diff options
Diffstat (limited to 'fs/splice.c')
| -rw-r--r-- | fs/splice.c | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/fs/splice.c b/fs/splice.c index 5d3eda64703..8d57e89924a 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -125,12 +125,19 @@ static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info, kunmap(buf->page); } +static void page_cache_pipe_buf_get(struct pipe_inode_info *info, + struct pipe_buffer *buf) +{ + page_cache_get(buf->page); +} + static struct pipe_buf_operations page_cache_pipe_buf_ops = { .can_merge = 0, .map = page_cache_pipe_buf_map, .unmap = page_cache_pipe_buf_unmap, .release = page_cache_pipe_buf_release, .steal = page_cache_pipe_buf_steal, + .get = page_cache_pipe_buf_get, }; /* @@ -963,3 +970,182 @@ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in, return error; } + +/* + * Link contents of ipipe to opipe. + */ +static int link_pipe(struct pipe_inode_info *ipipe, + struct pipe_inode_info *opipe, + size_t len, unsigned int flags) +{ + struct pipe_buffer *ibuf, *obuf; + int ret = 0, do_wakeup = 0, i; + + /* + * Potential ABBA deadlock, work around it by ordering lock + * grabbing by inode address. Otherwise two different processes + * could deadlock (one doing tee from A -> B, the other from B -> A). + */ + if (ipipe->inode < opipe->inode) { + mutex_lock(&ipipe->inode->i_mutex); + mutex_lock(&opipe->inode->i_mutex); + } else { + mutex_lock(&opipe->inode->i_mutex); + mutex_lock(&ipipe->inode->i_mutex); + } + + for (i = 0;; i++) { + if (!opipe->readers) { + send_sig(SIGPIPE, current, 0); + if (!ret) + ret = -EPIPE; + break; + } + if (ipipe->nrbufs - i) { + ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1)); + + /* + * If we have room, fill this buffer + */ + if (opipe->nrbufs < PIPE_BUFFERS) { + int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1); + + /* + * Get a reference to this pipe buffer, + * so we can copy the contents over. + */ + ibuf->ops->get(ipipe, ibuf); + + obuf = opipe->bufs + nbuf; + *obuf = *ibuf; + + if (obuf->len > len) + obuf->len = len; + + opipe->nrbufs++; + do_wakeup = 1; + ret += obuf->len; + len -= obuf->len; + + if (!len) + break; + if (opipe->nrbufs < PIPE_BUFFERS) + continue; + } + + /* + * We have input available, but no output room. + * If we already copied data, return that. + */ + if (flags & SPLICE_F_NONBLOCK) { + if (!ret) + ret = -EAGAIN; + break; + } + if (signal_pending(current)) { + if (!ret) + ret = -ERESTARTSYS; + break; + } + if (do_wakeup) { + smp_mb(); + if (waitqueue_active(&opipe->wait)) + wake_up_interruptible(&opipe->wait); + kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); + do_wakeup = 0; + } + + opipe->waiting_writers++; + pipe_wait(opipe); + opipe->waiting_writers--; + continue; + } + + /* + * No input buffers, do the usual checks for available + * writers and blocking and wait if necessary + */ + if (!ipipe->writers) + break; + if (!ipipe->waiting_writers) { + if (ret) + break; + } + if (flags & SPLICE_F_NONBLOCK) { + if (!ret) + ret = -EAGAIN; + break; + } + if (signal_pending(current)) { + if (!ret) + ret = -ERESTARTSYS; + break; + } + + if (waitqueue_active(&ipipe->wait)) + wake_up_interruptible_sync(&ipipe->wait); + kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT); + + pipe_wait(ipipe); + } + + mutex_unlock(&ipipe->inode->i_mutex); + mutex_unlock(&opipe->inode->i_mutex); + + if (do_wakeup) { + smp_mb(); + if (waitqueue_active(&opipe->wait)) + wake_up_interruptible(&opipe->wait); + kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN); + } + + return ret; +} + +/* + * This is a tee(1) implementation that works on pipes. It doesn't copy + * any data, it simply references the 'in' pages on the 'out' pipe. + * The 'flags' used are the SPLICE_F_* variants, currently the only + * applicable one is SPLICE_F_NONBLOCK. + */ +static long do_tee(struct file *in, struct file *out, size_t len, + unsigned int flags) +{ + struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe; + struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe; + + /* + * Link ipipe to the two output pipes, consuming as we go along. + */ + if (ipipe && opipe) + return link_pipe(ipipe, opipe, len, flags); + + return -EINVAL; +} + +asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags) +{ + struct file *in; + int error, fput_in; + + if (unlikely(!len)) + return 0; + + error = -EBADF; + in = fget_light(fdin, &fput_in); + if (in) { + if (in->f_mode & FMODE_READ) { + int fput_out; + struct file *out = fget_light(fdout, &fput_out); + + if (out) { + if (out->f_mode & FMODE_WRITE) + error = do_tee(in, out, len, flags); + fput_light(out, fput_out); + } + } + fput_light(in, fput_in); + } + + return error; +} |