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![Peter Xu](/assets/img/avatar_default.png)
We tried to do something similar inb569a17607
("userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork") previously, but it's not doing it all right.. A few fixes around the code path: 1. We were referencing VM_UFFD_WP vm_flags on the _old_ vma rather than the new vma. That's overlooked inb569a17607
, so it won't work as expected. Thanks to the recent rework on fork code (7a4830c380
), we can easily get the new vma now, so switch the checks to that. 2. Dropping the uffd-wp bit in copy_huge_pmd() could be wrong if the huge pmd is a migration huge pmd. When it happens, instead of using pmd_uffd_wp(), we should use pmd_swp_uffd_wp(). The fix is simply to handle them separately. 3. Forget to carry over uffd-wp bit for a write migration huge pmd entry. This also happens in copy_huge_pmd(), where we converted a write huge migration entry into a read one. 4. In copy_nonpresent_pte(), drop uffd-wp if necessary for swap ptes. 5. In copy_present_page() when COW is enforced when fork(), we also need to pass over the uffd-wp bit if VM_UFFD_WP is armed on the new vma, and when the pte to be copied has uffd-wp bit set. Remove the comment in copy_present_pte() about this. It won't help a huge lot to only comment there, but comment everywhere would be an overkill. Let's assume the commit messages would help. [peterx@redhat.com: fix a few thp pmd missing uffd-wp bit] Link: https://lkml.kernel.org/r/20210428225030.9708-4-peterx@redhat.com Link: https://lkml.kernel.org/r/20210428225030.9708-3-peterx@redhat.com Fixes:b569a17607
("userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork") Signed-off-by: Peter Xu <peterx@redhat.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: Brian Geffon <bgeffon@google.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Joe Perches <joe@perches.com> Cc: Kirill A. Shutemov <kirill@shutemov.name> Cc: Lokesh Gidra <lokeshgidra@google.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Oliver Upton <oupton@google.com> Cc: Shaohua Li <shli@fb.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Wang Qing <wangqing@vivo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
381 lines
9 KiB
C
381 lines
9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_SWAPOPS_H
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#define _LINUX_SWAPOPS_H
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#include <linux/radix-tree.h>
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#include <linux/bug.h>
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#include <linux/mm_types.h>
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#ifdef CONFIG_MMU
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/*
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* swapcache pages are stored in the swapper_space radix tree. We want to
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* get good packing density in that tree, so the index should be dense in
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* the low-order bits.
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*
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* We arrange the `type' and `offset' fields so that `type' is at the seven
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* high-order bits of the swp_entry_t and `offset' is right-aligned in the
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* remaining bits. Although `type' itself needs only five bits, we allow for
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* shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
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*
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* swp_entry_t's are *never* stored anywhere in their arch-dependent format.
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*/
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#define SWP_TYPE_SHIFT (BITS_PER_XA_VALUE - MAX_SWAPFILES_SHIFT)
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#define SWP_OFFSET_MASK ((1UL << SWP_TYPE_SHIFT) - 1)
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/* Clear all flags but only keep swp_entry_t related information */
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static inline pte_t pte_swp_clear_flags(pte_t pte)
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{
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if (pte_swp_soft_dirty(pte))
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pte = pte_swp_clear_soft_dirty(pte);
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if (pte_swp_uffd_wp(pte))
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pte = pte_swp_clear_uffd_wp(pte);
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return pte;
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}
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/*
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* Store a type+offset into a swp_entry_t in an arch-independent format
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*/
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static inline swp_entry_t swp_entry(unsigned long type, pgoff_t offset)
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{
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swp_entry_t ret;
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ret.val = (type << SWP_TYPE_SHIFT) | (offset & SWP_OFFSET_MASK);
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return ret;
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}
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/*
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* Extract the `type' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline unsigned swp_type(swp_entry_t entry)
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{
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return (entry.val >> SWP_TYPE_SHIFT);
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}
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/*
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* Extract the `offset' field from a swp_entry_t. The swp_entry_t is in
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* arch-independent format
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*/
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static inline pgoff_t swp_offset(swp_entry_t entry)
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{
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return entry.val & SWP_OFFSET_MASK;
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}
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/* check whether a pte points to a swap entry */
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static inline int is_swap_pte(pte_t pte)
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{
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return !pte_none(pte) && !pte_present(pte);
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}
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/*
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* Convert the arch-dependent pte representation of a swp_entry_t into an
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* arch-independent swp_entry_t.
