linux/mm, branch v4.5

mm/mempool: avoid KASAN marking mempool poison checks as use-after-free

2016-03-12T00:17:47Z

When removing an element from the mempool, mark it as unpoisoned in KASAN before verifying its contents for SLUB/SLAB debugging. Otherwise KASAN will flag the reads checking the element use-after-free writes as use-after-free reads. Signed-off-by: Matthew Dawson Acked-by: Andrey Ryabinin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: use EOPNOTSUPP in hugetlb sysctl handlers

2016-03-09T23:43:42Z

Replace ENOTSUPP with EOPNOTSUPP. If hugepages are not supported, this value is propagated to userspace. EOPNOTSUPP is part of uapi and is widely supported by libc libraries. It gives nicer message to user, rather than: # cat /proc/sys/vm/nr_hugepages cat: /proc/sys/vm/nr_hugepages: Unknown error 524 And also LTP's proc01 test was failing because this ret code (524) was unexpected: proc01 1 TFAIL : proc01.c:396: read failed: /proc/sys/vm/nr_hugepages: errno=???(524): Unknown error 524 proc01 2 TFAIL : proc01.c:396: read failed: /proc/sys/vm/nr_hugepages_mempolicy: errno=???(524): Unknown error 524 proc01 3 TFAIL : proc01.c:396: read failed: /proc/sys/vm/nr_overcommit_hugepages: errno=???(524): Unknown error 524 Signed-off-by: Jan Stancek Acked-by: Naoya Horiguchi Acked-by: Kirill A. Shutemov Acked-by: David Rientjes Acked-by: Hillf Danton Cc: Mike Kravetz Cc: Dave Hansen Cc: Paul Gortmaker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, thp: fix migration of PTE-mapped transparent huge pages

2016-03-09T23:43:42Z

We don't have native support of THP migration, so we have to split huge page into small pages in order to migrate it to different node. This includes PTE-mapped huge pages. I made mistake in refcounting patchset: we don't actually split PTE-mapped huge page in queue_pages_pte_range(), if we step on head page. The result is that the head page is queued for migration, but none of tail pages: putting head page on queue takes pin on the page and any subsequent attempts of split_huge_pages() would fail and we skip queuing tail pages. unmap_and_move_huge_page() will eventually split the huge pages, but only one of 512 pages would get migrated. Let's fix the situation. Fixes: 248db92da13f2507 ("migrate_pages: try to split pages on queuing") Signed-off-by: Kirill A. Shutemov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kasan: add functions to clear stack poison

2016-03-09T23:43:42Z

Functions which the compiler has instrumented for ASAN place poison on the stack shadow upon entry and remove this poison prior to returning. In some cases (e.g. hotplug and idle), CPUs may exit the kernel a number of levels deep in C code. If there are any instrumented functions on this critical path, these will leave portions of the idle thread stack shadow poisoned. If a CPU returns to the kernel via a different path (e.g. a cold entry), then depending on stack frame layout subsequent calls to instrumented functions may use regions of the stack with stale poison, resulting in (spurious) KASAN splats to the console. Contemporary GCCs always add stack shadow poisoning when ASAN is enabled, even when asked to not instrument a function [1], so we can't simply annotate functions on the critical path to avoid poisoning. Instead, this series explicitly removes any stale poison before it can be hit. In the common hotplug case we clear the entire stack shadow in common code, before a CPU is brought online. On architectures which perform a cold return as part of cpu idle may retain an architecture-specific amount of stack contents. To retain the poison for this retained context, the arch code must call the core KASAN code, passing a "watermark" stack pointer value beyond which shadow will be cleared. Architectures which don't perform a cold return as part of idle do not need any additional code. This patch (of 3): Functions which the compiler has instrumented for KASAN place poison on the stack shadow upon entry and remove this poision prior to returning. In some cases (e.g. hotplug and idle), CPUs may exit the kernel a number of levels deep in C code. If there are any instrumented functions on this critical path, these will leave portions of the stack shadow poisoned. If a CPU returns to the kernel via a different path (e.g. a cold entry), then depending on stack frame layout subsequent calls to instrumented functions may use regions of the stack with stale poison, resulting in (spurious) KASAN splats to the console. To avoid this, we must clear stale poison from the stack prior to instrumented functions being called. This patch adds functions to the KASAN core for removing poison from (portions of) a task's stack. These will be used by subsequent patches to avoid problems with hotplug and idle. Signed-off-by: Mark Rutland Acked-by: Catalin Marinas Reviewed-by: Andrey Ryabinin Cc: Alexander Potapenko Cc: Lorenzo Pieralisi Cc: Will Deacon Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: __delete_from_page_cache show Bad page if mapped

