diff options
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/dax.c | 114 |
1 files changed, 114 insertions, 0 deletions
@@ -1354,4 +1354,118 @@ iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter, return done ? done : ret; } EXPORT_SYMBOL_GPL(iomap_dax_rw); + +/** + * iomap_dax_fault - handle a page fault on a DAX file + * @vma: The virtual memory area where the fault occurred + * @vmf: The description of the fault + * @ops: iomap ops passed from the file system + * + * When a page fault occurs, filesystems may call this helper in their fault + * or mkwrite handler for DAX files. Assumes the caller has done all the + * necessary locking for the page fault to proceed successfully. + */ +int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf, + struct iomap_ops *ops) +{ + struct address_space *mapping = vma->vm_file->f_mapping; + struct inode *inode = mapping->host; + unsigned long vaddr = (unsigned long)vmf->virtual_address; + loff_t pos = (loff_t)vmf->pgoff << PAGE_SHIFT; + sector_t sector; + struct iomap iomap = { 0 }; + unsigned flags = 0; + int error, major = 0; + void *entry; + + /* + * Check whether offset isn't beyond end of file now. Caller is supposed + * to hold locks serializing us with truncate / punch hole so this is + * a reliable test. + */ + if (pos >= i_size_read(inode)) + return VM_FAULT_SIGBUS; + + entry = grab_mapping_entry(mapping, vmf->pgoff); + if (IS_ERR(entry)) { + error = PTR_ERR(entry); + goto out; + } + + if ((vmf->flags & FAULT_FLAG_WRITE) && !vmf->cow_page) + flags |= IOMAP_WRITE; + + /* + * Note that we don't bother to use iomap_apply here: DAX required + * the file system block size to be equal the page size, which means + * that we never have to deal with more than a single extent here. + */ + error = ops->iomap_begin(inode, pos, PAGE_SIZE, flags, &iomap); + if (error) + goto unlock_entry; + if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) { + error = -EIO; /* fs corruption? */ + goto unlock_entry; + } + + sector = iomap.blkno + (((pos & PAGE_MASK) - iomap.offset) >> 9); + + if (vmf->cow_page) { + switch (iomap.type) { + case IOMAP_HOLE: + case IOMAP_UNWRITTEN: + clear_user_highpage(vmf->cow_page, vaddr); + break; + case IOMAP_MAPPED: + error = copy_user_dax(iomap.bdev, sector, PAGE_SIZE, + vmf->cow_page, vaddr); + break; + default: + WARN_ON_ONCE(1); + error = -EIO; + break; + } + + if (error) + goto unlock_entry; + if (!radix_tree_exceptional_entry(entry)) { + vmf->page = entry; + return VM_FAULT_LOCKED; + } + vmf->entry = entry; + return VM_FAULT_DAX_LOCKED; + } + + switch (iomap.type) { + case IOMAP_MAPPED: + if (iomap.flags & IOMAP_F_NEW) { + count_vm_event(PGMAJFAULT); + mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT); + major = VM_FAULT_MAJOR; + } + error = dax_insert_mapping(mapping, iomap.bdev, sector, + PAGE_SIZE, &entry, vma, vmf); + break; + case IOMAP_UNWRITTEN: + case IOMAP_HOLE: + if (!(vmf->flags & FAULT_FLAG_WRITE)) + return dax_load_hole(mapping, entry, vmf); + /*FALLTHRU*/ + default: + WARN_ON_ONCE(1); + error = -EIO; + break; + } + + unlock_entry: + put_locked_mapping_entry(mapping, vmf->pgoff, entry); + out: + if (error == -ENOMEM) + return VM_FAULT_OOM | major; + /* -EBUSY is fine, somebody else faulted on the same PTE */ + if (error < 0 && error != -EBUSY) + return VM_FAULT_SIGBUS | major; + return VM_FAULT_NOPAGE | major; +} +EXPORT_SYMBOL_GPL(iomap_dax_fault); #endif /* CONFIG_FS_IOMAP */ |