x86/boot/e820: Rename memblock_x86_fill() to e820__memblock_setup() and improve the explanations

So memblock_x86_fill() is another E820 code misnomer:

 - nothing in its name tells us that it's part of the E820 subsystem ...

 - The 'fill' wording is ambiguous and doesn't tell us whether it's a single
   entry or some process - while the _real_ purpose of the function is hidden,
   which is to do a complete setup of the (platform independent) memblock regions.

So rename it accordingly, to e820__memblock_setup().

Also translate this incomprehensible and misleading comment:

        /*
	 * EFI may have more than 128 entries
	 * We are safe to enable resizing, beause memblock_x86_fill()
	 * is rather later for x86
	 */
        memblock_allow_resize();

The worst aspect of this comment isn't even the sloppy typos, but that it
casually mentions a '128' number with no explanation, which makes one lead
to the assumption that this is related to the well-known limit of a maximum
of 128 E820 entries passed via legacy bootloaders.

But no, the _real_ meaning of 128 here is that of the memblock subsystem,
which too happens to have a 128 entries limit for very early memblock
regions (which is unrelated to E820), via INIT_MEMBLOCK_REGIONS ...

So change the comment to a more comprehensible version:

        /*
         * The bootstrap memblock region count maximum is 128 entries
         * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries
         * than that - so allow memblock resizing.
         *
         * This is safe, because this call happens pretty late during x86 setup,
         * so we know about reserved memory regions already. (This is important
         * so that memblock resizing does no stomp over reserved areas.)
         */
        memblock_allow_resize();

No change in functionality.

Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Jackson <pj@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

arch/x86/include/asm/e820/api.h

@@ -21,7 +21,7 @@ extern void parse_e820_ext(u64 phys_addr, u32 data_len);
 extern unsigned long e820_end_of_ram_pfn(void);
 extern unsigned long e820_end_of_low_ram_pfn(void);
 extern u64  early_reserve_e820(u64 sizet, u64 align);
-extern void memblock_x86_fill(void);
+extern void e820__memblock_setup(void);
 extern void memblock_find_dma_reserve(void);
 extern void finish_e820_parsing(void);
 extern void e820_reserve_resources(void);

arch/x86/kernel/e820.c

@@ -1138,15 +1138,19 @@ void __init e820__memory_setup(void)
 	e820_print_map(who);
 }
 
-void __init memblock_x86_fill(void)
+void __init e820__memblock_setup(void)
 {
 	int i;
 	u64 end;
 
 	/*
-	 * EFI may have more than 128 entries
-	 * We are safe to enable resizing, beause memblock_x86_fill()
-	 * is rather later for x86
+	 * The bootstrap memblock region count maximum is 128 entries
+	 * (INIT_MEMBLOCK_REGIONS), but EFI might pass us more E820 entries
+	 * than that - so allow memblock resizing.
+	 *
+	 * This is safe, because this call happens pretty late during x86 setup,
+	 * so we know about reserved memory regions already. (This is important
+	 * so that memblock resizing does no stomp over reserved areas.)
 	 */
 	memblock_allow_resize();
 
@@ -1163,7 +1167,7 @@ void __init memblock_x86_fill(void)
 		memblock_add(ei->addr, ei->size);
 	}
 
-	/* throw away partial pages */
+	/* Throw away partial pages: */
 	memblock_trim_memory(PAGE_SIZE);
 
 	memblock_dump_all();

arch/x86/kernel/setup.c

@@ -1109,7 +1109,7 @@ void __init setup_arch(char **cmdline_p)
 	early_alloc_pgt_buf();
 
 	/*
-	 * Need to conclude brk, before memblock_x86_fill()
+	 * Need to conclude brk, before e820__memblock_setup()
 	 *  it could use memblock_find_in_range, could overlap with
 	 *  brk area.
 	 */
@@ -1118,7 +1118,7 @@ void __init setup_arch(char **cmdline_p)
 	cleanup_highmap();
 
 	memblock_set_current_limit(ISA_END_ADDRESS);
-	memblock_x86_fill();
+	e820__memblock_setup();
 
 	reserve_bios_regions();