diff options
Diffstat (limited to 'fs/pipe.c')
-rw-r--r-- | fs/pipe.c | 317 |
1 files changed, 178 insertions, 139 deletions
@@ -36,7 +36,7 @@ */ /* Drop the inode semaphore and wait for a pipe event, atomically */ -void pipe_wait(struct inode * inode) +void pipe_wait(struct pipe_inode_info *pipe) { DEFINE_WAIT(wait); @@ -44,11 +44,14 @@ void pipe_wait(struct inode * inode) * Pipes are system-local resources, so sleeping on them * is considered a noninteractive wait: */ - prepare_to_wait(PIPE_WAIT(*inode), &wait, TASK_INTERRUPTIBLE|TASK_NONINTERACTIVE); - mutex_unlock(PIPE_MUTEX(*inode)); + prepare_to_wait(&pipe->wait, &wait, + TASK_INTERRUPTIBLE | TASK_NONINTERACTIVE); + if (pipe->inode) + mutex_unlock(&pipe->inode->i_mutex); schedule(); - finish_wait(PIPE_WAIT(*inode), &wait); - mutex_lock(PIPE_MUTEX(*inode)); + finish_wait(&pipe->wait, &wait); + if (pipe->inode) + mutex_lock(&pipe->inode->i_mutex); } static int @@ -91,7 +94,8 @@ pipe_iov_copy_to_user(struct iovec *iov, const void *from, unsigned long len) return 0; } -static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buffer *buf) +static void anon_pipe_buf_release(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) { struct page *page = buf->page; @@ -100,42 +104,46 @@ static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buff /* * 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 + * allocation cache. (Otherwise just release our reference to it) */ - if (page_count(page) == 1 && !info->tmp_page) { - info->tmp_page = page; - return; - } - - /* - * Otherwise just release our reference to it - */ - page_cache_release(page); + if (page_count(page) == 1 && !pipe->tmp_page) + pipe->tmp_page = page; + else + page_cache_release(page); } -static void *anon_pipe_buf_map(struct file *file, struct pipe_inode_info *info, struct pipe_buffer *buf) +static void * anon_pipe_buf_map(struct file *file, struct pipe_inode_info *pipe, + struct pipe_buffer *buf) { return kmap(buf->page); } -static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer *buf) +static void anon_pipe_buf_unmap(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) { kunmap(buf->page); } -static int anon_pipe_buf_steal(struct pipe_inode_info *info, +static int anon_pipe_buf_steal(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { buf->flags |= PIPE_BUF_FLAG_STOLEN; return 0; } +static void anon_pipe_buf_get(struct pipe_inode_info *info, + struct pipe_buffer *buf) +{ + page_cache_get(buf->page); +} + static struct pipe_buf_operations anon_pipe_buf_ops = { .can_merge = 1, .map = anon_pipe_buf_map, .unmap = anon_pipe_buf_unmap, .release = anon_pipe_buf_release, .steal = anon_pipe_buf_steal, + .get = anon_pipe_buf_get, }; static ssize_t @@ -143,7 +151,7 @@ pipe_readv(struct file *filp, const struct iovec *_iov, unsigned long nr_segs, loff_t *ppos) { struct inode *inode = filp->f_dentry->d_inode; - struct pipe_inode_info *info; + struct pipe_inode_info *pipe; int do_wakeup; ssize_t ret; struct iovec *iov = (struct iovec *)_iov; @@ -156,13 +164,13 @@ pipe_readv(struct file *filp, const struct iovec *_iov, do_wakeup = 0; ret = 0; - mutex_lock(PIPE_MUTEX(*inode)); - info = inode->i_pipe; + mutex_lock(&inode->i_mutex); + pipe = inode->i_pipe; for (;;) { - int bufs = info->nrbufs; + int bufs = pipe->nrbufs; if (bufs) { - int curbuf = info->curbuf; - struct pipe_buffer *buf = info->bufs + curbuf; + int curbuf = pipe->curbuf; + struct pipe_buffer *buf = pipe->bufs + curbuf; struct pipe_buf_operations *ops = buf->ops; void *addr; size_t chars = buf->len; @@ -171,16 +179,17 @@ pipe_readv(struct file *filp, const struct iovec *_iov, if (chars > total_len) chars = total_len; - addr = ops->map(filp, info, buf); + addr = ops->map(filp, pipe, buf); if (IS_ERR(addr)) { if (!ret) ret = PTR_ERR(addr); break; } error = pipe_iov_copy_to_user(iov, addr + buf->offset, chars); - ops->unmap(info, buf); + ops->unmap(pipe, buf); if (unlikely(error)) { - if (!ret) ret = -EFAULT; + if (!ret) + ret = -EFAULT; break; } ret += chars; @@ -188,10 +197,10 @@ pipe_readv(struct file *filp, const struct iovec *_iov, buf->len -= chars; if (!buf->len) { buf->ops = NULL; - ops->release(info, buf); + ops->release(pipe, buf); curbuf = (curbuf + 1) & (PIPE_BUFFERS-1); - info->curbuf = curbuf; - info->nrbufs = --bufs; + pipe->curbuf = curbuf; + pipe->nrbufs = --bufs; do_wakeup = 1; } total_len -= chars; @@ -200,9 +209,9 @@ pipe_readv(struct file *filp, const struct iovec *_iov, } if (bufs) /* More to do? */ continue; - if (!PIPE_WRITERS(*inode)) + if (!pipe->writers) break; - if (!PIPE_WAITING_WRITERS(*inode)) { + 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 @@ -216,20 +225,22 @@ pipe_readv(struct file *filp, const struct iovec *_iov, } } if (signal_pending(current)) { - if (!ret) ret = -ERESTARTSYS; + if (!ret) + ret = -ERESTARTSYS; break; } if (do_wakeup) { - wake_up_interruptible_sync(PIPE_WAIT(*inode)); - kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT); + wake_up_interruptible_sync(&pipe->wait); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } - pipe_wait(inode); + pipe_wait(pipe); } - mutex_unlock(PIPE_MUTEX(*inode)); - /* Signal writers asynchronously that there is more room. */ + mutex_unlock(&inode->i_mutex); + + /* Signal writers asynchronously that there is more room. */ if (do_wakeup) { - wake_up_interruptible(PIPE_WAIT(*inode)); - kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT); + wake_up_interruptible(&pipe->wait); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } if (ret > 0) file_accessed(filp); @@ -240,6 +251,7 @@ static ssize_t pipe_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) { struct iovec iov = { .iov_base = buf, .iov_len = count }; + return pipe_readv(filp, &iov, 1, ppos); } @@ -248,7 +260,7 @@ pipe_writev(struct file *filp, const struct iovec *_iov, unsigned long nr_segs, loff_t *ppos) { struct inode *inode = filp->f_dentry->d_inode; - struct pipe_inode_info *info; + struct pipe_inode_info *pipe; ssize_t ret; int do_wakeup; struct iovec *iov = (struct iovec *)_iov; @@ -262,10 +274,10 @@ pipe_writev(struct file *filp, const struct iovec *_iov, do_wakeup = 0; ret = 0; - mutex_lock(PIPE_MUTEX(*inode)); - info = inode->i_pipe; + mutex_lock(&inode->i_mutex); + pipe = inode->i_pipe; - if (!PIPE_READERS(*inode)) { + if (!pipe->readers) { send_sig(SIGPIPE, current, 0); ret = -EPIPE; goto out; @@ -273,23 +285,25 @@ pipe_writev(struct file *filp, const struct iovec *_iov, /* We try to merge small writes */ chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */ - if (info->nrbufs && chars != 0) { - int lastbuf = (info->curbuf + info->nrbufs - 1) & (PIPE_BUFFERS-1); - struct pipe_buffer *buf = info->bufs + lastbuf; + if (pipe->nrbufs && chars != 0) { + int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) & + (PIPE_BUFFERS-1); + struct pipe_buffer *buf = pipe->bufs + lastbuf; struct pipe_buf_operations *ops = buf->ops; int offset = buf->offset + buf->len; + if (ops->can_merge && offset + chars <= PAGE_SIZE) { void *addr; int error; - addr = ops->map(filp, info, buf); + addr = ops->map(filp, pipe, buf); if (IS_ERR(addr)) { error = PTR_ERR(addr); goto out; } error = pipe_iov_copy_from_user(offset + addr, iov, chars); - ops->unmap(info, buf); + ops->unmap(pipe, buf); ret = error; do_wakeup = 1; if (error) @@ -304,16 +318,18 @@ pipe_writev(struct file *filp, const struct iovec *_iov, for (;;) { int bufs; - if (!PIPE_READERS(*inode)) { + + if (!pipe->readers) { send_sig(SIGPIPE, current, 0); - if (!ret) ret = -EPIPE; + if (!ret) + ret = -EPIPE; break; } - bufs = info->nrbufs; + bufs = pipe->nrbufs; if (bufs < PIPE_BUFFERS) { - int newbuf = (info->curbuf + bufs) & (PIPE_BUFFERS-1); - struct pipe_buffer *buf = info->bufs + newbuf; - struct page *page = info->tmp_page; + int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS-1); + struct pipe_buffer *buf = pipe->bufs + newbuf; + struct page *page = pipe->tmp_page; int error; if (!page) { @@ -322,9 +338,9 @@ pipe_writev(struct file *filp, const struct iovec *_iov, ret = ret ? : -ENOMEM; break; } - info->tmp_page = page; + pipe->tmp_page = page; } - /* Always wakeup, even if the copy fails. Otherwise + /* 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? @@ -337,7 +353,8 @@ pipe_writev(struct file *filp, const struct iovec *_iov, error = pipe_iov_copy_from_user(kmap(page), iov, chars); kunmap(page); if (unlikely(error)) { - if (!ret) ret = -EFAULT; + if (!ret) + ret = -EFAULT; break; } ret += chars; @@ -347,8 +364,8 @@ pipe_writev(struct file *filp, const struct iovec *_iov, buf->ops = &anon_pipe_buf_ops; buf->offset = 0; buf->len = chars; - info->nrbufs = ++bufs; - info->tmp_page = NULL; + pipe->nrbufs = ++bufs; + pipe->tmp_page = NULL; total_len -= chars; if (!total_len) @@ -357,27 +374,29 @@ pipe_writev(struct file *filp, const struct iovec *_iov, if (bufs < PIPE_BUFFERS) continue; if (filp->f_flags & O_NONBLOCK) { - if (!ret) ret = -EAGAIN; + if (!ret) + ret = -EAGAIN; break; } if (signal_pending(current)) { - if (!ret) ret = -ERESTARTSYS; + if (!ret) + ret = -ERESTARTSYS; break; } if (do_wakeup) { - wake_up_interruptible_sync(PIPE_WAIT(*inode)); - kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN); + wake_up_interruptible_sync(&pipe->wait); + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); do_wakeup = 0; } - PIPE_WAITING_WRITERS(*inode)++; - pipe_wait(inode); - PIPE_WAITING_WRITERS(*inode)--; + pipe->waiting_writers++; + pipe_wait(pipe); + pipe->waiting_writers--; } out: - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_unlock(&inode->i_mutex); if (do_wakeup) { - wake_up_interruptible(PIPE_WAIT(*inode)); - kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN); + wake_up_interruptible(&pipe->wait); + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); } if (ret > 0) file_update_time(filp); @@ -389,6 +408,7 @@ pipe_write(struct file *filp, const char __user *buf, size_t count, loff_t *ppos) { struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = count }; + return pipe_writev(filp, &iov, 1, ppos); } @@ -399,7 +419,8 @@ bad_pipe_r(struct file *filp, char __user *buf, size_t count, loff_t *ppos) } static ssize_t -bad_pipe_w(struct file *filp, const char __user *buf, size_t count, loff_t *ppos) +bad_pipe_w(struct file *filp, const char __user *buf, size_t count, + loff_t *ppos) { return -EBADF; } @@ -409,21 +430,22 @@ pipe_ioctl(struct inode *pino, struct file *filp, unsigned int cmd, unsigned long arg) { struct inode *inode = filp->f_dentry->d_inode; - struct pipe_inode_info *info; + struct pipe_inode_info *pipe; int count, buf, nrbufs; switch (cmd) { case FIONREAD: - mutex_lock(PIPE_MUTEX(*inode)); - info = inode->i_pipe; + mutex_lock(&inode->i_mutex); + pipe = inode->i_pipe; count = 0; - buf = info->curbuf; - nrbufs = info->nrbufs; + buf = pipe->curbuf; + nrbufs = pipe->nrbufs; while (--nrbufs >= 0) { - count += info->bufs[buf].len; + count += pipe->bufs[buf].len; buf = (buf+1) & (PIPE_BUFFERS-1); } - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_unlock(&inode->i_mutex); + return put_user(count, (int __user *)arg); default: return -EINVAL; @@ -436,17 +458,17 @@ pipe_poll(struct file *filp, poll_table *wait) { unsigned