[RFC PATCH v3 0/5] add provenance time (ptime)

[RFC PATCH v3 0/5] add provenance time (ptime)

[koraynilay]

This is an initial implementation of a new timestamp to indicate the
time when a file/directory was initially created.

This patch series takes inspiration from the one by Sean Smith
<defendthedisabled@gmail.com> [1], but using
file_setattr()/file_getattr() as suggested by Darrick J. Wong
<djwong@kernel.org> in [2].

The semantics of this new timestamp should be at least these:
- it should be the same as btime on a newly created file
- it's user-settable, so it can be preserved for backups, filesystem
  conversions, archives and any similar operation
- it should be preserved every time mtime gets preserved

and the correspondence with the other timestamps is as follows:

ctime <-> btime
mtime <-> ptime

Examples:
1) a .zsh_history file created in 2019, then after a few years the user
   decides to switch to another filesystem, copying the .zsh_history to
   the new home, in that case btime would have the timestamp of the copy
   and ptime would have the 2019 timestamp (just like mtime would have
   been preserved)
2) a symlink created in 2020 from the home directory to a /path going
   through the same process as the .zsh_history, in this case it would
   also make sense to sync the ptime to the 2020 timestamp instead of
   keeping only the btime (so the inode creation time).

The proof-of-concept code (for testing) for stat(1) and cp(1) is
available at https://github.com/koraynilay/coreutils (master branch)
(Note: these coreutils code changes are a prototype and won't be
submitted upstream as-is, but they work as expected in simple stat and
cp -a/--preserve=ptime tests)

Lastly, the name "provenance" and "ptime" are not final, I personally
don't have a strong opinion on any name, but while testing with stat(1)
I noticed that "Provenance" is definitely too long for the normal
output, so another option which would fit well is "Origin time",
abbreviated as "ntime" (OrigiN time) and not as "otime", as that would
conflict with btrfs' internal naming and create confusion.

v2 changes:
- fix permission bypass leading to ptime update on immutable and
  append-only files (found by sashiko[3])
- normalize ptime timestamp as done in fs/attr.c:notify_change() (found
  by sashiko[3])
- fix wording in vfs patch to be like the cover-letter

v3 changes:
- vfs: reject setting ptime with -EOPNOTSUPP on filesystems that do not
  support it instead of silently ignoring it (found by sashiko[4])
- vfs: fix not being able to clear immutable and append-only on files
  with ptime, and allow updating immutable/append-only atomically along
  with ptime (found by sashiko[4])
- btrfs: validate on-disk ptime nanoseconds and reset to otime if
  invalid (found by sashiko[4])
- btrfs: avoid re-assigning ptime on unrelated chattr calls (found by
  sashiko[4])
- add ntfs3 and exfat support as suggested by Amir Goldstein[5], but no
  vfat, smb, or nfs4 yet as they are a bit more complex
- move the introduction of fileattr_has_fsx_mask() from the btrfs patch
  to a standalone patch in the series
- btrfs: add fileattr_[gs]et to symlink and special file operations

Thanks.

[1]: https://lore.kernel.org/20260405195007.1306-2-DefendTheDisabled@gmail.com
[2]: https://lore.kernel.org/20260407014129.GC6192@frogsfrogsfrogs
[3]: https://sashiko.dev/#/patchset/20261027220532.736352-1-koray.fra%40gmail.com
[4]: https://sashiko.dev/#/patchset/20261028134728.294127-1-koray.fra%40gmail.com
[5]: https://lore.kernel.org/linux-btrfs/CAOQ4uxiuy0VwZj+3M-zRqQ49WTpHZpiaQ+6MZ8z8WdLjyQM_zA@mail.gmail.com/

koraynilay (5):
  vfs: add provenance time (ptime)
  vfs: add fileattr_has_fsx_mask()
  ntfs3: make crtime user-settable using ptime
  exfat: make crtime user-settable using ptime
  btrfs: add provenance time (ptime)

 fs/btrfs/btrfs_inode.h          |  4 ++++
 fs/btrfs/delayed-inode.c        |  6 ++++++
 fs/btrfs/inode.c                | 29 +++++++++++++++++++++++++-
 fs/btrfs/ioctl.c                | 12 ++++++++++-
 fs/btrfs/print-tree.c           |  1 +
 fs/btrfs/tree-log.c             |  3 +++
 fs/exfat/exfat_fs.h             |  2 ++
 fs/exfat/file.c                 | 36 ++++++++++++++++++++++++++++++++-
 fs/exfat/namei.c                |  1 +
 fs/file_attr.c                  | 33 ++++++++++++++++++++++++++++--
 fs/ntfs3/file.c                 | 14 +++++++++++--
 fs/ntfs3/frecord.c              |  8 +++++++-
 fs/stat.c                       |  2 ++
 include/linux/fileattr.h        | 26 +++++++++++++++++++++---
 include/linux/stat.h            |  1 +
 include/uapi/linux/btrfs_tree.h |  3 ++-
 include/uapi/linux/fs.h         |  8 +++++++-
 include/uapi/linux/stat.h       |  7 ++++++-
 18 files changed, 182 insertions(+), 14 deletions(-)


base-commit: cbbddb6b08cc9900a87cccaa9b22bbe06aa4f50a
-- 
2.56.0

[RFC PATCH v3 1/5] vfs: add provenance time (ptime)

[koraynilay]

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@gmail.com>, following the advice[2] from Darrick J.
  Wong <djwong@kernel.org> of using file_setattr() instead of updating
  utimensat() ]

