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From: Michal Hocko <mhocko@kernel.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: trivial@kernel.org, akpm@linux-foundation.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal()
Date: Wed, 21 Dec 2016 14:22:01 +0100	[thread overview]
Message-ID: <20161221132200.GK31118@dhcp22.suse.cz> (raw)
In-Reply-To: <20161221131332.GB23096@vultr.guest>

On Wed 21-12-16 13:13:32, Wei Yang wrote:
> On Wed, Dec 21, 2016 at 08:51:16AM +0100, Michal Hocko wrote:
> >On Tue 20-12-16 16:48:23, Wei Yang wrote:
> >> On Mon, Dec 19, 2016 at 04:21:57PM +0100, Michal Hocko wrote:
> >> >On Sun 18-12-16 14:47:50, Wei Yang wrote:
> >> >> memblock_reserve() may fail in case there is not enough regions.
> >> >
> >> >Have you seen this happenning in the real setups or this is a by-review
> >> >driven change?
> >> 
> >> This is a by-review driven change.
> >> 
> >> >[...]
> >> >>  again:
> >> >>  	alloc = memblock_find_in_range_node(size, align, min_addr, max_addr,
> >> >>  					    nid, flags);
> >> >> -	if (alloc)
> >> >> +	if (alloc && !memblock_reserve(alloc, size))
> >> >>  		goto done;
> >
> >So how exactly does the reserve fail when memblock_find_in_range_node
> >found a suitable range for the given size?
> >
> 
> Even memblock_find_in_range_node() gets a suitable range, memblock_reserve()
> still could fail. And the case just happens when memblock can't resize.
> memblock_reserve() reserve a range by adding a range to memblock.reserved. In
> case the memblock.reserved is full and can't resize, this fails.

Sorry for being dense but what does it mean that the reserved will get
full? Also how probable is such a situation? Is it even real? In other
words does this fix a real or only a theoretical problem?

Anyway this all should be part of the changelog.
-- 
Michal Hocko
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: Wei Yang <richard.weiyang@gmail.com>
Cc: trivial@kernel.org, akpm@linux-foundation.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal()
Date: Wed, 21 Dec 2016 14:22:01 +0100	[thread overview]
Message-ID: <20161221132200.GK31118@dhcp22.suse.cz> (raw)
In-Reply-To: <20161221131332.GB23096@vultr.guest>

On Wed 21-12-16 13:13:32, Wei Yang wrote:
> On Wed, Dec 21, 2016 at 08:51:16AM +0100, Michal Hocko wrote:
> >On Tue 20-12-16 16:48:23, Wei Yang wrote:
> >> On Mon, Dec 19, 2016 at 04:21:57PM +0100, Michal Hocko wrote:
> >> >On Sun 18-12-16 14:47:50, Wei Yang wrote:
> >> >> memblock_reserve() may fail in case there is not enough regions.
> >> >
> >> >Have you seen this happenning in the real setups or this is a by-review
> >> >driven change?
> >> 
> >> This is a by-review driven change.
> >> 
> >> >[...]
> >> >>  again:
> >> >>  	alloc = memblock_find_in_range_node(size, align, min_addr, max_addr,
> >> >>  					    nid, flags);
> >> >> -	if (alloc)
> >> >> +	if (alloc && !memblock_reserve(alloc, size))
> >> >>  		goto done;
> >
> >So how exactly does the reserve fail when memblock_find_in_range_node
> >found a suitable range for the given size?
> >
> 
> Even memblock_find_in_range_node() gets a suitable range, memblock_reserve()
> still could fail. And the case just happens when memblock can't resize.
> memblock_reserve() reserve a range by adding a range to memblock.reserved. In
> case the memblock.reserved is full and can't resize, this fails.

Sorry for being dense but what does it mean that the reserved will get
full? Also how probable is such a situation? Is it even real? In other
words does this fix a real or only a theoretical problem?

Anyway this all should be part of the changelog.
-- 
Michal Hocko
SUSE Labs

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  reply	other threads:[~2016-12-21 13:22 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-18 14:47 [PATCH V2 0/2] mm/memblock.c: fix potential bug and code refine Wei Yang
2016-12-18 14:47 ` Wei Yang
2016-12-18 14:47 ` [PATCH V2 1/2] mm/memblock.c: trivial code refine in memblock_is_region_memory() Wei Yang
2016-12-18 14:47   ` Wei Yang
2016-12-19 15:15   ` Michal Hocko
2016-12-19 15:15     ` Michal Hocko
2016-12-20 16:35     ` Wei Yang
2016-12-20 16:35       ` Wei Yang
2016-12-21  7:48       ` Michal Hocko
2016-12-21  7:48         ` Michal Hocko
2016-12-21 12:43         ` Wei Yang
2016-12-21 12:43           ` Wei Yang
2016-12-21 12:48           ` Michal Hocko
2016-12-21 12:48             ` Michal Hocko
2016-12-21 13:15             ` Wei Yang
2016-12-21 13:15               ` Wei Yang
2016-12-18 14:47 ` [PATCH V2 2/2] mm/memblock.c: check return value of memblock_reserve() in memblock_virt_alloc_internal() Wei Yang
2016-12-18 14:47   ` Wei Yang
2016-12-19 15:21   ` Michal Hocko
2016-12-19 15:21     ` Michal Hocko
2016-12-20 16:48     ` Wei Yang
2016-12-20 16:48       ` Wei Yang
2016-12-21  7:51       ` Michal Hocko
2016-12-21  7:51         ` Michal Hocko
2016-12-21 13:13         ` Wei Yang
2016-12-21 13:13           ` Wei Yang
2016-12-21 13:22           ` Michal Hocko [this message]
2016-12-21 13:22             ` Michal Hocko
2016-12-21 14:39             ` Wei Yang
2016-12-21 14:39               ` Wei Yang
2016-12-21 14:52               ` Michal Hocko
2016-12-21 14:52                 ` Michal Hocko

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