[PATCH RFC 1/9] fs: switch timespec64 fields in inode to discrete integers

Jeff Layton
2023-10-18T17:41:46Z

This shaves 8 bytes off struct inode with a garden-variety Fedora
Kconfig, but it moves the i_lock into the previous cacheline, away from
the fields it protects. To remedy that, move the i_generation just after
the nanosecond fields, which moves the 4 byte hole down next to
i_fsnotify_mask.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
include/linux/fs.h | 56 +++++++++++++++++++++++++++++++-----------------------
1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index cc29518517f7..78786c1c32fd 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -671,9 +671,13 @@ struct inode {
};
dev_t i_rdev;
loff_t i_size;
- struct timespec64 __i_atime;
- struct timespec64 __i_mtime;
- struct timespec64 __i_ctime; /* use inode_*_ctime accessors! */
+ time64_t i_atime_sec;
+ time64_t i_mtime_sec;
+ time64_t i_ctime_sec;
+ u32 i_atime_nsec;
+ u32 i_mtime_nsec;
+ u32 i_ctime_nsec;
+ u32 i_generation;
spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
unsigned short i_bytes;
u8 i_blkbits;
@@ -730,10 +734,10 @@ struct inode {
unsigned i_dir_seq;
};

- __u32 i_generation;

#ifdef CONFIG_FSNOTIFY
__u32 i_fsnotify_mask; /* all events this inode cares about */
+ /* 32bit hole reserved for expanding i_fsnotify_mask to 64bit */
struct fsnotify_mark_connector __rcu *i_fsnotify_marks;
#endif

@@ -1513,23 +1517,27 @@ struct timespec64 inode_set_ctime_current(struct inode *inode);

static inline time64_t inode_get_atime_sec(const struct inode *inode)
{
- return inode->__i_atime.tv_sec;
+ return inode->i_atime_sec;
}

static inline long inode_get_atime_nsec(const struct inode *inode)
{
- return inode->__i_atime.tv_nsec;
+ return inode->i_atime_nsec;
}

static inline struct timespec64 inode_get_atime(const struct inode *inode)
{
- return inode->__i_atime;
+ struct timespec64 ts = { .tv_sec = inode_get_atime_sec(inode),
+ .tv_nsec = inode_get_atime_nsec(inode) };
+
+ return ts;
}

static inline struct timespec64 inode_set_atime_to_ts(struct inode *inode,
struct timespec64 ts)
{
- inode->__i_atime = ts;
+ inode->i_atime_sec = ts.tv_sec;
+ inode->i_atime_nsec = ts.tv_nsec;
return ts;
}

@@ -1538,28 +1546,32 @@ static inline struct timespec64 inode_set_atime(struct inode *inode,
{
struct timespec64 ts = { .tv_sec = sec,
.tv_nsec = nsec };
+
return inode_set_atime_to_ts(inode, ts);
}

static inline time64_t inode_get_mtime_sec(const struct inode *inode)
{
- return inode->__i_mtime.tv_sec;
+ return inode->i_mtime_sec;
}

static inline long inode_get_mtime_nsec(const struct inode *inode)
{
- return inode->__i_mtime.tv_nsec;
+ return inode->i_mtime_nsec;
}

static inline struct timespec64 inode_get_mtime(const struct inode *inode)
{
- return inode->__i_mtime;
+ struct timespec64 ts = { .tv_sec = inode_get_mtime_sec(inode),
+ .tv_nsec = inode_get_mtime_nsec(inode) };
+ return ts;
}

static inline struct timespec64 inode_set_mtime_to_ts(struct inode *inode,
struct timespec64 ts)
{
- inode->__i_mtime = ts;
+ inode->i_mtime_sec = ts.tv_sec;
+ inode->i_mtime_nsec = ts.tv_nsec;
return ts;
}

@@ -1573,34 +1585,30 @@ static inline struct timespec64 inode_set_mtime(struct inode *inode,

static inline time64_t inode_get_ctime_sec(const struct inode *inode)
{
- return inode->__i_ctime.tv_sec;
+ return inode->i_ctime_sec;
}

static inline long inode_get_ctime_nsec(const struct inode *inode)
{
- return inode->__i_ctime.tv_nsec;
+ return inode->i_ctime_nsec;
}

static inline struct timespec64 inode_get_ctime(const struct inode *inode)
{
- return inode->__i_ctime;
+ struct timespec64 ts = { .tv_sec = inode_get_ctime_sec(inode),
+ .tv_nsec = inode_get_ctime_nsec(inode) };
+
+ return ts;
}

static inline struct timespec64 inode_set_ctime_to_ts(struct inode *inode,
struct timespec64 ts)
{
- inode->__i_ctime = ts;
+ inode->i_ctime_sec = ts.tv_sec;
+ inode->i_ctime_nsec = ts.tv_nsec;
return ts;
}

-/**
- * inode_set_ctime - set the ctime in the inode
- * @inode: inode in which to set the ctime
- * @sec: tv_sec value to set
- * @nsec: tv_nsec value to set
- *
- * Set the ctime in @inode to { @sec, @nsec }
- */
static inline struct timespec64 inode_set_ctime(struct inode *inode,
time64_t sec, long nsec)
{

--
2.41.0