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nfs: use time64_t internally

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The timestamps for the cache are all in boottime seconds, so they
don't overflow 32-bit values, but the use of time_t is deprecated
because it generally does overflow when used with wall-clock time.

There are multiple possible ways of avoiding it:

- leave time_t, which is safe here, but forces others to
  look into this code to determine that it is over and over.

- use a more generic type, like 'int' or 'long', which is known
  to be sufficient here but loses the documentation of referring
  to timestamps

- use ktime_t everywhere, and convert into seconds in the few
  places where we want realtime-seconds. The conversion is
  sometimes expensive, but not more so than the conversion we
  do today.

- use time64_t to clarify that this code is safe. Nothing would
  change for 64-bit architectures, but it is slightly less
  efficient on 32-bit architectures.

Without a clear winner of the three approaches above, this picks
the last one, favouring readability over a small performance
loss on 32-bit architectures.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann 2017-10-20 16:34:42 +02:00
parent 294ec5b87a
commit f559935e7c
4 changed files with 37 additions and 33 deletions
Download patch file Download diff file Expand all files Collapse all files

42
include/linux/sunrpc/cache.h
View file

@ -45,8 +45,8 @@
*/
struct cache_head {
struct hlist_node cache_list;
time_t expiry_time; /* After time time, don't use the data */
time_t last_refresh; /* If CACHE_PENDING, this is when upcall was
time64_t expiry_time; /* After time time, don't use the data */
time64_t last_refresh; /* If CACHE_PENDING, this is when upcall was
* sent, else this is when update was
* received, though it is alway set to
* be *after* ->flush_time.
@ -95,22 +95,22 @@ struct cache_detail {
/* fields below this comment are for internal use
* and should not be touched by cache owners
*/
time_t flush_time; /* flush all cache items with
time64_t flush_time; /* flush all cache items with
* last_refresh at or earlier
* than this. last_refresh
* is never set at or earlier
* than this.
*/
struct list_head others;
time_t nextcheck;
time64_t nextcheck;
int entries;
/* fields for communication over channel */
struct list_head queue;
atomic_t writers; /* how many time is /channel open */
time_t last_close; /* if no writers, when did last close */
time_t last_warn; /* when we last warned about no writers */
time64_t last_close; /* if no writers, when did last close */
time64_t last_warn; /* when we last warned about no writers */
union {
struct proc_dir_entry *procfs;
@ -147,18 +147,22 @@ struct cache_deferred_req {
* timestamps kept in the cache are expressed in seconds
* since boot. This is the best for measuring differences in
* real time.
* This reimplemnts ktime_get_boottime_seconds() in a slightly
* faster but less accurate way. When we end up converting
* back to wallclock (CLOCK_REALTIME), that error often
* cancels out during the reverse operation.
*/
static inline time_t seconds_since_boot(void)
static inline time64_t seconds_since_boot(void)
{
struct timespec boot;
getboottime(&boot);
return get_seconds() - boot.tv_sec;
struct timespec64 boot;
getboottime64(&boot);
return ktime_get_real_seconds() - boot.tv_sec;
}
static inline time_t convert_to_wallclock(time_t sinceboot)
static inline time64_t convert_to_wallclock(time64_t sinceboot)
{
struct timespec boot;
getboottime(&boot);
struct timespec64 boot;
getboottime64(&boot);
return boot.tv_sec + sinceboot;
}
@ -273,7 +277,7 @@ static inline int get_uint(char **bpp, unsigned int *anint)
return 0;
}
static inline int get_time(char **bpp, time_t *time)
static inline int get_time(char **bpp, time64_t *time)
{
char buf[50];
long long ll;
@ -287,20 +291,20 @@ static inline int get_time(char **bpp, time_t *time)
if (kstrtoll(buf, 0, &ll))
return -EINVAL;
*time = (time_t)ll;
*time = ll;
return 0;
}
static inline time_t get_expiry(char **bpp)
static inline time64_t get_expiry(char **bpp)
{
time_t rv;
struct timespec boot;
time64_t rv;
struct timespec64 boot;
if (get_time(bpp, &rv))
return 0;
if (rv < 0)
return 0;
getboottime(&boot);
getboottime64(&boot);
return rv - boot.tv_sec;
}