On Wed, Jan 24, 2018 at 3:56 AM, Arnd Bergmann arnd@arndb.de wrote:
On Tue, Jan 23, 2018 at 5:25 PM, Deepa Dinamani deepa.kernel@gmail.com wrote:
On Mon, Jan 22, 2018 at 12:25 PM, Linus Torvalds torvalds@linux-foundation.org wrote:
On Sun, Jan 21, 2018 at 6:04 PM, Deepa Dinamani deepa.kernel@gmail.com wrote:
t.tv_nsec -= t.tv_nsec % gran;This doesn't actuall ywork if tv_nsec is negative.
Right.
Which may not be an issue in most cases, but did somebody check utimensat() or whatever?
I checked POSIX again. There is no mention of tv_nsec being positive always for utimes. And, the long term plan is to replace all the callers of timespec_trunc() to use this new api instead for filesystems. So this will need to be fixed. I will fix this and post an update.
I found this on http://pubs.opengroup.org/onlinepubs/9699919799/functions/utimes.html
ERRORS These functions shall fail if: ... [EINVAL] Either of the times argument structures specified a tv_nsec value that was neither UTIME_NOW nor UTIME_OMIT, and was a value less than zero or greater than or equal to 1000 million.
which is the same as the Linux man page and what the kernel actually does for all the syscalls. The POSIX description seems a bit ambiguous to whether it also expects or allows EINVAL for utimes() with a tv_usec over 1000000 microseconds, or if it just applies to the utimensat and futimens(). Older descriptions that only explain utimes() don't mention the range check on tv_usec either.
Right. This is in keeping with the kernel implementation of the corresponding syscalls.
But, this timespec_truncate() is being called from current_time() and will be extended to other calls.
C99 says "When integers are divided, the result of the / operator is the algebraic quotient with any fractional part discarded (often called "truncation toward zero"). If the quotient a/b is representable, the expression (a/b)*b + a%b shall equal a."
Also, we are already checking for gran being non-zero and in the nanoseconds range.
So I think the right answer here is to add a comment that the function expects timespec to be normalized, and the functions calling it can take care of validation.
-Deepa