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 <jmoyer@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
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
--
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