From 79c92dbd7028a9782b85fcbbbe123e1c44cbaec1 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Sun, 11 Apr 2021 06:41:31 +0100 Subject: [PATCH] touch: switch to using utimensat() and futimens() This patch changes the functions used to update timestamps in touch. Before, utimes() and lutimes() were used, which had certain disadvantages. They are unable to handle nanosecond timestamps, and implementations of certain features like -a and -m require running stat() in a loop. Almost all implementations of utimes() and lutimes() are wrappers for utimensat(), this is the case for glibc, ulibc and musl libc. function old new delta __futimens_time64 - 24 +24 __lutimes_time64 80 - -80 touch_main 539 456 -83 ------------------------------------------------------------------------------ (add/remove: 2/2 grow/shrink: 0/1 up/down: 24/-163) Total: -139 bytes Signed-off-by: urmum-69 Signed-off-by: Denys Vlasenko --- coreutils/touch.c | 57 +++++++++++++---------------------------------- 1 file changed, 16 insertions(+), 41 deletions(-) diff --git a/coreutils/touch.c b/coreutils/touch.c index 690517e66..8d3f8dbbe 100644 --- a/coreutils/touch.c +++ b/coreutils/touch.c @@ -25,7 +25,6 @@ //config: depends on TOUCH //config: help //config: Enable touch to have the -h option. -//config: This requires libc support for lutimes() function. //config: //config:config FEATURE_TOUCH_SUSV3 //config: bool "Add support for SUSV3 features (-a -d -m -t -r)" @@ -97,8 +96,6 @@ int touch_main(int argc UNUSED_PARAM, char **argv) OPT_a = (1 << (4+ENABLE_FEATURE_TOUCH_NODEREF)) * ENABLE_FEATURE_TOUCH_SUSV3, OPT_m = (1 << (5+ENABLE_FEATURE_TOUCH_NODEREF)) * ENABLE_FEATURE_TOUCH_SUSV3, }; - /* NULL = use current time */ - const struct timeval *newtime = NULL; #if ENABLE_LONG_OPTS static const char touch_longopts[] ALIGN1 = /* name, has_arg, val */ @@ -112,12 +109,11 @@ int touch_main(int argc UNUSED_PARAM, char **argv) char *reference_file = NULL; char *date_str = NULL; /* timebuf[0] is atime, timebuf[1] is mtime */ - struct timeval timebuf[2]; - timebuf[1].tv_usec = timebuf[0].tv_usec = 0; + struct timespec timebuf[2]; #else # define reference_file NULL # define date_str NULL -# define timebuf ((struct timeval*)NULL) +# define timebuf ((struct timespec*)NULL) #endif /* -d and -t both set time. In coreutils, @@ -140,16 +136,15 @@ int touch_main(int argc UNUSED_PARAM, char **argv) bb_show_usage(); } + timebuf[0].tv_nsec = timebuf[1].tv_nsec = UTIME_NOW; + if (reference_file) { struct stat stbuf; xstat(reference_file, &stbuf); timebuf[0].tv_sec = stbuf.st_atime; timebuf[1].tv_sec = stbuf.st_mtime; - /* Can use .st_mtim.tv_nsec - * (or is it .st_mtimensec?? see date.c) - * to set microseconds too. - */ - newtime = timebuf; + timebuf[0].tv_nsec = stbuf.st_atim.tv_nsec; + timebuf[1].tv_nsec = stbuf.st_mtim.tv_nsec; } if (date_str) { @@ -167,39 +162,19 @@ int touch_main(int argc UNUSED_PARAM, char **argv) t = validate_tm_time(date_str, &tm_time); timebuf[1].tv_sec = timebuf[0].tv_sec = t; - newtime = timebuf; + timebuf[1].tv_nsec = timebuf[0].tv_nsec = 0; } - if ((opts & (OPT_a | OPT_m)) && !newtime) { - time(&timebuf[0].tv_sec); - timebuf[1].tv_sec = timebuf[0].tv_sec; - newtime = timebuf; + if (opts & OPT_a) { + timebuf[1].tv_nsec = UTIME_OMIT; + } + if (opts & OPT_m) { + timebuf[0].tv_nsec = UTIME_OMIT; } do { - int result; - - if (opts & (OPT_a | OPT_m)) { - /* Save original times */ - struct stat stbuf; - if (stat(*argv, &stbuf) == 0) { - /* As we must set both times, we lose original - * file time microseconds. - * Can use .st_mtim.tv_nsec - * (or is it .st_mtimensec?? see date.c) - * to set microseconds too. - * Also, utimensat(2) allows to omit one of the - * times to be set. But it is SUSv4. - */ - if (!(opts & OPT_a)) - timebuf[0].tv_sec = stbuf.st_atime; - if (!(opts & OPT_m)) - timebuf[1].tv_sec = stbuf.st_mtime; - } - } - - result = (ENABLE_FEATURE_TOUCH_NODEREF && (opts & OPT_h) ? lutimes : utimes)(*argv, newtime); - + int result = utimensat(AT_FDCWD, *argv, timebuf, + (opts & OPT_h) ? AT_SYMLINK_NOFOLLOW : 0); if (result != 0) { if (errno == ENOENT) { /* no such file? */ if (opts & OPT_c) { @@ -209,9 +184,9 @@ int touch_main(int argc UNUSED_PARAM, char **argv) /* Try to create the file */ fd = open(*argv, O_RDWR | O_CREAT, 0666); if (fd >= 0) { - xclose(fd); if (reference_file || date_str) - utimes(*argv, newtime); + futimens(fd, timebuf); + xclose(fd); continue; } }