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| author | Hugh Dickins <hugh@veritas.com> | 2005-06-21 17:15:12 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-06-21 18:46:21 -0700 |
| commit | c475a8ab625d567eacf5e30ec35d6d8704558062 (patch) | |
| tree | 0971bef7b876f1b3eb160621fc2b61cb5313827b /mm/memory.c | |
| parent | d296e9cd02c92e576ecce5344026a4df4353cdb2 (diff) | |
| download | lwn-c475a8ab625d567eacf5e30ec35d6d8704558062.tar.gz lwn-c475a8ab625d567eacf5e30ec35d6d8704558062.zip | |
[PATCH] can_share_swap_page: use page_mapcount
Remember that ironic get_user_pages race? when the raised page_count on a
page swapped out led do_wp_page to decide that it had to copy on write, so
substituted a different page into userspace. 2.6.7 onwards have Andrea's
solution, where try_to_unmap_one backs out if it finds page_count raised.
Which works, but is unsatisfying (rmap.c has no other page_count heuristics),
and was found a few months ago to hang an intensive page migration test. A
year ago I was hesitant to engage page_mapcount, now it seems the right fix.
So remove the page_count hack from try_to_unmap_one; and use activate_page in
unuse_mm when dropping lock, to replace its secondary effect of helping
swapoff to make progress in that case.
Simplify can_share_swap_page (now called only on anonymous pages) to check
page_mapcount + page_swapcount == 1: still needs the page lock to stabilize
their (pessimistic) sum, but does not need swapper_space.tree_lock for that.
In do_swap_page, move swap_free and unlock_page below page_add_anon_rmap, to
keep sum on the high side, and correct when can_share_swap_page called.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/memory.c')
| -rw-r--r-- | mm/memory.c | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/mm/memory.c b/mm/memory.c index 1c0a3db78a05..da91b7bf9986 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1686,10 +1686,6 @@ static int do_swap_page(struct mm_struct * mm, } /* The page isn't present yet, go ahead with the fault. */ - - swap_free(entry); - if (vm_swap_full()) - remove_exclusive_swap_page(page); inc_mm_counter(mm, rss); pte = mk_pte(page, vma->vm_page_prot); @@ -1697,12 +1693,16 @@ static int do_swap_page(struct mm_struct * mm, pte = maybe_mkwrite(pte_mkdirty(pte), vma); write_access = 0; } - unlock_page(page); flush_icache_page(vma, page); set_pte_at(mm, address, page_table, pte); page_add_anon_rmap(page, vma, address); + swap_free(entry); + if (vm_swap_full()) + remove_exclusive_swap_page(page); + unlock_page(page); + if (write_access) { if (do_wp_page(mm, vma, address, page_table, pmd, pte) == VM_FAULT_OOM) |