[PATCH v2 1/8] ext2: mark s_next_generation as guarded by s_next_gen_lock

[Timothy Day <timday@thelustrecollective.com>]

s_next_generation is only ever modified while holding s_next_gen_lock
(in ext2_new_inode()), so annotate it with __guarded_by() for Clang's
context analysis.

The only other write is the initialisation in ext2_fill_super(), which
runs before the superblock is live. No concurrent access should be
possible. Convert the spinlock initialization to use
scoped_guard(spinlock_init, ...) and place the write under the guard
to prevent a warning.

Signed-off-by: Timothy Day <timday@thelustrecollective.com>
---
 fs/ext2/ext2.h  | 2 +-
 fs/ext2/super.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
index 79f7b395258c..e851d2a6be66 100644
--- a/fs/ext2/ext2.h
+++ b/fs/ext2/ext2.h
@@ -93,7 +93,7 @@ struct ext2_sb_info {
 	int s_inode_size;
 	int s_first_ino;
 	spinlock_t s_next_gen_lock;
-	u32 s_next_generation;
+	u32 s_next_generation __guarded_by(&s_next_gen_lock);
 	unsigned long s_dir_count;
 	u8 *s_debts;
 	struct percpu_counter s_freeblocks_counter;
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 3999f8f3b156..b8bb1f88a620 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -1125,8 +1125,8 @@ static int ext2_fill_super(struct super_block *sb, struct fs_context *fc)
 		goto failed_mount2;
 	}
 	sbi->s_gdb_count = db_count;
-	sbi->s_next_generation = get_random_u32();
-	spin_lock_init(&sbi->s_next_gen_lock);
+	scoped_guard(spinlock_init, &sbi->s_next_gen_lock)
+		sbi->s_next_generation = get_random_u32();
 
 	/* per filesystem reservation list head & lock */
 	spin_lock_init(&sbi->s_rsv_window_lock);
-- 
2.43.0