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SubjectRe: [PATCH 4/6] kexec: A new system call, kexec_file_load, for in kernel kexec
On 11/20/13 at 12:50pm, Vivek Goyal wrote:
> + * that kexec_mutex is held.
> + */

I think kexec_add_buffer is guaranteed to be called before allocating
control pages, why not updating image->control_page after each time
kexec_add_buffer is called. Then when control page is needed, effective
address in crash_kernel region can be given. This can be a little more
efficient.

> +int kexec_add_buffer(struct kimage *image, char *buffer,
> + unsigned long bufsz, unsigned long memsz,
> + unsigned long buf_align, unsigned long buf_min,
> + unsigned long buf_max, int top_down, unsigned long *load_addr)
> +{
> +
> + unsigned long nr_segments = image->nr_segments, new_nr_segments;
> + struct kexec_segment *ksegment;
> + struct kexec_buf *kbuf;
> +
> + /* Currently adding segment this way is allowed only in file mode */
> + if (!image->file_mode)
> + return -EINVAL;
> +
> + if (nr_segments >= KEXEC_SEGMENT_MAX)
> + return -EINVAL;
> +
> + /*
> + * Make sure we are not trying to add buffer after allocating
> + * control pages. All segments need to be placed first before
> + * any control pages are allocated. As control page allocation
> + * logic goes through list of segments to make sure there are
> + * no destination overlaps.
> + */
> + WARN_ONCE(!list_empty(&image->control_pages), "Adding kexec buffer"
> + " after allocating control pages\n");
> +
> + kbuf = kzalloc(sizeof(struct kexec_buf), GFP_KERNEL);
> + if (!kbuf)
> + return -ENOMEM;
> +
> + kbuf->image = image;
> + kbuf->buffer = buffer;
> + kbuf->bufsz = bufsz;
> + /* Align memsz to next page boundary */
> + kbuf->memsz = ALIGN(memsz, PAGE_SIZE);
> +
> + /* Align to atleast page size boundary */
> + kbuf->buf_align = max(buf_align, PAGE_SIZE);
> + kbuf->buf_min = buf_min;
> + kbuf->buf_max = buf_max;
> + kbuf->top_down = top_down;
> +
> + /* Walk the RAM ranges and allocate a suitable range for the buffer */
> + walk_system_ram_res(0, -1, kbuf, walk_ram_range_callback);
> +
> + kbuf->image = NULL;
> + kfree(kbuf);
> +
> + /*
> + * If range could be found successfully, it would have incremented
> + * the nr_segments value.
> + */
> + new_nr_segments = image->nr_segments;
> +
> + /* A suitable memory range could not be found for buffer */
> + if (new_nr_segments == nr_segments)
> + return -EADDRNOTAVAIL;
> +
> + /* Found a suitable memory range */
> +
> + ksegment = &image->segment[new_nr_segments - 1];
> + *load_addr = ksegment->mem;
> + return 0;
> +}
> +
> +



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