[PATCH 4/7] bcachefs: Implement blk_holder_ops

Kent Overstreet
2025-03-07T13:49:45Z

We can't use the standard fs_holder_ops because they're meant for single
device filesystems - fs_bdev_mark_dead() in particular - and they assume
that the blk_holder is the super_block, which also doesn't work for a
multi device filesystem.

These generally follow the standard fs_holder_ops; the
locking/refcounting is a bit simplified because c->ro_ref suffices, and
bch2_fs_bdev_mark_dead() is not necessarily shutting down the entire
filesystem.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/bcachefs/super-io.c | 3 --
fs/bcachefs/super.c | 97 ++++++++++++++++++++++++++++++++++++++++++
fs/bcachefs/super.h | 2 +
3 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index bd24b4f7eeb6..dcb69c72555e 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -25,9 +25,6 @@
#include <linux/sort.h>
#include <linux/string_choices.h>

-static const struct blk_holder_ops bch2_sb_handle_bdev_ops = {
-};
-
struct bch2_metadata_version {
u16 version;
const char *name;
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index b653dd480591..05a2dc5ef513 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -1075,6 +1075,7 @@ int bch2_fs_start(struct bch_fs *c)
}

set_bit(BCH_FS_started, &c->flags);
+ wake_up(&c->ro_ref_wait);

if (c->opts.read_only) {
bch2_fs_read_only(c);
@@ -2023,6 +2024,102 @@ struct bch_dev *bch2_dev_lookup(struct bch_fs *c, const char *name)
return ERR_PTR(-BCH_ERR_ENOENT_dev_not_found);
}

+/* blk_holder_ops: */
+
+static struct bch_fs *bdev_get_fs(struct block_device *bdev)
+ __releases(&bdev->bd_holder_lock)
+{
+ struct bch_sb_handle_holder *holder = bdev->bd_holder;
+ struct bch_fs *c = holder->c;
+
+ if (c && !bch2_ro_ref_tryget(c))
+ c = NULL;
+
+ mutex_unlock(&bdev->bd_holder_lock);
+
+ if (c)
+ wait_event(c->ro_ref_wait, test_bit(BCH_FS_started, &c->flags));
+ return c;
+}
+
+/* returns with ref on ca->ref */
+static struct bch_dev *bdev_to_bch_dev(struct bch_fs *c, struct block_device *bdev)
+{
+ for_each_member_device(c, ca)
+ if (ca->disk_sb.bdev == bdev)
+ return ca;
+ return NULL;
+}
+
+static void bch2_fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
+{
+ struct bch_fs *c = bdev_get_fs(bdev);
+ if (!c)
+ return;
+
+ struct super_block *sb = c->vfs_sb;
+ if (sb) {
+ /*
+ * Not necessary, c->ro_ref guards against the filesystem being
+ * unmounted - we only take this to avoid a warning in
+ * sync_filesystem:
+ */
+ down_read(&sb->s_umount);
+ }
+
+ down_write(&c->state_lock);
+ struct bch_dev *ca = bdev_to_bch_dev(c, bdev);
+ if (!ca)
+ goto unlock;
+
+ if (bch2_dev_state_allowed(c, ca, BCH_MEMBER_STATE_failed, BCH_FORCE_IF_DEGRADED)) {
+ __bch2_dev_offline(c, ca);
+ } else {
+ if (sb) {
+ if (!surprise)
+ sync_filesystem(sb);
+ shrink_dcache_sb(sb);
+ invalidate_inodes(sb);
+ }
+
+ bch2_journal_flush(&c->journal);
+ bch2_fs_emergency_read_only(c);
+ }
+
+ bch2_dev_put(ca);
+unlock:
+ if (sb)
+ up_read(&sb->s_umount);
+ up_write(&c->state_lock);
+ bch2_ro_ref_put(c);
+}
+
+static void bch2_fs_bdev_sync(struct block_device *bdev)
+{
+ struct bch_fs *c = bdev_get_fs(bdev);
+ if (!c)
+ return;
+
+ struct super_block *sb = c->vfs_sb;
+ if (sb) {
+ /*
+ * Not necessary, c->ro_ref guards against the filesystem being
+ * unmounted - we only take this to avoid a warning in
+ * sync_filesystem:
+ */
+ down_read(&sb->s_umount);
+ sync_filesystem(sb);
+ up_read(&sb->s_umount);
+ }
+
+ bch2_ro_ref_put(c);
+}
+
+const struct blk_holder_ops bch2_sb_handle_bdev_ops = {
+ .mark_dead = bch2_fs_bdev_mark_dead,
+ .sync = bch2_fs_bdev_sync,
+};
+
/* Filesystem open: */

static inline int sb_cmp(struct bch_sb *l, struct bch_sb *r)
diff --git a/fs/bcachefs/super.h b/fs/bcachefs/super.h
index 04f8287eff5c..23533bce5709 100644
--- a/fs/bcachefs/super.h
+++ b/fs/bcachefs/super.h
@@ -42,4 +42,6 @@ void bch2_fs_stop(struct bch_fs *);
int bch2_fs_start(struct bch_fs *);
struct bch_fs *bch2_fs_open(char * const *, unsigned, struct bch_opts);

+extern const struct blk_holder_ops bch2_sb_handle_bdev_ops;
+
#endif /* _BCACHEFS_SUPER_H */
--
2.47.2