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*/
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static inline swp_entry_t pte_to_swp_entry(pte_t pte)
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{
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swp_entry_t arch_entry;
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pte = pte_swp_clear_flags(pte);
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arch_entry = __pte_to_swp_entry(pte);
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return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
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}
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/*
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* Convert the arch-independent representation of a swp_entry_t into the
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* arch-dependent pte representation.
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*/
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static inline pte_t swp_entry_to_pte(swp_entry_t entry)
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{
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swp_entry_t arch_entry;
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arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
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return __swp_entry_to_pte(arch_entry);
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}
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static inline swp_entry_t radix_to_swp_entry(void *arg)
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{
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swp_entry_t entry;
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entry.val = xa_to_value(arg);
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return entry;
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}
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static inline void *swp_to_radix_entry(swp_entry_t entry)
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{
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return xa_mk_value(entry.val);
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}
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#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
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static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
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{
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return swp_entry(write ? SWP_DEVICE_WRITE : SWP_DEVICE_READ,
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page_to_pfn(page));
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}
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static inline bool is_device_private_entry(swp_entry_t entry)
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{
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int type = swp_type(entry);
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return type == SWP_DEVICE_READ || type == SWP_DEVICE_WRITE;
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}
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static inline void make_device_private_entry_read(swp_entry_t *entry)
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{
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*entry = swp_entry(SWP_DEVICE_READ, swp_offset(*entry));
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}
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static inline bool is_write_device_private_entry(swp_entry_t entry)
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{
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return unlikely(swp_type(entry) == SWP_DEVICE_WRITE);
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}
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static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry)
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{
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return swp_offset(entry);
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}
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static inline struct page *device_private_entry_to_page(swp_entry_t entry)
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{
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return pfn_to_page(swp_offset(entry));
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}
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#else /* CONFIG_DEVICE_PRIVATE */
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static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
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{
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return swp_entry(0, 0);
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}
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static inline void make_device_private_entry_read(swp_entry_t *entry)
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{
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}
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static inline bool is_device_private_entry(swp_entry_t entry)
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{
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return false;
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}
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static inline bool is_write_device_private_entry(swp_entry_t entry)
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{
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return false;
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}
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static inline unsigned long device_private_entry_to_pfn(swp_entry_t entry)
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{
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return 0;
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}
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static inline struct page *device_private_entry_to_page(swp_entry_t entry)
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{
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return NULL;
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}
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#endif /* CONFIG_DEVICE_PRIVATE */
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#ifdef CONFIG_MIGRATION
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static inline swp_entry_t make_migration_entry(struct page *page, int write)
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{
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BUG_ON(!PageLocked(compound_head(page)));
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return swp_entry(write ? SWP_MIGRATION_WRITE : SWP_MIGRATION_READ,
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page_to_pfn(page));
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}
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static inline int is_migration_entry(swp_entry_t entry)
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{
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return unlikely(swp_type(entry) == SWP_MIGRATION_READ ||
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swp_type(entry) == SWP_MIGRATION_WRITE);
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}
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static inline int is_write_migration_entry(swp_entry_t entry)
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{
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return unlikely(swp_type(entry) == SWP_MIGRATION_WRITE);
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}
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static inline unsigned long migration_entry_to_pfn(swp_entry_t entry)
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{
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return swp_offset(entry);
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}
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static inline struct page *migration_entry_to_page(swp_entry_t entry)
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{
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struct page *p = pfn_to_page(swp_offset(entry));
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/*
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* Any use of migration entries may only occur while the
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* corresponding page is locked
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*/
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BUG_ON(!PageLocked(compound_head(p)));
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return p;
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}
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static inline void make_migration_entry_read(swp_entry_t *entry)
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{
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*entry = swp_entry(SWP_MIGRATION_READ, swp_offset(*entry));
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}
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extern void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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spinlock_t *ptl);
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extern void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address);
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extern void migration_entry_wait_huge(struct vm_area_struct *vma,
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struct mm_struct *mm, pte_t *pte);
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#else
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#define make_migration_entry(page, write) swp_entry(0, 0)
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static inline int is_migration_entry(swp_entry_t swp)
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{
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return 0;
