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From: Oscar Salvador <osalvador@suse.de>
To: Laurent Cremmer <laurent@oss.volkswagen.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mina Almasry <almasrymina@google.com>,
	David Rientjes <rientjes@google.com>,
	linux-mm@kvack.org, Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH] hugetlb: fix locking in region_add,region_cgh,allocate_file_region_entries
Date: Fri, 23 Oct 2020 13:02:08 +0200	[thread overview]
Message-ID: <20201023110204.GA3925@linux> (raw)
In-Reply-To: <20201023074759.46605-1-laurent@oss.volkswagen.com>

On Fri, Oct 23, 2020 at 09:47:59AM +0200, Laurent Cremmer wrote:
> The third instance spotted by manual examination.

It is friday, I might be overlooking something obvious, so bear with me.

> In static long region_add(...) and static long region_cgh(...) , releasing
> the acquired lock when exiting via their error path was removed.
> This will cause these functions to return with a lock held if they do not
> succeed.

If they do not suceed, it means that allocate_file_region_entries returned
non-zero, which means that we hit:

	spin_unlock(&resv->lock);
	for (i = 0; i < to_allocate; i++) {
		trg = kmalloc(sizeof(*trg), GFP_KERNEL);
		if (!trg)
			goto out_of_memory;
		list_add(&trg->link, &allocated_regions);
	 }

So, we do spin_unlock before jumping to out_of_memory.

> A a new function allocate_file_region_entries was also introduced  that
> must be called with a lock held and returned with the lock held.
> However the lock is temporarily released during processing but will not
> be reacquired on error.

As stated above, region_add/region_chr exit immediately on allocate_file_region_entries
failure, so it does not need to acquire the lock.


-- 
Oscar Salvador
SUSE L3


  parent reply	other threads:[~2020-10-23 11:02 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-23  7:47 [PATCH] hugetlb: fix locking in region_add,region_cgh,allocate_file_region_entries Laurent Cremmer
2020-10-23 10:12 ` David Hildenbrand
2020-10-23 11:25   ` Laurent Cremmer
2020-10-23 11:39     ` David Hildenbrand
2020-10-23 11:02 ` Oscar Salvador [this message]
2020-10-23 11:32   ` Laurent Cremmer
2020-10-23 12:11     ` Oscar Salvador
2020-10-23 16:47       ` Mike Kravetz
2020-10-27  7:34         ` Laurent Cremmer
2020-10-28 19:18 ` Mina Almasry

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