kernel.git/mm/swapfile.c, branch linux-4.20.y

mm/swap: use nr_node_ids for avail_lists in swap_info_struct

2019-01-26T08:20:50Z

[ Upstream commit 66f71da9dd38af17dc17209cdde7987d4679a699 ] Since a2468cc9bfdf ("swap: choose swap device according to numa node"), avail_lists field of swap_info_struct is changed to an array with MAX_NUMNODES elements. This made swap_info_struct size increased to 40KiB and needs an order-4 page to hold it. This is not optimal in that: 1 Most systems have way less than MAX_NUMNODES(1024) nodes so it is a waste of memory; 2 It could cause swapon failure if the swap device is swapped on after system has been running for a while, due to no order-4 page is available as pointed out by Vasily Averin. Solve the above two issues by using nr_node_ids(which is the actual possible node number the running system has) for avail_lists instead of MAX_NUMNODES. nr_node_ids is unknown at compile time so can't be directly used when declaring this array. What I did here is to declare avail_lists as zero element array and allocate space for it when allocating space for swap_info_struct. The reason why keep using array but not pointer is plist_for_each_entry needs the field to be part of the struct, so pointer will not work. This patch is on top of Vasily Averin's fix commit. I think the use of kvzalloc for swap_info_struct is still needed in case nr_node_ids is really big on some systems. Link: http://lkml.kernel.org/r/20181115083847.GA11129@intel.com Signed-off-by: Aaron Lu Reviewed-by: Andrew Morton Acked-by: Michal Hocko Cc: Vasily Averin Cc: Huang Ying Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin

mm, swap: fix swapoff with KSM pages

2019-01-13T08:24:04Z

commit 7af7a8e19f0c5425ff639b0f0d2d244c2a647724 upstream. KSM pages may be mapped to the multiple VMAs that cannot be reached from one anon_vma. So during swapin, a new copy of the page need to be generated if a different anon_vma is needed, please refer to comments of ksm_might_need_to_copy() for details. During swapoff, unuse_vma() uses anon_vma (if available) to locate VMA and virtual address mapped to the page, so not all mappings to a swapped out KSM page could be found. So in try_to_unuse(), even if the swap count of a swap entry isn't zero, the page needs to be deleted from swap cache, so that, in the next round a new page could be allocated and swapin for the other mappings of the swapped out KSM page. But this contradicts with the THP swap support. Where the THP could be deleted from swap cache only after the swap count of every swap entry in the huge swap cluster backing the THP has reach 0. So try_to_unuse() is changed in commit e07098294adf ("mm, THP, swap: support to reclaim swap space for THP swapped out") to check that before delete a page from swap cache, but this has broken KSM swapoff too. Fortunately, KSM is for the normal pages only, so the original behavior for KSM pages could be restored easily via checking PageTransCompound(). That is how this patch works. The bug is introduced by e07098294adf ("mm, THP, swap: support to reclaim swap space for THP swapped out"), which is merged by v4.14-rc1. So I think we should backport the fix to from 4.14 on. But Hugh thinks it may be rare for the KSM pages being in the swap device when swapoff, so nobody reports the bug so far. Link: http://lkml.kernel.org/r/20181226051522.28442-1-ying.huang@intel.com Fixes: e07098294adf ("mm, THP, swap: support to reclaim swap space for THP swapped out") Signed-off-by: "Huang, Ying" Reported-by: Hugh Dickins Tested-by: Hugh Dickins Acked-by: Hugh Dickins Cc: Rik van Riel Cc: Johannes Weiner Cc: Minchan Kim Cc: Shaohua Li Cc: Daniel Jordan Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm/swapfile.c: use kvzalloc for swap_info_struct allocation

2018-11-18T18:15:09Z

Commit a2468cc9bfdf ("swap: choose swap device according to numa node") changed 'avail_lists' field of 'struct swap_info_struct' to an array. In popular linux distros it increased size of swap_info_struct up to 40 Kbytes and now swap_info_struct allocation requires order-4 page. Switch to kvzmalloc allows to avoid unexpected allocation failures. Link: http://lkml.kernel.org/r/fc23172d-3c75-21e2-d551-8b1808cbe593@virtuozzo.com Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node") Signed-off-by: Vasily Averin Acked-by: Aaron Lu Acked-by: Michal Hocko Reviewed-by: Andrew Morton Cc: Huang Ying Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: export add_swap_extent()

2018-10-26T23:38:15Z

Btrfs currently does not support swap files because swap's use of bmap does not work with copy-on-write and multiple devices. See 35054394c4b3 ("Btrfs: stop providing a bmap operation to avoid swapfile corruptions"). However, the swap code has a mechanism for the filesystem to manually add swap extents using add_swap_extent() from the ->swap_activate() aop. iomap has done this since 67482129cdab ("iomap: add a swapfile activation function"). Btrfs will do the same in a later patch, so export add_swap_extent(). Link: http://lkml.kernel.org/r/bb1208575e02829aae51b538709476964f97b1ea.1536704650.git.osandov@fb.com Signed-off-by: Omar Sandoval Reviewed-by: Andrew Morton Cc: David Sterba Cc: Johannes Weiner Cc: Nikolay Borisov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: split SWP_FILE into SWP_ACTIVATED and SWP_FS

