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authorDmitry V. Levin <ldv@altlinux.org>2017-04-26 14:50:00 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2017-04-26 21:19:05 -0400
commit1741937d475d91ed95abb37f07e8571e23b9a7fe (patch)
treeaed1220a5aa1c62bcf2f18c0d8c22bc26a8c376d /include
parent85128b2be6738fe36c224995c5ee80fe80fbb1b5 (diff)
uapi: change the type of struct statx_timestamp.tv_nsec to unsigned
The comment asserting that the value of struct statx_timestamp.tv_nsec must be negative when statx_timestamp.tv_sec is negative, is wrong, as could be seen from the following example: #define _FILE_OFFSET_BITS 64 #include <assert.h> #include <fcntl.h> #include <stdio.h> #include <sys/stat.h> #include <unistd.h> #include <asm/unistd.h> #include <linux/stat.h> int main(void) { static const struct timespec ts[2] = { { .tv_nsec = UTIME_OMIT }, { .tv_sec = -2, .tv_nsec = 42 } }; assert(utimensat(AT_FDCWD, ".", ts, 0) == 0); struct stat st; assert(stat(".", &st) == 0); printf("st_mtim.tv_sec = %lld, st_mtim.tv_nsec = %lu\n", (long long) st.st_mtim.tv_sec, (unsigned long) st.st_mtim.tv_nsec); struct statx stx; assert(syscall(__NR_statx, AT_FDCWD, ".", 0, 0, &stx) == 0); printf("stx_mtime.tv_sec = %lld, stx_mtime.tv_nsec = %lu\n", (long long) stx.stx_mtime.tv_sec, (unsigned long) stx.stx_mtime.tv_nsec); return 0; } It expectedly prints: st_mtim.tv_sec = -2, st_mtim.tv_nsec = 42 stx_mtime.tv_sec = -2, stx_mtime.tv_nsec = 42 The more generic comment asserting that the value of struct statx_timestamp.tv_nsec might be negative is confusing to say the least. It contradicts both the struct stat.st_[acm]time_nsec tradition and struct timespec.tv_nsec requirements in utimensat syscall. If statx syscall ever returns a stx_[acm]time containing a negative tv_nsec that cannot be passed unmodified to utimensat syscall, it will cause an immense confusion. Fix this source of confusion by changing the type of struct statx_timestamp.tv_nsec from __s32 to __u32. Fixes: a528d35e8bfc ("statx: Add a system call to make enhanced file info available") Signed-off-by: Dmitry V. Levin <ldv@altlinux.org> Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-api@vger.kernel.org cc: mtk.manpages@gmail.com Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'include')
-rw-r--r--include/uapi/linux/stat.h8
1 files changed, 2 insertions, 6 deletions
diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h
index d538897b8e08..17b10304c393 100644
--- a/include/uapi/linux/stat.h
+++ b/include/uapi/linux/stat.h
@@ -48,17 +48,13 @@
* tv_sec holds the number of seconds before (negative) or after (positive)
* 00:00:00 1st January 1970 UTC.
*
- * tv_nsec holds a number of nanoseconds before (0..-999,999,999 if tv_sec is
- * negative) or after (0..999,999,999 if tv_sec is positive) the tv_sec time.
- *
- * Note that if both tv_sec and tv_nsec are non-zero, then the two values must
- * either be both positive or both negative.
+ * tv_nsec holds a number of nanoseconds (0..999,999,999) after the tv_sec time.
*
* __reserved is held in case we need a yet finer resolution.
*/
struct statx_timestamp {
__s64 tv_sec;
- __s32 tv_nsec;
+ __u32 tv_nsec;
__s32 __reserved;
};