The i_state member is an unsigned long so that it can be used with the
wait bit infrastructure which expects unsigned long. This wastes 4 bytes
which we're unlikely to ever use. Switch to using the var event wait
mechanism using the address of the bit. Thanks to Linus for the address
idea.
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
fs/inode.c | 11 +++++++++++
include/linux/fs.h | 16 ++++++++++++++++
2 files changed, 27 insertions(+)
diff --git a/fs/inode.c b/fs/inode.c
index 154f8689457f..d0f614677798 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -472,6 +472,17 @@ static void __inode_add_lru(struct inode *inode, bool rotate)
inode->i_state |= I_REFERENCED;
}
+struct wait_queue_head *inode_bit_waitqueue(struct wait_bit_queue_entry *wqe,
+ struct inode *inode, int bit);
+{
+ struct wait_queue_head *wq_head;
+ void *bit_address;
+
+ bit_address = inode_state_wait_address(inode, __I_SYNC);
+ init_wait_var_entry(wqe, bit_address, 0);
+ return __var_waitqueue(bit_address);
+}
+
/*
* Add inode to LRU if needed (inode is unused and clean).
*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 23e7d46b818a..f854f83e91af 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -744,6 +744,22 @@ struct inode {
void *i_private; /* fs or device private pointer */
} __randomize_layout;
+/*
+ * Get bit address from inode->i_state to use with wait_var_event()
+ * infrastructre.
+ */
+#define inode_state_wait_address(inode, bit) ((char *)&(inode)->i_state + (bit))
+
+struct wait_queue_head *inode_bit_waitqueue(struct wait_bit_queue_entry *wqe,
+ struct inode *inode, int bit);
+
+static inline void inode_wake_up_bit(struct inode *inode, unsigned int bit)
+{
+ /* Ensure @bit will be seen cleared/set when caller is woken up. */
+ smp_mb();
+ wake_up_var(inode_state_wait_address(inode, bit));
+}
+
struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode);
static inline unsigned int i_blocksize(const struct inode *node)
--
2.43.0
