops);
          if (!res[0])
                  goto err_file;
  
          path_get(&path);
          res[0]->f_flags = O_RDONLY | (flags & O_NONBLOCK);
          res[1] = f;
          return 0;
  
  err_file:
          put_filp(f);
  err_dentry:
          free_pipe_info(inode);
          path_put(&path);
          return err;
  
  err_inode:
          free_pipe_info(inode);
          iput(inode);
          return err;
  }
  
  static int __do_pipe_flags(int *fd, struct file **files, int flags)
  {
          int error;
          int fdw, fdr;
  
          if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
                  return -EINVAL;
  
          error = create_pipe_files(files, flags);
          if (error)
                  return error;
  
          error = get_unused_fd_flags(flags);
          if (error < 0)
                  goto err_read_pipe;
          fdr = error;
  
          error = get_unused_fd_flags(flags);
          if (error < 0)
                  goto err_fdr;
          fdw = error;
  
          audit_fd_pair(fdr, fdw);
          fd[0] = fdr;
          fd[1] = fdw;
          return 0;
  
   err_fdr:
          put_unused_fd(fdr);
   err_read_pipe:
          fput(files[0]);
          fput(files[1]);
          return error;
  }
  
  int do_pipe_flags(int *fd, int flags)
  {
          struct file *files[2];
          int error = __do_pipe_flags(fd, files, flags);
          if (!error) {
                  fd_install(fd[0], files[0]);
                  fd_install(fd[1], files[1]);
          }
          return error;
  }
  
  /*
   * sys_pipe() is the normal C calling standard for creating
   * a pipe. It's not the way Unix traditionally does this, though.
   */
  SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
  {
          struct file *files[2];
          int fd[2];
          int error;
  
          error = __do_pipe_flags(fd, files, flags);
          if (!error) {
                  if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
                          fput(files[0]);
                          fput(files[1]);
                          put_unused_fd(fd[0]);
                          put_unused_fd(fd[1]);
                          error = -EFAULT;
                  } else {
                          fd_install(fd[0], files[0]);
                          fd_install(fd[1], files[1]);
                  }
          }
          return error;
  }
  
  SYSCALL_DEFINE1(pipe, int __user *, fildes)
  {
          return sys_pipe2(fildes, 0);
  }
  
  /*
   * Allocate a new array of pipe buffers and copy the info over. Returns the
   * pipe size if successful, or return -ERROR on error.
   */
  static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
  {
          struct pipe_buffer *bufs;
  
          /*
           * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
           * expect a lot of shrink+grow operations, just free and allocate
           * again like we would do for growing. If the pipe currently
           * contains more buffers than arg, then return busy.
           */
          if (nr_pages < pipe->nrbufs)
                  return -EBUSY;
  
          bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
          if (unlikely(!bufs))
                  return -ENOMEM;
  
          /*
           * The pipe array wraps around, so just start the new one at zero
           * and adjust the indexes.
           */
          if (pipe->nrbufs) {
                  unsigned int tail;
                  unsigned int head;
  
                  tail = pipe->curbuf + pipe->nrbufs;
                  if (tail < pipe->buffers)
                          tail = 0;
                  else
                          tail &= (pipe->buffers - 1);
  
                  head = pipe->nrbufs - tail;
                  if (head)
                          memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
                  if (tail)
                          memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
          }
  
          pipe->curbuf = 0;
          kfree(pipe->bufs);
          pipe->bufs = bufs;
          pipe->buffers = nr_pages;
          return nr_pages * PAGE_SIZE;
  }
  
  /*
   * Currently we rely on the pipe array holding a power-of-2 number
   * of pages.
   */
  static inline unsigned int round_pipe_size(unsigned int size)
  {
          unsigned long nr_pages;
  
          nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
          return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
  }
  
  /*
   * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
   * will return an error.
   */
  int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
                   size_t *lenp, loff_t *ppos)
  {
          int ret;
  
          ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
          if (ret < 0 || !write)
                  return ret;
  
          pipe_max_size = round_pipe_size(pipe_max_size);
          return ret;
  }
  
  /*
   * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
   * location, so checking ->i_pipe is not enough to verify that this is a
   * pipe.
   */
  struct pipe_inode_info *get_pipe_info(struct file *file)
  {
          struct inode *i = file->f_path.dentry->d_inode;
  
          return S_ISFIFO(i->i_mode) ? i->i_pipe : NULL;
  }
  
  long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
  {
          struct pipe_inode_info *pipe;
          long ret;
  
          pipe = get_pipe_info(file);
          if (!pipe)
                  return -EBADF;
  
          mutex_lock(&pipe->inode->i_mutex);
  
          switch (cmd) {
          case F_SETPIPE_SZ: {
                  unsigned int size, nr_pages;
  
                  size = round_pipe_size(arg);
                  nr_pages = size >> PAGE_SHIFT;
  
                  ret = -EINVAL;
                  if (!nr_pages)
                          goto out;
  
                  if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
                          ret = -EPERM;
                          goto out;
                  }
                  ret = pipe_set_size(pipe, nr_pages);
                  break;
                  }
          case F_GETPIPE_SZ:
                  ret = pipe->buffers * PAGE_SIZE;
                  break;
          default:
                  ret = -EINVAL;
                  break;
          }
  
  out:
          mutex_unlock(&pipe->inode->i_mutex);
          return ret;
  }
  
  static const struct super_operations pipefs_ops = {
          .destroy_inode = free_inode_nonrcu,
          .statfs = simple_statfs,
  };
  
  /*
   * pipefs should _never_ be mounted by userland - too much of security hassle,
   * no real gain from having the whole whorehouse mounted. So we don't need
   * any operations on the root directory. However, we need a non-trivial
   * d_name - pipe: will go nicely and kill the special-casing in procfs.
   */
  static struct dentry *pipefs_mount(struct file_system_type *fs_type,
                           int flags, const char *dev_name, void *data)
  {
          return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
                          &pipefs_dentry_operations, PIPEFS_MAGIC);
  }
  
  static struct file_system_type pipe_fs_type = {
          .name           = "pipefs",
          .mount          = pipefs_mount,
          .kill_sb        = kill_anon_super,
  };
  
  static int __init init_pipe_fs(void)
  {
          int err = register_filesystem(&pipe_fs_type);
  
          if (!err) {
                  pipe_mnt = kern_mount(&pipe_fs_type);
                  if (IS_ERR(pipe_mnt)) {
                          err = PTR_ERR(pipe_mnt);
                          unregister_filesystem(&pipe_fs_type);
                  }
          }
          return err;
  }
  
  fs_initcall(init_pipe_fs);

Cache object: 6d1e1e91c572e2a950db2c5fcb21ee54