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Date:   Thu, 12 Jul 2018 15:45:52 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Pavel Tatashin <pasha.tatashin@oracle.com>
Cc:     steven.sistare@oracle.com, daniel.m.jordan@oracle.com,
        linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com,
        mhocko@suse.com, linux-mm@kvack.org, dan.j.williams@intel.com,
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        bhe@redhat.com, gregkh@linuxfoundation.org, vbabka@suse.cz,
        richard.weiyang@gmail.com, dave.hansen@intel.com,
        rientjes@google.com, mingo@kernel.org,
        osalvador@techadventures.net, abdhalee@linux.vnet.ibm.com,
        mpe@ellerman.id.au
Subject: Re: [PATCH v5 1/5] mm/sparse: abstract sparse buffer allocations
Message-Id: <20180712154552.db99d1893bcba7f9503534a0@linux-foundation.org>
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        <20180712203730.8703-2-pasha.tatashin@oracle.com>
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On Thu, 12 Jul 2018 16:37:26 -0400 Pavel Tatashin <pasha.tatashin@oracle.com> wrote:

> When struct pages are allocated for sparse-vmemmap VA layout, we first
> try to allocate one large buffer, and than if that fails allocate struct
> pages for each section as we go.
> 
> The code that allocates buffer is uses global variables and is spread
> across several call sites.
> 
> Cleanup the code by introducing three functions to handle the global
> buffer:
> 
> sparse_buffer_init()	initialize the buffer
> sparse_buffer_fini()	free the remaining part of the buffer
> sparse_buffer_alloc()	alloc from the buffer, and if buffer is empty
> return NULL
> 
> Define these functions in sparse.c instead of sparse-vmemmap.c because
> later we will use them for non-vmemmap sparse allocations as well.
> 
> ...
>
> +void * __meminit sparse_buffer_alloc(unsigned long size)
> +{
> +	void *ptr = NULL;
> +
> +	if (sparsemap_buf) {
> +		ptr = (void *)ALIGN((unsigned long)sparsemap_buf, size);
> +		if (ptr + size > sparsemap_buf_end)
> +			ptr = NULL;
> +		else
> +			sparsemap_buf = ptr + size;
> +	}
> +	return ptr;
> +}

tweak...

diff -puN mm/sparse.c~mm-sparse-abstract-sparse-buffer-allocations-fix mm/sparse.c
--- a/mm/sparse.c~mm-sparse-abstract-sparse-buffer-allocations-fix
+++ a/mm/sparse.c
@@ -491,7 +491,7 @@ void * __meminit sparse_buffer_alloc(uns
 	void *ptr = NULL;
 
 	if (sparsemap_buf) {
-		ptr = (void *)ALIGN((unsigned long)sparsemap_buf, size);
+		ptr = PTR_ALIGN(sparsemap_buf, size);
 		if (ptr + size > sparsemap_buf_end)
 			ptr = NULL;
 		else