From: Kent Gibson <warthog618@gmail.com>
To: Andy Shevchenko <andy@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
brgl@bgdev.pl, linus.walleij@linaro.org
Subject: Re: [PATCH 2/4] gpiolib: cdev: allocate linereq using kvzalloc()
Date: Wed, 20 Dec 2023 22:53:07 +0800 [thread overview]
Message-ID: <ZYL_077xycZ0ZVBy@rigel> (raw)
In-Reply-To: <ZYL6gIpG5GBONVSO@smile.fi.intel.com>
On Wed, Dec 20, 2023 at 04:30:24PM +0200, Andy Shevchenko wrote:
> On Wed, Dec 20, 2023 at 09:51:04AM +0800, Kent Gibson wrote:
> > The size of struct linereq may exceed a page, so allocate space for
> > it using kvzalloc() instead of kzalloc().
>
> It might be this needs a bit of elaboration. The kmalloc() tries to allocate
> a contiguous (in physical address space) chunk of memory and with fragmented
> memory it might be not possible. So the above issue might (rarely) happen.
> In most cases the call to kmalloc() will succeed.
>
For sure, the kzalloc() generally works - or we wouldn't've gotten this
far as tests with MAX_LINES would've been failing.
We are targetting a very niche failure mode here.
The size allocated can only be determined at runtime, may be more or
less than a page, and we don't care whether the physical memory allocated
is contiguous.
As such kvzalloc() is the appropriate allocator.
Are you suggesting repeating the relevant sections of the
kmalloc/vmalloc() documentation or Memory Allocation Guide as part of the
checkin comment?
Cheers,
Kent.
next prev parent reply other threads:[~2023-12-20 14:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-20 1:51 [PATCH 0/4] gpiolib: cdev: guard tidying Kent Gibson
2023-12-20 1:51 ` [PATCH 1/4] gpiolib: cdev: include overflow.h Kent Gibson
2023-12-20 1:51 ` [PATCH 2/4] gpiolib: cdev: allocate linereq using kvzalloc() Kent Gibson
2023-12-20 14:30 ` Andy Shevchenko
2023-12-20 14:53 ` Kent Gibson [this message]
2023-12-20 14:58 ` Andy Shevchenko
2023-12-20 1:51 ` [PATCH 3/4] gpiolib: cdev: replace locking wrappers for config_mutex with guards Kent Gibson
2023-12-20 1:51 ` [PATCH 4/4] gpiolib: cdev: replace locking wrappers for gpio_device " Kent Gibson
2023-12-20 11:55 ` Linus Walleij
2023-12-20 12:05 ` Bartosz Golaszewski
2023-12-20 12:13 ` Kent Gibson
2023-12-20 12:16 ` Bartosz Golaszewski
2023-12-20 12:23 ` Kent Gibson
2023-12-20 12:30 ` Bartosz Golaszewski
2023-12-20 12:53 ` Kent Gibson
2023-12-20 13:19 ` Bartosz Golaszewski
2023-12-20 13:28 ` Kent Gibson
2023-12-20 13:47 ` Bartosz Golaszewski
2023-12-20 13:53 ` Kent Gibson
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