On Fri, Sep 22, 2023 at 6:07 PM Brian Geffon <bgeffon@xxxxxxxxxx> wrote:
>
> In snapshot_write_next sync_read is set and unset in three different
> spots unnecessiarly. As a result there is a subtle bug where the first
> page after the meta data has been loaded unconditionally sets sync_read
> to 0. If this first pfn was actually a highmem page then the returned
> buffer will be the global "buffer," and the page needs to be loaded
> synchronously.
>
> That is, I'm not sure we can always assume the following to be safe:
> handle->buffer = get_buffer(&orig_bm, &ca);
> handle->sync_read = 0;
>
> Because get_buffer can call get_highmem_page_buffer which can
> return 'buffer'
>
> The easiest way to address this is just set sync_read before
> snapshot_write_next returns if handle->buffer == buffer.
>
> Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx>
> Fixes: 8357376d3df2 ("[PATCH] swsusp: Improve handling of highmem")
> Cc: stable@xxxxxxxxxxxxxxx
If you send an update of a patch, it is always better to give it a
higher version number to avoid any possible confusion.
> ---
> kernel/power/snapshot.c | 6 +-----
> 1 file changed, 1 insertion(+), 5 deletions(-)
>
> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
> index 190ed707ddcc..362e6bae5891 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -2780,8 +2780,6 @@ int snapshot_write_next(struct snapshot_handle *handle)
> if (handle->cur > 1 && handle->cur > nr_meta_pages + nr_copy_pages + nr_zero_pages)
> return 0;
>
> - handle->sync_read = 1;
> -
> if (!handle->cur) {
> if (!buffer)
> /* This makes the buffer be freed by swsusp_free() */
> @@ -2824,7 +2822,6 @@ int snapshot_write_next(struct snapshot_handle *handle)
> memory_bm_position_reset(&zero_bm);
> restore_pblist = NULL;
> handle->buffer = get_buffer(&orig_bm, &ca);
> - handle->sync_read = 0;
> if (IS_ERR(handle->buffer))
> return PTR_ERR(handle->buffer);
> }
> @@ -2834,9 +2831,8 @@ int snapshot_write_next(struct snapshot_handle *handle)
> handle->buffer = get_buffer(&orig_bm, &ca);
> if (IS_ERR(handle->buffer))
> return PTR_ERR(handle->buffer);
> - if (handle->buffer != buffer)
> - handle->sync_read = 0;
> }
> + handle->sync_read = (handle->buffer == buffer);
> handle->cur++;
>
> /* Zero pages were not included in the image, memset it and move on. */
> --
Anyway, applied as 6.7 material with some minor edits in the subject
and changelog.
Thanks!
