[RFC PATCH 2/6] fs: add AT_UTIME_BTIME for utimensat()

Omar Sandoval
2019-02-14T10:01:02Z

From: Omar Sandoval <osandov@fb.com>

Now that we have a btime iattr, use it to allow updating btime from
utimensat(). We do so by adding a new AT_UTIME_BTIME flag. Iff this flag
is given, the btime is set to times[2] (unless times is NULL, in which
case the current time is used).

Signed-off-by: Omar Sandoval <osandov@fb.com>
---
fs/utimes.c | 86 +++++++++++++++++++++++---------------
include/uapi/linux/fcntl.h | 2 +
2 files changed, 55 insertions(+), 33 deletions(-)

diff --git a/fs/utimes.c b/fs/utimes.c
index bdcf2daf39c1..cb9fe77e5f91 100644
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -16,7 +16,20 @@ static bool nsec_valid(long nsec)
return nsec >= 0 && nsec <= 999999999;
}

-static int utimes_common(const struct path *path, struct timespec64 *times)
+static void init_time_attr(struct iattr *newattrs, struct timespec64 *time_attr,
+ struct timespec64 time, unsigned int attr,
+ unsigned int attr_set)
+{
+ if (time.tv_nsec == UTIME_OMIT) {
+ newattrs->ia_valid &= ~attr;
+ } else {
+ *time_attr = time;
+ newattrs->ia_valid |= attr_set;
+ }
+}
+
+static int utimes_common(const struct path *path, struct timespec64 *times,
+ bool btime)
{
int error;
struct iattr newattrs;
@@ -28,25 +41,21 @@ static int utimes_common(const struct path *path, struct timespec64 *times)
goto out;

if (times && times[0].tv_nsec == UTIME_NOW &&
- times[1].tv_nsec == UTIME_NOW)
+ times[1].tv_nsec == UTIME_NOW &&
+ (!btime || times[2].tv_nsec == UTIME_NOW))
times = NULL;

newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
+ if (btime)
+ newattrs.ia_valid |= ATTR_BTIME;
if (times) {
- if (times[0].tv_nsec == UTIME_OMIT)
- newattrs.ia_valid &= ~ATTR_ATIME;
- else if (times[0].tv_nsec != UTIME_NOW) {
- newattrs.ia_atime.tv_sec = times[0].tv_sec;
- newattrs.ia_atime.tv_nsec = times[0].tv_nsec;
- newattrs.ia_valid |= ATTR_ATIME_SET;
- }
-
- if (times[1].tv_nsec == UTIME_OMIT)
- newattrs.ia_valid &= ~ATTR_MTIME;
- else if (times[1].tv_nsec != UTIME_NOW) {
- newattrs.ia_mtime.tv_sec = times[1].tv_sec;
- newattrs.ia_mtime.tv_nsec = times[1].tv_nsec;
- newattrs.ia_valid |= ATTR_MTIME_SET;
+ init_time_attr(&newattrs, &newattrs.ia_atime, times[0],
+ ATTR_ATIME, ATTR_ATIME_SET);
+ init_time_attr(&newattrs, &newattrs.ia_mtime, times[1],
+ ATTR_MTIME, ATTR_MTIME_SET);
+ if (btime) {
+ init_time_attr(&newattrs, &newattrs.ia_btime, times[2],
+ ATTR_BTIME, ATTR_BTIME_SET);
}
/*
* Tell setattr_prepare(), that this is an explicit time
@@ -90,14 +99,16 @@ static int utimes_common(const struct path *path, struct timespec64 *times)
long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
int flags)
{
+ bool btime = flags & AT_UTIME_BTIME;
int error = -EINVAL;

if (times && (!nsec_valid(times[0].tv_nsec) ||
- !nsec_valid(times[1].tv_nsec))) {
+ !nsec_valid(times[1].tv_nsec) ||
+ (btime && !nsec_valid(times[2].tv_nsec)))) {
goto out;
}

- if (flags & ~AT_SYMLINK_NOFOLLOW)
+ if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_UTIME_BTIME))
goto out;

if (filename == NULL && dfd != AT_FDCWD) {
@@ -111,7 +122,7 @@ long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
if (!f.file)
goto out;

- error = utimes_common(&f.file->f_path, times);
+ error = utimes_common(&f.file->f_path, times, btime);
fdput(f);
} else {
struct path path;
@@ -124,7 +135,7 @@ long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
if (error)
goto out;

- error = utimes_common(&path, times);
+ error = utimes_common(&path, times, btime);
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
@@ -139,16 +150,20 @@ long do_utimes(int dfd, const char __user *filename, struct timespec64 *times,
SYSCALL_DEFINE4(utimensat, int, dfd, const char __user *, filename,
struct __kernel_timespec __user *, utimes, int, flags)
{
- struct timespec64 tstimes[2];
+ struct timespec64 tstimes[3];

if (utimes) {
- if ((get_timespec64(&tstimes[0], &utimes[0]) ||
- get_timespec64(&tstimes[1], &utimes[1])))
- return -EFAULT;
-
+ int i, n = (flags & AT_UTIME_BTIME) ? 3 : 2;
+ bool all_omit = true;
+
+ for (i = 0; i < n; i++) {
+ if (get_timespec64(&tstimes[i], &utimes[i]))
+ return -EFAULT;
+ if (tstimes[i].tv_nsec != UTIME_OMIT)
+ all_omit = false;
+ }
/* Nothing to do, we must not even check the path. */
- if (tstimes[0].tv_nsec == UTIME_OMIT &&
- tstimes[1].tv_nsec == UTIME_OMIT)
+ if (all_omit)
return 0;
}

@@ -242,14 +257,19 @@ COMPAT_SYSCALL_DEFINE2(utime, const char __user *, filename,

COMPAT_SYSCALL_DEFINE4(utimensat, unsigned int, dfd, const char __user *, filename, struct old_timespec32 __user *, t, int, flags)
{
- struct timespec64 tv[2];
+ struct timespec64 tv[3];

if (t) {
- if (get_old_timespec32(&tv[0], &t[0]) ||
- get_old_timespec32(&tv[1], &t[1]))
- return -EFAULT;
-
- if (tv[0].tv_nsec == UTIME_OMIT && tv[1].tv_nsec == UTIME_OMIT)
+ int i, n = (flags & AT_UTIME_BTIME) ? 3 : 2;
+ bool all_omit = true;
+
+ for (i = 0; i < n; i++) {
+ if (get_old_timespec32(&tv[i], &t[i]))
+ return -EFAULT;
+ if (tv[i].tv_nsec != UTIME_OMIT)
+ all_omit = false;
+ }
+ if (all_omit)
return 0;
}
return do_utimes(dfd, filename, t ? tv : NULL, flags);
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 6448cdd9a350..fc5b02439697 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -90,5 +90,7 @@
#define AT_STATX_FORCE_SYNC 0x2000 /* - Force the attributes to be sync'd with the server */
#define AT_STATX_DONT_SYNC 0x4000 /* - Don't sync attributes with the server */

+#define AT_UTIME_BTIME 0x8000 /* Also update file creation time */
+

#endif /* _UAPI_LINUX_FCNTL_H */
--
2.20.1