[PATCH] mm: unlink_file_vma, remove_vma
authorHugh Dickins <hugh@veritas.com>
Sun, 30 Oct 2005 01:15:57 +0000 (18:15 -0700)
committerLinus Torvalds <torvalds@g5.osdl.org>
Sun, 30 Oct 2005 04:40:37 +0000 (21:40 -0700)
commita8fb5618dab7e45c8990f3155628d772a9ed45f9
tree77977b8fb2f57c855da9e3168977521e8393776a
parent2c0b381467bc2997be9d741a152f3fc75785eedc
[PATCH] mm: unlink_file_vma, remove_vma

Divide remove_vm_struct into two parts: first anon_vma_unlink plus
unlink_file_vma, to unlink the vma from the list and tree by which rmap or
vmtruncate might find it; then remove_vma to close, fput and free.

The intention here is to do the anon_vma_unlink and unlink_file_vma earlier,
in free_pgtables before freeing any page tables: so we can be sure that any
page tables traversed by rmap and vmtruncate are stable (and other, ordinary
cases are stabilized by holding mmap_sem).

This will be crucial to traversing pgd,pud,pmd without page_table_lock.  But
testing the split-out patch showed that lifting the page_table_lock is
symbiotically necessary to make this change - the lock ordering is wrong to
move those unlinks into free_pgtables while it's under ptlock.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
include/linux/mm.h
mm/mmap.c