[1]: https://lore.kernel.org/20260405195007.1306-2-DefendTheDisabled@gmail.com
[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@gmail.com>
---
 fs/file_attr.c            | 33 +++++++++++++++++++++++++++++++--
 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, 52 insertions(+), 4 deletions(-)

diff --git a/fs/file_attr.c b/fs/file_attr.c
index 833e03810b24..c0645cb22bf3 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 +239,20 @@ 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 (!(old_ma->fsx_xflags & FS_XFLAG_PTIME))
+			return -EOPNOTSUPP;
+
+		if ((unsigned long)fa->fsx_ptime.tv_nsec >= NSEC_PER_SEC)
+			return -EINVAL;
+
+		fa->fsx_ptime = timestamp_truncate(fa->fsx_ptime, inode);
+
+		if (!timespec64_equal(&old_ma->fsx_ptime, &fa->fsx_ptime) &&
+		    (fa->flags & old_ma->flags) & (FS_APPEND_FL | FS_IMMUTABLE_FL))
+			return -EPERM;
+	}
+
 	/*
 	 * It is only valid to set the DAX flag on regular files and
 	 * directories on filesystems.
@@ -293,6 +314,7 @@ 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 +445,10 @@ 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 +485,9 @@ 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

[RFC PATCH v3 2/5] vfs: add fileattr_has_fsx_mask()

[koraynilay]

Add fileattr_has_fsx_mask() as a helper to let filesystems check for
unsupported xflags while allowing supported ones. Can be used in the
same way as fileattr_has_fsx().

Also make fileattr_has_fsx() a wrapper around fileattr_has_fsx_mask().

Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7
Signed-off-by: koraynilay <koray.fra@gmail.com>
---
 include/linux/fileattr.h | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/fileattr.h b/include/linux/fileattr.h
index 0b93f9609284..16acc61c9af1 100644
--- a/include/linux/fileattr.h
+++ b/include/linux/fileattr.h
@@ -64,6 +64,23 @@ int copy_fsxattr_to_user(const struct file_kattr *fa, struct fsxattr __user *ufa
 void fileattr_fill_xflags(struct file_kattr *fa, u32 xflags);
 void fileattr_fill_flags(struct file_kattr *fa, u32 flags);
 
+/**
+ * fileattr_has_fsx_mask - check for extended flags/attributes
+ * @fa:				fileattr pointer
+ * @allowed_xflags_mask:	additional xflags permitted
+ *
+ * Return: true if any attributes are present that are not represented in
+ * ->flags or @allowed_xflags_mask.
+ */
+static inline bool fileattr_has_fsx_mask(const struct file_kattr *fa,
+					 u32 allowed_xflags_mask)
+{
+	return fa->fsx_valid &&
+		((fa->fsx_xflags & ~(FS_XFLAG_COMMON | allowed_xflags_mask)) ||
+		 fa->fsx_extsize != 0 || fa->fsx_projid != 0 ||
+		 fa->fsx_cowextsize != 0);
+}
+
 /**
  * fileattr_has_fsx - check for extended flags/attributes
  * @fa:		fileattr pointer
@@ -73,9 +90,7 @@ void fileattr_fill_flags(struct file_kattr *fa, u32 flags);
  */
 static inline bool fileattr_has_fsx(const struct file_kattr *fa)
 {
-	return fa->fsx_valid &&
-		((fa->fsx_xflags & ~FS_XFLAG_COMMON) || fa->fsx_extsize != 0 ||
-		 fa->fsx_projid != 0 ||	fa->fsx_cowextsize != 0);
+	return fileattr_has_fsx_mask(fa, 0);
 }
 
 int vfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
-- 
2.56.0

[RFC PATCH v3 3/5] ntfs3: make crtime user-settable using ptime

[koraynilay]

Since NTFS supports user-settable file creation timestamps, map
provenance time (ptime) to NTFS file creation time (crtime) by using the
newly introduced ptime API (in commit "vfs: add provenance time
(ptime)").

To do this, update ntfs_fileattr_[gs]et(), ntfs_getattr() and make it
persist to disk in ni_write_inode().

The timestamp is now retrievable by using file_getattr() or statx(), and
is settable by using file_setattr() with the FS_XFLAG_PTIME flag.

Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7
Signed-off-by: koraynilay <koray.fra@gmail.com>
---
 fs/ntfs3/file.c    | 14 ++++++++++++--
 fs/ntfs3/frecord.c |  8 +++++++-
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 1624f9b014e0..b334449e9beb 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -124,6 +124,10 @@ int ntfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 
 	fileattr_fill_flags(fa, flags);
 
+	fa->fsx_ptime.tv_sec = ni->i_crtime.tv_sec;
+	fa->fsx_ptime.tv_nsec = ni->i_crtime.tv_nsec;
+	fa->fsx_xflags |= FS_XFLAG_PTIME;
+
 	return 0;
 }
 
@@ -142,7 +146,7 @@ int ntfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
 	if (unlikely(is_bad_ni(ni)))
 		return -EINVAL;
 
-	if (fileattr_has_fsx(fa))
+	if (fileattr_has_fsx_mask(fa, FS_XFLAG_PTIME))
 		return -EOPNOTSUPP;
 
 	if (flags & ~(FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL))
@@ -154,6 +158,11 @@ int ntfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
 	if (flags & FS_APPEND_FL)
 		new_fl |= S_APPEND;
 
+	if (fa->fsx_xflags & FS_XFLAG_PTIME) {
+		ni->i_crtime.tv_sec = fa->fsx_ptime.tv_sec;
+		ni->i_crtime.tv_nsec = fa->fsx_ptime.tv_nsec;
+	}
+
 	inode_set_flags(inode, new_fl, S_IMMUTABLE | S_APPEND);
 
 	/* Save nodump flag to return in ntfs_getattr. */
@@ -275,8 +284,9 @@ int ntfs_getattr(const struct mnt_idmap *idmap, const struct path *path,
 	if (unlikely(is_bad_ni(ni)))
 		return -EINVAL;
 
