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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
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16
net/sunrpc/cache.c
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@@ -42,7 +42,7 @@ static bool cache_listeners_exist(struct cache_detail *detail);
static void cache_init(struct cache_head *h, struct cache_detail *detail)
{
time_t now = seconds_since_boot();
time64_t now = seconds_since_boot();
INIT_HLIST_NODE(&h->cache_list);
h->flags = 0;
kref_init(&h->ref);
@@ -139,10 +139,10 @@ EXPORT_SYMBOL_GPL(sunrpc_cache_lookup_rcu);
static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
static void cache_fresh_locked(struct cache_head *head, time_t expiry,
static void cache_fresh_locked(struct cache_head *head, time64_t expiry,
struct cache_detail *detail)
{
time_t now = seconds_since_boot();
time64_t now = seconds_since_boot();
if (now <= detail->flush_time)
/* ensure it isn't immediately treated as expired */
now = detail->flush_time + 1;
@@ -274,7 +274,7 @@ int cache_check(struct cache_detail *detail,
struct cache_head *h, struct cache_req *rqstp)
{
int rv;
long refresh_age, age;
time64_t refresh_age, age;
/* First decide return status as best we can */
rv = cache_is_valid(h);
@@ -288,7 +288,7 @@ int cache_check(struct cache_detail *detail,
rv = -ENOENT;
} else if (rv == -EAGAIN ||
(h->expiry_time != 0 && age > refresh_age/2)) {
dprintk("RPC: Want update, refage=%ld, age=%ld\n",
dprintk("RPC: Want update, refage=%lld, age=%lld\n",
refresh_age, age);
if (!test_and_set_bit(CACHE_PENDING, &h->flags)) {
switch (cache_make_upcall(detail, h)) {
@@ -1404,7 +1404,7 @@ static int c_show(struct seq_file *m, void *p)
return cd->cache_show(m, cd, NULL);
ifdebug(CACHE)
seq_printf(m, "# expiry=%ld refcnt=%d flags=%lx\n",
seq_printf(m, "# expiry=%lld refcnt=%d flags=%lx\n",
convert_to_wallclock(cp->expiry_time),
kref_read(&cp->ref), cp->flags);
cache_get(cp);
@@ -1477,7 +1477,7 @@ static ssize_t read_flush(struct file *file, char __user *buf,
char tbuf[22];
size_t len;
len = snprintf(tbuf, sizeof(tbuf), "%lu\n",
len = snprintf(tbuf, sizeof(tbuf), "%llu\n",
convert_to_wallclock(cd->flush_time));
return simple_read_from_buffer(buf, count, ppos, tbuf, len);
}
@@ -1488,7 +1488,7 @@ static ssize_t write_flush(struct file *file, const char __user *buf,
{
char tbuf[20];
char *ep;
time_t now;
time64_t now;
if (*ppos || count > sizeof(tbuf)-1)
return -EINVAL;