summaryrefslogtreecommitdiff
path: root/fs/pipe.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/pipe.c')
-rw-r--r--fs/pipe.c1125
1 files changed, 1125 insertions, 0 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
new file mode 100644
index 000000000..8865f7963
--- /dev/null
+++ b/fs/pipe.c
@@ -0,0 +1,1125 @@
+/*
+ * 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>
+
+#include "internal.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->files)
+ mutex_lock_nested(&pipe->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->files)
+ mutex_unlock(&pipe->mutex);
+}
+EXPORT_SYMBOL(pipe_unlock);
+
+static inline void __pipe_lock(struct pipe_inode_info *pipe)
+{
+ mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
+}
+
+static inline void __pipe_unlock(struct pipe_inode_info *pipe)
+{
+ mutex_unlock(&pipe->mutex);
+}
+
+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 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_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,
+ .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,
+ .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, struct iov_iter *to)
+{
+ size_t total_len = iov_iter_count(to);
+ struct file *filp = iocb->ki_filp;
+ struct pipe_inode_info *pipe = filp->private_data;
+ int do_wakeup;
+ ssize_t ret;
+
+ /* Null read succeeds. */
+ if (unlikely(total_len == 0))
+ return 0;
+
+ do_wakeup = 0;
+ ret = 0;
+ __pipe_lock(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;
+ size_t chars = buf->len;
+ size_t written;
+ int error;
+
+ if (chars > total_len)
+ chars = total_len;
+
+ error = ops->confirm(pipe, buf);
+ if (error) {
+ if (!ret)
+ ret = error;
+ break;
+ }
+
+ written = copy_page_to_iter(buf->page, buf->offset, chars, to);
+ if (unlikely(written < chars)) {
+ if (!ret)
+ ret = -EFAULT;
+ 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);
+ }
+ __pipe_unlock(pipe);
+
+ /* 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, struct iov_iter *from)
+{
+ struct file *filp = iocb->ki_filp;
+ struct pipe_inode_info *pipe = filp->private_data;
+ ssize_t ret = 0;
+ int do_wakeup = 0;
+ size_t total_len = iov_iter_count(from);
+ ssize_t chars;
+
+ /* Null write succeeds. */
+ if (unlikely(total_len == 0))
+ return 0;
+
+ __pipe_lock(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 = ops->confirm(pipe, buf);
+ if (error)
+ goto out;
+
+ ret = copy_page_from_iter(buf->page, offset, chars, from);
+ if (unlikely(ret < chars)) {
+ error = -EFAULT;
+ goto out;
+ }
+ do_wakeup = 1;
+ buf->len += chars;
+ ret = chars;
+ if (!iov_iter_count(from))
+ 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;
+ int copied;
+
+ 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;
+ copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
+ if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
+ if (!ret)
+ ret = -EFAULT;
+ break;
+ }
+ ret += copied;
+
+ /* Insert it into the buffer array */
+ buf->page = page;
+ buf->ops = &anon_pipe_buf_ops;
+ buf->offset = 0;
+ buf->len = copied;
+ 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;
+
+ if (!iov_iter_count(from))
+ 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:
+ __pipe_unlock(pipe);
+ if (do_wakeup) {
+ wake_up_interruptible_sync_poll(&pipe->wait, POLLIN | POLLRDNORM);
+ kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
+ }
+ if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
+ int err = file_update_time(filp);
+ if (err)
+ ret = err;
+ sb_end_write(file_inode(filp)->i_sb);
+ }
+ return ret;
+}
+
+static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+ struct pipe_inode_info *pipe = filp->private_data;
+ int count, buf, nrbufs;
+
+ switch (cmd) {
+ case FIONREAD:
+ __pipe_lock(pipe);
+ count = 0;
+ buf = pipe->curbuf;
+ nrbufs = pipe->nrbufs;
+ while (--nrbufs >= 0) {
+ count += pipe->bufs[buf].len;
+ buf = (buf+1) & (pipe->buffers - 1);
+ }
+ __pipe_unlock(pipe);
+
+ 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 pipe_inode_info *pipe = filp->private_data;
+ 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 void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
+{
+ int kill = 0;
+
+ spin_lock(&inode->i_lock);
+ if (!--pipe->files) {
+ inode->i_pipe = NULL;
+ kill = 1;
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (kill)
+ free_pipe_info(pipe);
+}
+
+static int
+pipe_release(struct inode *inode, struct file *file)
+{
+ struct pipe_inode_info *pipe = file->private_data;
+
+ __pipe_lock(pipe);
+ if (file->f_mode & FMODE_READ)
+ pipe->readers--;
+ if (file->f_mode & FMODE_WRITE)
+ pipe->writers--;
+
+ if (pipe->readers || pipe->writers) {
+ 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);
+ }
+ __pipe_unlock(pipe);
+
+ put_pipe_info(inode, pipe);
+ return 0;
+}
+
+static int
+pipe_fasync(int fd, struct file *filp, int on)
+{
+ struct pipe_inode_info *pipe = filp->private_data;
+ int retval = 0;
+
+ __pipe_lock(pipe);
+ if (filp->f_mode & FMODE_READ)
+ retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