int mask; struct inode *inode = filp->f_dentry->d_inode; - struct pipe_inode_info *info = inode->i_pipe; + struct pipe_inode_info *pipe = inode->i_pipe; int nrbufs; - poll_wait(filp, PIPE_WAIT(*inode), wait); + poll_wait(filp, &pipe->wait, wait); /* Reading only -- no need for acquiring the semaphore. */ - nrbufs = info->nrbufs; + nrbufs = pipe->nrbufs; mask = 0; if (filp->f_mode & FMODE_READ) { mask = (nrbufs > 0) ? POLLIN | POLLRDNORM : 0; - if (!PIPE_WRITERS(*inode) && filp->f_version != PIPE_WCOUNTER(*inode)) + if (!pipe->writers && filp->f_version != pipe->w_counter) mask |= POLLHUP; } @@ -456,7 +478,7 @@ pipe_poll(struct file *filp, poll_table *wait) * Most Unices do not set POLLERR for FIFOs but on Linux they * behave exactly like pipes for poll(). */ - if (!PIPE_READERS(*inode)) + if (!pipe->readers) mask |= POLLERR; } @@ -466,17 +488,21 @@ pipe_poll(struct file *filp, poll_table *wait) static int pipe_release(struct inode *inode, int decr, int decw) { - mutex_lock(PIPE_MUTEX(*inode)); - PIPE_READERS(*inode) -= decr; - PIPE_WRITERS(*inode) -= decw; - if (!PIPE_READERS(*inode) && !PIPE_WRITERS(*inode)) { + 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(PIPE_WAIT(*inode)); - kill_fasync(PIPE_FASYNC_READERS(*inode), SIGIO, POLL_IN); - kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT); + wake_up_interruptible(&pipe->wait); + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_unlock(&inode->i_mutex); return 0; } @@ -487,9 +513,9 @@ pipe_read_fasync(int fd, struct file *filp, int on) struct inode *inode = filp->f_dentry->d_inode; int retval; - mutex_lock(PIPE_MUTEX(*inode)); - retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode)); - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); + retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_readers); + mutex_unlock(&inode->i_mutex); if (retval < 0) return retval; @@ -504,9 +530,9 @@ pipe_write_fasync(int fd, struct file *filp, int on) struct inode *inode = filp->f_dentry->d_inode; int retval; - mutex_lock(PIPE_MUTEX(*inode)); - retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode)); - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); + retval = fasync_helper(fd, filp, on, &inode->i_pipe->fasync_writers); + mutex_unlock(&inode->i_mutex); if (retval < 0) return retval; @@ -519,16 +545,17 @@ static int pipe_rdwr_fasync(int fd, struct file *filp, int on) { struct inode *inode = filp->f_dentry->d_inode; + struct pipe_inode_info *pipe = inode->i_pipe; int retval; - mutex_lock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); - retval = fasync_helper(fd, filp, on, PIPE_FASYNC_READERS(*inode)); + retval = fasync_helper(fd, filp, on, &pipe->fasync_readers); if (retval >= 0) - retval = fasync_helper(fd, filp, on, PIPE_FASYNC_WRITERS(*inode)); + retval = fasync_helper(fd, filp, on, &pipe->fasync_writers); - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_unlock(&inode->i_mutex); if (retval < 0) return retval; @@ -567,9 +594,9 @@ pipe_read_open(struct inode *inode, struct file *filp) { /* We could have perhaps used atomic_t, but this and friends below are the only places. So it doesn't seem worthwhile. */ - mutex_lock(PIPE_MUTEX(*inode)); - PIPE_READERS(*inode)++; - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); + inode->i_pipe->readers++; + mutex_unlock(&inode->i_mutex); return 0; } @@ -577,9 +604,9 @@ pipe_read_open(struct inode *inode, struct file *filp) static int pipe_write_open(struct inode *inode, struct file *filp) { - mutex_lock(PIPE_MUTEX(*inode)); - PIPE_WRITERS(*inode)++; - mutex_unlock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); + inode->i_pipe->writers++; + mutex_unlock(&inode->i_mutex); return 0; } @@ -587,12 +614,12 @@ pipe_write_open(struct