[PATCH 2/7] bcachefs: Stash a pointer to the filesystem for blk_holder_ops

Kent Overstreet
2025-03-07T13:49:43Z

Note that we open block devices before we allocate bch_fs, but once
attached to a filesystem they will be closed before the bch_fs is torn
down - so stashing a pointer without a refcount looks incorrect but it's
not.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/bcachefs/super-io.c | 2 +-
fs/bcachefs/super.c | 7 +++++++
fs/bcachefs/super_types.h | 8 +++++++-
3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index 28724aee2c09..bd24b4f7eeb6 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -748,7 +748,7 @@ static int __bch2_read_super(const char *path, struct bch_opts *opts,
memset(sb, 0, sizeof(*sb));
sb->mode = BLK_OPEN_READ;
sb->have_bio = true;
- sb->holder = kmalloc(1, GFP_KERNEL);
+ sb->holder = kzalloc(sizeof(*sb->holder), GFP_KERNEL);
if (!sb->holder)
return -ENOMEM;

diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index 10c281ad96eb..b653dd480591 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -1431,6 +1431,13 @@ static int __bch2_dev_attach_bdev(struct bch_dev *ca, struct bch_sb_handle *sb)
ca->disk_sb = *sb;
memset(sb, 0, sizeof(*sb));

+ /*
+ * Stash pointer to the filesystem for blk_holder_ops - note that once
+ * attached to a filesystem, we will always close the block device
+ * before tearing down the filesystem object.
+ */
+ ca->disk_sb.holder->c = ca->fs;
+
ca->dev = ca->disk_sb.bdev->bd_dev;

percpu_ref_reinit(&ca->io_ref);
diff --git a/fs/bcachefs/super_types.h b/fs/bcachefs/super_types.h
index 368a63d938cf..3a899f799d1d 100644
--- a/fs/bcachefs/super_types.h
+++ b/fs/bcachefs/super_types.h
@@ -2,13 +2,19 @@
#ifndef _BCACHEFS_SUPER_TYPES_H
#define _BCACHEFS_SUPER_TYPES_H

+struct bch_fs;
+
+struct bch_sb_handle_holder {
+ struct bch_fs *c;
+};
+
struct bch_sb_handle {
struct bch_sb *sb;
struct file *s_bdev_file;
struct block_device *bdev;
char *sb_name;
struct bio *bio;
- void *holder;
+ struct bch_sb_handle_holder *holder;
size_t buffer_size;
blk_mode_t mode;
unsigned have_layout:1;
--
2.47.2