diff mbox series

PM: hibernate: clean up sync_read handling in snapshot_write_next

Message ID 20230922155336.507220-1-bgeffon@google.com (mailing list archive)
State Superseded, archived
Headers show
Series PM: hibernate: clean up sync_read handling in snapshot_write_next | expand

Commit Message

Brian Geffon Sept. 22, 2023, 3:53 p.m. UTC
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@google.com>
Cc: stable@vger.kernel.org
---
 kernel/power/snapshot.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
diff mbox series

Patch

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. */