+ if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
+ retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
+ if (retval < 0 && (filp->f_mode & FMODE_READ))
+ /* this can happen only if on == T */
+ fasync_helper(-1, filp, 0, &pipe->fasync_readers);
+ }
+ __pipe_unlock(pipe);
+ return retval;
+}
+
+struct pipe_inode_info *alloc_pipe_info(void)
+{
+ 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->buffers = PIPE_DEF_BUFFERS;
+ mutex_init(&pipe->mutex);
+ 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);
+}
+
+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]",
+ d_inode(dentry)->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();
+ if (!pipe)
+ goto fail_iput;
+
+ inode->i_pipe = pipe;
+ pipe->files = 2;
+ pipe->readers = pipe->writers = 1;
+ inode->i_fop = &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, &pipefifo_fops);
+ if (IS_ERR(f))
+ goto err_dentry;
+
+ f->f_flags = O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT));
+ f->private_data = inode->i_pipe;
+
+ res[0] = alloc_file(&path, FMODE_READ, &pipefifo_fops);
+ if (IS_ERR(res[0]))
+ goto err_file;
+
+ path_get(&path);
+ res[0]->private_data = inode->i_pipe;
+ 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->i_pipe);
+ path_put(&path);
+ return err;
+
+err_inode:
+ free_pipe_info(inode->i_pipe);
+ 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);
+}
+
+static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
+{
+ int cur = *cnt;
+
+ while (cur == *cnt) {
+ pipe_wait(pipe);
+ if (signal_pending(current))
+ break;
+ }
+ return cur == *cnt ? -ERESTARTSYS : 0;
+}
+
+static void wake_up_partner(struct pipe_inode_info *pipe)
+{
+ wake_up_interruptible(&pipe->wait);
+}
+
+static int fifo_open(struct inode *inode, struct file *filp)
+{
+ struct pipe_inode_info *pipe;
+ bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
+ int ret;
+
+ filp->f_version = 0;
+
+ spin_lock(&inode->i_lock);
+ if (inode->i_pipe) {
+ pipe = inode->i_pipe;
+ pipe->files++;
+ spin_unlock(&inode->i_lock);
+ } else {
+ spin_unlock(&inode->i_lock);
+ pipe = alloc_pipe_info();
+ if (!pipe)
+ return -ENOMEM;
+ pipe->files = 1;
+ spin_lock(&inode->i_lock);
+ if (unlikely(inode->i_pipe)) {
+ inode->i_pipe->files++;
+ spin_unlock(&inode->i_lock);
+ free_pipe_info(pipe);
+ pipe = inode->i_pipe;
+ } else {
+ inode->i_pipe = pipe;
+ spin_unlock(&inode->i_lock);
+ }
+ }
+ filp->private_data = pipe;
+ /* OK, we have a pipe and it's pinned down */
+
+ __pipe_lock(pipe);
+
+ /* We can only do regular read/write on fifos */
+ filp->f_mode &= (FMODE_READ | FMODE_WRITE);
+
+ switch (filp->f_mode) {
+ case FMODE_READ:
+ /*
+ * O_RDONLY
+ * POSIX.1 says that O_NONBLOCK means return with the FIFO
+ * opened, even when there is no process writing the FIFO.
+ */
+ pipe->r_counter++;
+ if (pipe->readers++ == 0)
+ wake_up_partner(pipe);
+
+ if (!is_pipe && !pipe->writers) {
+ if ((filp->f_flags & O_NONBLOCK)) {
+ /* suppress POLLHUP until we have
+ * seen a writer */
+ filp->f_version = pipe->w_counter;
+ } else {
+ if (wait_for_partner(pipe, &pipe->w_counter))
+ goto err_rd;
+ }
+ }
+ break;
+
+ case FMODE_WRITE:
+ /*
+ * O_WRONLY
+ * POSIX.1 says that O_NONBLOCK means return -1 with
+ * errno=ENXIO when there is no process reading the FIFO.
+ */
+ ret = -ENXIO;
+ if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
+ goto err;
+
+ pipe->w_counter++;
+ if (!pipe->writers++)
+ wake_up_partner(pipe);
+
+ if (!is_pipe && !pipe->readers) {
+ if (wait_for_partner(pipe, &pipe->r_counter))
+ goto err_wr;
+ }
+ break;
+
+ case FMODE_READ | FMODE_WRITE:
+ /*
+ * O_RDWR
+ * POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
+ * This implementation will NEVER block on a O_RDWR open, since
+ * the process can at least talk to itself.
+ */
+
+ pipe->readers++;
+ pipe->writers++;
+ pipe->r_counter++;
+ pipe->w_counter++;
+ if (pipe->readers == 1 || pipe->writers == 1)
+ wake_up_partner(pipe);
+ break;
+
+ default:
+ ret = -EINVAL;
+ goto err;
+ }
+
+ /* Ok! */
+ __pipe_unlock(pipe);
+ return 0;
+
+err_rd:
+ if (!--pipe->readers)
+ wake_up_interruptible(&pipe->wait);
+ ret = -ERESTARTSYS;
+ goto err;
+
+err_wr:
+ if (!--pipe->writers)
+ wake_up_interruptible(&pipe->wait);
+ ret = -ERESTARTSYS;
+ goto err;
+
+err:
+ __pipe_unlock(pipe);
+
+ put_pipe_info(inode, pipe);
+ return ret;
+}
+
+const struct file_operations pipefifo_fops = {
+ .open = fifo_open,
+ .llseek = no_llseek,
+ .read_iter = pipe_read,
+ .write_iter = pipe_write,
+ .poll = pipe_poll,
+ .unlocked_ioctl = pipe_ioctl,
+ .release = pipe_release,
+ .fasync = pipe_fasync,
+};
+
+/*
+ * 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)
+{
+ return file->f_op == &pipefifo_fops ? file->private_data : 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;
+
+ __pipe_lock(pipe);
+
+ 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:
+ __pipe_unlock(pipe);
+ 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);
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-18 14:23:49 +0000