If an application wants exclusive access to all of the persistent memory provided by an NVDIMM namespace it can use this raw-block-dax facility to forgo establishing a filesystem. This capability is targeted primarily to hypervisors wanting to provision persistent memory for guests.
Cc: Jeff Moyer <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Al Viro <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Ross Zwisler <[email protected]> Cc: Xiao Guangrong <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- Only lighted tested so far, but seems to work, is the shortest path to a DAX mapping, and makes it easier to trigger the pmd_fault path (no fs-block-allocator interactions). fs/block_dev.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 83 insertions(+), 1 deletion(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index 5277dd83d254..498b71455570 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1687,13 +1687,95 @@ static const struct address_space_operations def_blk_aops = { .is_dirty_writeback = buffer_check_dirty_writeback, }; +#ifdef CONFIG_FS_DAX +static int blkdev_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct inode *bd_inode = file_bd_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + int ret; + + mutex_lock(&bdev->bd_mutex); + ret = __dax_fault(vma, vmf, blkdev_get_block, NULL); + mutex_unlock(&bdev->bd_mutex); + + return ret; +} + +static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr, + pmd_t *pmd, unsigned int flags) +{ + struct inode *bd_inode = file_bd_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + int ret; + + mutex_lock(&bdev->bd_mutex); + ret = __dax_pmd_fault(vma, addr, pmd, flags, blkdev_get_block, NULL); + mutex_unlock(&bdev->bd_mutex); + + return ret; +} + +static int blkdev_dax_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf) +{ + struct inode *bd_inode = file_bd_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + int ret; + + mutex_lock(&bdev->bd_mutex); + ret = __dax_mkwrite(vma, vmf, blkdev_get_block, NULL); + mutex_unlock(&bdev->bd_mutex); + + return ret; +} + +static int blkdev_dax_pfn_mkwrite(struct vm_area_struct *vma, + struct vm_fault *vmf) +{ + struct inode *bd_inode = file_bd_inode(vma->vm_file); + struct block_device *bdev = I_BDEV(bd_inode); + int ret = VM_FAULT_NOPAGE; + loff_t size; + + /* check that the faulting page hasn't raced with bdev resize */ + mutex_lock(&bdev->bd_mutex); + size = (i_size_read(bd_inode) + PAGE_SIZE - 1) >> PAGE_SHIFT; + if (vmf->pgoff >= size) + ret = VM_FAULT_SIGBUS; + mutex_unlock(&bdev->bd_mutex); + + return ret; +} + +static const struct vm_operations_struct blkdev_dax_vm_ops = { + .fault = blkdev_dax_fault, + .pmd_fault = blkdev_dax_pmd_fault, + .page_mkwrite = blkdev_dax_mkwrite, + .pfn_mkwrite = blkdev_dax_pfn_mkwrite, +}; + +static int blkdev_mmap(struct file *file, struct vm_area_struct *vma) +{ + struct inode *bd_inode = file_bd_inode(file); + + if (!IS_DAX(bd_inode)) + return generic_file_mmap(file, vma); + + file_accessed(file); + vma->vm_ops = &blkdev_dax_vm_ops; + vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE; + return 0; +} +#else +#define blkdev_mmap generic_file_mmap +#endif + const struct file_operations def_blk_fops = { .open = blkdev_open, .release = blkdev_close, .llseek = block_llseek, .read_iter = blkdev_read_iter, .write_iter = blkdev_write_iter, - .mmap = generic_file_mmap, + .mmap = blkdev_mmap, .fsync = blkdev_fsync, .unlocked_ioctl = block_ioctl, #ifdef CONFIG_COMPAT -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
