[PATCH v2 16/24] nfs: use time64_t internally

From: Arnd Bergmann
Date: Fri Dec 13 2019 - 15:57:17 EST

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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@xxxxxxxx>
---
include/linux/sunrpc/cache.h | 42 +++++++++++++++++--------------
net/sunrpc/auth_gss/svcauth_gss.c | 2 +-
net/sunrpc/cache.c | 16 ++++++------
net/sunrpc/svcauth_unix.c | 10 ++++----
4 files changed, 37 insertions(+), 33 deletions(-)

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index f8603724fbee..0f64de7caa39 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -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;
}

diff --git a/net/sunrpc/auth_gss/svcauth_gss.c b/net/sunrpc/auth_gss/svcauth_gss.c
index 0c3e22838ddf..311181720d79 100644
--- a/net/sunrpc/auth_gss/svcauth_gss.c
+++ b/net/sunrpc/auth_gss/svcauth_gss.c
@@ -203,7 +203,7 @@ static int rsi_parse(struct cache_detail *cd,
char *ep;
int len;
struct rsi rsii, *rsip = NULL;
- time_t expiry;
+ time64_t expiry;
int status = -EINVAL;

memset(&rsii, 0, sizeof(rsii));
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index f740cb51802a..d996bf872a7c 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -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;
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 5c04ba7d456b..04aa80a2d752 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -166,7 +166,7 @@ static void ip_map_request(struct cache_detail *cd,
}

static struct ip_map *__ip_map_lookup(struct cache_detail *cd, char *class, struct in6_addr *addr);
-static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm, struct unix_domain *udom, time_t expiry);
+static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm, struct unix_domain *udom, time64_t expiry);

static int ip_map_parse(struct cache_detail *cd,
char *mesg, int mlen)
@@ -187,7 +187,7 @@ static int ip_map_parse(struct cache_detail *cd,

struct ip_map *ipmp;
struct auth_domain *dom;
- time_t expiry;
+ time64_t expiry;

if (mesg[mlen-1] != '\n')
return -EINVAL;
@@ -308,7 +308,7 @@ static inline struct ip_map *ip_map_lookup(struct net *net, char *class,
}

static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
- struct unix_domain *udom, time_t expiry)
+ struct unix_domain *udom, time64_t expiry)
{
struct ip_map ip;
struct cache_head *ch;
@@ -328,7 +328,7 @@ static int __ip_map_update(struct cache_detail *cd, struct ip_map *ipm,
}

static inline int ip_map_update(struct net *net, struct ip_map *ipm,
- struct unix_domain *udom, time_t expiry)
+ struct unix_domain *udom, time64_t expiry)
{
struct sunrpc_net *sn;

@@ -491,7 +491,7 @@ static int unix_gid_parse(struct cache_detail *cd,
int rv;
int i;
int err;
- time_t expiry;
+ time64_t expiry;
struct unix_gid ug, *ugp;

if (mesg[mlen - 1] != '\n')
--
2.20.0

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