[PATCH 3/3] ext4: store creation time in separate seconds and nanoseconds

[Max Kellermann <max.kellermann@ionos.com>]

Keep 64-bit seconds and 32-bit nanoseconds and place the latter next
to i_raw_lock. Preserve the existing on-disk encoding and timestamp
range while saving 8 bytes per inode without fast commit.

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 fs/ext4/ext4.h   | 18 +++++++++++++-----
 fs/ext4/ialloc.c |  3 ++-
 fs/ext4/inode.c  |  4 ++--
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index c2c242f60700..9b6df2632fdd 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -930,9 +930,15 @@ do {										\
 	EXT4_INODE_SET_XTIME_VAL(i_ctime, inode, raw_inode, inode_get_ctime(inode))
 
 #define EXT4_EINODE_SET_XTIME(xtime, einode, raw_inode)				\
+do {									\
+	struct timespec64 ts = {						\
+		.tv_sec = (einode)->xtime ## _sec,			\
+		.tv_nsec = (einode)->xtime ## _nsec,			\
+	};								\
 	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime))			\
 		EXT4_INODE_SET_XTIME_VAL(xtime, &((einode)->vfs_inode),		\
-					 raw_inode, (einode)->xtime)
+					 raw_inode, ts);			\
+} while (0)
 
 #define EXT4_INODE_GET_XTIME_VAL(xtime, inode, raw_inode)			\
 	(EXT4_FITS_IN_INODE(raw_inode, EXT4_I(inode), xtime ## _extra) ?	\
@@ -962,12 +968,13 @@ do {										\
 
 #define EXT4_EINODE_GET_XTIME(xtime, einode, raw_inode)				\
 do {										\
+	struct timespec64 ts = { 0, 0 };					\
 	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime)) 			\
-		(einode)->xtime =						\
+		ts =								\
 			EXT4_INODE_GET_XTIME_VAL(xtime, &(einode->vfs_inode),	\
 						 raw_inode);			\
-	else									\
-		(einode)->xtime = (struct timespec64){0, 0};			\
+	(einode)->xtime ## _sec = ts.tv_sec;				\
+	(einode)->xtime ## _nsec = ts.tv_nsec;				\
 } while (0)
 
 #define i_disk_version osd1.linux1.l_i_version
@@ -1123,6 +1130,7 @@ struct ext4_inode_info {
 #endif
 
 	spinlock_t i_raw_lock;	/* protects updates to the raw inode */
+	u32 i_crtime_nsec;
 
 #ifdef CONFIG_EXT4_FS_FAST_COMMIT
 	/*
@@ -1168,7 +1176,7 @@ struct ext4_inode_info {
 	 * File creation time. Its function is same as that of
 	 * struct timespec64 i_{a,c,m}time in the generic inode.
 	 */
-	struct timespec64 i_crtime;
+	time64_t i_crtime_sec;
 
 	/* mballoc */
 	atomic_t i_prealloc_active;
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 527f1f703c3e..1d73dd35e000 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -1261,7 +1261,8 @@ struct inode *__ext4_new_inode(const struct mnt_idmap *idmap,
 	/* This is the optimal IO size (for stat), not the fs block size */
 	inode->i_blocks = 0;
 	simple_inode_init_ts(inode);
-	ei->i_crtime = inode_get_mtime(inode);
+	ei->i_crtime_sec = inode_get_mtime_sec(inode);
+	ei->i_crtime_nsec = inode_get_mtime_nsec(inode);
 
 	memset(ei->i_data, 0, sizeof(ei->i_data));
 	ei->i_dir_start_lookup = 0;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 829095aedbe6..5dc22f8747ff 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -7190,8 +7190,8 @@ int ext4_getattr(const struct mnt_idmap *idmap, const struct path *path,
 	if ((request_mask & STATX_BTIME) &&
 	    EXT4_FITS_IN_INODE(raw_inode, ei, i_crtime)) {
 		stat->result_mask |= STATX_BTIME;
-		stat->btime.tv_sec = ei->i_crtime.tv_sec;
-		stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
+		stat->btime.tv_sec = ei->i_crtime_sec;
+		stat->btime.tv_nsec = ei->i_crtime_nsec;
 	}
 
 	/* Return the DIO alignment restrictions if requested. */
-- 
2.53.0