[PATCH 1/2] pm-hibernate: flush disk cache when suspending

[Mikulas Patocka <mpatocka@redhat.com>]

[PATCH 1/2] pm-hibernate: flush disk cache when suspending

There was reported failure that suspend doesn't work with dm-integrity.
The reason for the failure is that the suspend code doesn't issue the
FLUSH bio - the data still sits in the dm-integrity cache and they are
lost when poweroff happens.

This commit fixes the suspend code so that it issues flushes before
writing the header and after writing the header.

Note that the system may lose power during suspend - in this situation,
we don't want to attempt to resume with invalid data. So, we flush the
cache before writing the header (with REQ_PREFLUSH) and after writing the
header (with REQ_FUA).

The call to flush_swap_writer was moved up in swap_writer_finish, so that
it writes the data before mark_swapfiles writes the header.

REQ_FUA is also needed on resume, when marking resumed image with the
original swap header.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: Askar Safin <safinaskar@gmail.com>
Link: https://lore.kernel.org/dm-devel/a48a37e3-2c22-44fb-97a4-0e57dc20421a@gmail.com/T/

---
 kernel/power/swap.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Index: linux-2.6/kernel/power/swap.c
===================================================================
--- linux-2.6.orig/kernel/power/swap.c
+++ linux-2.6/kernel/power/swap.c
@@ -320,7 +320,7 @@ static int mark_swapfiles(struct swap_ma
 		swsusp_header->flags = flags;
 		if (flags & SF_CRC32_MODE)
 			swsusp_header->crc32 = handle->crc32;
-		error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC,
+		error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH | REQ_FUA,
 				      swsusp_resume_block, swsusp_header);
 	} else {
 		pr_err("Swap header not found!\n");
@@ -486,11 +486,12 @@ static int flush_swap_writer(struct swap
 static int swap_writer_finish(struct swap_map_handle *handle,
 		unsigned int flags, int error)
 {
+	if (!error)
+		error = flush_swap_writer(handle);
 	if (!error) {
 		pr_info("S");
 		error = mark_swapfiles(handle, flags);
 		pr_cont("|\n");
-		flush_swap_writer(handle);
 	}
 
 	if (error)
@@ -1587,7 +1588,7 @@ int swsusp_check(bool exclusive)
 			memcpy(swsusp_header->sig, swsusp_header->orig_sig, 10);
 			swsusp_header_flags = swsusp_header->flags;
 			/* Reset swap signature now */
-			error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC,
+			error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC | REQ_FUA,
 						swsusp_resume_block,
 						swsusp_header);
 		} else {
@@ -1641,7 +1642,7 @@ int swsusp_unmark(void)
 	hib_submit_io_sync(REQ_OP_READ, swsusp_resume_block, swsusp_header);
 	if (!memcmp(HIBERNATE_SIG,swsusp_header->sig, 10)) {
 		memcpy(swsusp_header->sig,swsusp_header->orig_sig, 10);
-		error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC,
+		error = hib_submit_io_sync(REQ_OP_WRITE | REQ_SYNC | REQ_FUA,
 					swsusp_resume_block,
 					swsusp_header);
 	} else {