diff options
| author | Christian Brauner <brauner@kernel.org> | 2026-06-16 13:58:14 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2026-06-29 10:31:49 +0200 |
| commit | ea4e4cc263011910eb7c62f3bb4fa094a1573c61 (patch) | |
| tree | 9e99938b22316fcc6a58850aa15ebb2a25908843 /include | |
| parent | dc59e4fea9d83f03bad6bddf3fa2e52491777482 (diff) | |
block: allow making a block device unfreezable
Add bdev_deny_freeze() and bdev_allow_freeze(), modeled on
deny_write_access()/allow_write_access(). bd_fsfreeze_count becomes a
signed counter: > 0 counts active freezes, < 0 counts deniers, and the
two regimes are mutually exclusive. bdev_freeze() refuses with -EBUSY
while a deny is held, and bdev_deny_freeze() refuses while the device is
frozen.
A filesystem that mutates a device's membership (a btrfs device add,
remove or replace) denies freezing on the device for the duration, so a
claim a freeze walk might act on is never added or torn down behind the
freezer's back.
The deny/allow helpers are a single atomic on bd_fsfreeze_count and take
no lock, so they can be called while holding s_umount without inverting
against bdev_freeze()'s bd_fsfreeze_mutex -> s_umount order.
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260616-work-super-freeze_deny_upstream-v2-1-b3567c7f994b@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/blk_types.h | 2 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 2 |
2 files changed, 3 insertions, 1 deletions
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 8808ee76e73c..5a725a0cd35f 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -66,7 +66,7 @@ struct block_device { int bd_holders; struct kobject *bd_holder_dir; - atomic_t bd_fsfreeze_count; /* number of freeze requests */ + atomic_t bd_fsfreeze_count; /* >0 freeze requests, <0 freeze deniers */ struct mutex bd_fsfreeze_mutex; /* serialize freeze/thaw */ struct partition_meta_info *bd_meta_info; diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 9213a5716f95..c419117be083 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1837,6 +1837,8 @@ static inline int early_lookup_bdev(const char *pathname, dev_t *dev) int bdev_freeze(struct block_device *bdev); int bdev_thaw(struct block_device *bdev); +int bdev_deny_freeze(struct block_device *bdev); +void bdev_allow_freeze(struct block_device *bdev); void bdev_fput(struct file *bdev_file); struct io_comp_batch { |