From: Sergey Shtylyov <s.shtylyov@omp.ru>
To: Roman Smirnov <r.smirnov@omp.ru>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>
Cc: <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<lvc-project@linuxtesting.org>
Subject: Re: [PATCH] fs: buffer: set the expression type to unsigned long in folio_create_buffers()
Date: Tue, 16 Jul 2024 18:41:49 +0300 [thread overview]
Message-ID: <5002a830-6a66-82fc-19e3-ec1e907eeb49@omp.ru> (raw)
In-Reply-To: <20240716090105.72179-1-r.smirnov@omp.ru>
On 7/16/24 12:01 PM, Roman Smirnov wrote:
> Shift without specifying the type casts the expression to int,
You mean the result of the shift? Or what expression?
> which is then passed as an unsigned long argument. It is necessary
And here we'll have at least one potential problem (that you neglected
to describe): with 1 << 31, that 1 will land in a sign bit and then, when
it's implicitly cast to *unsigned long*, the 32-bit value will be sign-
extended to 64-bit on 64-bit arches) and then we'll have an incorrect size
(0xffffffff80000000) passed to create_empty_buffers()...
> to use 1UL instead.
Perphas was worth noting that using 1UL saves us 1 movsx instruction on
x86_64...
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <r.smirnov@omp.ru>
[...]
MBR, Sergey
next prev parent reply other threads:[~2024-07-16 15:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-16 9:01 Roman Smirnov
2024-07-16 15:41 ` Sergey Shtylyov [this message]
2024-07-16 15:51 ` Matthew Wilcox
2024-07-17 13:41 ` Jan Kara
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=5002a830-6a66-82fc-19e3-ec1e907eeb49@omp.ru \
--to=s.shtylyov@omp.ru \
--cc=brauner@kernel.org \
--cc=jack@suse.cz \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lvc-project@linuxtesting.org \
--cc=r.smirnov@omp.ru \
--cc=viro@zeniv.linux.org.uk \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®