[PATCH 3/8] bdev: infrastructure for flags

Al Viro
2024-04-28T05:16:22Z

Replace bd_partno with a 32bit field (__bd_flags). The lower 8 bits
contain the partition number, the upper 24 are for flags.

Helpers: bdev_{test,set,clear}_flag(bdev, flag), where flag numbers
are zero-based. Use cmpxchg() to set/clear - all architectures support
it for u32.

NOTE: this commit does not actuall move any flags over there - they
are still bool fields. As the result, it shifts the fields wrt
cacheline boundaries; that's going to be restored once the first
3 flags are dealt with.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
block/bdev.c | 2 +-
include/linux/blk_types.h | 2 +-
include/linux/blkdev.h | 33 ++++++++++++++++++++++++++++++++-
3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 7a5f611c3d2e..0c55f7abaac3 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -411,7 +411,7 @@ struct block_device *bdev_alloc(struct gendisk *disk, u8 partno)
mutex_init(&bdev->bd_fsfreeze_mutex);
spin_lock_init(&bdev->bd_size_lock);
mutex_init(&bdev->bd_holder_lock);
- bdev->bd_partno = partno;
+ bdev->__bd_flags = partno;
bdev->bd_inode = inode;
bdev->bd_queue = disk->queue;
if (partno)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index cb1526ec44b5..274f7eb4138f 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -45,8 +45,8 @@ struct block_device {
struct request_queue * bd_queue;
struct disk_stats __percpu *bd_stats;
unsigned long bd_stamp;
+ u32 __bd_flags; // partition number + flags
bool bd_read_only; /* read-only policy */
- u8 bd_partno;
bool bd_write_holder;
bool bd_has_submit_bio;
dev_t bd_dev;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 32549d675955..b9dbfb811533 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -722,7 +722,38 @@ void disk_uevent(struct gendisk *disk, enum kobject_action action);

static inline u8 bdev_partno(const struct block_device *bdev)
{
- return bdev->bd_partno;
+ return bdev->__bd_flags & 0xff;
+}
+
+static inline bool bdev_test_flag(const struct block_device *bdev, int flag)
+{
+ return bdev->__bd_flags & (1 << (flag + 8));
+}
+
+static inline void bdev_set_flag(struct block_device *bdev, int flag)
+{
+ u32 v = bdev->__bd_flags;
+
+ for (;;) {
+ u32 w = cmpxchg(&bdev->__bd_flags, v, v | (1 << (flag + 8)));
+
+ if (v == w)
+ return;
+ v = w;
+ }
+}
+
+static inline void bdev_clear_flag(struct block_device *bdev, int flag)
+{
+ u32 v = bdev->__bd_flags;
+
+ for (;;) {
+ u32 w = cmpxchg(&bdev->__bd_flags, v, v & ~(1 << (flag + 8)));
+
+ if (v == w)
+ return;
+ v = w;
+ }
}

static inline int get_disk_ro(struct gendisk *disk)
--
2.39.2