[ 107/218] MIPS: mm: Add compound tail page _mapcount when mapped

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jovi Zhang <bookjovi@xxxxxxxxx>

commit af89fa3986b9d034a286544ab1ed95096496a2f9 upstream.

See commit b6999b191 which did the same modification for x86's mm/gup,

Quote from commit b6999b191:
    "If compound pages are used and the page is a
    tail page, gup_huge_pmd() increases _mapcount to record tail page are
    mapped while gup_huge_pud does not do that."

[ralf@xxxxxxxxxxxxxx: fixed rejects caused by the original patch getting
linewrapped.]

Signed-off-by: Jovi Zhang <boojovi@xxxxxxxxx>
Cc: Youquan Song <youquan.song@xxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Patchwork: https://patchwork.linux-mips.org/patch/4291/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/mips/mm/gup.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/mips/mm/gup.c
+++ b/arch/mips/mm/gup.c
@@ -152,6 +152,8 @@ static int gup_huge_pud(pud_t pud, unsig
 	do {
 		VM_BUG_ON(compound_head(page) != head);
 		pages[*nr] = page;
+		if (PageTail(page))
+			get_huge_page_tail(page);
 		(*nr)++;
 		page++;
 		refs++;


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