[PATCH v2] tmpfs: support for file creation time

[Xavier Roche <xavier.roche@algolia.com>]

Various filesystems (including ext4) now support file creation time.
This patch adds such support for tmpfs-based filesystems.

Signed-off-by: Xavier Roche <xavier.roche@algolia.com>
Tested-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
---
 include/linux/shmem_fs.h |  1 +
 mm/shmem.c               | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index e65b80ed09e7..29787767c3b9 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -25,6 +25,7 @@ struct shmem_inode_info {
 	struct simple_xattrs	xattrs;		/* list of xattrs */
 	atomic_t		stop_eviction;	/* hold when working on inode */
 	struct inode		vfs_inode;
+	struct timespec64	i_crtime;	/* file creation time */
 };
 
 struct shmem_sb_info {
diff --git a/mm/shmem.c b/mm/shmem.c
index a09b29ec2b45..5a3907712c4f 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1061,6 +1061,12 @@ static int shmem_getattr(struct user_namespace *mnt_userns,
 	if (shmem_is_huge(NULL, inode, 0))
 		stat->blksize = HPAGE_PMD_SIZE;
 
+	if ((request_mask & STATX_BTIME)) {
+		stat->result_mask |= STATX_BTIME;
+		stat->btime.tv_sec = info->i_crtime.tv_sec;
+		stat->btime.tv_nsec = info->i_crtime.tv_nsec;
+	}
+
 	return 0;
 }
 
@@ -2265,6 +2271,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 		atomic_set(&info->stop_eviction, 0);
 		info->seals = F_SEAL_SEAL;
 		info->flags = flags & VM_NORESERVE;
+		info->i_crtime = inode->i_mtime;
 		INIT_LIST_HEAD(&info->shrinklist);
 		INIT_LIST_HEAD(&info->swaplist);
 		simple_xattrs_init(&info->xattrs);
@@ -3196,6 +3203,7 @@ static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
 #endif /* CONFIG_TMPFS_XATTR */
 
 static const struct inode_operations shmem_short_symlink_operations = {
+	.getattr	= shmem_getattr,
 	.get_link	= simple_get_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
@@ -3203,6 +3211,7 @@ static const struct inode_operations shmem_short_symlink_operations = {
 };
 
 static const struct inode_operations shmem_symlink_inode_operations = {
+	.getattr	= shmem_getattr,
 	.get_link	= shmem_get_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
@@ -3790,6 +3799,7 @@ static const struct inode_operations shmem_inode_operations = {
 
 static const struct inode_operations shmem_dir_inode_operations = {
 #ifdef CONFIG_TMPFS
+	.getattr	= shmem_getattr,
 	.create		= shmem_create,
 	.lookup		= simple_lookup,
 	.link		= shmem_link,
@@ -3811,6 +3821,7 @@ static const struct inode_operations shmem_dir_inode_operations = {
 };
 
 static const struct inode_operations shmem_special_inode_operations = {
+	.getattr	= shmem_getattr,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
 #endif
-- 
2.25.1