diff options
Diffstat (limited to 'fs')
-rw-r--r-- | fs/splice.c | 217 |
1 files changed, 143 insertions, 74 deletions
diff --git a/fs/splice.c b/fs/splice.c index c18aa7e..fd6b278 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -601,107 +601,176 @@ out: return ret; } +static void wakeup_pipe_writers(struct pipe_inode_info *pipe) +{ + smp_mb(); + if (waitqueue_active(&pipe->wait)) + wake_up_interruptible(&pipe->wait); + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); +} + /** - * __splice_from_pipe - splice data from a pipe to given actor + * splice_from_pipe_feed - feed available data from a pipe to a file * @pipe: pipe to splice from * @sd: information to @actor * @actor: handler that splices the data * * Description: - * This function does little more than loop over the pipe and call - * @actor to do the actual moving of a single struct pipe_buffer to - * the desired destination. See pipe_to_file, pipe_to_sendpage, or - * pipe_to_user. + + * This function loops over the pipe and calls @actor to do the + * actual moving of a single struct pipe_buffer to the desired + * destination. It returns when there's no more buffers left in + * the pipe or if the requested number of bytes (@sd->total_len) + * have been copied. It returns a positive number (one) if the + * pipe needs to be filled with more data, zero if the required + * number of bytes have been copied and -errno on error. * + * This, together with splice_from_pipe_{begin,end,next}, may be + * used to implement the functionality of __splice_from_pipe() when + * locking is required around copying the pipe buffers to the + * destination. */ -ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, - splice_actor *actor) +int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd, + splice_actor *actor) { - int ret, do_wakeup, err; - - ret = 0; - do_wakeup = 0; - - for (;;) { - if (pipe->nrbufs) { - struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; - const struct pipe_buf_operations *ops = buf->ops; + int ret; - sd->len = buf->len; - if (sd->len > sd->total_len) - sd->len = sd->total_len; + while (pipe->nrbufs) { + struct pipe_buffer *buf = pipe->bufs + pipe->curbuf; + const struct pipe_buf_operations *ops = buf->ops; - err = actor(pipe, buf, sd); - if (err <= 0) { - if (!ret && err != -ENODATA) - ret = err; + sd->len = buf->len; + if (sd->len > sd->total_len) + sd->len = sd->total_len; - break; - } + ret = actor(pipe, buf, sd); + if (ret <= 0) { + if (ret == -ENODATA) + ret = 0; + return ret; + } + buf->offset += ret; + buf->len -= ret; - ret += err; - buf->offset += err; - buf->len -= err; + sd->num_spliced += ret; + sd->len -= ret; + sd->pos += ret; + sd->total_len -= ret; - sd->len -= err; - sd->pos += err; - sd->total_len -= err; - if (sd->len) - continue; + if (!buf->len) { + buf->ops = NULL; + ops->release(pipe, buf); + pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1); + pipe->nrbufs--; + if (pipe->inode) + sd->need_wakeup = true; + } - if (!buf->len) { - buf->ops = NULL; - ops->release(pipe, buf); - pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1); - pipe->nrbufs--; - if (pipe->inode) - do_wakeup = 1; - } + if (!sd->total_len) + return 0; + } - if (!sd->total_len) - break; - } + return 1; +} +EXPORT_SYMBOL(splice_from_pipe_feed); - if (pipe->nrbufs) - continue; +/** + * splice_from_pipe_next - wait for some data to splice from + * @pipe: pipe to splice from + * @sd: information about the splice operation + * + * Description: + * This function will wait for some data and return a positive + * value (one) if pipe buffers are available. It will return zero + * or -errno if no more data needs to be spliced. + */ +int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) +{ + while (!pipe->nrbufs) { if (!pipe->writers) - break; - if (!pipe->waiting_writers) { - if (ret) - break; - } + return 0; - if (sd->flags & SPLICE_F_NONBLOCK) { - if (!ret) - ret = -EAGAIN; - break; - } + if (!pipe->waiting_writers && sd->num_spliced) + return 0; - if (signal_pending(current)) { - if (!ret) - ret = -ERESTARTSYS; - break; - } + if (sd->flags & SPLICE_F_NONBLOCK) + return -EAGAIN; - if (do_wakeup) { - smp_mb(); - if (waitqueue_active(&pipe->wait)) - wake_up_interruptible_sync(&pipe->wait); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); - do_wakeup = 0; + if (signal_pending(current)) + return -ERESTARTSYS; + + if (sd->need_wakeup) { + wakeup_pipe_writers(pipe); + sd->need_wakeup = false; } pipe_wait(pipe); } - if (do_wakeup) { - smp_mb(); - if (waitqueue_active(&pipe->wait)) - wake_up_interruptible(&pipe->wait); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); - } + return 1; +} +EXPORT_SYMBOL(splice_from_pipe_next); - return ret; +/** + * splice_from_pipe_begin - start splicing from pipe + * @pipe: pipe to splice from + * + * Description: + * This function should be called before a loop containing + * splice_from_pipe_next() and splice_from_pipe_feed() to + * initialize the necessary fields of @sd. + */ +void splice_from_pipe_begin(struct splice_desc *sd) +{ + sd->num_spliced = 0; + sd->need_wakeup = false; +} +EXPORT_SYMBOL(splice_from_pipe_begin); + +/** + * splice_from_pipe_end - finish splicing from pipe + * @pipe: pipe to splice from + * @sd: information about the splice operation + * + * Description: + * This function will wake up pipe writers if necessary. It should + * be called after a loop containing splice_from_pipe_next() and + * splice_from_pipe_feed(). + */ +void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd) +{ + if (sd->need_wakeup) + wakeup_pipe_writers(pipe); +} +EXPORT_SYMBOL(splice_from_pipe_end); + +/** + * __splice_from_pipe - splice data from a pipe to given actor + * @pipe: pipe to splice from + * @sd: information to @actor + * @actor: handler that splices the data + * + * Description: + * This function does little more than loop over the pipe and call + * @actor to do the actual moving of a single struct pipe_buffer to + * the desired destination. See pipe_to_file, pipe_to_sendpage, or + * pipe_to_user. + * + */ +ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd, + splice_actor *actor) +{ + int ret; + + splice_from_pipe_begin(sd); + do { + ret = splice_from_pipe_next(pipe, sd); + if (ret > 0) + ret = splice_from_pipe_feed(pipe, sd, actor); + } while (ret > 0); + splice_from_pipe_end(pipe, sd); + + return sd->num_spliced ? sd->num_spliced : ret; } EXPORT_SYMBOL(__splice_from_pipe); |