2018-10-26T23:38:15Z

The SWP_FILE flag serves two purposes: to make swap_{read,write}page() go through the filesystem, and to make swapoff() call ->swap_deactivate(). For Btrfs, we want the latter but not the former, so split this flag into two. This makes us always call ->swap_deactivate() if ->swap_activate() succeeded, not just if it didn't add any swap extents itself. This also resolves the issue of the very misleading name of SWP_FILE, which is only used for swap files over NFS. Link: http://lkml.kernel.org/r/6d63d8668c4287a4f6d203d65696e96f80abdfc7.1536704650.git.osandov@fb.com Signed-off-by: Omar Sandoval Reviewed-by: Nikolay Borisov Reviewed-by: Andrew Morton Cc: Johannes Weiner Cc: David Sterba Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/swapfile.c: clear si->swap_map[] in swap_free_cluster()

2018-10-26T23:25:19Z

si->swap_map[] of the swap entries in cluster needs to be cleared during freeing. Previously, this is done in the caller of swap_free_cluster(). This may cause code duplication (one user now, will add more users later) and lock/unlock cluster unnecessarily. In this patch, the clearing code is moved to swap_free_cluster() to avoid the downside. Link: http://lkml.kernel.org/r/20180827075535.17406-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" Reviewed-by: Andrew Morton Cc: Dave Hansen Cc: Michal Hocko Cc: Johannes Weiner Cc: Shaohua Li Cc: Hugh Dickins Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/swapfile.c: call free_swap_slot() in __swap_entry_free()

2018-10-26T23:25:19Z

This is a code cleanup patch without functionality change. Originally, when __swap_entry_free() is called, and its return value is 0, free_swap_slot() will always be called to free the swap entry to the per-CPU pool. So move the call to free_swap_slot() to __swap_entry_free() to simplify the code. Link: http://lkml.kernel.org/r/20180827075535.17406-3-ying.huang@intel.com Signed-off-by: "Huang, Ying" Reviewed-by: Andrew Morton Cc: Dave Hansen Cc: Michal Hocko Cc: Johannes Weiner Cc: Shaohua Li Cc: Hugh Dickins Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/swapfile.c: use __try_to_reclaim_swap() in free_swap_and_cache()

2018-10-26T23:25:19Z

The code path to reclaim the swap entry in free_swap_and_cache() is almost same as that of __try_to_reclaim_swap(). The largest difference is just coding style. So the support to the additional requirement of free_swap_and_cache() is added into __try_to_reclaim_swap(). free_swap_and_cache() is changed to call __try_to_reclaim_swap(), and delete the duplicated code. This will improve code readability and reduce the potential bugs. There are 2 functionality differences between __try_to_reclaim_swap() and swap entry reclaim code of free_swap_and_cache(). - free_swap_and_cache() only reclaims the swap entry if the page is unmapped or swap is getting full. The support has been added into __try_to_reclaim_swap(). - try_to_free_swap() (called by __try_to_reclaim_swap()) checks pm_suspended_storage(), while free_swap_and_cache() not. I think this is OK. Because the page and the swap entry can be reclaimed later eventually. Link: http://lkml.kernel.org/r/20180827075535.17406-2-ying.huang@intel.com Signed-off-by: "Huang, Ying" Reviewed-by: Andrew Morton Cc: Dave Hansen Cc: Michal Hocko Cc: Johannes Weiner Cc: Shaohua Li Cc: Hugh Dickins Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/swapfile.c: put_swap_page: share more between huge/normal code path

2018-08-22T17:52:44Z

In this patch, locking related code is shared between huge/normal code path in put_swap_page() to reduce code duplication. The `free_entries == 0` case is merged into the more general `free_entries != SWAPFILE_CLUSTER` case, because the new locking method makes it easy. The added lines is same as the removed lines. But the code size is increased when CONFIG_TRANSPARENT_HUGEPAGE=n. text data bss dec hex filename base: 24123 2004 340 26467 6763 mm/swapfile.o unified: 24485 2004 340 26829 68cd mm/swapfile.o Dig on step deeper with `size -A mm/swapfile.o` for base and unified kernel and compare the result, yields, -.text 17723 0 +.text 17835 0 -.orc_unwind_ip 1380 0 +.orc_unwind_ip 1480 0 -.orc_unwind 2070 0 +.orc_unwind 2220 0 -Total 26686 +Total 27048 The total difference is the same. The text segment difference is much smaller: 112. More difference comes from the ORC unwinder segments: (1480 + 2220) - (1380 + 2070) = 250. If the frame pointer unwinder is used, this costs nothing. Link: http://lkml.kernel.org/r/20180720071845.17920-9-ying.huang@intel.com Signed-off-by: "Huang, Ying" Reviewed-by: Daniel Jordan Acked-by: Dave Hansen Cc: Michal Hocko Cc: Johannes Weiner Cc: Shaohua Li Cc: Hugh Dickins Cc: Minchan Kim Cc: Rik van Riel Cc: Dan Williams Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/swapfile.c: add __swap_entry_free_locked()

2018-08-22T17:52:44Z

The part of __swap_entry_free() with lock held is separated into a new function __swap_entry_free_locked(). Because we want to reuse that piece of code in some other places. Just mechanical code refactoring, there is no any functional change in this function. Link: http://lkml.kernel.org/r/20180720071845.17920-8-ying.huang@intel.com Signed-off-by: "Huang, Ying" Reviewed-by: Daniel Jordan Acked-by: Dave Hansen Cc: Michal Hocko Cc: Johannes Weiner Cc: Shaohua Li Cc: Hugh Dickins Cc: Minchan Kim Cc: Rik van Riel Cc: Dan Williams Cc: Matthew Wilcox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds