[PATCH AUTOSEL 6.16-5.10] dm-mpath: don't print the "loaded" message if registering fails

[Sasha Levin <sashal@kernel.org>]

From: Mikulas Patocka <mpatocka@redhat.com>

[ Upstream commit 6e11952a6abc4641dc8ae63f01b318b31b44e8db ]

If dm_register_path_selector, don't print the "version X loaded" message.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

**Backport Status: YES**

This commit is a clear candidate for backporting to stable kernel trees.
Here's my extensive analysis:

## Bug Analysis

The commit fixes a logic error in the error handling of four device-
mapper path selector modules. Looking at the code changes:

1. **Original buggy behavior**: When `dm_register_path_selector()` fails
   (returns r < 0), the code would:
   - Print "register failed" error message
   - **Continue to print "version X loaded" message**
   - Return the error code

2. **Fixed behavior**: When registration fails:
   - Print "register failed" error message
   - **Return immediately with the error code**
   - Skip the misleading "loaded" message

## Why This Should Be Backported

1. **Clear Bug Fix**: This is a straightforward bug fix that corrects
   misleading log messages. When module registration fails, it
   incorrectly reports success with "version X loaded".

2. **Small and Contained**: The fix is minimal - just adding an early
   return statement in four similar init functions:
   - `dm_hst_init()` in dm-ps-historical-service-time.c
   - `dm_ql_init()` in dm-ps-queue-length.c
   - `dm_rr_init()` in dm-ps-round-robin.c
   - `dm_st_init()` in dm-ps-service-time.c

3. **No Side Effects**: The change only affects error path behavior and
   logging. It doesn't introduce new functionality or change any
   successful operation paths.

4. **User-Visible Issue**: This fixes a user-visible problem where
   system logs would incorrectly indicate a module loaded successfully
   when it actually failed.

5. **Consistent Pattern**: All four files have the identical bug and
   identical fix, showing this is a systematic issue that should be
   addressed.

6. **Low Risk**: The change is trivial - adding an early return on
   error. There's virtually no risk of regression since:
   - It only changes behavior when registration already failed
   - The function already returns the error code at the end
   - This just makes it return earlier without printing the misleading
     message

7. **Affects Core Subsystem**: Device-mapper is a critical storage
   subsystem, and accurate error reporting is important for system
   administrators debugging storage issues.

The commit perfectly fits stable kernel criteria: it's a small, obvious
fix for a real bug that affects users (through misleading log messages),
with minimal risk of introducing new problems.

 drivers/md/dm-ps-historical-service-time.c | 4 +++-
 drivers/md/dm-ps-queue-length.c            | 4 +++-
 drivers/md/dm-ps-round-robin.c             | 4 +++-
 drivers/md/dm-ps-service-time.c            | 4 +++-
 4 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-ps-historical-service-time.c b/drivers/md/dm-ps-historical-service-time.c
index b49e10d76d03..2c8626a83de4 100644
--- a/drivers/md/dm-ps-historical-service-time.c
+++ b/drivers/md/dm-ps-historical-service-time.c
@@ -541,8 +541,10 @@ static int __init dm_hst_init(void)
 {
 	int r = dm_register_path_selector(&hst_ps);
 
-	if (r < 0)
+	if (r < 0) {
 		DMERR("register failed %d", r);
+		return r;
+	}
 
 	DMINFO("version " HST_VERSION " loaded");
 
diff --git a/drivers/md/dm-ps-queue-length.c b/drivers/md/dm-ps-queue-length.c
index e305f05ad1e5..eb543e6431e0 100644
--- a/drivers/md/dm-ps-queue-length.c
+++ b/drivers/md/dm-ps-queue-length.c
@@ -260,8 +260,10 @@ static int __init dm_ql_init(void)
 {
 	int r = dm_register_path_selector(&ql_ps);
 
-	if (r < 0)
+	if (r < 0) {
 		DMERR("register failed %d", r);
+		return r;
+	}
 
 	DMINFO("version " QL_VERSION " loaded");
 
diff --git a/drivers/md/dm-ps-round-robin.c b/drivers/md/dm-ps-round-robin.c
index d1745b123dc1..66a15ac0c22c 100644
--- a/drivers/md/dm-ps-round-robin.c
+++ b/drivers/md/dm-ps-round-robin.c
@@ -220,8 +220,10 @@ static int __init dm_rr_init(void)
 {
 	int r = dm_register_path_selector(&rr_ps);
 
-	if (r < 0)
+	if (r < 0) {
 		DMERR("register failed %d", r);
+		return r;
+	}
 
 	DMINFO("version " RR_VERSION " loaded");
 
diff --git a/drivers/md/dm-ps-service-time.c b/drivers/md/dm-ps-service-time.c
index 969d31c40272..f8c43aecdb27 100644
--- a/drivers/md/dm-ps-service-time.c
+++ b/drivers/md/dm-ps-service-time.c
@@ -341,8 +341,10 @@ static int __init dm_st_init(void)
 {
 	int r = dm_register_path_selector(&st_ps);
 
-	if (r < 0)
+	if (r < 0) {
 		DMERR("register failed %d", r);
+		return r;
+	}
 
 	DMINFO("version " ST_VERSION " loaded");
 
-- 
2.39.5