From: Michal Hocko <mhocko@xxxxxxxx> empty_bad_page and empty_bad_pte_table seems to be a relict from old days which is not used by any code for a long time. I have tried to find when exactly but this is not really all that straightforward due to many code movements - traces disappear around 2.4 times. Anyway no code really references neither empty_bad_page nor empty_bad_pte_table. We only allocate the storage which is not used by anybody so remove them. Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx> Cc: David Howells <dhowells@xxxxxxxxxx> Cc: Rich Felker <dalias@xxxxxxxx> Cc: Jeff Dike <jdike@xxxxxxxxxxx> Cc: Richard Weinberger <richard@xxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: <uclinux-h8-devel@xxxxxxxxxxxxxxxxxxxx> Cc: <linux-mips@xxxxxxxxxxxxxx> Cc: <linux-sh@xxxxxxxxxxxxxxx> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> --- Hi, Pasha Tatashin made me look closer at include/linux/page-flags.h * PG_reserved is set for special pages, which can never be swapped out. Some * of them might not even exist (eg empty_bad_page)... in http://lkml.kernel.org/r/691dba28-718c-e9a9-d006-88505eb5cd7e@xxxxxxxxxx because it was the first time I have heard about empty_bad_page. It seems that this is no longer needed but there are some relicts in arch code. Please note that I have no ways to test this other than run it through my compile (cross arch) test battery and there were no failures. arch/frv/mm/init.c | 14 -------------- arch/h8300/mm/init.c | 13 ------------- arch/mips/include/asm/pgtable-64.h | 8 +------- arch/mn10300/kernel/head.S | 8 -------- arch/sh/kernel/head_64.S | 8 -------- arch/um/kernel/mem.c | 3 --- include/linux/page-flags.h | 2 +- 7 files changed, 2 insertions(+), 54 deletions(-) diff --git a/arch/frv/mm/init.c b/arch/frv/mm/init.c index 328f0a292316..cf464100e838 100644 --- a/arch/frv/mm/init.c +++ b/arch/frv/mm/init.c @@ -42,21 +42,9 @@ #undef DEBUG /* - * BAD_PAGE is the page that is used for page faults when linux - * is out-of-memory. Older versions of linux just did a - * do_exit(), but using this instead means there is less risk - * for a process dying in kernel mode, possibly leaving a inode - * unused etc.. - * - * BAD_PAGETABLE is the accompanying page-table: it is initialized - * to point to BAD_PAGE entries. - * * ZERO_PAGE is a special page that is used for zero-initialized * data and COW. */ -static unsigned long empty_bad_page_table; -static unsigned long empty_bad_page; - unsigned long empty_zero_page; EXPORT_SYMBOL(empty_zero_page); @@ -72,8 +60,6 @@ void __init paging_init(void) unsigned long zones_size[MAX_NR_ZONES] = {0, }; /* allocate some pages for kernel housekeeping tasks */ - empty_bad_page_table = (unsigned long) alloc_bootmem_pages(PAGE_SIZE); - empty_bad_page = (unsigned long) alloc_bootmem_pages(PAGE_SIZE); empty_zero_page = (unsigned long) alloc_bootmem_pages(PAGE_SIZE); memset((void *) empty_zero_page, 0, PAGE_SIZE); diff --git a/arch/h8300/mm/init.c b/arch/h8300/mm/init.c index 495a3d6b539b..85c51cf782a5 100644 --- a/arch/h8300/mm/init.c +++ b/arch/h8300/mm/init.c @@ -39,20 +39,9 @@ #include <asm/sections.h> /* - * BAD_PAGE is the page that is used for page faults when linux - * is out-of-memory. Older versions of linux just did a - * do_exit(), but using this instead means there is less risk - * for a process dying in kernel mode, possibly leaving a inode - * unused etc.. - * - * BAD_PAGETABLE is the accompanying page-table: it is initialized - * to point to BAD_PAGE entries. - * * ZERO_PAGE is a special page that is used for zero-initialized * data and COW. */ -static unsigned long empty_bad_page_table; -static unsigned long empty_bad_page; unsigned long empty_zero_page; /* @@ -77,8 +66,6 @@ void __init paging_init(void) * Initialize the bad page table and bad page to point * to a couple of allocated pages. */ - empty_bad_page_table = (unsigned long)alloc_bootmem_pages(PAGE_SIZE); - empty_bad_page = (unsigned long)alloc_bootmem_pages(PAGE_SIZE); empty_zero_page = (unsigned long)alloc_bootmem_pages(PAGE_SIZE); memset((void *)empty_zero_page, 0, PAGE_SIZE); diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h index 67fe6dc5211c..0036ea0c7173 100644 --- a/arch/mips/include/asm/pgtable-64.h +++ b/arch/mips/include/asm/pgtable-64.h @@ -31,12 +31,7 @@ * tables. Each page table is also a single 4K page, giving 512 (== * PTRS_PER_PTE) 8 byte ptes. Each pud entry is initialized to point to * invalid_pmd_table, each pmd entry is initialized to point to - * invalid_pte_table, each pte is initialized to 0. When memory is low, - * and a pmd table or a page table allocation fails, empty_bad_pmd_table - * and empty_bad_page_table is returned back to higher layer code, so - * that the failure is recognized later on. Linux does not seem to - * handle these failures very well though. The empty_bad_page_table has - * invalid pte entries in it, to force page faults. + * invalid_pte_table, each pte is initialized to 0. * * Kernel mappings: kernel mappings are held in the swapper_pg_table. * The layout is identical to userspace except it's indexed with the @@ -175,7 +170,6 @@ printk("%s:%d: bad pgd %016lx.\n", __FILE__, __LINE__, pgd_val(e)) extern pte_t invalid_pte_table[PTRS_PER_PTE]; -extern pte_t empty_bad_page_table[PTRS_PER_PTE]; #ifndef __PAGETABLE_PUD_FOLDED /* diff --git a/arch/mn10300/kernel/head.S b/arch/mn10300/kernel/head.S index 73e00fc78072..0b15f759e0d2 100644 --- a/arch/mn10300/kernel/head.S +++ b/arch/mn10300/kernel/head.S @@ -433,14 +433,6 @@ ENTRY(swapper_pg_dir) ENTRY(empty_zero_page) .space PAGE_SIZE - .balign PAGE_SIZE -ENTRY(empty_bad_page) - .space PAGE_SIZE - - .balign PAGE_SIZE -ENTRY(empty_bad_pte_table) - .space PAGE_SIZE - .balign PAGE_SIZE ENTRY(large_page_table) .space PAGE_SIZE diff --git a/arch/sh/kernel/head_64.S b/arch/sh/kernel/head_64.S index defd851abefa..cca491397a28 100644 --- a/arch/sh/kernel/head_64.S +++ b/arch/sh/kernel/head_64.S @@ -101,14 +101,6 @@ mmu_pdtp_cache: .space PAGE_SIZE, 0 - .global empty_bad_page -empty_bad_page: - .space PAGE_SIZE, 0 - - .global empty_bad_pte_table -empty_bad_pte_table: - .space PAGE_SIZE, 0 - .global fpu_in_use fpu_in_use: .quad 0 diff --git a/arch/um/kernel/mem.c b/arch/um/kernel/mem.c index e7437ec62710..3c0e470ea646 100644 --- a/arch/um/kernel/mem.c +++ b/arch/um/kernel/mem.c @@ -22,8 +22,6 @@ /* allocated in paging_init, zeroed in mem_init, and unchanged thereafter */ unsigned long *empty_zero_page = NULL; EXPORT_SYMBOL(empty_zero_page); -/* allocated in paging_init and unchanged thereafter */ -static unsigned long *empty_bad_page = NULL; /* * Initialized during boot, and readonly for initializing page tables @@ -146,7 +144,6 @@ void __init paging_init(void) int i; empty_zero_page = (unsigned long *) alloc_bootmem_low_pages(PAGE_SIZE); - empty_bad_page = (unsigned long *) alloc_bootmem_low_pages(PAGE_SIZE); for (i = 0; i < ARRAY_SIZE(zones_size); i++) zones_size[i] = 0; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index ba2d470d2d0a..048b763e939d 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -17,7 +17,7 @@ * Various page->flags bits: * * PG_reserved is set for special pages, which can never be swapped out. Some - * of them might not even exist (eg empty_bad_page)... + * of them might not even exist... * * The PG_private bitflag is set on pagecache pages if they contain filesystem * specific data (which is normally at page->private). It can be used by -- 2.14.2
