[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <3f53f0e8bdd7e598740f6ebf7d96c7cec1de7269.1756222465.git.josef@toxicpanda.com>
Date: Tue, 26 Aug 2025 11:39:04 -0400
From: Josef Bacik <josef@...icpanda.com>
To: linux-fsdevel@...r.kernel.org,
linux-btrfs@...r.kernel.org,
kernel-team@...com,
linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org,
brauner@...nel.org,
viro@...IV.linux.org.uk,
amir73il@...il.com
Subject: [PATCH v2 04/54] fs: add an i_obj_count refcount to the inode
Currently the inode's lifetime is controlled by it's main refcount,
i_count. We overload the eviction of the inode (the final unlink) with
the deletion of the in-memory object, which leads to some hilarity when
we iput() in unfortunate places.
In order to make this less of a footgun, we want to separate the notion
of "is this inode in use by a user" and "is this inode object currently
in use", since deleting an inode is a much heavier operation that
deleting the object and cleaning up its memory.
To that end, introduce ->i_obj_count to the inode. This will be used to
control the lifetime of the inode object itself. We will continue to use
the ->i_count refcount as normal to reduce the churn of adding a new
refcount to inode. Subsequent patches will expand the usage of
->i_obj_count for internal uses, and then I will separate out the
tear down operations of the inode, and then finally adjust the refount
rules for ->i_count to be more consistent with all other refcounts.
Signed-off-by: Josef Bacik <josef@...icpanda.com>
---
fs/inode.c | 20 ++++++++++++++++++++
include/linux/fs.h | 12 ++++++++++++
2 files changed, 32 insertions(+)
diff --git a/fs/inode.c b/fs/inode.c
index 13e80b434323..d426f54c05d9 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -235,6 +235,7 @@ int inode_init_always_gfp(struct super_block *sb, struct inode *inode, gfp_t gfp
inode->i_flags = 0;
inode->i_state = 0;
atomic64_set(&inode->i_sequence, 0);
+ refcount_set(&inode->i_obj_count, 1);
atomic_set(&inode->i_count, 1);
inode->i_op = &empty_iops;
inode->i_fop = &no_open_fops;
@@ -831,6 +832,11 @@ static void evict(struct inode *inode)
inode_wake_up_bit(inode, __I_NEW);
BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
+ /*
+ * refcount_dec_and_test must be used here to avoid the underflow
+ * warning.
+ */
+ WARN_ON(!refcount_dec_and_test(&inode->i_obj_count));
destroy_inode(inode);
}
@@ -1930,6 +1936,20 @@ void iput(struct inode *inode)
}
EXPORT_SYMBOL(iput);
+/**
+ * iobj_put - put a object reference on an inode
+ * @inode: inode to put
+ *
+ * Puts a object reference on an inode.
+ */
+void iobj_put(struct inode *inode)
+{
+ if (!inode)
+ return;
+ refcount_dec(&inode->i_obj_count);
+}
+EXPORT_SYMBOL(iobj_put);
+
#ifdef CONFIG_BLOCK
/**
* bmap - find a block number in a file
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 56041d3387fe..84f5218755c3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -871,6 +871,7 @@ struct inode {
#if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING)
atomic_t i_readcount; /* struct files open RO */
#endif
+ refcount_t i_obj_count;
union {
const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
void (*free_inode)(struct inode *);
@@ -2809,6 +2810,7 @@ extern int current_umask(void);
extern void ihold(struct inode * inode);
extern void iput(struct inode *);
+extern void iobj_put(struct inode *inode);
int inode_update_timestamps(struct inode *inode, int flags);
int generic_update_time(struct inode *, int);
@@ -3364,6 +3366,16 @@ static inline bool is_zero_ino(ino_t ino)
return (u32)ino == 0;
}
+static inline void iobj_get(struct inode *inode)
+{
+ refcount_inc(&inode->i_obj_count);
+}
+
+static inline unsigned int iobj_count_read(const struct inode *inode)
+{
+ return refcount_read(&inode->i_obj_count);
+}
+
/*
* inode->i_lock must be held
*/
--
2.49.0
Powered by blists - more mailing lists