From d7782145e1ad537df4ce74e58c50f1f732a1462d Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Sat, 6 Oct 2018 10:56:11 -0700 Subject: filesystem-dax: Fix dax_layout_busy_page() livelock In the presence of multi-order entries the typical pagevec_lookup_entries() pattern may loop forever: while (index < end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { ... for (i = 0; i < pagevec_count(&pvec); i++) { index = indices[i]; ... } index++; /* BUG */ } The loop updates 'index' for each index found and then increments to the next possible page to continue the lookup. However, if the last entry in the pagevec is multi-order then the next possible page index is more than 1 page away. Fix this locally for the filesystem-dax case by checking for dax-multi-order entries. Going forward new users of multi-order entries need to be similarly careful, or we need a generic way to report the page increment in the radix iterator. Fixes: 5fac7408d828 ("mm, fs, dax: handle layout changes to pinned dax...") Cc: Cc: Ross Zwisler Cc: Matthew Wilcox Reviewed-by: Jan Kara Signed-off-by: Dan Williams --- fs/dax.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 4becbf168b7f..0fb270f0a0ef 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -666,6 +666,8 @@ struct page *dax_layout_busy_page(struct address_space *mapping) while (index < end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { + pgoff_t nr_pages = 1; + for (i = 0; i < pagevec_count(&pvec); i++) { struct page *pvec_ent = pvec.pages[i]; void *entry; @@ -680,8 +682,15 @@ struct page *dax_layout_busy_page(struct address_space *mapping) xa_lock_irq(&mapping->i_pages); entry = get_unlocked_mapping_entry(mapping, index, NULL); - if (entry) + if (entry) { page = dax_busy_page(entry); + /* + * Account for multi-order entries at + * the end of the pagevec. + */ + if (i + 1 >= pagevec_count(&pvec)) + nr_pages = 1UL << dax_radix_order(entry); + } put_unlocked_mapping_entry(mapping, index, entry); xa_unlock_irq(&mapping->i_pages); if (page) @@ -696,7 +705,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping) */ pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); - index++; + index += nr_pages; if (page) break; -- cgit v1.2.3-70-g09d2 From 4628a64591e6cee181237060961e98c615c33966 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 9 Oct 2018 12:19:17 +0200 Subject: mm: Preserve _PAGE_DEVMAP across mprotect() calls Currently _PAGE_DEVMAP bit is not preserved in mprotect(2) calls. As a result we will see warnings such as: BUG: Bad page map in process JobWrk0013 pte:800001803875ea25 pmd:7624381067 addr:00007f0930720000 vm_flags:280000f9 anon_vma: (null) mapping:ffff97f2384056f0 index:0 file:457-000000fe00000030-00000009-000000ca-00000001_2001.fileblock fault:xfs_filemap_fault [xfs] mmap:xfs_file_mmap [xfs] readpage: (null) CPU: 3 PID: 15848 Comm: JobWrk0013 Tainted: G W 4.12.14-2.g7573215-default #1 SLE12-SP4 (unreleased) Hardware name: Intel Corporation S2600WFD/S2600WFD, BIOS SE5C620.86B.01.00.0833.051120182255 05/11/2018 Call Trace: dump_stack+0x5a/0x75 print_bad_pte+0x217/0x2c0 ? enqueue_task_fair+0x76/0x9f0 _vm_normal_page+0xe5/0x100 zap_pte_range+0x148/0x740 unmap_page_range+0x39a/0x4b0 unmap_vmas+0x42/0x90 unmap_region+0x99/0xf0 ? vma_gap_callbacks_rotate+0x1a/0x20 do_munmap+0x255/0x3a0 vm_munmap+0x54/0x80 SyS_munmap+0x1d/0x30 do_syscall_64+0x74/0x150 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 ... when mprotect(2) gets used on DAX mappings. Also there is a wide variety of other failures that can result from the missing _PAGE_DEVMAP flag when the area gets used by get_user_pages() later. Fix the problem by including _PAGE_DEVMAP in a set of flags that get preserved by mprotect(2). Fixes: 69660fd797c3 ("x86, mm: introduce _PAGE_DEVMAP") Fixes: ebd31197931d ("powerpc/mm: Add devmap support for ppc64") Cc: Signed-off-by: Jan Kara Acked-by: Michal Hocko Reviewed-by: Johannes Thumshirn Signed-off-by: Dan Williams --- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 ++-- arch/x86/include/asm/pgtable_types.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index 2fdc865ca374..2a2486526d1f 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -114,7 +114,7 @@ */ #define _HPAGE_CHG_MASK (PTE_RPN_MASK | _PAGE_HPTEFLAGS | _PAGE_DIRTY | \ _PAGE_ACCESSED | H_PAGE_THP_HUGE | _PAGE_PTE | \ - _PAGE_SOFT_DIRTY) + _PAGE_SOFT_DIRTY | _PAGE_DEVMAP) /* * user access blocked by key */ @@ -132,7 +132,7 @@ */ #define _PAGE_CHG_MASK (PTE_RPN_MASK | _PAGE_HPTEFLAGS | _PAGE_DIRTY | \ _PAGE_ACCESSED | _PAGE_SPECIAL | _PAGE_PTE | \ - _PAGE_SOFT_DIRTY) + _PAGE_SOFT_DIRTY | _PAGE_DEVMAP) #define H_PTE_PKEY (H_PTE_PKEY_BIT0 | H_PTE_PKEY_BIT1 | H_PTE_PKEY_BIT2 | \ H_PTE_PKEY_BIT3 | H_PTE_PKEY_BIT4) diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index b64acb08a62b..106b7d0e2dae 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -124,7 +124,7 @@ */ #define _PAGE_CHG_MASK (PTE_PFN_MASK | _PAGE_PCD | _PAGE_PWT | \ _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY | \ - _PAGE_SOFT_DIRTY) + _PAGE_SOFT_DIRTY | _PAGE_DEVMAP) #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE) /* -- cgit v1.2.3-70-g09d2