projects/linux·commit 0965549d

Merge tag 'vfs-6.17-rc1.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

0965549d · Linus Torvalds <[email protected]> · 2025-07-28 15:50:15 -07:00

Pull superblock callback update from Christian Brauner:
 "Currently all filesystems which implement super_operations::shutdown()
  can not afford losing a device.

  Thus fs_bdev_mark_dead() will just call the ->shutdown() callback for
  the involved filesystem.

  But it will no longer be the case, as multi-device filesystems like
  btrfs can handle certain device loss without the need to shutdown the
  whole filesystem.

  To allow those multi-device filesystems to be integrated to use
  fs_holder_ops:

   - Add a new super_operations::remove_bdev() callback

   - Try ->remove_bdev() callback first inside fs_bdev_mark_dead().

     If the callback returned 0, meaning the fs can handling the device
     loss, then exit without doing anything else.

     If there is no such callback or the callback returned non-zero
     value, continue to shutdown the filesystem as usual.

  This means the new remove_bdev() should only do the check on whether
  the operation can continue, and if so do the fs specific handlings.
  The shutdown handling should still be handled by the existing
  ->shutdown() callback.

  For all existing filesystems with shutdown callback, there is no
  change to the code nor behavior.

  Btrfs is going to implement both the ->remove_bdev() and ->shutdown()
  callbacks soon"

* tag 'vfs-6.17-rc1.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  fs: add a new remove_bdev() callback
Commit
0965549d6f5f23e9250cd9c642f4ea5fd682eddb
Parents
57fcb7d9 · d9c37a49

Merge commit. Changes below are compared with the first parent: 57fcb7d9.

Changes

2 files changed · +20 −0

FileStatusAddDelContent
fs/super.cmodified+11−0View file
include/linux/fs.hmodified+9−0View file

fs/super.c

View file
diff --git a/fs/super.c b/fs/super.c
index 80418ca..7f876f3 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1459,6 +1459,17 @@ static void fs_bdev_mark_dead(struct block_device *bdev, bool surprise)
if (!sb)
return;
+ if (sb->s_op->remove_bdev) {
+ int ret;
+
+ ret = sb->s_op->remove_bdev(sb, bdev);
+ if (!ret) {
+ super_unlock_shared(sb);
+ return;
+ }
+ /* Fallback to shutdown. */
+ }
+
if (!surprise)
sync_filesystem(sb);
shrink_dcache_sb(sb);

include/linux/fs.h

View file
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 1f7aa7a..2ec4807 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2367,6 +2367,15 @@ struct super_operations {
struct shrink_control *);
long (*free_cached_objects)(struct super_block *,
struct shrink_control *);
+ /*
+ * If a filesystem can support graceful removal of a device and
+ * continue read-write operations, implement this callback.
+ *
+ * Return 0 if the filesystem can continue read-write.
+ * Non-zero return value or no such callback means the fs will be shutdown
+ * as usual.
+ */
+ int (*remove_bdev)(struct super_block *sb, struct block_device *bdev);
void (*shutdown)(struct super_block *sb);
};