WSL2-Linux-Kernel/arch/sh
David Howells 8feae13110 NOMMU: Make VMAs per MM as for MMU-mode linux
Make VMAs per mm_struct as for MMU-mode linux.  This solves two problems:

 (1) In SYSV SHM where nattch for a segment does not reflect the number of
     shmat's (and forks) done.

 (2) In mmap() where the VMA's vm_mm is set to point to the parent mm by an
     exec'ing process when VM_EXECUTABLE is specified, regardless of the fact
     that a VMA might be shared and already have its vm_mm assigned to another
     process or a dead process.

A new struct (vm_region) is introduced to track a mapped region and to remember
the circumstances under which it may be shared and the vm_list_struct structure
is discarded as it's no longer required.

This patch makes the following additional changes:

 (1) Regions are now allocated with alloc_pages() rather than kmalloc() and
     with no recourse to __GFP_COMP, so the pages are not composite.  Instead,
     each page has a reference on it held by the region.  Anything else that is
     interested in such a page will have to get a reference on it to retain it.
     When the pages are released due to unmapping, each page is passed to
     put_page() and will be freed when the page usage count reaches zero.

 (2) Excess pages are trimmed after an allocation as the allocation must be
     made as a power-of-2 quantity of pages.

 (3) VMAs are added to the parent MM's R/B tree and mmap lists.  As an MM may
     end up with overlapping VMAs within the tree, the VMA struct address is
     appended to the sort key.

 (4) Non-anonymous VMAs are now added to the backing inode's prio list.

 (5) Holes may be punched in anonymous VMAs with munmap(), releasing parts of
     the backing region.  The VMA and region structs will be split if
     necessary.

 (6) sys_shmdt() only releases one attachment to a SYSV IPC shared memory
     segment instead of all the attachments at that addresss.  Multiple
     shmat()'s return the same address under NOMMU-mode instead of different
     virtual addresses as under MMU-mode.

 (7) Core dumping for ELF-FDPIC requires fewer exceptions for NOMMU-mode.

 (8) /proc/maps is now the global list of mapped regions, and may list bits
     that aren't actually mapped anywhere.

 (9) /proc/meminfo gains a line (tagged "MmapCopy") that indicates the amount
     of RAM currently allocated by mmap to hold mappable regions that can't be
     mapped directly.  These are copies of the backing device or file if not
     anonymous.

These changes make NOMMU mode more similar to MMU mode.  The downside is that
NOMMU mode requires some extra memory to track things over NOMMU without this
patch (VMAs are no longer shared, and there are now region structs).

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Mike Frysinger <vapier.adi@gmail.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
2009-01-08 12:04:47 +00:00
..
boards sh: mach-sh03: Fix up pata_platform build breakage. 2008-12-22 18:44:49 +09:00
boot sh: FTRACE renamed to FUNCTION_TRACER. 2008-10-31 16:20:36 +09:00
cchips sh: Switch HD64461 from hw_interrupt_type to irq_chip 2008-12-22 18:43:50 +09:00
configs sh: Add a simple edosk7705_defconfig for build testing. 2008-12-22 18:44:46 +09:00
drivers PCI: sh: use generic INTx swizzle from PCI core 2009-01-07 11:13:15 -08:00
include NOMMU: Make VMAs per MM as for MMU-mode linux 2009-01-08 12:04:47 +00:00
kernel remove linux/hardirq.h from asm-generic/local.h 2009-01-06 15:59:13 -08:00
lib sh: Add plain udivsi3 (not _i4*) for gcc-4.1 and lower. 2008-12-22 18:43:53 +09:00
lib64 sh: Provide sdivsi3/udivsi3/udivdi3 for sh64, kill off libgcc linking. 2008-12-22 18:44:05 +09:00
math-emu sh: Fix up the math-emu build. 2007-06-11 15:57:42 +09:00
mm mm: show node to memory section relationship with symlinks in sysfs 2009-01-06 15:59:00 -08:00
oprofile sh: oprofile: Fix up the module build. 2008-12-22 19:32:27 +09:00
tools sh: Consolidate rsk7203/7201 in to a new mach-rsk. 2008-12-22 18:44:02 +09:00
Kconfig sh: dma: Kill off ISA DMA wrapper. 2008-12-22 18:44:47 +09:00
Kconfig.cpu sh: Disable big endian for SH-5. 2008-02-14 14:22:10 +09:00
Kconfig.debug sh: Conditionalize the code dumper on CONFIG_DUMP_CODE. 2008-12-22 18:44:47 +09:00
Makefile sh: mach-rsk: Use uImage generation by default for rsk7201/7203. 2008-12-22 18:44:49 +09:00