block: use the holder as indication for exclusive opens

The current interface for exclusive opens is rather confusing as it
requires both the FMODE_EXCL flag and a holder.  Remove the need to pass
FMODE_EXCL and just key off the exclusive open off a non-NULL holder.

For blkdev_put this requires adding the holder argument, which provides
better debug checking that only the holder actually releases the hold,
but at the same time allows removing the now superfluous mode argument.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Acked-by: Christian Brauner <brauner@kernel.org>
Acked-by: David Sterba <dsterba@suse.com>		[btrfs]
Acked-by: Jack Wang <jinpu.wang@ionos.com>		[rnbd]
Link: https://lore.kernel.org/r/20230608110258.189493-16-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

3 files changed, 14 insertions, 21 deletions

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 7ae95ec72f99..f62e89d0d906 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -688,22 +688,18 @@ static int load_image_and_restore(bool snapshot_test)
 {
 	int error;
 	unsigned int flags;
-	fmode_t mode = FMODE_READ;
-
-	if (snapshot_test)
-		mode |= FMODE_EXCL;
 
 	pm_pr_dbg("Loading hibernation image.\n");
 
 	lock_device_hotplug();
 	error = create_basic_memory_bitmaps();
 	if (error) {
-		swsusp_close(mode);
+		swsusp_close(snapshot_test);
 		goto Unlock;
 	}
 
 	error = swsusp_read(&flags);
-	swsusp_close(mode);
+	swsusp_close(snapshot_test);
 	if (!error)
 		error = hibernation_restore(flags & SF_PLATFORM_MODE);
 
@@ -956,7 +952,7 @@ static int software_resume(void)
 	/* The snapshot device should not be opened while we're running */
 	if (!hibernate_acquire()) {
 		error = -EBUSY;
-		swsusp_close(FMODE_READ | FMODE_EXCL);
+		swsusp_close(false);
 		goto Unlock;
 	}
 
@@ -991,7 +987,7 @@ static int software_resume(void)
 	pm_pr_dbg("Hibernation image not present or could not be loaded.\n");
 	return error;
  Close_Finish:
-	swsusp_close(FMODE_READ | FMODE_EXCL);
+	swsusp_close(false);
 	goto Finish;
 }
 
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 978189fcafd1..a8e0c44b804e 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -177,7 +177,7 @@ int swsusp_check(bool snapshot_test);
 extern void swsusp_free(void);
 extern int swsusp_read(unsigned int *flags_p);
 extern int swsusp_write(unsigned int flags);
-extern void swsusp_close(fmode_t);
+void swsusp_close(bool snapshot_test);
 #ifdef CONFIG_SUSPEND
 extern int swsusp_unmark(void);
 #endif
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index b03ff1a33c7f..cc9259307c94 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -363,7 +363,7 @@ static int swsusp_swap_check(void)
 
 	res = set_blocksize(hib_resume_bdev, PAGE_SIZE);
 	if (res < 0)
-		blkdev_put(hib_resume_bdev, FMODE_WRITE);
+		blkdev_put(hib_resume_bdev, NULL);
 
 	return res;
 }
@@ -443,7 +443,7 @@ static int get_swap_writer(struct swap_map_handle *handle)
 err_rel:
 	release_swap_writer(handle);
 err_close:
-	swsusp_close(FMODE_WRITE);
+	swsusp_close(false);
 	return ret;
 }
 
@@ -508,7 +508,7 @@ static int swap_writer_finish(struct swap_map_handle *handle,
 	if (error)
 		free_all_swap_pages(root_swap);
 	release_swap_writer(handle);
-	swsusp_close(FMODE_WRITE);
+	swsusp_close(false);
 
 	return error;
 }
@@ -1518,14 +1518,11 @@ static void *swsusp_holder;
 
 int swsusp_check(bool snapshot_test)
 {
+	void *holder = snapshot_test ? &swsusp_holder : NULL;
 	int error;
-	fmode_t mode = FMODE_READ;
 
-	if (snapshot_test)
-		mode |= FMODE_EXCL;
-
-	hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
-					    mode, &swsusp_holder, NULL);
+	hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device, FMODE_READ,
+					    holder, NULL);
 	if (!IS_ERR(hib_resume_bdev)) {
 		set_blocksize(hib_resume_bdev, PAGE_SIZE);
 		clear_page(swsusp_header);
@@ -1552,7 +1549,7 @@ int swsusp_check(bool snapshot_test)
 
 put:
 		if (error)
-			blkdev_put(hib_resume_bdev, mode);
+			blkdev_put(hib_resume_bdev, holder);
 		else
 			pr_debug("Image signature found, resuming\n");
 	} else {
@@ -1569,14 +1566,14 @@ put:
  *	swsusp_close - close swap device.
  */
 
-void swsusp_close(fmode_t mode)
+void swsusp_close(bool snapshot_test)
 {
 	if (IS_ERR(hib_resume_bdev)) {
 		pr_debug("Image device not initialised\n");
 		return;
 	}
 
-	blkdev_put(hib_resume_bdev, mode);
+	blkdev_put(hib_resume_bdev, snapshot_test ? &swsusp_holder : NULL);
 }
 
 /**