From: Hongbo Li <lihongbo22@huawei.com>
To: <kent.overstreet@linux.dev>, <bfoster@redhat.com>
Cc: <linux-bcachefs@vger.kernel.org>, <lihongbo22@huawei.com>
Subject: [PATCH 1/2] bcachefs: eliminate the uninitialized compilation warning in bch2_reconstruct_snapshots
Date: Fri, 19 Apr 2024 15:48:50 +0800 [thread overview]
Message-ID: <20240419074851.1583392-2-lihongbo22@huawei.com> (raw)
In-Reply-To: <20240419074851.1583392-1-lihongbo22@huawei.com>
[BUG]
When compiling the bcachefs-tools, the following compilation warning
is reported:
libbcachefs/snapshot.c: In function ‘bch2_reconstruct_snapshots’:
libbcachefs/snapshot.c:915:19: warning: ‘tree_id’ may be used uninitialized in this function [-Wmaybe-uninitialized]
915 | snapshot->v.tree = cpu_to_le32(tree_id);
libbcachefs/snapshot.c:903:6: note: ‘tree_id’ was declared here
903 | u32 tree_id;
| ^~~~~~~
[CAUSE]
This is a false alert, because @tree_id is changed in
bch2_snapshot_tree_create after it returns 0. And if this function
returns other value, @tree_id wouldn't be used. Thus there should
be nothing wrong in logical.
[FIX]
Although the report itself is a false alert, we can still make it more
explicit by:
- check the input parameter 'u32 *tree_id' with WARN_ON_ONCE
- initialize @tree_id to U32_MAX
- add extra WARN_ON_ONCE to make sure @tree_id is updated
Fixes: a292be3b68f3 ("bcachefs: Reconstruct missing snapshot nodes")
Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
---
fs/bcachefs/snapshot.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index 0b26dee17a5a..cad3408903b2 100644
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -78,6 +78,7 @@ __bch2_snapshot_tree_create(struct btree_trans *trans)
static int bch2_snapshot_tree_create(struct btree_trans *trans,
u32 root_id, u32 subvol_id, u32 *tree_id)
{
+ WARN_ON_ONCE(!tree_id);
struct bkey_i_snapshot_tree *n_tree =
__bch2_snapshot_tree_create(trans);
@@ -900,7 +901,7 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id)
if (bch2_snapshot_equiv(c, id))
return 0;
- u32 tree_id;
+ u32 tree_id = U32_MAX;
int ret = bch2_snapshot_tree_create(trans, id, 0, &tree_id);
if (ret)
return ret;
@@ -910,6 +911,8 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id)
if (ret)
return ret;
+ /* bch2_snapshot_tree_create returned 0, @tree_id must be updated. */
+ WARN_ON_ONCE(tree_id == U32_MAX);
bkey_snapshot_init(&snapshot->k_i);
snapshot->k.p = POS(0, id);
snapshot->v.tree = cpu_to_le32(tree_id);
--
2.34.1
next prev parent reply other threads:[~2024-04-19 7:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 7:48 [PATCH 0/2] eliminate the uninitialized compilation warning Hongbo Li
2024-04-19 7:48 ` Hongbo Li [this message]
2024-04-25 3:34 ` [PATCH 1/2] bcachefs: eliminate the uninitialized compilation warning in bch2_reconstruct_snapshots Kent Overstreet
2024-04-25 3:55 ` Hongbo Li
2024-04-25 17:08 ` Kent Overstreet
2024-04-26 1:31 ` Hongbo Li
2024-04-19 7:48 ` [PATCH 2/2] bcachefs: eliminate the uninitialized compilation warning in __do_six_trylock Hongbo Li
2024-04-25 3:39 ` Kent Overstreet
2024-04-24 1:14 ` [PATCH 0/2] eliminate the uninitialized compilation warning Hongbo Li
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