On Tue, Aug 26, 2025 at 11:39:22AM -0400, Josef Bacik wrote:
> Now that we do not allow i_count to drop to 0 and be used we can convert
> it to a refcount_t and benefit from the protections those helpers add.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/inode.c | 2 +-
> fs/inode.c | 9 +++++----
> include/linux/fs.h | 6 +++---
> 3 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index e16df38e0eef..eb9496342346 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -3418,7 +3418,7 @@ void btrfs_add_delayed_iput(struct btrfs_inode *inode)
> struct btrfs_fs_info *fs_info = inode->root->fs_info;
> unsigned long flags;
>
> - if (atomic_add_unless(&inode->vfs_inode.i_count, -1, 1)) {
> + if (refcount_dec_not_one(&inode->vfs_inode.i_count)) {
Now this is the only place outside core VFS where we open-access
i_count. Add a helper and reuse it iput() as well? icount_maybe_dec()?
icount_dec_not_one()?
> iobj_put(&inode->vfs_inode);
> return;
> }
> diff --git a/fs/inode.c b/fs/inode.c
> index 1992db5cd70a..0be1c137bf1e 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -236,7 +236,7 @@ int inode_init_always_gfp(struct super_block *sb, struct inode *inode, gfp_t gfp
> inode->i_state = 0;
> atomic64_set(&inode->i_sequence, 0);
> refcount_set(&inode->i_obj_count, 1);
> - atomic_set(&inode->i_count, 1);
> + refcount_set(&inode->i_count, 1);
> inode->i_op = &empty_iops;
> inode->i_fop = &no_open_fops;
> inode->i_ino = 0;
> @@ -545,7 +545,8 @@ static void init_once(void *foo)
> void ihold(struct inode *inode)
> {
> iobj_get(inode);
> - WARN_ON(atomic_inc_return(&inode->i_count) < 2);
> + refcount_inc(&inode->i_count);
> + WARN_ON(icount_read(inode) < 2);
> }
> EXPORT_SYMBOL(ihold);
>
> @@ -2011,7 +2012,7 @@ static void __iput(struct inode *inode, bool skip_lru)
> return;
> BUG_ON(inode->i_state & I_CLEAR);
>
> - if (atomic_add_unless(&inode->i_count, -1, 1)) {
> + if (refcount_dec_not_one(&inode->i_count)) {
> iobj_put(inode);
> return;
> }
> @@ -2031,7 +2032,7 @@ static void __iput(struct inode *inode, bool skip_lru)
> */
> drop = maybe_add_lru(inode, skip_lru);
>
> - if (atomic_dec_and_test(&inode->i_count)) {
> + if (refcount_dec_and_test(&inode->i_count)) {
> /* iput_final() drops i_lock */
> iput_final(inode, drop);
> } else {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 999ffea2aac1..fc23e37ca250 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -875,7 +875,7 @@ struct inode {
> };
> atomic64_t i_version;
> atomic64_t i_sequence; /* see futex */
> - atomic_t i_count;
> + refcount_t i_count;
> atomic_t i_dio_count;
> atomic_t i_writecount;
> #if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING)
> @@ -3399,12 +3399,12 @@ static inline unsigned int iobj_count_read(const struct inode *inode)
> static inline void __iget(struct inode *inode)
> {
> iobj_get(inode);
> - atomic_inc(&inode->i_count);
> + refcount_inc(&inode->i_count);
> }
>
> static inline int icount_read(const struct inode *inode)
> {
> - return atomic_read(&inode->i_count);
> + return refcount_read(&inode->i_count);
> }
>
> extern void iget_failed(struct inode *);
> --
> 2.49.0
>
