>From 819088d701e3a821db8e08ed83d46c00c27cc772 Mon Sep 17 00:00:00 2001 From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Date: Tue, 7 Apr 2009 19:35:07 -0700 Subject: When the backing store of a file becomes inaccessible we need a function to remove that file from the page tables and arrange for page faults to receive SIGBUS until the file is unmapped. Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> --- include/linux/mm.h | 1 + mm/memory.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 88 insertions(+), 0 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index bff1f0d..96d8342 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -807,6 +807,7 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping, extern int vmtruncate(struct inode * inode, loff_t offset); extern int vmtruncate_range(struct inode * inode, loff_t offset, loff_t end); +extern void remap_file_mappings(struct file *file, struct vm_operations_struct *vm_ops); #ifdef CONFIG_MMU extern int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma, diff --git a/mm/memory.c b/mm/memory.c index cf6873e..dcd0a3c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2325,6 +2325,93 @@ void unmap_mapping_range(struct address_space *mapping, } EXPORT_SYMBOL(unmap_mapping_range); +static void remap_vma(struct vm_area_struct *vma, + struct vm_operations_struct *vm_ops) +{ + struct file *file = vma->vm_file; + struct address_space *mapping = file->f_mapping; + unsigned long start_addr, end_addr, size; + struct mm_struct *mm; + + start_addr = vma->vm_start; + end_addr = vma->vm_end; + + /* Has this vma already been processed? */ + if (vma->vm_ops == vm_ops) + return; + + /* Switch out the locks so I can maninuplate this under the mm sem. + * Needed so I can call vm_ops->close. + */ + mm = vma->vm_mm; + atomic_inc(&mm->mm_users); + spin_unlock(&mapping->i_mmap_lock); + + /* Block page faults and other code modifying the mm. */ + down_write(&mm->mmap_sem); + + /* Lookup a vma for my file address */ + vma = find_vma(mm, start_addr); + if (vma->vm_file != file) + goto out; + if (vma->vm_ops == vm_ops) + goto out; + + start_addr = vma->vm_start; + end_addr = vma->vm_end; + size = end_addr - start_addr; + + /* Unmap the vma */ + zap_page_range(vma, start_addr, size, NULL); + + /* Close the vma */ + if (vma->vm_ops && vma->vm_ops->close) + vma->vm_ops->close(vma); + + /* Repurpose the vma */ + vma->vm_private_data = NULL; + vma->vm_ops = vm_ops; + if (vm_ops->open) + vm_ops->open(vma); +out: + up_write(&mm->mmap_sem); + spin_lock(&mapping->i_mmap_lock); +} + +void remap_file_mappings(struct file *file, struct vm_operations_struct *vm_ops) +{ + /* After file->f_ops has been changed update the vmas */ + struct address_space *mapping = file->f_mapping; + struct vm_area_struct *vma; + struct prio_tree_iter iter; + + spin_lock(&mapping->i_mmap_lock); + +restart_tree: + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX) { + /* Skip quickly over vmas that do not need to be touched */ + if (vma->vm_file != file) + continue; + if (vma->vm_ops == vm_ops) + continue; + remap_vma(vma, vm_ops); + goto restart_tree; + } + +restart_list: + list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) { + /* Skip quickly over vmas that do not need to be touched */ + if (vma->vm_file != file) + continue; + if (vma->vm_ops == vm_ops) + continue; + remap_vma(vma, vm_ops); + goto restart_list; + } + + spin_unlock(&mapping->i_mmap_lock); +} + /** * vmtruncate - unmap mappings "freed" by truncate() syscall * @inode: inode of the file used -- 1.6.1.2.350.g88cc -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html