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| author | Hugh Dickins <hugh@veritas.com> | 2007-10-04 16:56:06 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-04 10:13:09 -0700 |
| commit | 16abfa086096895d438b19198e408ee96da7b508 (patch) | |
| tree | 1d82091f35f069d7b2a7636b5f488987671bdade /mm | |
| parent | 804b3f9a16e446cb023417faec58b6506c834052 (diff) | |
| download | lwn-16abfa086096895d438b19198e408ee96da7b508.tar.gz lwn-16abfa086096895d438b19198e408ee96da7b508.zip | |
Fix sys_remap_file_pages BUG at highmem.c:15!
Gurudas Pai reports kernel BUG at arch/i386/mm/highmem.c:15! below
sys_remap_file_pages, while running Oracle database test on x86 in 6GB
RAM: kunmap thinks we're in_interrupt because the preempt count has
wrapped.
That's because __do_fault expected to unmap page_table, but one of its
two callers do_nonlinear_fault already unmapped it: let do_linear_fault
unmap it first too, and then there's no need to pass the page_table arg
down.
Why have we been so slow to notice this? Probably through forgetting
that the mapping_cap_account_dirty test means that sys_remap_file_pages
nowadays only goes the full nonlinear vma route on a few memory-backed
filesystems like ramfs, tmpfs and hugetlbfs.
[ It also depends on CONFIG_HIGHPTE, so it becomes even harder to
trigger in practice. Many who have need of large memory have probably
migrated to x86-64..
Problem introduced by commit d0217ac04ca6591841e5665f518e38064f4e65bd
("mm: fault feedback #1") -- Linus ]
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: gurudas pai <gurudas.pai@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/memory.c | 14 |
1 files changed, 6 insertions, 8 deletions
diff --git a/mm/memory.c b/mm/memory.c index ca8cac11bd2c..c0e7741a98de 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2307,13 +2307,14 @@ oom: * do not need to flush old virtual caches or the TLB. * * We enter with non-exclusive mmap_sem (to exclude vma changes, - * but allow concurrent faults), and pte mapped but not yet locked. + * but allow concurrent faults), and pte neither mapped nor locked. * We return with mmap_sem still held, but pte unmapped and unlocked. */ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma, - unsigned long address, pte_t *page_table, pmd_t *pmd, + unsigned long address, pmd_t *pmd, pgoff_t pgoff, unsigned int flags, pte_t orig_pte) { + pte_t *page_table; spinlock_t *ptl; struct page *page; pte_t entry; @@ -2327,7 +2328,6 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma, vmf.flags = flags; vmf.page = NULL; - pte_unmap(page_table); BUG_ON(vma->vm_flags & VM_PFNMAP); if (likely(vma->vm_ops->fault)) { @@ -2468,8 +2468,8 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma, - vma->vm_start) >> PAGE_CACHE_SHIFT) + vma->vm_pgoff; unsigned int flags = (write_access ? FAULT_FLAG_WRITE : 0); - return __do_fault(mm, vma, address, page_table, pmd, pgoff, - flags, orig_pte); + pte_unmap(page_table); + return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); } @@ -2552,9 +2552,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma, } pgoff = pte_to_pgoff(orig_pte); - - return __do_fault(mm, vma, address, page_table, pmd, pgoff, - flags, orig_pte); + return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte); } /* |