-	stat->result_mask |= STATX_BTIME;
+	stat->result_mask |= (STATX_BTIME | STATX_PTIME);
 	stat->btime = ni->i_crtime;
+	stat->ptime = ni->i_crtime;
 	stat->blksize = ni->mi.sbi->cluster_size; /* 512, 1K, ..., 2M */
 
 	if (inode->i_flags & S_IMMUTABLE)
diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c
index 16ac847de48d..5e4f743a5930 100644
--- a/fs/ntfs3/frecord.c
+++ b/fs/ntfs3/frecord.c
@@ -3215,6 +3215,13 @@ int ni_write_inode(struct inode *inode, int sync, const char *hint)
 		}
 
 		/* Update the access times if they have changed. */
+		ts = ni->i_crtime;
+		dup.cr_time = kernel2nt(&ts);
+		if (std->cr_time != dup.cr_time) {
+			std->cr_time = dup.cr_time;
+			modified = true;
+		}
+
 		ts = inode_get_mtime(inode);
 		dup.m_time = kernel2nt(&ts);
 		if (std->m_time != dup.m_time) {
@@ -3250,7 +3257,6 @@ int ni_write_inode(struct inode *inode, int sync, const char *hint)
 		    (modified || (ni->ni_flags & NI_FLAG_UPDATE_PARENT))
 		    /* Avoid __wait_on_freeing_inode(inode). */
 		    && (sb->s_flags & SB_ACTIVE)) {
-			dup.cr_time = std->cr_time;
 			/* Not critical if this function fail. */
 			re_dirty = ni_update_parent(ni, &dup, sync);
 
-- 
2.56.0

[RFC PATCH v3 4/5] exfat: make crtime user-settable using ptime

[koraynilay]

Since exFAT supports user-settable file creation timestamps, map
provenance time (ptime) to exFAT file creation time (crtime) using the
newly introduced ptime API (in commit "vfs: add provenance time
(ptime)").

To do this, implement exfat_fileattr_set(), set .fileattr_set to it for
both file_inode and dir_inode operations and update exfat_fileattr_get()
and exfat_getattr().

The timestamp is now retrievable by using file_getattr() or statx(), and
is settable by using file_setattr() with the FS_XFLAG_PTIME flag.

Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7
Signed-off-by: koraynilay <koray.fra@gmail.com>
---
 fs/exfat/exfat_fs.h |  2 ++
 fs/exfat/file.c     | 36 +++++++++++++++++++++++++++++++++++-
 fs/exfat/namei.c    |  1 +
 3 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index eee573d1697c..aff96afa258a 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -619,6 +619,8 @@ int exfat_getattr(const struct mnt_idmap *idmap, const struct path *path,
 		  unsigned int query_flags);
 struct file_kattr;
 int exfat_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
+int exfat_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
+		       struct file_kattr *fa);
 int exfat_file_fsync(struct file *file, loff_t start, loff_t end, int datasync);
 long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
 long exfat_compat_ioctl(struct file *filp, unsigned int cmd,
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 1386149916bb..70e226cb4ab7 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -384,15 +384,20 @@ int exfat_getattr(const struct mnt_idmap *idmap, const struct path *path,
 
 	generic_fillattr(idmap, request_mask, inode, stat);
 	exfat_truncate_atime(&stat->atime);
-	stat->result_mask |= STATX_BTIME;
+	stat->result_mask |= (STATX_BTIME | STATX_PTIME);
 	stat->btime.tv_sec = ei->i_crtime.tv_sec;
 	stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
+	stat->ptime.tv_sec = ei->i_crtime.tv_sec;
+	stat->ptime.tv_nsec = ei->i_crtime.tv_nsec;
 	stat->blksize = EXFAT_SB(inode->i_sb)->cluster_size;
 	return 0;
 }
 
 int exfat_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 {
+	struct inode *inode = d_backing_inode(dentry);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+
 	/*
 	 * exFAT compares filenames through an upcase table, so lookup
 	 * is always case-insensitive. Long names are stored in UTF-16
@@ -400,6 +405,11 @@ int exfat_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 	 */
 	fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
 	fa->flags |= FS_CASEFOLD_FL;
+
+	fa->fsx_ptime.tv_sec = ei->i_crtime.tv_sec;
+	fa->fsx_ptime.tv_nsec = ei->i_crtime.tv_nsec;
+	fa->fsx_xflags |= FS_XFLAG_PTIME;
+
 	return 0;
 }
 
@@ -485,6 +495,29 @@ int exfat_setattr(const struct mnt_idmap *idmap, struct dentry *dentry,
 	return error;
 }
 
+int exfat_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
+		      struct file_kattr *fa)
+{
+	struct inode *inode = d_backing_inode(dentry);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+
+	if (fileattr_has_fsx_mask(fa, FS_XFLAG_PTIME))
+		return -EOPNOTSUPP;
+
+	if (fa->flags & ~FS_CASEFOLD_FL)
+		return -EOPNOTSUPP;
+
+	if (fa->fsx_xflags & FS_XFLAG_PTIME) {
+		ei->i_crtime.tv_sec = fa->fsx_ptime.tv_sec;
+		ei->i_crtime.tv_nsec = fa->fsx_ptime.tv_nsec;
+	}
+
+	inode_set_ctime_current(inode);
+	mark_inode_dirty(inode);
+
+	return 0;
+}
+
 /*
  * modified ioctls from fat/file.c by Welmer Almesberger
  */
@@ -1110,4 +1143,5 @@ const struct inode_operations exfat_file_inode_operations = {
 	.setattr	= exfat_setattr,
 	.getattr	= exfat_getattr,
 	.fileattr_get	= exfat_fileattr_get,
+	.fileattr_set	= exfat_fileattr_set,
 };
diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
index 68ddb9c5504f..15ec7f1942c8 100644
--- a/fs/exfat/namei.c
+++ b/fs/exfat/namei.c
@@ -1349,4 +1349,5 @@ const struct inode_operations exfat_dir_inode_operations = {
 	.setattr	= exfat_setattr,
 	.getattr	= exfat_getattr,
 	.fileattr_get	= exfat_fileattr_get,
+	.fileattr_set	= exfat_fileattr_set,
 };
-- 
2.56.0