2016-03-09T23:43:42Z

Commit e1534ae95004 ("mm: differentiate page_mapped() from page_mapcount() for compound pages") changed the famous BUG_ON(page_mapped(page)) in __delete_from_page_cache() to VM_BUG_ON_PAGE(page_mapped(page)): which gives us more info when CONFIG_DEBUG_VM=y, but nothing at all when not. Although it has not usually been very helpul, being hit long after the error in question, we do need to know if it actually happens on users' systems; but reinstating a crash there is likely to be opposed :) In the non-debug case, pr_alert("BUG: Bad page cache") plus dump_page(), dump_stack(), add_taint() - I don't really believe LOCKDEP_NOW_UNRELIABLE, but that seems to be the standard procedure now. Move that, or the VM_BUG_ON_PAGE(), up before the deletion from tree: so that the unNULLified page->mapping gives a little more information. If the inode is being evicted (rather than truncated), it won't have any vmas left, so it's safe(ish) to assume that the raised mapcount is erroneous, and we can discount it from page_count to avoid leaking the page (I'm less worried by leaking the occasional 4kB, than losing a potential 2MB page with each 4kB page leaked). Signed-off-by: Hugh Dickins Acked-by: Kirill A. Shutemov Cc: Joonsoo Kim Cc: Sasha Levin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/hugetlb: hugetlb_no_page: rate-limit warning message

2016-03-09T23:43:42Z

The warning message "killed due to inadequate hugepage pool" simply indicates that SIGBUS was sent, not that the process was forcibly killed. If the process has a signal handler installed does not fix the problem, this message can rapidly spam the kernel log. On my amd64 dev machine that does not have hugepages configured, I can reproduce the repeated warnings easily by setting vm.nr_hugepages=2 (i.e., 4 megabytes of huge pages) and running something that sets a signal handler and forks, like #include #include #include #include sig_atomic_t counter = 10; void handler(int signal) { if (counter-- == 0) exit(0); } int main(void) { int status; char *addr = mmap(NULL, 4 * 1048576, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, -1, 0); if (addr == MAP_FAILED) {perror("mmap"); return 1;} *addr = 'x'; switch (fork()) { case -1: perror("fork"); return 1; case 0: signal(SIGBUS, handler); *addr = 'x'; break; default: *addr = 'x'; wait(&status); if (WIFSIGNALED(status)) { psignal(WTERMSIG(status), "child"); } break; } } Signed-off-by: Geoffrey Thomas Cc: Naoya Horiguchi Cc: Hillf Danton Cc: "Kirill A. Shutemov" Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

dax: move writeback calls into the filesystems

2016-02-27T18:28:52Z

Previously calls to dax_writeback_mapping_range() for all DAX filesystems (ext2, ext4 & xfs) were centralized in filemap_write_and_wait_range(). dax_writeback_mapping_range() needs a struct block_device, and it used to get that from inode->i_sb->s_bdev. This is correct for normal inodes mounted on ext2, ext4 and XFS filesystems, but is incorrect for DAX raw block devices and for XFS real-time files. Instead, call dax_writeback_mapping_range() directly from the filesystem ->writepages function so that it can supply us with a valid block device. This also fixes DAX code to properly flush caches in response to sync(2). Signed-off-by: Ross Zwisler Signed-off-by: Jan Kara Cc: Al Viro Cc: Dan Williams Cc: Dave Chinner Cc: Jens Axboe Cc: Matthew Wilcox Cc: Theodore Ts'o Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: numa: quickly fail allocations for NUMA balancing on full nodes

