Commit 5a023cdb authored by Dan Williams's avatar Dan Williams

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: default avatarkbuild test robot <fengguang.wu@intel.com>
Reviewed-by: default avatarJan Kara <jack@suse.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 4ebb16ca
......@@ -406,6 +406,62 @@ static inline int is_unrecognized_ioctl(int ret)
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 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
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:
......
......@@ -1235,8 +1235,11 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
}
}
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 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
else if (ret == -ENOMEDIUM)
invalidate_partitions(disk, bdev);
}
if (ret)
goto out_clear;
} else {
......@@ -1270,12 +1274,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
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 @@ static const struct address_space_operations def_blk_aops = {
.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
......
......@@ -482,6 +482,9 @@ struct block_device {
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 struct super_block *freeze_bdev(struct block_device *);
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;
......
......@@ -152,6 +152,8 @@ struct inodes_stat_t {
#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 */
......
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