[RFC PATCH v3 5/5] btrfs: add provenance time (ptime)

[koraynilay]

Implement provenance time (ptime) in Btrfs, as introduced in a
previous commit ("vfs: add provenance time (ptime)").

Update the on-disk format by claiming 12 bytes from the reserved[] space
in btrfs_inode_item, putting ptime before other timestamps.

Also, set .fileattr_[gs]et to btrfs_fileattr_[gs]et() for both
symlinks and special files.

Assisted-by: Gemini:3.8-flash-high antigravity-cli-1.4.7
Signed-off-by: koraynilay <koray.fra@gmail.com>
---
 fs/btrfs/btrfs_inode.h          |  4 ++++
 fs/btrfs/delayed-inode.c        |  6 ++++++
 fs/btrfs/inode.c                | 29 ++++++++++++++++++++++++++++-
 fs/btrfs/ioctl.c                | 13 ++++++++++++-
 fs/btrfs/print-tree.c           |  1 +
 fs/btrfs/tree-log.c             |  3 +++
 include/uapi/linux/btrfs_tree.h |  3 ++-
 7 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index 0782f917fccc..c9822340567a 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -332,6 +332,10 @@ struct btrfs_inode {
 	u64 i_otime_sec;
 	u32 i_otime_nsec;
 
+	/* File *data* creation (provenance) time. */
+	s64 i_ptime_sec;
+	u32 i_ptime_nsec;
+
 	/* Hook into fs_info->delayed_iputs */
 	struct list_head delayed_iput;
 
diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index 333ce8b52489..eef73ebb4a52 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1932,6 +1932,9 @@ static void fill_stack_inode_item(struct btrfs_trans_handle *trans,
 
 	btrfs_set_stack_timespec_sec(&inode_item->otime, inode->i_otime_sec);
 	btrfs_set_stack_timespec_nsec(&inode_item->otime, inode->i_otime_nsec);
+
+	btrfs_set_stack_timespec_sec(&inode_item->ptime, inode->i_ptime_sec);
+	btrfs_set_stack_timespec_nsec(&inode_item->ptime, inode->i_ptime_nsec);
 }
 
 int btrfs_fill_inode(struct btrfs_inode *inode, u32 *rdev)
@@ -1981,6 +1984,9 @@ int btrfs_fill_inode(struct btrfs_inode *inode, u32 *rdev)
 	inode->i_otime_sec = btrfs_stack_timespec_sec(&inode_item->otime);
 	inode->i_otime_nsec = btrfs_stack_timespec_nsec(&inode_item->otime);
 
+	inode->i_ptime_sec = btrfs_stack_timespec_sec(&inode_item->ptime);
+	inode->i_ptime_nsec = btrfs_stack_timespec_nsec(&inode_item->ptime);
+
 	vfs_inode->i_generation = inode->generation;
 	if (S_ISDIR(vfs_inode->i_mode))
 		inode->index_cnt = (u64)-1;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index abaa33471456..6ac7fa774ccf 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4057,6 +4057,17 @@ static int btrfs_read_locked_inode(struct btrfs_inode *inode, struct btrfs_path
 	inode->i_otime_sec = btrfs_timespec_sec(leaf, &inode_item->otime);
 	inode->i_otime_nsec = btrfs_timespec_nsec(leaf, &inode_item->otime);
 
+	inode->i_ptime_sec = btrfs_timespec_sec(leaf, &inode_item->ptime);
+	inode->i_ptime_nsec = btrfs_timespec_nsec(leaf, &inode_item->ptime);
+	/* Avoid old garbage on-disk data making btrfs load a bad value */
+	if (unlikely(inode->i_ptime_nsec >= NSEC_PER_SEC)) {
+		btrfs_warn(fs_info,
+			   "invalid ptime.nsec %u on ino %llu from disk, setting ptime to otime",
+			   inode->i_ptime_nsec, btrfs_ino(inode));
+		inode->i_ptime_sec = inode->i_otime_sec;
+		inode->i_ptime_nsec = inode->i_otime_nsec;
+	}
+
 	inode_set_bytes(vfs_inode, btrfs_inode_nbytes(leaf, inode_item));
 	inode->generation = btrfs_inode_generation(leaf, inode_item);
 	inode->last_trans = btrfs_inode_transid(leaf, inode_item);
@@ -4249,6 +4260,9 @@ static void fill_inode_item(struct btrfs_trans_handle *trans,
 	btrfs_set_timespec_sec(leaf, &item->otime, BTRFS_I(inode)->i_otime_sec);
 	btrfs_set_timespec_nsec(leaf, &item->otime, BTRFS_I(inode)->i_otime_nsec);
 
