From 3359b54c8c07338f3a863d1109b42eebccdcf379 Mon Sep 17 00:00:00 2001 From: "Seth, Rohit" Date: Tue, 18 Oct 2005 14:15:12 -0700 Subject: [PATCH] [PATCH] Handle spurious page fault for hugetlb region The hugetlb pages are currently pre-faulted. At the time of mmap of hugepages, we populate the new PTEs. It is possible that HW has already cached some of the unused PTEs internally. These stale entries never get a chance to be purged in existing control flow. This patch extends the check in page fault code for hugepages. Check if a faulted address falls with in size for the hugetlb file backing it. We return VM_FAULT_MINOR for these cases (assuming that the arch specific page-faulting code purges the stale entry for the archs that need it). Signed-off-by: Rohit Seth [ This is apparently arguably an ia64 port bug. But the code won't hurt, and for now it fixes a real problem on some ia64 machines ] Signed-off-by: Linus Torvalds --- include/linux/hugetlb.h | 13 +++++++++++++ mm/memory.c | 14 ++++++++++++-- 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index e670b0d..42cb7d70 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -155,11 +155,24 @@ static inline void set_file_hugepages(struct file *file) { file->f_op = &hugetlbfs_file_operations; } + +static inline int valid_hugetlb_file_off(struct vm_area_struct *vma, + unsigned long address) +{ + struct inode *inode = vma->vm_file->f_dentry->d_inode; + loff_t file_off = address - vma->vm_start; + + file_off += (vma->vm_pgoff << PAGE_SHIFT); + + return (file_off < inode->i_size); +} + #else /* !CONFIG_HUGETLBFS */ #define is_file_hugepages(file) 0 #define set_file_hugepages(file) BUG() #define hugetlb_zero_setup(size) ERR_PTR(-ENOSYS) +#define valid_hugetlb_file_off(vma, address) 0 #endif /* !CONFIG_HUGETLBFS */ diff --git a/mm/memory.c b/mm/memory.c index ae8161f..8c88b97 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2045,8 +2045,18 @@ int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct * vma, inc_page_state(pgfault); - if (is_vm_hugetlb_page(vma)) - return VM_FAULT_SIGBUS; /* mapping truncation does this. */ + if (unlikely(is_vm_hugetlb_page(vma))) { + if (valid_hugetlb_file_off(vma, address)) + /* We get here only if there was a stale(zero) TLB entry + * (because of HW prefetching). + * Low-level arch code (if needed) should have already + * purged the stale entry as part of this fault handling. + * Here we just return. + */ + return VM_FAULT_MINOR; + else + return VM_FAULT_SIGBUS; /* mapping truncation does this. */ + } /* * We need the page table lock to synchronize with kswapd -- 2.7.4