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}
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static inline unsigned long migration_entry_to_pfn(swp_entry_t entry)
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{
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return 0;
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}
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static inline struct page *migration_entry_to_page(swp_entry_t entry)
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{
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return NULL;
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}
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static inline void make_migration_entry_read(swp_entry_t *entryp) { }
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static inline void __migration_entry_wait(struct mm_struct *mm, pte_t *ptep,
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spinlock_t *ptl) { }
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static inline void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd,
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unsigned long address) { }
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static inline void migration_entry_wait_huge(struct vm_area_struct *vma,
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struct mm_struct *mm, pte_t *pte) { }
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static inline int is_write_migration_entry(swp_entry_t entry)
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{
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return 0;
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}
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#endif
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struct page_vma_mapped_walk;
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#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
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extern void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
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struct page *page);
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extern void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
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struct page *new);
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extern void pmd_migration_entry_wait(struct mm_struct *mm, pmd_t *pmd);
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static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
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{
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swp_entry_t arch_entry;
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if (pmd_swp_soft_dirty(pmd))
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pmd = pmd_swp_clear_soft_dirty(pmd);
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if (pmd_swp_uffd_wp(pmd))
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pmd = pmd_swp_clear_uffd_wp(pmd);
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arch_entry = __pmd_to_swp_entry(pmd);
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return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
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}
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static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
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{
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swp_entry_t arch_entry;
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arch_entry = __swp_entry(swp_type(entry), swp_offset(entry));
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return __swp_entry_to_pmd(arch_entry);
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}
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static inline int is_pmd_migration_entry(pmd_t pmd)
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{
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return !pmd_present(pmd) && is_migration_entry(pmd_to_swp_entry(pmd));
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}
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#else
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static inline void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
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struct page *page)
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{
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BUILD_BUG();
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}
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static inline void remove_migration_pmd(struct page_vma_mapped_walk *pvmw,
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struct page *new)
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{
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BUILD_BUG();
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}
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static inline void pmd_migration_entry_wait(struct mm_struct *m, pmd_t *p) { }
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static inline swp_entry_t pmd_to_swp_entry(pmd_t pmd)
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{
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return swp_entry(0, 0);
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}
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static inline pmd_t swp_entry_to_pmd(swp_entry_t entry)
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{
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return __pmd(0);
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}
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static inline int is_pmd_migration_entry(pmd_t pmd)
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{
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return 0;
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}
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#endif
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#ifdef CONFIG_MEMORY_FAILURE
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extern atomic_long_t num_poisoned_pages __read_mostly;
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/*
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* Support for hardware poisoned pages
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*/
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static inline swp_entry_t make_hwpoison_entry(struct page *page)
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{
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BUG_ON(!PageLocked(page));
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return swp_entry(SWP_HWPOISON, page_to_pfn(page));
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}
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static inline int is_hwpoison_entry(swp_entry_t entry)
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{
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return swp_type(entry) == SWP_HWPOISON;
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}
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static inline unsigned long hwpoison_entry_to_pfn(swp_entry_t entry)
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{
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return swp_offset(entry);
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}
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static inline void num_poisoned_pages_inc(void)
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{
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atomic_long_inc(&num_poisoned_pages);
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}
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static inline void num_poisoned_pages_dec(void)
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{
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atomic_long_dec(&num_poisoned_pages);
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}
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#else
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static inline swp_entry_t make_hwpoison_entry(struct page *page)
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{
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return swp_entry(0, 0);
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}
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static inline int is_hwpoison_entry(swp_entry_t swp)
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{
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return 0;
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}
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static inline void num_poisoned_pages_inc(void)
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{
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}
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#endif
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#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) || \
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defined(CONFIG_DEVICE_PRIVATE)
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static inline int non_swap_entry(swp_entry_t entry)
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{
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return swp_type(entry) >= MAX_SWAPFILES;
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}
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#else
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static inline int non_swap_entry(swp_entry_t entry)
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{
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return 0;
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}
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#endif
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#endif /* CONFIG_MMU */
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#endif /* _LINUX_SWAPOPS_H */
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