+	btrfs_set_timespec_sec(leaf, &item->ptime, BTRFS_I(inode)->i_ptime_sec);
+	btrfs_set_timespec_nsec(leaf, &item->ptime, BTRFS_I(inode)->i_ptime_nsec);
+
 	btrfs_set_inode_nbytes(leaf, item, inode_get_bytes(inode));
 	btrfs_set_inode_generation(leaf, item, BTRFS_I(inode)->generation);
 	btrfs_set_inode_sequence(leaf, item, inode_peek_iversion(inode));
@@ -5988,6 +6002,8 @@ static struct btrfs_inode *new_simple_dir(struct inode *dir,
 	inode_set_atime_to_ts(vfs_inode, inode_get_atime(dir));
 	inode->i_otime_sec = ts.tv_sec;
 	inode->i_otime_nsec = ts.tv_nsec;
+	inode->i_ptime_sec = ts.tv_sec;
+	inode->i_ptime_nsec = ts.tv_nsec;
 
 	vfs_inode->i_uid = dir->i_uid;
 	vfs_inode->i_gid = dir->i_gid;
@@ -6714,6 +6730,8 @@ int btrfs_create_new_inode(struct btrfs_trans_handle *trans,
 	ts = simple_inode_init_ts(inode);
 	BTRFS_I(inode)->i_otime_sec = ts.tv_sec;
 	BTRFS_I(inode)->i_otime_nsec = ts.tv_nsec;
+	BTRFS_I(inode)->i_ptime_sec = ts.tv_sec;
+	BTRFS_I(inode)->i_ptime_nsec = ts.tv_nsec;
 
 	/*
 	 * We're going to fill the inode item now, so at this point the inode
@@ -8048,6 +8066,9 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
 	ei->i_otime_sec = 0;
 	ei->i_otime_nsec = 0;
 
+	ei->i_ptime_sec = 0;
+	ei->i_ptime_nsec = 0;
+
 	inode = &ei->vfs_inode;
 	btrfs_extent_map_tree_init(&ei->extent_tree);
 
@@ -8186,9 +8207,11 @@ static int btrfs_getattr(const struct mnt_idmap *idmap,
 	u32 blocksize = btrfs_sb(inode->i_sb)->sectorsize;
 	u32 bi_flags = BTRFS_I(inode)->flags;
 
-	stat->result_mask |= STATX_BTIME;
+	stat->result_mask |= (STATX_BTIME | STATX_PTIME);
 	stat->btime.tv_sec = BTRFS_I(inode)->i_otime_sec;
 	stat->btime.tv_nsec = BTRFS_I(inode)->i_otime_nsec;
+	stat->ptime.tv_sec = BTRFS_I(inode)->i_ptime_sec;
+	stat->ptime.tv_nsec = BTRFS_I(inode)->i_ptime_nsec;
 	if (bi_flags & BTRFS_INODE_APPEND)
 		stat->attributes |= STATX_ATTR_APPEND;
 	if (bi_flags & BTRFS_INODE_COMPRESS)
@@ -10779,6 +10802,8 @@ static const struct inode_operations btrfs_special_inode_operations = {
 	.get_inode_acl	= btrfs_get_acl,
 	.set_acl	= btrfs_set_acl,
 	.update_time	= btrfs_update_time,
+	.fileattr_get	= btrfs_fileattr_get,
+	.fileattr_set	= btrfs_fileattr_set,
 };
 static const struct inode_operations btrfs_symlink_inode_operations = {
 	.get_link	= page_get_link,
@@ -10787,6 +10812,8 @@ static const struct inode_operations btrfs_symlink_inode_operations = {
 	.permission	= btrfs_permission,
 	.listxattr	= btrfs_listxattr,
 	.update_time	= btrfs_update_time,
+	.fileattr_get	= btrfs_fileattr_get,
+	.fileattr_set	= btrfs_fileattr_set,
 };
 
 const struct dentry_operations btrfs_dentry_operations = {
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f3e2afe221be..dfcf710d828c 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -275,6 +275,9 @@ int btrfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
 	const struct btrfs_inode *inode = BTRFS_I(d_inode(dentry));
 
 	fileattr_fill_flags(fa, btrfs_inode_flags_to_fsflags(inode));
+	fa->fsx_ptime.tv_sec = inode->i_ptime_sec;
+	fa->fsx_ptime.tv_nsec = inode->i_ptime_nsec;
+	fa->fsx_xflags |= FS_XFLAG_PTIME;
 	return 0;
 }
 
@@ -294,7 +297,11 @@ int btrfs_fileattr_set(const struct mnt_idmap *idmap,
 	if (btrfs_root_readonly(root))
 		return -EROFS;
 
-	if (fileattr_has_fsx(fa))
+	/*
+	 * We now support FS_XFLAG_PTIME, so exclude it from the unsupported
+	 * check
+	 */
+	if (fileattr_has_fsx_mask(fa, FS_XFLAG_PTIME))
 		return -EOPNOTSUPP;
 
 	fsflags = btrfs_mask_fsflags_for_type(&inode->vfs_inode, fa->flags);
@@ -436,6 +443,10 @@ int btrfs_fileattr_set(const struct mnt_idmap *idmap,
 	}
 
 update_flags:
+	if (!fa->flags_valid && (fa->fsx_xflags & FS_XFLAG_PTIME)) {
+		inode->i_ptime_sec = fa->fsx_ptime.tv_sec;
+		inode->i_ptime_nsec = fa->fsx_ptime.tv_nsec;
+	}
 	inode->flags = inode_flags;
 	btrfs_update_inode_mapping_flags(inode);
 	btrfs_sync_inode_flags_to_i_flags(inode);
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index 53e726119ca7..ba385d0ed9ed 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -263,6 +263,7 @@ static void print_inode_item(const struct extent_buffer *eb, int i)
 	print_timespec(eb, &ii->ctime, "\t\tctime ", "\n");
 	print_timespec(eb, &ii->mtime, "\t\tmtime ", "\n");
 	print_timespec(eb, &ii->otime, "\t\totime ", "\n");
+	print_timespec(eb, &ii->ptime, "\t\tptime ", "\n");
 }
 
 static void print_dir_item(const struct extent_buffer *eb, int i)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 1d9dfb63fc5a..72a4a92b40b9 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -4631,6 +4631,9 @@ static void fill_inode_item(struct btrfs_trans_handle *trans,
 	btrfs_set_timespec_sec(leaf, &item->otime, inode->i_otime_sec);
 	btrfs_set_timespec_nsec(leaf, &item->otime, inode->i_otime_nsec);
 
