| Message ID | 20240823-work-i_state-v3-1-5cd5fd207a57@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | inode: turn i_state into u32 | expand |
On Fri 23-08-24 14:47:35, Christian Brauner wrote: > 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@kernel.org> Looks good. Interesting trick with the wakeup address. I'm not sure we 100% need it since e.g. __I_NEW waiters are unlikely to combine with __I_SYNC waiters so sharing a waitqueue should not cause big issues but I guess we'll deal with that if we run out of waiting bits with the current scheme. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/inode.c | 11 +++++++++++ > include/linux/fs.h | 15 +++++++++++++++ > 2 files changed, 26 insertions(+) > > diff --git a/fs/inode.c b/fs/inode.c > index 154f8689457f..877c64a1bf63 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, u32 bit) > +{ > + void *bit_address; > + > + bit_address = inode_state_wait_address(inode, bit); > + init_wait_var_entry(wqe, bit_address, 0); > + return __var_waitqueue(bit_address); > +} > +EXPORT_SYMBOL(inode_bit_waitqueue); > + > /* > * 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..1d895b8cb801 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -744,6 +744,21 @@ 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, u32 bit); > + > +static inline void inode_wake_up_bit(struct inode *inode, u32 bit) > +{ > + /* Caller is responsible for correct memory barriers. */ > + 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 >
diff --git a/fs/inode.c b/fs/inode.c index 154f8689457f..877c64a1bf63 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, u32 bit) +{ + void *bit_address; + + bit_address = inode_state_wait_address(inode, bit); + init_wait_var_entry(wqe, bit_address, 0); + return __var_waitqueue(bit_address); +} +EXPORT_SYMBOL(inode_bit_waitqueue); + /* * 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..1d895b8cb801 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -744,6 +744,21 @@ 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, u32 bit); + +static inline void inode_wake_up_bit(struct inode *inode, u32 bit) +{ + /* Caller is responsible for correct memory barriers. */ + 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)
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@kernel.org> --- fs/inode.c | 11 +++++++++++ include/linux/fs.h | 15 +++++++++++++++ 2 files changed, 26 insertions(+)