From 910321ea817a202ff70fac666e37e2c8e2f88823 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Thu, 9 Sep 2010 16:38:07 -0700 Subject: swap: revert special hibernation allocation Please revert 2.6.36-rc commit d2997b1042ec150616c1963b5e5e919ffd0b0ebf "hibernation: freeze swap at hibernation". It complicated matters by adding a second swap allocation path, just for hibernation; without in any way fixing the issue that it was intended to address - page reclaim after fixing the hibernation image might free swap from a page already imaged as swapcache, letting its swap be reallocated to store a different page of the image: resulting in data corruption if the imaged page were freed as clean then swapped back in. Pages freed to si->swap_map were still in danger of being reallocated by the alternative allocation path. I guess it inadvertently fixed slow SSD swap allocation for hibernation, as reported by Nigel Cunningham: by missing out the discards that occur on the usual swap allocation path; but that was unintentional, and needs a separate fix. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: KOSAKI Motohiro Cc: "Rafael J. Wysocki" Cc: Ondrej Zary Cc: Andrea Gelmini Cc: Balbir Singh Cc: Andrea Arcangeli Cc: Nigel Cunningham Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 94 ++++++++++++++--------------------------------------------- 1 file changed, 22 insertions(+), 72 deletions(-) (limited to 'mm/swapfile.c') diff --git a/mm/swapfile.c b/mm/swapfile.c index 1f3f9c59a73a..f08d165871b3 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -47,8 +47,6 @@ long nr_swap_pages; long total_swap_pages; static int least_priority; -static bool swap_for_hibernation; - static const char Bad_file[] = "Bad swap file entry "; static const char Unused_file[] = "Unused swap file entry "; static const char Bad_offset[] = "Bad swap offset entry "; @@ -453,8 +451,6 @@ swp_entry_t get_swap_page(void) spin_lock(&swap_lock); if (nr_swap_pages <= 0) goto noswap; - if (swap_for_hibernation) - goto noswap; nr_swap_pages--; for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) { @@ -487,6 +483,28 @@ noswap: return (swp_entry_t) {0}; } +/* The only caller of this function is now susupend routine */ +swp_entry_t get_swap_page_of_type(int type) +{ + struct swap_info_struct *si; + pgoff_t offset; + + spin_lock(&swap_lock); + si = swap_info[type]; + if (si && (si->flags & SWP_WRITEOK)) { + nr_swap_pages--; + /* This is called for allocating swap entry, not cache */ + offset = scan_swap_map(si, 1); + if (offset) { + spin_unlock(&swap_lock); + return swp_entry(type, offset); + } + nr_swap_pages++; + } + spin_unlock(&swap_lock); + return (swp_entry_t) {0}; +} + static struct swap_info_struct *swap_info_get(swp_entry_t entry) { struct swap_info_struct *p; @@ -746,74 +764,6 @@ int mem_cgroup_count_swap_user(swp_entry_t ent, struct page **pagep) #endif #ifdef CONFIG_HIBERNATION - -static pgoff_t hibernation_offset[MAX_SWAPFILES]; -/* - * Once hibernation starts to use swap, we freeze swap_map[]. Otherwise, - * saved swap_map[] image to the disk will be an incomplete because it's - * changing without synchronization with hibernation snap shot. - * At resume, we just make swap_for_hibernation=false. We can forget - * used maps easily. - */ -void hibernation_freeze_swap(void) -{ - int i; - - spin_lock(&swap_lock); - - printk(KERN_INFO "PM: Freeze Swap\n"); - swap_for_hibernation = true; - for (i = 0; i < MAX_SWAPFILES; i++) - hibernation_offset[i] = 1; - spin_unlock(&swap_lock); -} - -void hibernation_thaw_swap(void) -{ - spin_lock(&swap_lock); - if (swap_for_hibernation) { - printk(KERN_INFO "PM: Thaw Swap\n"); - swap_for_hibernation = false; - } - spin_unlock(&swap_lock); -} - -/* - * Because updateing swap_map[] can make not-saved-status-change, - * we use our own easy allocator. - * Please see kernel/power/swap.c, Used swaps are recorded into - * RB-tree. - */ -swp_entry_t get_swap_for_hibernation(int type) -{ - pgoff_t off; - swp_entry_t val = {0}; - struct swap_info_struct *si; - - spin_lock(&swap_lock); - - si = swap_info[type]; - if (!si || !(si->flags & SWP_WRITEOK)) - goto done; - - for (off = hibernation_offset[type]; off < si->max; ++off) { - if (!si->swap_map[off]) - break; - } - if (off < si->max) { - val = swp_entry(type, off); - hibernation_offset[type] = off + 1; - } -done: - spin_unlock(&swap_lock); - return val; -} - -void swap_free_for_hibernation(swp_entry_t ent) -{ - /* Nothing to do */ -} - /* * Find the swap type that corresponds to given device (if any). * -- cgit v1.2.3-59-g8ed1b