block: enable dax for raw block devices
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. It can be disabled / enabled dynamically via the new BLKDAXSET
ioctl.
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Reviewed-by: Jan Kara <jack@suse.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
diff --git a/block/ioctl.c b/block/ioctl.c
index 0918aed..7a964d8 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -406,6 +406,62 @@
ret == -ENOIOCTLCMD;
}
+#ifdef CONFIG_FS_DAX
+bool blkdev_dax_capable(struct block_device *bdev)
+{
+ struct gendisk *disk = bdev->bd_disk;
+
+ if (!disk->fops->direct_access)
+ return false;
+
+ /*
+ * If the partition is not aligned on a page boundary, we can't
+ * do dax I/O to it.
+ */
+ if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512))
+ || (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
+ return false;
+
+ return true;
+}
+
+static int blkdev_daxset(struct block_device *bdev, unsigned long argp)
+{
+ unsigned long arg;
+ int rc = 0;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EACCES;
+
+ if (get_user(arg, (int __user *)(argp)))
+ return -EFAULT;
+ arg = !!arg;
+ if (arg == !!(bdev->bd_inode->i_flags & S_DAX))
+ return 0;
+
+ if (arg)
+ arg = S_DAX;
+
+ if (arg && !blkdev_dax_capable(bdev))
+ return -ENOTTY;
+
+ mutex_lock(&bdev->bd_inode->i_mutex);
+ if (bdev->bd_map_count == 0)
+ inode_set_flags(bdev->bd_inode, arg, S_DAX);
+ else
+ rc = -EBUSY;
+ mutex_unlock(&bdev->bd_inode->i_mutex);
+ return rc;
+}
+#else
+static int blkdev_daxset(struct block_device *bdev, int arg)
+{
+ if (arg)
+ return -ENOTTY;
+ return 0;
+}
+#endif
+
static int blkdev_flushbuf(struct block_device *bdev, fmode_t mode,
unsigned cmd, unsigned long arg)
{
@@ -568,6 +624,11 @@
case BLKTRACESETUP:
case BLKTRACETEARDOWN:
return blk_trace_ioctl(bdev, cmd, argp);
+ case BLKDAXSET:
+ return blkdev_daxset(bdev, arg);
+ case BLKDAXGET:
+ return put_int(arg, !!(bdev->bd_inode->i_flags & S_DAX));
+ break;
case IOC_PR_REGISTER:
return blkdev_pr_register(bdev, argp);
case IOC_PR_RESERVE:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 52248bc..5c0b2cb 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1235,8 +1235,11 @@
}
}
- if (!ret)
+ if (!ret) {
bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
+ if (!blkdev_dax_capable(bdev))
+ bdev->bd_inode->i_flags &= ~S_DAX;
+ }
/*
* If the device is invalidated, rescan partition
@@ -1250,6 +1253,7 @@
else if (ret == -ENOMEDIUM)
invalidate_partitions(disk, bdev);
}
+
if (ret)
goto out_clear;
} else {
@@ -1270,12 +1274,7 @@
goto out_clear;
}
bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);
- /*
- * If the partition is not aligned on a page
- * boundary, we can't do dax I/O to it.
- */
- if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512)) ||
- (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
+ if (!blkdev_dax_capable(bdev))
bdev->bd_inode->i_flags &= ~S_DAX;
}
} else {
@@ -1713,13 +1712,101 @@
.is_dirty_writeback = buffer_check_dirty_writeback,
};
+#ifdef CONFIG_FS_DAX
+/*
+ * In the raw block case we do not need to contend with truncation nor
+ * unwritten file extents. Without those concerns there is no need for
+ * additional locking beyond the mmap_sem context that these routines
+ * are already executing under.
+ *
+ * Note, there is no protection if the block device is dynamically
+ * resized (partition grow/shrink) during a fault. A stable block device
+ * size is already not enforced in the blkdev_direct_IO path.
+ *
+ * For DAX, it is the responsibility of the block device driver to
+ * ensure the whole-disk device size is stable while requests are in
+ * flight.
+ *
+ * Finally, unlike the filemap_page_mkwrite() case there is no
+ * filesystem superblock to sync against freezing. We still include a
+ * pfn_mkwrite callback for dax drivers to receive write fault
+ * notifications.
+ */
+static int blkdev_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
+{
+ return __dax_fault(vma, vmf, blkdev_get_block, NULL);
+}
+
+static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
+ pmd_t *pmd, unsigned int flags)
+{
+ return __dax_pmd_fault(vma, addr, pmd, flags, blkdev_get_block, NULL);
+}
+
+static void blkdev_vm_open(struct vm_area_struct *vma)
+{
+ struct inode *bd_inode = bdev_file_inode(vma->vm_file);
+ struct block_device *bdev = I_BDEV(bd_inode);
+
+ mutex_lock(&bd_inode->i_mutex);
+ bdev->bd_map_count++;
+ mutex_unlock(&bd_inode->i_mutex);
+}
+
+static void blkdev_vm_close(struct vm_area_struct *vma)
+{
+ struct inode *bd_inode = bdev_file_inode(vma->vm_file);
+ struct block_device *bdev = I_BDEV(bd_inode);
+
+ mutex_lock(&bd_inode->i_mutex);
+ bdev->bd_map_count--;
+ mutex_unlock(&bd_inode->i_mutex);
+}
+
+static const struct vm_operations_struct blkdev_dax_vm_ops = {
+ .open = blkdev_vm_open,
+ .close = blkdev_vm_close,
+ .fault = blkdev_dax_fault,
+ .pmd_fault = blkdev_dax_pmd_fault,
+ .pfn_mkwrite = blkdev_dax_fault,
+};
+
+static const struct vm_operations_struct blkdev_default_vm_ops = {
+ .open = blkdev_vm_open,
+ .close = blkdev_vm_close,
+ .fault = filemap_fault,
+ .map_pages = filemap_map_pages,
+};
+
+static int blkdev_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct inode *bd_inode = bdev_file_inode(file);
+ struct block_device *bdev = I_BDEV(bd_inode);
+
+ file_accessed(file);
+ mutex_lock(&bd_inode->i_mutex);
+ bdev->bd_map_count++;
+ if (IS_DAX(bd_inode)) {
+ vma->vm_ops = &blkdev_dax_vm_ops;
+ vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;
+ } else {
+ vma->vm_ops = &blkdev_default_vm_ops;
+ }
+ mutex_unlock(&bd_inode->i_mutex);
+
+ 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
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3aa5142..96fabc9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -482,6 +482,9 @@
int bd_fsfreeze_count;
/* Mutex for freeze */
struct mutex bd_fsfreeze_mutex;
+#ifdef CONFIG_FS_DAX
+ int bd_map_count;
+#endif
};
/*
@@ -2264,6 +2267,14 @@
extern void emergency_thaw_all(void);
extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
extern int fsync_bdev(struct block_device *);
+#ifdef CONFIG_FS_DAX
+extern bool blkdev_dax_capable(struct block_device *bdev);
+#else
+static inline bool blkdev_dax_capable(struct block_device *bdev)
+{
+ return false;
+}
+#endif
extern struct super_block *blockdev_superblock;
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index f15d980..401c409 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -152,6 +152,8 @@
#define BLKSECDISCARD _IO(0x12,125)
#define BLKROTATIONAL _IO(0x12,126)
#define BLKZEROOUT _IO(0x12,127)
+#define BLKDAXSET _IO(0x12,128)
+#define BLKDAXGET _IO(0x12,129)
#define BMAP_IOCTL 1 /* obsolete - kept for compatibility */
#define FIBMAP _IO(0x00,1) /* bmap access */