block: revert runtime dax control of the raw block device

Dynamically enabling DAX requires that the page cache first be flushed
and invalidated.  This must occur atomically with the change of DAX mode
otherwise we confuse the fsync/msync tracking and violate data
durability guarantees.  Eliminate the possibilty of DAX-disabled to
DAX-enabled transitions for now and revisit this for the next cycle.

Cc: Jan Kara <jack@suse.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 0 insertions, 28 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7b9cd49622b1..afb437484362 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1736,37 +1736,13 @@ static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
         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);
-
-        inode_lock(bd_inode);
-        bdev->bd_map_count++;
-        inode_unlock(bd_inode);
-}
-
-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);
-
-        inode_lock(bd_inode);
-        bdev->bd_map_count--;
-        inode_unlock(bd_inode);
-}
-
 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,
 };
@@ -1774,18 +1750,14 @@ static const struct vm_operations_struct blkdev_default_vm_ops = {
 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);
-        inode_lock(bd_inode);
-        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;
         }
-        inode_unlock(bd_inode);
 
         return 0;
 }