+	btrfs_set_timespec_sec(leaf, &item->ptime, inode->i_ptime_sec);
+	btrfs_set_timespec_nsec(leaf, &item->ptime, inode->i_ptime_nsec);
+
 	/*
 	 * We do not need to set the nbytes field, in fact during a fast fsync
 	 * its value may not even be correct, since a fast fsync does not wait
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 47ee52859b45..c360b3e95f45 100644
--- a/include/uapi/linux/btrfs_tree.h
+++ b/include/uapi/linux/btrfs_tree.h
@@ -900,7 +900,8 @@ struct btrfs_inode_item {
 	 * a little future expansion, for more than this we can
 	 * just grow the inode item and version it
 	 */
-	__le64 reserved[4];
+	__le32 reserved[5];
+	struct btrfs_timespec ptime;
 	struct btrfs_timespec atime;
 	struct btrfs_timespec ctime;
 	struct btrfs_timespec mtime;
-- 
2.56.0

Re: [RFC PATCH v3 1/5] vfs: add provenance time (ptime)

[Amir Goldstein]

On Sun, Nov 1, 2026 at 2:57 AM koraynilay <koray.fra@gmail.com> wrote:
>
> 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@gmail.com>, following the advice[2] from Darrick J.
>   Wong <djwong@kernel.org> of using file_setattr() instead of updating
>   utimensat() ]
>
> [1]: https://lore.kernel.org/20260405195007.1306-2-DefendTheDisabled@gmail.com
> [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@gmail.com>
> ---
>  fs/file_attr.c            | 33 +++++++++++++++++++++++++++++++--
>  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, 52 insertions(+), 4 deletions(-)
>
> diff --git a/fs/file_attr.c b/fs/file_attr.c
> index 833e03810b24..c0645cb22bf3 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;

That is not the correct way to extend this API.
This fixed mask was added as a placeholder for
"We intend to add support for more xflags to selective filesystems":
https://lore.kernel.org/linux-fsdevel/20250329143312.1350603-2-amir73il@gmail.com/

Please see this POC patch for filesystems to publish their supported
xflags mask:
https://lore.kernel.org/linux-fsdevel/20250329143312.1350603-3-amir73il@gmail.com/

This will allow callers of file_getattr() to know if the filesystem
supports ptime
without trying to set it and failing.

Thanks,
Amir.

Re: [RFC PATCH v3 3/5] ntfs3: make crtime user-settable using ptime

[Pali Rohár]

On Sunday 01 November 2026 02:55:49 koraynilay wrote:
> @@ -154,6 +158,11 @@ int ntfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
>  	if (flags & FS_APPEND_FL)
>  		new_fl |= S_APPEND;
>  
> +	if (fa->fsx_xflags & FS_XFLAG_PTIME) {
> +		ni->i_crtime.tv_sec = fa->fsx_ptime.tv_sec;
> +		ni->i_crtime.tv_nsec = fa->fsx_ptime.tv_nsec;
> +	}
> +
>  	inode_set_flags(inode, new_fl, S_IMMUTABLE | S_APPEND);
>  
>  	/* Save nodump flag to return in ntfs_getattr. */
> @@ -275,8 +284,9 @@ int ntfs_getattr(const struct mnt_idmap *idmap, const struct path *path,
>  	if (unlikely(is_bad_ni(ni)))
>  		return -EINVAL;
>  
> -	stat->result_mask |= STATX_BTIME;
> +	stat->result_mask |= (STATX_BTIME | STATX_PTIME);
>  	stat->btime = ni->i_crtime;
> +	stat->ptime = ni->i_crtime;

For me this patch looks dangerous. Somehow I would expect that the
"btime" will never change for existing inode.

But because the ptime is mapped to i_crtime and ptime is settable from
userspace, with this patch it is directly possible to change btime.



I was thinking more about it... Is not this just misunderstanding of how
the security model around the times is working on different systems?
Because on NTFS there is stored just one field which says when the file
was created. There are not two fields like "time set by user and time
set by system".

Windows security model allows anybody with WRITE_ATTRIBUTES access to
change that create time. Linux security model does not allow to change it.

NTFS in this view is just a filesystem like any other (ext4, btrfs, ...).
In my opinion if the ext4 or btrfs filesystem is correctly implemented
on Windows systems, then Windows security model should handle it in the
same way like for NTFS or exFAT. So if something grants WRITE_ATTRIBUTES
access, then Windows should allow to change also btime on ext4 or btrfs.



On the other hand, I understand the use case to have two creation times.
One time which would never be changed and could be used for any kind of
atomic / synchronization by userspace application logic (this btime).
And another time for human which can be changed at any time to any value
which user wants (this ptime).

In any case, I would suggest that filesystem driver would not report to
userspace unsupported values and would not try to invent other values
and lying about them.

