[RFC PATCH v2 1/2] vfs: add provenance time (ptime)
From: koraynilay
Date: Wed Oct 28 2026 - 09:50:45 EST
Add provenance time (ptime), indicating the time when a file or
directory was created. This is user-settable via file_setattr() and
retrievable via statx(2) (using STATX_PTIME) or file_getattr().
The semantics of when to preserve this new timestamp are the same as
mtime, the idea being that there is a correspondence like this:
ctime <-> btime
mtime <-> ptime
so every operation (copying, moving, ...) that currently preserves mtime
should also preserve ptime.
Furthermore, in order to avoid the legacy FS_IOC_FSSETXATTR accepting
FS_XFLAG_PTIME, add an FS_FILE_ATTR_XFLAGS_MASK mask to support new
xflags, and use it in fileattr_to_file_attr()/file_attr_to_fileattr() to
allow ptime to be used with the file_setattr()/file_getattr() syscalls.
[ This is a re-implementation of the initial patch[1] by Sean Smith
<defendthedisabled@xxxxxxxxx>, following the advice[2] from Darrick J.
Wong <djwong@xxxxxxxxxx> of using file_setattr() instead of updating
utimensat() ]
[1]: https://lore.kernel.org/20260405195007.1306-2-DefendTheDisabled@xxxxxxxxx
[2]: https://lore.kernel.org/20260407014129.GC6192@frogsfrogsfrogs
Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7
Signed-off-by: koraynilay <koray.fra@xxxxxxxxx>
---
fs/file_attr.c | 29 +++++++++++++++++++++++++++--
fs/stat.c | 2 ++
include/linux/fileattr.h | 5 +++++
include/linux/stat.h | 1 +
include/uapi/linux/fs.h | 8 +++++++-
include/uapi/linux/stat.h | 7 ++++++-
6 files changed, 48 insertions(+), 4 deletions(-)
diff --git a/fs/file_attr.c b/fs/file_attr.c
index 833e03810b24..9c1dfdba6b4d 100644
--- a/fs/file_attr.c
+++ b/fs/file_attr.c
@@ -102,7 +102,7 @@ EXPORT_SYMBOL(vfs_fileattr_get);
static void fileattr_to_file_attr(const struct file_kattr *fa,
struct file_attr *fattr)
{
- __u32 mask = FS_XFLAGS_MASK;
+ __u32 mask = FS_FILE_ATTR_XFLAGS_MASK;
memset(fattr, 0, sizeof(struct file_attr));
fattr->fa_xflags = fa->fsx_xflags & mask;
@@ -110,6 +110,8 @@ static void fileattr_to_file_attr(const struct file_kattr *fa,
fattr->fa_nextents = fa->fsx_nextents;
fattr->fa_projid = fa->fsx_projid;
fattr->fa_cowextsize = fa->fsx_cowextsize;
+ fattr->fa_ptime_sec = fa->fsx_ptime.tv_sec;
+ fattr->fa_ptime_nsec = fa->fsx_ptime.tv_nsec;
}
/**
@@ -141,15 +143,20 @@ EXPORT_SYMBOL(copy_fsxattr_to_user);
static int file_attr_to_fileattr(const struct file_attr *fattr,
struct file_kattr *fa)
{
- __u64 mask = FS_XFLAGS_MASK;
+ __u64 mask = FS_FILE_ATTR_XFLAGS_MASK;
if (fattr->fa_xflags & ~mask)
return -EINVAL;
+ if (fattr->fa_pad != 0)
+ return -EINVAL;
+
fileattr_fill_xflags(fa, fattr->fa_xflags & ~FS_XFLAG_RDONLY_MASK);
fa->fsx_extsize = fattr->fa_extsize;
fa->fsx_projid = fattr->fa_projid;
fa->fsx_cowextsize = fattr->fa_cowextsize;
+ fa->fsx_ptime.tv_sec = fattr->fa_ptime_sec;
+ fa->fsx_ptime.tv_nsec = fattr->fa_ptime_nsec;
return 0;
}
@@ -232,6 +239,16 @@ static int fileattr_set_prepare(struct inode *inode,
!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
return -EINVAL;
+ if (fa->fsx_xflags & FS_XFLAG_PTIME) {
+ if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
+ return -EPERM;
+
+ if ((unsigned long)fa->fsx_ptime.tv_nsec >= NSEC_PER_SEC)
+ return -EINVAL;
+
+ fa->fsx_ptime = timestamp_truncate(fa->fsx_ptime, inode);
+ }
+
/*
* It is only valid to set the DAX flag on regular files and
* directories on filesystems.