inode *inode, struct file *filp) static int pipe_rdwr_open(struct inode *inode, struct file *filp) { - mutex_lock(PIPE_MUTEX(*inode)); + mutex_lock(&inode->i_mutex); if (filp->f_mode & FMODE_READ) - PIPE_READERS(*inode)++; + inode->i_pipe->readers++; if (filp->f_mode & FMODE_WRITE) - PIPE_WRITERS(*inode)++; - mutex_unlock(PIPE_MUTEX(*inode)); + inode->i_pipe->writers++; + mutex_unlock(&inode->i_mutex); return 0; } @@ -675,37 +702,38 @@ static struct file_operations rdwr_pipe_fops = { .fasync = pipe_rdwr_fasync, }; -void free_pipe_info(struct inode *inode) +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) { + init_waitqueue_head(&pipe->wait); + pipe->r_counter = pipe->w_counter = 1; + pipe->inode = inode; + } + + return pipe; +} + +void __free_pipe_info(struct pipe_inode_info *pipe) { int i; - struct pipe_inode_info *info = inode->i_pipe; - inode->i_pipe = NULL; for (i = 0; i < PIPE_BUFFERS; i++) { - struct pipe_buffer *buf = info->bufs + i; + struct pipe_buffer *buf = pipe->bufs + i; if (buf->ops) - buf->ops->release(info, buf); + buf->ops->release(pipe, buf); } - if (info->tmp_page) - __free_page(info->tmp_page); - kfree(info); + if (pipe->tmp_page) + __free_page(pipe->tmp_page); + kfree(pipe); } -struct inode* pipe_new(struct inode* inode) +void free_pipe_info(struct inode *inode) { - struct pipe_inode_info *info; - - info = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL); - if (!info) - goto fail_page; - inode->i_pipe = info; - - init_waitqueue_head(PIPE_WAIT(*inode)); - PIPE_RCOUNTER(*inode) = PIPE_WCOUNTER(*inode) = 1; - - return inode; -fail_page: - return NULL; + __free_pipe_info(inode->i_pipe); + inode->i_pipe = NULL; } static struct vfsmount *pipe_mnt __read_mostly; @@ -713,6 +741,7 @@ static int pipefs_delete_dentry(struct dentry *dentry) { return 1; } + static struct dentry_operations pipefs_dentry_operations = { .d_delete = pipefs_delete_dentry, }; @@ -720,13 +749,17 @@ static struct dentry_operations pipefs_dentry_operations = { static struct inode * get_pipe_inode(void) { struct inode *inode = new_inode(pipe_mnt->mnt_sb); + struct pipe_inode_info *pipe; if (!inode) goto fail_inode; - if(!pipe_new(inode)) + pipe = alloc_pipe_info(inode); + if (!pipe) goto fail_iput; - PIPE_READERS(*inode) = PIPE_WRITERS(*inode) = 1; + inode->i_pipe = pipe; + + pipe->readers = pipe->writers = 1; inode->i_fop = &rdwr_pipe_fops; /* @@ -741,10 +774,12 @@ static struct inode * get_pipe_inode(void) inode->i_gid = current->fsgid; inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; inode->i_blksize = PAGE_SIZE; + return inode; fail_iput: iput(inode); + fail_inode: return NULL; } @@ -757,7 +792,7 @@ int do_pipe(int *fd) struct inode * inode; struct file *f1, *f2; int error; - int i,j; + int i, j; error = -ENFILE; f1 = get_empty_filp(); @@ -790,6 +825,7 @@ int do_pipe(int *fd) dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this); if (!dentry) goto close_f12_inode_i_j; + dentry->d_op = &pipefs_dentry_operations; d_add(dentry, inode); f1->f_vfsmnt = f2->f_vfsmnt = mntget(mntget(pipe_mnt)); @@ -813,6 +849,7 @@ int do_pipe(int *fd) fd_install(j, f2); fd[0] = i; fd[1] = j; + return 0; close_f12_inode_i_j: @@ -837,8 +874,9 @@ no_files: * d_name - pipe: will go nicely and kill the special-casing in procfs. */ -static struct super_block *pipefs_get_sb(struct file_system_type *fs_type, - int flags, const char *dev_name, void *data) +static struct super_block * +pipefs_get_sb(struct file_system_type *fs_type, int flags, + const char *dev_name, void *data) { return get_sb_pseudo(fs_type, "pipe:", NULL, PIPEFS_MAGIC); } @@ -852,6 +890,7 @@ static struct file_system_type pipe_fs_type = { 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)) { |