Merge series 'Open block devices as files' of https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-0-adbd023e19cc@kernel.org

Pull block devices as files from Christian Brauner:

This opens block devices as files. Instead of introducing a separate
indirection into bdev_open_by_*() vis struct bdev_handle we can just
make bdev_file_open_by_*() return a struct file. Opening and closing a
block device from setup_bdev_super() and in all other places just
becomes equivalent to opening and closing a file.

This has held up in xfstests and in blktests so far and it seems stable
and clean. The equivalence of opening and closing block devices to
regular files is a win in and of itself imho. Added to that is the
ability to do away with struct bdev_handle completely and make various
low-level helpers private to the block layer.

All places were we currently stash a struct bdev_handle we just stash a
file and use an accessor such as file_bdev() akin to I_BDEV() to get to
the block device.

It's now also possible to use file->f_mapping as a replacement for
bdev->bd_inode->i_mapping and file->f_inode or file->f_mapping->host as
an alternative to bdev->bd_inode allowing us to significantly reduce or
even fully remove bdev->bd_inode in follow-up patches.

In addition, we could get rid of sb->s_bdev and various other places
that stash the block device directly and instead stash the block device
file. Again, this is follow-up work if we want this.

* series 'Open block devices as files' of https://lore.kernel.org/r/20240123-vfs-bdev-file-v2-0-adbd023e19cc@kernel.org: (35 commits)
  file: add alloc_file_pseudo_noaccount()
  file: prepare for new helper
  init: flush async file closing
  block: remove bdev_handle completely
  block: don't rely on BLK_OPEN_RESTRICT_WRITES when yielding write access
  bdev: remove bdev pointer from struct bdev_handle
  bdev: make struct bdev_handle private to the block layer
  bdev: make bdev_{release, open_by_dev}() private to block layer
  bdev: remove bdev_open_by_path()
  reiserfs: port block device access to file
  ocfs2: port block device access to file
  nfs: port block device access to files
  jfs: port block device access to file
  f2fs: port block device access to files
  ext4: port block device access to file
  erofs: port device access to file
  btrfs: port device access to file
  bcachefs: port block device access to file
  target: port block device access to file
  s390: port block device access to file
  nvme: port block device access to file
  block2mtd: port device access to files
  bcache: port block device access to files
  ...

Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 9 insertions, 9 deletions

diff --git a/fs/super.c b/fs/super.c
index d35e85295489..08dcc3371aa0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1532,16 +1532,16 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 		struct fs_context *fc)
 {
 	blk_mode_t mode = sb_open_mode(sb_flags);
-	struct bdev_handle *bdev_handle;
+	struct file *bdev_file;
 	struct block_device *bdev;
 
-	bdev_handle = bdev_open_by_dev(sb->s_dev, mode, sb, &fs_holder_ops);
-	if (IS_ERR(bdev_handle)) {
+	bdev_file = bdev_file_open_by_dev(sb->s_dev, mode, sb, &fs_holder_ops);
+	if (IS_ERR(bdev_file)) {
 		if (fc)
 			errorf(fc, "%s: Can't open blockdev", fc->source);
-		return PTR_ERR(bdev_handle);
+		return PTR_ERR(bdev_file);
 	}
-	bdev = bdev_handle->bdev;
+	bdev = file_bdev(bdev_file);
 
 	/*
 	 * This really should be in blkdev_get_by_dev, but right now can't due
@@ -1549,7 +1549,7 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 	 * writable from userspace even for a read-only block device.
 	 */
 	if ((mode & BLK_OPEN_WRITE) && bdev_read_only(bdev)) {
-		bdev_release(bdev_handle);
+		fput(bdev_file);
 		return -EACCES;
 	}
 
@@ -1560,11 +1560,11 @@ int setup_bdev_super(struct super_block *sb, int sb_flags,
 	if (atomic_read(&bdev->bd_fsfreeze_count) > 0) {
 		if (fc)
 			warnf(fc, "%pg: Can't mount, blockdev is frozen", bdev);
-		bdev_release(bdev_handle);
+		fput(bdev_file);
 		return -EBUSY;
 	}
 	spin_lock(&sb_lock);
-	sb->s_bdev_handle = bdev_handle;
+	sb->s_bdev_file = bdev_file;
 	sb->s_bdev = bdev;
 	sb->s_bdi = bdi_get(bdev->bd_disk->bdi);
 	if (bdev_stable_writes(bdev))
@@ -1680,7 +1680,7 @@ void kill_block_super(struct super_block *sb)
 	generic_shutdown_super(sb);
 	if (bdev) {
 		sync_blockdev(bdev);
-		bdev_release(sb->s_bdev_handle);
+		fput(sb->s_bdev_file);
 	}
 }