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authorPeter Xu <peterx@redhat.com>2022-05-13 06:22:55 +0300
committerAndrew Morton <akpm@linux-foundation.org>2022-05-13 17:20:11 +0300
commit05e90bd05eea33fc77d6b11e121e2da01fee379f (patch)
tree0a005eadeaff344f70c4eb7eb6625b0f86f3b362 /fs/hugetlbfs
parent60dfaad65aa97fb6755b9798a6b3c9e79bcd5930 (diff)
downloadlinux-05e90bd05eea33fc77d6b11e121e2da01fee379f.tar.xz
mm/hugetlb: only drop uffd-wp special pte if required
As with shmem uffd-wp special ptes, only drop the uffd-wp special swap pte if unmapping an entire vma or synchronized such that faults can not race with the unmap operation. This requires passing zap_flags all the way to the lowest level hugetlb unmap routine: __unmap_hugepage_range. In general, unmap calls originated in hugetlbfs code will pass the ZAP_FLAG_DROP_MARKER flag as synchronization is in place to prevent faults. The exception is hole punch which will first unmap without any synchronization. Later when hole punch actually removes the page from the file, it will check to see if there was a subsequent fault and if so take the hugetlb fault mutex while unmapping again. This second unmap will pass in ZAP_FLAG_DROP_MARKER. The justification of "whether to apply ZAP_FLAG_DROP_MARKER flag when unmap a hugetlb range" is (IMHO): we should never reach a state when a page fault could errornously fault in a page-cache page that was wr-protected to be writable, even in an extremely short period. That could happen if e.g. we pass ZAP_FLAG_DROP_MARKER when hugetlbfs_punch_hole() calls hugetlb_vmdelete_list(), because if a page faults after that call and before remove_inode_hugepages() is executed, the page cache can be mapped writable again in the small racy window, that can cause unexpected data overwritten. [peterx@redhat.com: fix sparse warning] Link: https://lkml.kernel.org/r/Ylcdw8I1L5iAoWhb@xz-m1.local [akpm@linux-foundation.org: move zap_flags_t from mm.h to mm_types.h to fix build issues] Link: https://lkml.kernel.org/r/20220405014915.14873-1-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nadav Amit <nadav.amit@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/hugetlbfs')
-rw-r--r--fs/hugetlbfs/inode.c15
1 files changed, 9 insertions, 6 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 591599829e2a..5945caccf003 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -405,7 +405,8 @@ static void remove_huge_page(struct page *page)
}
static void
-hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
+hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
+ zap_flags_t zap_flags)
{
struct vm_area_struct *vma;
@@ -439,7 +440,7 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end)
}
unmap_hugepage_range(vma, vma->vm_start + v_offset, v_end,
- NULL);
+ NULL, zap_flags);
}
}
@@ -517,7 +518,8 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
mutex_lock(&hugetlb_fault_mutex_table[hash]);
hugetlb_vmdelete_list(&mapping->i_mmap,
index * pages_per_huge_page(h),
- (index + 1) * pages_per_huge_page(h));
+ (index + 1) * pages_per_huge_page(h),
+ ZAP_FLAG_DROP_MARKER);
i_mmap_unlock_write(mapping);
}
@@ -583,7 +585,8 @@ static void hugetlb_vmtruncate(struct inode *inode, loff_t offset)
i_mmap_lock_write(mapping);
i_size_write(inode, offset);
if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
- hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0);
+ hugetlb_vmdelete_list(&mapping->i_mmap, pgoff, 0,
+ ZAP_FLAG_DROP_MARKER);
i_mmap_unlock_write(mapping);
remove_inode_hugepages(inode, offset, LLONG_MAX);
}
@@ -616,8 +619,8 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
i_mmap_lock_write(mapping);
if (!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root))
hugetlb_vmdelete_list(&mapping->i_mmap,
- hole_start >> PAGE_SHIFT,
- hole_end >> PAGE_SHIFT);
+ hole_start >> PAGE_SHIFT,
+ hole_end >> PAGE_SHIFT, 0);
i_mmap_unlock_write(mapping);
remove_inode_hugepages(inode, hole_start, hole_end);
inode_unlock(inode);