2016-02-27T18:28:52Z

Commit 4167e9b2cf10 ("mm: remove GFP_THISNODE") removed the GFP_THISNODE flag combination due to confusing semantics. It noted that alloc_misplaced_dst_page() was one such user after changes made by commit e97ca8e5b864 ("mm: fix GFP_THISNODE callers and clarify"). Unfortunately when GFP_THISNODE was removed, users of alloc_misplaced_dst_page() started waking kswapd and entering direct reclaim because the wrong GFP flags are cleared. The consequence is that workloads that used to fit into memory now get reclaimed which is addressed by this patch. The problem can be demonstrated with "mutilate" that exercises memcached which is software dedicated to memory object caching. The configuration uses 80% of memory and is run 3 times for varying numbers of clients. The results on a 4-socket NUMA box are mutilate 4.4.0 4.4.0 vanilla numaswap-v1 Hmean 1 8394.71 ( 0.00%) 8395.32 ( 0.01%) Hmean 4 30024.62 ( 0.00%) 34513.54 ( 14.95%) Hmean 7 32821.08 ( 0.00%) 70542.96 (114.93%) Hmean 12 55229.67 ( 0.00%) 93866.34 ( 69.96%) Hmean 21 39438.96 ( 0.00%) 85749.21 (117.42%) Hmean 30 37796.10 ( 0.00%) 50231.49 ( 32.90%) Hmean 47 18070.91 ( 0.00%) 38530.13 (113.22%) The metric is queries/second with the more the better. The results are way outside of the noise and the reason for the improvement is obvious from some of the vmstats 4.4.0 4.4.0 vanillanumaswap-v1r1 Minor Faults 1929399272 2146148218 Major Faults 19746529 3567 Swap Ins 57307366 9913 Swap Outs 50623229 17094 Allocation stalls 35909 443 DMA allocs 0 0 DMA32 allocs 72976349 170567396 Normal allocs 5306640898 5310651252 Movable allocs 0 0 Direct pages scanned 404130893 799577 Kswapd pages scanned 160230174 0 Kswapd pages reclaimed 55928786 0 Direct pages reclaimed 1843936 41921 Page writes file 2391 0 Page writes anon 50623229 17094 The vanilla kernel is swapping like crazy with large amounts of direct reclaim and kswapd activity. The figures are aggregate but it's known that the bad activity is throughout the entire test. Note that simple streaming anon/file memory consumers also see this problem but it's not as obvious. In those cases, kswapd is awake when it should not be. As there are at least two reclaim-related bugs out there, it's worth spelling out the user-visible impact. This patch only addresses bugs related to excessive reclaim on NUMA hardware when the working set is larger than a NUMA node. There is a bug related to high kswapd CPU usage but the reports are against laptops and other UMA hardware and is not addressed by this patch. Signed-off-by: Mel Gorman Cc: Vlastimil Babka Cc: Johannes Weiner Cc: David Rientjes Cc: [4.1+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: thp: fix SMP race condition between THP page fault and MADV_DONTNEED

2016-02-27T18:28:52Z

pmd_trans_unstable()/pmd_none_or_trans_huge_or_clear_bad() were introduced to locklessy (but atomically) detect when a pmd is a regular (stable) pmd or when the pmd is unstable and can infinitely transition from pmd_none() and pmd_trans_huge() from under us, while only holding the mmap_sem for reading (for writing not). While holding the mmap_sem only for reading, MADV_DONTNEED can run from under us and so before we can assume the pmd to be a regular stable pmd we need to compare it against pmd_none() and pmd_trans_huge() in an atomic way, with pmd_trans_unstable(). The old pmd_trans_huge() left a tiny window for a race. Useful applications are unlikely to notice the difference as doing MADV_DONTNEED concurrently with a page fault would lead to undefined behavior. [akpm@linux-foundation.org: tidy up comment grammar/layout] Signed-off-by: Andrea Arcangeli Reported-by: Kirill A. Shutemov Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

thp: call pmdp_invalidate() with correct virtual address

2016-02-24T18:46:30Z

Sebastian Ott and Gerald Schaefer reported random crashes on s390. It was bisected to my THP refcounting patchset. The problem is that pmdp_invalidated() called with wrong virtual address. It got offset up by HPAGE_PMD_SIZE by loop over ptes. The solution is to introduce new variable to be used in loop and don't touch 'haddr'. Signed-off-by: Kirill A. Shutemov Reported-and-tested-by: Gerald Schaefer Reported-and-tested-by Sebastian Ott Reviewed-by: Will Deacon Cc: Christian Borntraeger Cc: Martin Schwidefsky Cc: Aneesh Kumar K.V Cc: Andrea Arcangeli Cc: Sasha Levin Cc: Jerome Marchand Cc: Andrew Morton Signed-off-by: Linus Torvalds