x86/mm/pat: Make split_page_count() check for empty levels to fix /proc/meminfo output

kernelslacker · Ingo Molnar · commit c9e0d39126af · 2016-01-12T11:08:37.000+01:00
In CONFIG_PAGEALLOC_DEBUG=y builds, we disable 2M pages.

Unfortunatly when we split up mappings during boot,
split_page_count() doesn't take this into account, and
starts decrementing an empty direct_pages_count[] level.

This results in /proc/meminfo showing crazy things like:

  DirectMap2M:    18446744073709543424 kB

Signed-off-by: Dave Jones &lt;davej@codemonkey.org.uk&gt;
Cc: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Borislav Petkov &lt;bp@alien8.de&gt;
Cc: Brian Gerst &lt;brgerst@gmail.com&gt;
Cc: Denys Vlasenko &lt;dvlasenk@redhat.com&gt;
Cc: H. Peter Anvin &lt;hpa@zytor.com&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Luis R. Rodriguez &lt;mcgrof@suse.com&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Toshi Kani &lt;toshi.kani@hp.com&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
@@ -66,6 +66,9 @@ void update_page_count(int level, unsigned long pages)
 
 static void split_page_count(int level)
 {
+	if (direct_pages_count[level] == 0)
+		return;
+
 	direct_pages_count[level]--;
 	direct_pages_count[level - 1] += PTRS_PER_PTE;
 }

Original file line number	Diff line number	Diff line change
`@@ -66,6 +66,9 @@ void update_page_count(int level, unsigned long pages)`
`66`	`66`
`67`	`67`	`static void split_page_count(int level)`
`68`	`68`	`{`
	`69`	`+ if (direct_pages_count[level] == 0)`
	`70`	`+ return;`
	`71`	`+`
`69`	`72`	`direct_pages_count[level]--;`
`70`	`73`	`direct_pages_count[level - 1] += PTRS_PER_PTE;`
`71`	`74`	`}`