• Hugh Dickins's avatar
    [PATCH] mm: unlink_file_vma, remove_vma · a8fb5618
    Hugh Dickins authored
    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: default avatarHugh Dickins <hugh@veritas.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    a8fb5618
mmap.c 53.5 KB