* [PATCH] bcachefs: Fix subtraction underflow
@ 2025-01-27 9:12 Alan Huang
2025-01-28 0:00 ` Kent Overstreet
0 siblings, 1 reply; 2+ messages in thread
From: Alan Huang @ 2025-01-27 9:12 UTC (permalink / raw)
To: kent.overstreet; +Cc: linux-bcachefs, Alan Huang
When ancestor is less than IS_ANCESTOR_BITMAP, we would get an incorrect
result.
Signed-off-by: Alan Huang <mmpgouride@gmail.com>
---
fs/bcachefs/snapshot.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index c54091a28909..ede0b480e7d4 100644
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -146,8 +146,9 @@ bool __bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ancestor)
goto out;
}
- while (id && id < ancestor - IS_ANCESTOR_BITMAP)
- id = get_ancestor_below(t, id, ancestor);
+ if (likely(ancestor >= IS_ANCESTOR_BITMAP))
+ while (id && id < ancestor - IS_ANCESTOR_BITMAP)
+ id = get_ancestor_below(t, id, ancestor);
ret = id && id < ancestor
? test_ancestor_bitmap(t, id, ancestor)
--
2.47.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] bcachefs: Fix subtraction underflow
2025-01-27 9:12 [PATCH] bcachefs: Fix subtraction underflow Alan Huang
@ 2025-01-28 0:00 ` Kent Overstreet
0 siblings, 0 replies; 2+ messages in thread
From: Kent Overstreet @ 2025-01-28 0:00 UTC (permalink / raw)
To: Alan Huang; +Cc: linux-bcachefs
On Mon, Jan 27, 2025 at 05:12:41PM +0800, Alan Huang wrote:
> When ancestor is less than IS_ANCESTOR_BITMAP, we would get an incorrect
> result.
>
> Signed-off-by: Alan Huang <mmpgouride@gmail.com>
> ---
> fs/bcachefs/snapshot.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
> index c54091a28909..ede0b480e7d4 100644
> --- a/fs/bcachefs/snapshot.c
> +++ b/fs/bcachefs/snapshot.c
> @@ -146,8 +146,9 @@ bool __bch2_snapshot_is_ancestor(struct bch_fs *c, u32 id, u32 ancestor)
> goto out;
> }
>
> - while (id && id < ancestor - IS_ANCESTOR_BITMAP)
> - id = get_ancestor_below(t, id, ancestor);
> + if (likely(ancestor >= IS_ANCESTOR_BITMAP))
> + while (id && id < ancestor - IS_ANCESTOR_BITMAP)
> + id = get_ancestor_below(t, id, ancestor);
That's not right, if ancestor < IS_ANCESTOR_BITMAP the bitmap would
still need to be initialized.
^ permalink raw reply [flat|nested] 2+ messages in thread
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