Re: [RFC PATCH v3 0/5] add provenance time (ptime)

[Amir Goldstein]

On Sun, Nov 1, 2026 at 2:57 AM koraynilay <koray.fra@gmail.com> wrote:
>
> This is an initial implementation of a new timestamp to indicate the
> time when a file/directory was initially created.
>
> This patch series takes inspiration from the one by Sean Smith
> <defendthedisabled@gmail.com> [1], but using
> file_setattr()/file_getattr() as suggested by Darrick J. Wong
> <djwong@kernel.org> in [2].
>
> The semantics of this new timestamp should be at least these:
> - it should be the same as btime on a newly created file
> - it's user-settable, so it can be preserved for backups, filesystem
>   conversions, archives and any similar operation
> - it should be preserved every time mtime gets preserved
>
> and the correspondence with the other timestamps is as follows:
>
> ctime <-> btime
> mtime <-> ptime
>
> Examples:
> 1) a .zsh_history file created in 2019, then after a few years the user
>    decides to switch to another filesystem, copying the .zsh_history to
>    the new home, in that case btime would have the timestamp of the copy
>    and ptime would have the 2019 timestamp (just like mtime would have
>    been preserved)
> 2) a symlink created in 2020 from the home directory to a /path going
>    through the same process as the .zsh_history, in this case it would
>    also make sense to sync the ptime to the 2020 timestamp instead of
>    keeping only the btime (so the inode creation time).
>
> The proof-of-concept code (for testing) for stat(1) and cp(1) is
> available at https://github.com/koraynilay/coreutils (master branch)
> (Note: these coreutils code changes are a prototype and won't be
> submitted upstream as-is, but they work as expected in simple stat and
> cp -a/--preserve=ptime tests)
>
> Lastly, the name "provenance" and "ptime" are not final, I personally
> don't have a strong opinion on any name, but while testing with stat(1)
> I noticed that "Provenance" is definitely too long for the normal
> output, so another option which would fit well is "Origin time",
> abbreviated as "ntime" (OrigiN time) and not as "otime", as that would
> conflict with btrfs' internal naming and create confusion.

FWIW, I agree that given the existing uses of btime and crtime in the
kernel and various XXXprogs, using 'ptime' for kernel code is probably
the lesser evil.

The question of how to display this in stat and tool is a different question
that can be left to the userspace developers.

The UAPI headers uses Birth time language and stat displays:

Access: 2026-11-02 15:22:27.067329367 +0100
Modify: 2026-11-02 15:22:27.067329367 +0100
Change: 2026-11-02 15:22:27.067329367 +0100
 Birth: 2026-11-02 15:22:27.067329367 +0100

If the UAPI headers will use consistent language:

+       /* provenance (settable creation) time */

+       __s64 fa_ptime_sec;     /* provenance (settable creation) time
(seconds) */

I  think that the man pages could be unambiguous:

stat(1)
       %w     time of file birth (immutable), human-readable; - if unknown
       %W    time of file birth (immutable), seconds since Epoch; 0 if unknown
       %p     time of file creation (mutable), human-readable; - if unknown
       %P     time of file creation (mutable), seconds since Epoch; 0 if unknown

statx(2)
       stx_btime
              The file's (immutable) creation timestamp.
       stx_ptime
              The file's (mutable) creation timestamp.

And userspace tools could be displaying ptime as:

Access: 2026-11-02 15:22:27.067329367 +0100
Modify: 2026-11-02 15:22:27.067329367 +0100
Change: 2026-11-02 15:22:27.067329367 +0100
Create: 2026-11-02 15:22:27.067329367 +0100
 Birth: 2026-11-02 15:22:27.067329367 +0100

If they want to, without that being more confusing than Provenance.

>
> v2 changes:
> - fix permission bypass leading to ptime update on immutable and
>   append-only files (found by sashiko[3])
> - normalize ptime timestamp as done in fs/attr.c:notify_change() (found
>   by sashiko[3])
> - fix wording in vfs patch to be like the cover-letter
>
> v3 changes:
> - vfs: reject setting ptime with -EOPNOTSUPP on filesystems that do not
>   support it instead of silently ignoring it (found by sashiko[4])

Please see my review on patch 1/5 on exporting the supported mask
to userspace.

> - vfs: fix not being able to clear immutable and append-only on files
>   with ptime, and allow updating immutable/append-only atomically along
>   with ptime (found by sashiko[4])
> - btrfs: validate on-disk ptime nanoseconds and reset to otime if
>   invalid (found by sashiko[4])
> - btrfs: avoid re-assigning ptime on unrelated chattr calls (found by
>   sashiko[4])
> - add ntfs3 and exfat support as suggested by Amir Goldstein[5], but no
>   vfat, smb, or nfs4 yet as they are a bit more complex

Please explain what makes them more complex.
My concern is that I would like to see that the proposed API fits the existing
fs and we won't need to change the API again later to support them.

Thanks,
Amir.

Re: [RFC PATCH v3 3/5] ntfs3: make crtime user-settable using ptime

[Amir Goldstein]

