linux-kernel - [PATCH v3] tmpfs: support for file creation time

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Date:   Mon, 28 Feb 2022 09:43:01 +0100
From:   Xavier Roche <xavier.roche@...olia.com>
To:     torvalds@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jean Delvare <jdelvare@...e.de>,
        Xavier Roche <xavier.roche@...olia.com>, linux-mm@...ck.org
Subject: [PATCH v3] tmpfs: support for file creation time

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@...olia.com>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Tested-by: Jean Delvare <jdelvare@...e.de>
Reviewed-by: Jean Delvare <jdelvare@...e.de>
Cc: Xavier Roche <xavier.roche@...olia.com>
Cc: Jean Delvare <jdelvare@...e.de>
---
 include/linux/shmem_fs.h |  1 +
 mm/shmem.c               | 11 +++++++++++
 2 files changed, 12 insertions(+)

Index: linux/include/linux/shmem_fs.h
===================================================================
--- linux.orig/include/linux/shmem_fs.h
+++ linux/include/linux/shmem_fs.h
@@ -24,6 +24,7 @@ struct shmem_inode_info {
 	struct shared_policy	policy;		/* NUMA memory alloc policy */
 	struct simple_xattrs	xattrs;		/* list of xattrs */
 	atomic_t		stop_eviction;	/* hold when working on inode */
+	struct timespec64	i_crtime;	/* file creation time */
 	struct inode		vfs_inode;
 };
 
Index: linux/mm/shmem.c
===================================================================
--- linux.orig/mm/shmem.c
+++ linux/mm/shmem.c
@@ -476,6 +476,8 @@ bool shmem_is_huge(struct vm_area_struct
 {
 	loff_t i_size;
 
+	if (!S_ISREG(inode->i_mode))
+		return false;
 	if (shmem_huge == SHMEM_HUGE_DENY)
 		return false;
 	if (vma && ((vma->vm_flags & VM_NOHUGEPAGE) ||
@@ -1061,6 +1063,12 @@ static int shmem_getattr(struct user_nam
 	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;
 }
 
@@ -1854,9 +1862,6 @@ repeat:
 		return 0;
 	}
 
-	/* Never use a huge page for shmem_symlink() */
-	if (S_ISLNK(inode->i_mode))
-		goto alloc_nohuge;
 	if (!shmem_is_huge(vma, inode, index))
 		goto alloc_nohuge;
 
@@ -2265,6 +2270,7 @@ static struct inode *shmem_get_inode(str
 		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 +3202,7 @@ static ssize_t shmem_listxattr(struct de
 #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 +3210,7 @@ static const struct inode_operations shm
 };
 
 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 +3798,7 @@ static const struct inode_operations shm
 
 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 +3820,7 @@ static const struct inode_operations shm
 };
 
 static const struct inode_operations shmem_special_inode_operations = {
+	.getattr	= shmem_getattr,
 #ifdef CONFIG_TMPFS_XATTR
 	.listxattr	= shmem_listxattr,
 #endif