@@ -293,6 +310,7 @@ int vfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
fa->fsx_nextents = old_ma.fsx_nextents;
fa->fsx_projid = old_ma.fsx_projid;
fa->fsx_cowextsize = old_ma.fsx_cowextsize;
+ fa->fsx_ptime = old_ma.fsx_ptime;
} else {
fa->flags |= old_ma.flags & ~FS_COMMON_FL;
}
@@ -423,6 +441,10 @@ SYSCALL_DEFINE5(file_getattr, int, dfd, const char __user *, filename,
return error;
fileattr_to_file_attr(&fa, &fattr);
+
+ if (usize < FILE_ATTR_SIZE_VER1)
+ fattr.fa_xflags &= ~FS_XFLAG_PTIME;
+
error = copy_struct_to_user(ufattr, usize, &fattr,
sizeof(struct file_attr), NULL);
@@ -459,6 +481,9 @@ SYSCALL_DEFINE5(file_setattr, int, dfd, const char __user *, filename,
if (error)
return error;
+ if ((fattr.fa_xflags & FS_XFLAG_PTIME) && usize < FILE_ATTR_SIZE_VER1)
+ return -EINVAL;
+
error = file_attr_to_fileattr(&fattr, &fa);
if (error)
return error;
diff --git a/fs/stat.c b/fs/stat.c
index a2e63c6c45b7..e426f41253f6 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -728,6 +728,8 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer)
tmp.stx_ctime.tv_nsec = stat->ctime.tv_nsec;
tmp.stx_mtime.tv_sec = stat->mtime.tv_sec;
tmp.stx_mtime.tv_nsec = stat->mtime.tv_nsec;
+ tmp.stx_ptime.tv_sec = stat->ptime.tv_sec;
+ tmp.stx_ptime.tv_nsec = stat->ptime.tv_nsec;
tmp.stx_rdev_major = MAJOR(stat->rdev);
tmp.stx_rdev_minor = MINOR(stat->rdev);
tmp.stx_dev_major = MAJOR(stat->dev);
diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index 09e32b84e02a..0b93f9609284 100644
--- a/include/linux/fileattr.h
+++ b/include/linux/fileattr.h
@@ -35,6 +35,10 @@
(FS_XFLAG_COMMON | FS_XFLAG_RDONLY_MASK | FS_XFLAG_VALUES_MASK | \
FS_XFLAG_DIRONLY_MASK | FS_XFLAG_MISC_MASK)
+/* Flags only for fa_ fields */
+#define FS_FILE_ATTR_XFLAGS_MASK \
+ (FS_XFLAGS_MASK | FS_XFLAG_PTIME)
+
/*
* Merged interface for miscellaneous file attributes. 'flags' originates from
* ext* and 'fsx_flags' from xfs. There's some overlap between the two, which
@@ -49,6 +53,7 @@ struct file_kattr {
u32 fsx_nextents; /* nextents field value (get) */
u32 fsx_projid; /* project identifier (get/set) */
u32 fsx_cowextsize; /* CoW extsize field value (get/set)*/
+ struct timespec64 fsx_ptime; /* provenance (settable birth) time */
/* selectors: */
bool flags_valid:1;
bool fsx_valid:1;
diff --git a/include/linux/stat.h b/include/linux/stat.h
index 9c5709132862..69d2ecfd1bf2 100644
--- a/include/linux/stat.h
+++ b/include/linux/stat.h
@@ -48,6 +48,7 @@ struct kstat {
struct timespec64 mtime;
struct timespec64 ctime;
struct timespec64 btime; /* File creation time */
+ struct timespec64 ptime; /* File provenance (user-settable creation) time */
u64 blocks;
u64 mnt_id;
u64 change_cookie;
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index a46c33692aa2..c00e72fcfa3e 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -229,10 +229,14 @@ struct file_attr {
__u32 fa_nextents; /* nextents field value (get) */
__u32 fa_projid; /* project identifier (get/set) */
__u32 fa_cowextsize; /* CoW extsize field value (get/set) */
+ __s64 fa_ptime_sec; /* provenance (settable birth) time (seconds) */
+ __u32 fa_ptime_nsec; /* provenance (settable birth) time (nanoseconds) */
+ __u32 fa_pad;
};
#define FILE_ATTR_SIZE_VER0 24
-#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER0
+#define FILE_ATTR_SIZE_VER1 40
+#define FILE_ATTR_SIZE_LATEST FILE_ATTR_SIZE_VER1
/*
* Flags for the fsx_xflags field
@@ -261,6 +265,8 @@ struct file_attr {
*/
#define FS_XFLAG_CASEFOLD 0x00040000 /* case-insensitive lookups */
#define FS_XFLAG_CASENONPRESERVING 0x00080000 /* case not preserved */
+
+#define FS_XFLAG_PTIME 0x00100000 /* provenance time */
#define FS_XFLAG_HASATTR 0x80000000 /* no DIFLAG for this */
/* the read-only stuff doesn't really belong here, but any other place is
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index 1686861aae20..f3a1013ba022 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -187,7 +187,11 @@ struct statx {
__u32 __spare2[1];
/* 0xc0 */
- __u64 __spare3[8]; /* Spare space for future expansion */
+ /* Data provenance (creation) time */
+ struct statx_timestamp stx_ptime;
+
+ /* 0xd0 */
+ __u64 __spare3[6]; /* Spare space for future expansion */
/* 0x100 */
};
@@ -219,6 +223,7 @@ struct statx {
#define STATX_SUBVOL 0x00008000U /* Want/got stx_subvol */
#define STATX_WRITE_ATOMIC 0x00010000U /* Want/got atomic_write_* fields */
#define STATX_DIO_READ_ALIGN 0x00020000U /* Want/got dio read alignment info */
+#define STATX_PTIME 0x00040000U /* Want/got stx_ptime */
#define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */
--
2.56.0