mm/sparse: abstract sparse buffer allocations

Patch series "sparse_init rewrite", v6.

In sparse_init() we allocate two large buffers to temporary hold usemap
and memmap for the whole machine.  However, we can avoid doing that if
we changed sparse_init() to operated on per-node bases instead of doing
it on the whole machine beforehand.

As shown by Baoquan
  http://lkml.kernel.org/r/20180628062857.29658-1-bhe@redhat.com

The buffers are large enough to cause machine stop to boot on small
memory systems.

Another benefit of these changes is that they also obsolete
CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER.

This patch (of 5):

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.

[akpm@linux-foundation.org: use PTR_ALIGN()]
[akpm@linux-foundation.org: s/BUG_ON/WARN_ON/]
Link: http://lkml.kernel.org/r/20180712203730.8703-2-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>	[powerpc]
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Oscar Salvador <osalvador@suse.de>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 34 deletions

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 95e2c7638a5c..b05c7663c640 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -43,12 +43,9 @@ static void * __ref __earlyonly_bootmem_alloc(int node,
 				unsigned long goal)
 {
 	return memblock_virt_alloc_try_nid_raw(size, align, goal,
-					    BOOTMEM_ALLOC_ACCESSIBLE, node);
+					       BOOTMEM_ALLOC_ACCESSIBLE, node);
 }
 
-static void *vmemmap_buf;
-static void *vmemmap_buf_end;
-
 void * __meminit vmemmap_alloc_block(unsigned long size, int node)
 {
 	/* If the main allocator is up use that, fallback to bootmem. */
@@ -76,18 +73,10 @@ void * __meminit vmemmap_alloc_block(unsigned long size, int node)
 /* need to make sure size is all the same during early stage */
 void * __meminit vmemmap_alloc_block_buf(unsigned long size, int node)
 {
-	void *ptr;
-
-	if (!vmemmap_buf)
-		return vmemmap_alloc_block(size, node);
-
-	/* take the from buf */
-	ptr = (void *)ALIGN((unsigned long)vmemmap_buf, size);
-	if (ptr + size > vmemmap_buf_end)
-		return vmemmap_alloc_block(size, node);
-
-	vmemmap_buf = ptr + size;
+	void *ptr = sparse_buffer_alloc(size);
 
+	if (!ptr)
+		ptr = vmemmap_alloc_block(size, node);
 	return ptr;
 }
 
@@ -279,19 +268,9 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
 					  unsigned long map_count, int nodeid)
 {
 	unsigned long pnum;
-	unsigned long size = sizeof(struct page) * PAGES_PER_SECTION;
-	void *vmemmap_buf_start;
 	int nr_consumed_maps = 0;
 
-	size = ALIGN(size, PMD_SIZE);
-	vmemmap_buf_start = __earlyonly_bootmem_alloc(nodeid, size * map_count,
-			 PMD_SIZE, __pa(MAX_DMA_ADDRESS));
-
-	if (vmemmap_buf_start) {
-		vmemmap_buf = vmemmap_buf_start;
-		vmemmap_buf_end = vmemmap_buf_start + size * map_count;
-	}
-
+	sparse_buffer_init(section_map_size() * map_count, nodeid);
 	for (pnum = pnum_begin; pnum < pnum_end; pnum++) {
 		if (!present_section_nr(pnum))
 			continue;
@@ -303,12 +282,5 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
 		pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
 		       __func__);
 	}
-
-	if (vmemmap_buf_start) {
-		/* need to free left buf */
-		memblock_free_early(__pa(vmemmap_buf),
-				    vmemmap_buf_end - vmemmap_buf);
-		vmemmap_buf = NULL;
-		vmemmap_buf_end = NULL;
-	}
+	sparse_buffer_fini();
 }