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bcachefs: thread_with_stdio: eliminate double buffering
The output buffer lock has to be a spinlock so that we can write to it from interrupt context, so we can't use a direct copy_to_user; this switches thread_with_file_read() to use fault_in_writeable() and copy_to_user_nofault(), similar to how thread_with_file_write() works. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
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cb6fc943b6
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@ -67,16 +67,15 @@ int bch2_run_thread_with_file(struct thread_with_file *thr,
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static inline bool thread_with_stdio_has_output(struct thread_with_stdio *thr)
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{
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return thr->stdio.output_buf.pos ||
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thr->output2.nr ||
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thr->thr.done;
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return thr->stdio.output_buf.pos || thr->thr.done;
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}
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static ssize_t thread_with_stdio_read(struct file *file, char __user *buf,
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static ssize_t thread_with_stdio_read(struct file *file, char __user *ubuf,
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size_t len, loff_t *ppos)
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{
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struct thread_with_stdio *thr =
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container_of(file->private_data, struct thread_with_stdio, thr);
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struct printbuf *buf = &thr->stdio.output_buf;
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size_t copied = 0, b;
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int ret = 0;
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@ -89,44 +88,25 @@ static ssize_t thread_with_stdio_read(struct file *file, char __user *buf,
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if (ret)
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return ret;
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if (thr->thr.done)
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return 0;
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while (len) {
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ret = darray_make_room(&thr->output2, thr->stdio.output_buf.pos);
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if (ret)
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break;
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spin_lock_irq(&thr->stdio.output_lock);
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b = min_t(size_t, darray_room(thr->output2), thr->stdio.output_buf.pos);
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memcpy(&darray_top(thr->output2), thr->stdio.output_buf.buf, b);
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memmove(thr->stdio.output_buf.buf,
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thr->stdio.output_buf.buf + b,
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thr->stdio.output_buf.pos - b);
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thr->output2.nr += b;
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thr->stdio.output_buf.pos -= b;
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spin_unlock_irq(&thr->stdio.output_lock);
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b = min(len, thr->output2.nr);
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if (!b)
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break;
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b -= copy_to_user(buf, thr->output2.data, b);
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if (!b) {
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while (len && buf->pos) {
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if (fault_in_writeable(ubuf, len) == len) {
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ret = -EFAULT;
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break;
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}
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copied += b;
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buf += b;
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len -= b;
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spin_lock_irq(&thr->stdio.output_lock);
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b = min_t(size_t, len, buf->pos);
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memmove(thr->output2.data,
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thr->output2.data + b,
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thr->output2.nr - b);
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thr->output2.nr -= b;
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if (b && !copy_to_user_nofault(ubuf, buf->buf, b)) {
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memmove(buf->buf,
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buf->buf + b,
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buf->pos - b);
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buf->pos -= b;
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ubuf += b;
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len -= b;
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copied += b;
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}
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spin_unlock_irq(&thr->stdio.output_lock);
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}
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return copied ?: ret;
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@ -140,7 +120,6 @@ static int thread_with_stdio_release(struct inode *inode, struct file *file)
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bch2_thread_with_file_exit(&thr->thr);
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printbuf_exit(&thr->stdio.input_buf);
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printbuf_exit(&thr->stdio.output_buf);
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darray_exit(&thr->output2);
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thr->exit(thr);
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return 0;
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}
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@ -245,7 +224,6 @@ int bch2_run_thread_with_stdio(struct thread_with_stdio *thr,
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spin_lock_init(&thr->stdio.output_lock);
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init_waitqueue_head(&thr->stdio.output_wait);
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darray_init(&thr->output2);
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thr->exit = exit;
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return bch2_run_thread_with_file(&thr->thr, &thread_with_stdio_fops, fn);
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@ -20,7 +20,6 @@ int bch2_run_thread_with_file(struct thread_with_file *,
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struct thread_with_stdio {
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struct thread_with_file thr;
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struct stdio_redirect stdio;
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DARRAY(char) output2;
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void (*exit)(struct thread_with_stdio *);
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};
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