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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Subject: Re: [PATCH v3 3/4] hugetlbfs: remove hugetlb_add_hstate() warning
 for existing hstate
In-Reply-To: <20200417185049.275845-4-mike.kravetz@oracle.com>
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 <20200417185049.275845-4-mike.kravetz@oracle.com>
Date: Wed, 22 Apr 2020 16:12:26 +0530
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To: Mike Kravetz <mike.kravetz@oracle.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, sparclinux@vger.kernel.org, linux-doc@vger.kernel.org
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Heiko Carstens <heiko.carstens@de.ibm.com>, Vasily Gorbik <gor@linux.ibm.com>, Christian Borntraeger <borntraeger@de.ibm.com>, "David S . Miller" <davem@davemloft.net>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Dave Hansen <dave.hansen@linux.intel.com>, Jonathan Corbet <corbet@lwn.net>, Longpeng <longpeng2@huawei.com>, Christophe Leroy <christophe.leroy@c-s.fr>, Randy Dunlap <rdunlap@infradead.org>, Mina Almasry <almasrymina@google.com>, Peter Xu <peterx@redhat.com>, Nitesh Narayan Lal <nitesh@redhat.com>, Andrew Morton <akpm@linux-foundation.org>

Mike Kravetz <mike.kravetz@oracle.com> writes:

> The routine hugetlb_add_hstate prints a warning if the hstate already
> exists.  This was originally done as part of kernel command line
> parsing.  If 'hugepagesz=' was specified more than once, the warning
> 	pr_warn("hugepagesz= specified twice, ignoring\n");
> would be printed.
>
> Some architectures want to enable all huge page sizes.  They would
> call hugetlb_add_hstate for all supported sizes.  However, this was
> done after command line processing and as a result hstates could have
> already been created for some sizes.  To make sure no warning were
> printed, there would often be code like:
> 	if (!size_to_hstate(size)
> 		hugetlb_add_hstate(ilog2(size) - PAGE_SHIFT)
>
> The only time we want to print the warning is as the result of command
> line processing.

Does this patch break hugepages=x command line? I haven't tested this
yet. But one of the details w.r.t. skipping that hugetlb_add_hstate is
to make sure we can configure the max_huge_pages. 


>So, remove the warning from hugetlb_add_hstate and
> add it to the single arch independent routine processing "hugepagesz=".
> After this, calls to size_to_hstate() in arch specific code can be
> removed and hugetlb_add_hstate can be called without worrying about
> warning messages.
>

-aneesh