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, 4 insertions, 9 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 99e4f5e72213..2f5dbde23094 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -24,6 +24,7 @@
 #include <linux/sbitmap.h>
 #include <linux/uuid.h>
 #include <linux/xarray.h>
+#include <linux/file.h>
 
 struct module;
 struct request_queue;
@@ -1474,26 +1475,20 @@ extern const struct blk_holder_ops fs_holder_ops;
 	(BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES | \
 	 (((flags) & SB_RDONLY) ? 0 : BLK_OPEN_WRITE))
 
-struct bdev_handle {
-	struct block_device *bdev;
-	void *holder;
-	blk_mode_t mode;
-};
-
-struct bdev_handle *bdev_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
+struct file *bdev_file_open_by_dev(dev_t dev, blk_mode_t mode, void *holder,
 		const struct blk_holder_ops *hops);
-struct bdev_handle *bdev_open_by_path(const char *path, blk_mode_t mode,
+struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode,
 		void *holder, const struct blk_holder_ops *hops);
 int bd_prepare_to_claim(struct block_device *bdev, void *holder,
 		const struct blk_holder_ops *hops);
 void bd_abort_claiming(struct block_device *bdev, void *holder);
-void bdev_release(struct bdev_handle *handle);
 
 /* just for blk-cgroup, don't use elsewhere */
 struct block_device *blkdev_get_no_open(dev_t dev);
 void blkdev_put_no_open(struct block_device *bdev);
 
 struct block_device *I_BDEV(struct inode *inode);
+struct block_device *file_bdev(struct file *bdev_file);
 
 #ifdef CONFIG_BLOCK
 void invalidate_bdev(struct block_device *bdev);