From: Matthew Wilcox <willy@infradead.org>
To: Sergey Shtylyov <s.shtylyov@omp.ru>
Cc: Roman Smirnov <r.smirnov@omp.ru>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
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 16:51:17 +0100 [thread overview]
Message-ID: <ZpaW9ebdKyJremzp@casper.infradead.org> (raw)
In-Reply-To: <5002a830-6a66-82fc-19e3-ec1e907eeb49@omp.ru>
On Tue, Jul 16, 2024 at 06:41:49PM +0300, Sergey Shtylyov wrote:
> 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()...
Tell me more about this block device you have with a 2GB block size ... ?
(ie note that this is a purely theoretical issue)
> > to use 1UL instead.
>
> Perphas was worth noting that using 1UL saves us 1 movsx instruction on
> x86_64...
That is a worthwhile addition to the change log.
Also, you should cc the person who wrote that code, ie me.
next prev parent reply other threads:[~2024-07-16 15:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-16 9:01 [PATCH] fs: buffer: set the expression type to unsigned long in folio_create_buffers() Roman Smirnov
2024-07-16 15:41 ` Sergey Shtylyov
2024-07-16 15:51 ` Matthew Wilcox [this message]
2024-07-17 13:41 ` Jan Kara
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