linux-kernel - [PATCH] dm persistent data: fix return type of shadow

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Message-ID: <f271028d-182e-c665-f67b-a407a7f7674a@gmail.com>
Date:   Sun, 17 Jan 2021 11:49:33 +0000
From:   Jinoh Kang <jinoh.kang.kr@...il.com>
To:     dm-devel@...hat.com
Cc:     Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Joe Thornber <thornber@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] dm persistent data: fix return type of shadow_root

shadow_root() truncates 64-bit dm_block_t into 32-bit int.  This is
not an issue in practice, since dm metadata as of v5.11 can only hold at
most 4161600 blocks (255 index entries * ~16k metadata blocks).

Nevertheless, this can confuse users debugging some specific data
corruption scenarios.  Also, DM_SM_METADATA_MAX_BLOCKS may be bumped in
the future, or persistent-data may find its use in other places.

Therefore, switch the return type of shadow_root from int to dm_block_t.

Fixes: 3241b1d3e0aa ("dm: add persistent data library")
Cc: stable@...r.kernel.org
Signed-off-by: Jinoh Kang <jinoh.kang.kr@...il.com>
---
 drivers/md/persistent-data/dm-btree-internal.h | 2 +-
 drivers/md/persistent-data/dm-btree-spine.c    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/persistent-data/dm-btree-internal.h b/drivers/md/persistent-data/dm-btree-internal.h
index 564896659dd4..fe073d92f01e 100644
--- a/drivers/md/persistent-data/dm-btree-internal.h
+++ b/drivers/md/persistent-data/dm-btree-internal.h
@@ -100,7 +100,7 @@ struct dm_block *shadow_parent(struct shadow_spine *s);
 
 int shadow_has_parent(struct shadow_spine *s);
 
-int shadow_root(struct shadow_spine *s);
+dm_block_t shadow_root(struct shadow_spine *s);
 
 /*
  * Some inlines.
diff --git a/drivers/md/persistent-data/dm-btree-spine.c b/drivers/md/persistent-data/dm-btree-spine.c
index e03cb9e48773..8a2bfbfb218b 100644
--- a/drivers/md/persistent-data/dm-btree-spine.c
+++ b/drivers/md/persistent-data/dm-btree-spine.c
@@ -235,7 +235,7 @@ int shadow_has_parent(struct shadow_spine *s)
 	return s->count >= 2;
 }
 
-int shadow_root(struct shadow_spine *s)
+dm_block_t shadow_root(struct shadow_spine *s)
 {
 	return s->root;
 }
-- 
2.26.2