On Mon, Nov 2, 2026 at 3:24 PM Pali Rohár <pali@kernel.org> wrote:
>
> On Sunday 01 November 2026 02:55:49 koraynilay wrote:
> > @@ -154,6 +158,11 @@ int ntfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
> >       if (flags & FS_APPEND_FL)
> >               new_fl |= S_APPEND;
> >
> > +     if (fa->fsx_xflags & FS_XFLAG_PTIME) {
> > +             ni->i_crtime.tv_sec = fa->fsx_ptime.tv_sec;
> > +             ni->i_crtime.tv_nsec = fa->fsx_ptime.tv_nsec;
> > +     }
> > +
> >       inode_set_flags(inode, new_fl, S_IMMUTABLE | S_APPEND);
> >
> >       /* Save nodump flag to return in ntfs_getattr. */
> > @@ -275,8 +284,9 @@ int ntfs_getattr(const struct mnt_idmap *idmap, const struct path *path,
> >       if (unlikely(is_bad_ni(ni)))
> >               return -EINVAL;
> >
> > -     stat->result_mask |= STATX_BTIME;
> > +     stat->result_mask |= (STATX_BTIME | STATX_PTIME);
> >       stat->btime = ni->i_crtime;
> > +     stat->ptime = ni->i_crtime;
>
> For me this patch looks dangerous. Somehow I would expect that the
> "btime" will never change for existing inode.
>
> But because the ptime is mapped to i_crtime and ptime is settable from
> userspace, with this patch it is directly possible to change btime.
>
>
>
> I was thinking more about it... Is not this just misunderstanding of how
> the security model around the times is working on different systems?
> Because on NTFS there is stored just one field which says when the file
> was created. There are not two fields like "time set by user and time
> set by system".
>
> Windows security model allows anybody with WRITE_ATTRIBUTES access to
> change that create time. Linux security model does not allow to change it.
>
> NTFS in this view is just a filesystem like any other (ext4, btrfs, ...).
> In my opinion if the ext4 or btrfs filesystem is correctly implemented
> on Windows systems, then Windows security model should handle it in the
> same way like for NTFS or exFAT. So if something grants WRITE_ATTRIBUTES
> access, then Windows should allow to change also btime on ext4 or btrfs.
>
>
>
> On the other hand, I understand the use case to have two creation times.
> One time which would never be changed and could be used for any kind of
> atomic / synchronization by userspace application logic (this btime).
> And another time for human which can be changed at any time to any value
> which user wants (this ptime).
>
> In any case, I would suggest that filesystem driver would not report to
> userspace unsupported values and would not try to invent other values
> and lying about them.

But all those fs with mutable creation time already report it with STATX_BTIME
so what can we do about this?

If userspace requests both STATX_BTIME|STATX_PTIME in mask arg,
those fs could technically return only STATX_PTIME and it should not regress
existing programs.

But this is still a bit surprising behavior is it not?

Thanks,
Amir.

Re: [RFC PATCH v3 3/5] ntfs3: make crtime user-settable using ptime

[Pali Rohár]

On Monday 02 November 2026 16:09:41 Amir Goldstein wrote:
> On Mon, Nov 2, 2026 at 3:24 PM Pali Rohár <pali@kernel.org> wrote:
> >
> > On Sunday 01 November 2026 02:55:49 koraynilay wrote:
> > > @@ -154,6 +158,11 @@ int ntfs_fileattr_set(const struct mnt_idmap *idmap, struct dentry *dentry,
> > >       if (flags & FS_APPEND_FL)
> > >               new_fl |= S_APPEND;
> > >
> > > +     if (fa->fsx_xflags & FS_XFLAG_PTIME) {
> > > +             ni->i_crtime.tv_sec = fa->fsx_ptime.tv_sec;
> > > +             ni->i_crtime.tv_nsec = fa->fsx_ptime.tv_nsec;
> > > +     }
> > > +
> > >       inode_set_flags(inode, new_fl, S_IMMUTABLE | S_APPEND);
> > >
> > >       /* Save nodump flag to return in ntfs_getattr. */
> > > @@ -275,8 +284,9 @@ int ntfs_getattr(const struct mnt_idmap *idmap, const struct path *path,
> > >       if (unlikely(is_bad_ni(ni)))
> > >               return -EINVAL;
> > >
> > > -     stat->result_mask |= STATX_BTIME;
> > > +     stat->result_mask |= (STATX_BTIME | STATX_PTIME);
> > >       stat->btime = ni->i_crtime;
> > > +     stat->ptime = ni->i_crtime;
> >
> > For me this patch looks dangerous. Somehow I would expect that the
> > "btime" will never change for existing inode.
> >
> > But because the ptime is mapped to i_crtime and ptime is settable from
> > userspace, with this patch it is directly possible to change btime.
> >
> >
> >
> > I was thinking more about it... Is not this just misunderstanding of how
> > the security model around the times is working on different systems?
> > Because on NTFS there is stored just one field which says when the file
> > was created. There are not two fields like "time set by user and time
> > set by system".
> >
> > Windows security model allows anybody with WRITE_ATTRIBUTES access to
> > change that create time. Linux security model does not allow to change it.
> >
> > NTFS in this view is just a filesystem like any other (ext4, btrfs, ...).
> > In my opinion if the ext4 or btrfs filesystem is correctly implemented
> > on Windows systems, then Windows security model should handle it in the
> > same way like for NTFS or exFAT. So if something grants WRITE_ATTRIBUTES
> > access, then Windows should allow to change also btime on ext4 or btrfs.
> >
> >
> >
> > On the other hand, I understand the use case to have two creation times.
> > One time which would never be changed and could be used for any kind of
> > atomic / synchronization by userspace application logic (this btime).
> > And another time for human which can be changed at any time to any value
> > which user wants (this ptime).
> >
> > In any case, I would suggest that filesystem driver would not report to
> > userspace unsupported values and would not try to invent other values
> > and lying about them.
> 
> But all those fs with mutable creation time already report it with STATX_BTIME
> so what can we do about this?

Well, what I wanted above to point out is that the "mutability" of
creation time is not feature of filesystem, but in my opinion rather
property of the security model on the running operating system.

Maybe better question is: how ext4 btimes differs from the ntfs btime?
In my opinion there is no much difference, both of them has meaning
"time when was the file created".

> If userspace requests both STATX_BTIME|STATX_PTIME in mask arg,
> those fs could technically return only STATX_PTIME and it should not regress
> existing programs.
> 
> But this is still a bit surprising behavior is it not?
> 
> Thanks,
> Amir.

I'm not sure what to do with it.

If we allow to change btime of ntfs then for consistency we should also
allow to change btime of ext4.

Maybe another idea... define new capability which would allow to change
btime (on any filesystem)? This would at least make the consistency.