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mm: fix bad rss-counter if remap_file_pages raced migration

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Fix some "Bad rss-counter state" reports on exit, arising from the
interaction between page migration and remap_file_pages(): zap_pte()
must count a migration entry when zapping it.

And yes, it is possible (though very unusual) to find an anon page or
swap entry in a VM_SHARED nonlinear mapping: coming from that horrid
get_user_pages(write, force) case which COWs even in a shared mapping.

Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Sasha Levin sasha.levin@oracle.com>
Tested-by: Dave Jones davej@redhat.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2014-03-18 17:38:38 -07:00 committed by Linus Torvalds
parent 7c1cfacca2
commit 887843961c
1 changed files with 23 additions and 7 deletions
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30
mm/fremap.c
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@ -23,28 +23,44 @@
#include "internal.h"
static int mm_counter(struct page *page)
{
return PageAnon(page) ? MM_ANONPAGES : MM_FILEPAGES;
}
static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long addr, pte_t *ptep)
{
pte_t pte = *ptep;
struct page *page;
swp_entry_t entry;
if (pte_present(pte)) {
struct page *page;
flush_cache_page(vma, addr, pte_pfn(pte));
pte = ptep_clear_flush(vma, addr, ptep);
page = vm_normal_page(vma, addr, pte);
if (page) {
if (pte_dirty(pte))
set_page_dirty(page);
update_hiwater_rss(mm);
dec_mm_counter(mm, mm_counter(page));
page_remove_rmap(page);
page_cache_release(page);
update_hiwater_rss(mm);
dec_mm_counter(mm, MM_FILEPAGES);
}
} else {
if (!pte_file(pte))
free_swap_and_cache(pte_to_swp_entry(pte));
} else { /* zap_pte() is not called when pte_none() */
if (!pte_file(pte)) {
update_hiwater_rss(mm);
entry = pte_to_swp_entry(pte);
if (non_swap_entry(entry)) {
if (is_migration_entry(entry)) {
page = migration_entry_to_page(entry);
dec_mm_counter(mm, mm_counter(page));
}
} else {
free_swap_and_cache(entry);
dec_mm_counter(mm, MM_SWAPENTS);
}
}
pte_clear_not_present_full(mm, addr, ptep, 0);
}
}