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Commit af2cf278 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() 



So when memory hotplug removes a piece of physical memory from pagetable
mappings, it also frees the underlying PGD entry.

This complicates PGD management, so don't do this. We can keep the
PGD mapped and the PUD table all clear - it's only a single 4K page
per 512 GB of memory hotplugged.

Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <Waiman.Long@hp.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/064ff6c7275734537f969e876f6cd0baa954d2cc.1468527351.git.luto@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 38452af2

arch/x86/mm/init_64.c

+0 −27
Original line number Diff line number Diff line
@@ -702,27 +702,6 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud) 
	spin_unlock(&init_mm.page_table_lock);

}



/* Return true if pgd is changed, otherwise return false. */

static bool __meminit free_pud_table(pud_t *pud_start, pgd_t *pgd)

{

	pud_t *pud;

	int i;



	for (i = 0; i < PTRS_PER_PUD; i++) {

		pud = pud_start + i;

		if (!pud_none(*pud))

			return false;

	}



	/* free a pud table */

	free_pagetable(pgd_page(*pgd), 0);

	spin_lock(&init_mm.page_table_lock);

	pgd_clear(pgd);

	spin_unlock(&init_mm.page_table_lock);



	return true;

}



static void __meminit

remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,

		 bool direct)
@@ -913,7 +892,6 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct) 
	unsigned long addr;

	pgd_t *pgd;

	pud_t *pud;

	bool pgd_changed = false;



	for (addr = start; addr < end; addr = next) {

		next = pgd_addr_end(addr, end);
@@ -924,13 +902,8 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct) 


		pud = (pud_t *)pgd_page_vaddr(*pgd);

		remove_pud_table(pud, addr, next, direct);

		if (free_pud_table(pud, pgd))

			pgd_changed = true;

	}



	if (pgd_changed)

		sync_global_pgds(start, end - 1, 1);



	flush_tlb_all();

}