From: Andrew Morton <akpm@linux-foundation.org>
To: Dev Jain <dev.jain@arm.com>
Cc: willy@infradead.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
david@redhat.com, anshuman.khandual@arm.com,
ryan.roberts@arm.com, ziy@nvidia.com, aneesh.kumar@kernel.org
Subject: Re: [PATCH v2] xarray: Add a BUG_ON() to ensure caller is not sibling
Date: Tue, 3 Jun 2025 21:33:38 -0700 [thread overview]
Message-ID: <20250603213338.7d80bbe0e021052c20e1c5f5@linux-foundation.org> (raw)
In-Reply-To: <20250604041533.91198-1-dev.jain@arm.com>
On Wed, 4 Jun 2025 09:45:33 +0530 Dev Jain <dev.jain@arm.com> wrote:
> Suppose xas is pointing somewhere near the end of the multi-entry batch.
> Then it may happen that the computed slot already falls beyond the batch,
> thus breaking the loop due to !xa_is_sibling(), and computing the wrong
> order. For example, suppose we have a shift-6 node having an order-9
> entry => 8 - 1 = 7 siblings, so assume the slots are at offset 0 till 7 in
> this node. If xas->xa_offset is 6, then the code will compute order as
> 1 + xas->xa_node->shift = 7. Therefore, the order computation must start
> from the beginning of the multi-slot entries, that is, the non-sibling
> entry. Thus ensure that the caller is aware of this by triggering a BUG
> when the entry is a sibling entry.
Why check this thing in particular? There are a zillion things we
could check...
> Note that this BUG_ON() is only
> active while running selftests, so there is no overhead in a running
> kernel.
hm, how do we know this? Now and in the future? xa_get_order() and
xas_get_order() have callers all over the place.
next prev parent reply other threads:[~2025-06-04 4:33 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-04 4:15 [PATCH v2] xarray: Add a BUG_ON() to ensure caller is not sibling Dev Jain
2025-06-04 4:33 ` Andrew Morton [this message]
2025-06-04 4:53 ` Dev Jain
2025-06-04 13:40 ` Zi Yan
2025-06-10 4:41 ` Dev Jain
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20250603213338.7d80bbe0e021052c20e1c5f5@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=aneesh.kumar@kernel.org \
--cc=anshuman.khandual@arm.com \
--cc=david@redhat.com \
--cc=dev.jain@arm.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=ryan.roberts@arm.com \
--cc=willy@infradead.org \
--cc=ziy@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.