sunrpc: use seconds since boot in expiry cache

This protects us from confusion when the wallclock time changes.

We convert to and from wallclock when  setting or reading expiry
times.

Also use seconds since boot for last_clost time.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

4 files changed, 48 insertions, 24 deletions

diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c
index dba50a5625db..a6e711ad130f 100644
--- a/fs/nfs/dns_resolve.c
+++ b/fs/nfs/dns_resolve.c
@@ -167,7 +167,7 @@ static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
                 return 0;
         }
         item = container_of(h, struct nfs_dns_ent, h);
-        ttl = (long)item->h.expiry_time - (long)get_seconds();
+        ttl = item->h.expiry_time - seconds_since_boot();
         if (ttl < 0)
                 ttl = 0;
 
@@ -239,7 +239,7 @@ static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
         ttl = get_expiry(&buf);
         if (ttl == 0)
                 goto out;
-        key.h.expiry_time = ttl + get_seconds();
+        key.h.expiry_time = ttl + seconds_since_boot();
 
         ret = -ENOMEM;
         item = nfs_dns_lookup(cd, &key);
@@ -301,7 +301,7 @@ static int do_cache_lookup_nowait(struct cache_detail *cd,
                 goto out_err;
         ret = -ETIMEDOUT;
         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
-                        || (*item)->h.expiry_time < get_seconds()
+                        || (*item)->h.expiry_time < seconds_since_boot()
                         || cd->flush_time > (*item)->h.last_refresh)
                 goto out_put;
         ret = -ENOENT;
diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index c78dbf493424..808b33a4a090 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -550,7 +550,7 @@ do_idmap_lookup_nowait(struct ent *(*lookup_fn)(struct ent *),
                 goto out_err;
         ret = -ETIMEDOUT;
         if (!test_bit(CACHE_VALID, &(*item)->h.flags)
-                        || (*item)->h.expiry_time < get_seconds()
+                        || (*item)->h.expiry_time < seconds_since_boot()
                         || detail->flush_time > (*item)->h.last_refresh)
                 goto out_put;
         ret = -ENOENT;
diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
index 0e1febf4e5bc..ece432b7f87f 100644
--- a/include/linux/sunrpc/cache.h
+++ b/include/linux/sunrpc/cache.h
@@ -218,20 +218,42 @@ static inline int get_int(char **bpp, int *anint)
         return 0;
 }
 
+/*
+ * timestamps kept in the cache are expressed in seconds
+ * since boot.  This is the best for measuring differences in
+ * real time.
+ */
+static inline time_t seconds_since_boot(void)
+{
+        struct timespec boot;
+        getboottime(&boot);
+        return get_seconds() - boot.tv_sec;
+}
+
+static inline time_t convert_to_wallclock(time_t sinceboot)
+{
+        struct timespec boot;
+        getboottime(&boot);
+        return boot.tv_sec + sinceboot;
+}
+
 static inline time_t get_expiry(char **bpp)
 {
         int rv;
+        struct timespec boot;
+
         if (get_int(bpp, &rv))
                 return 0;
         if (rv < 0)
                 return 0;
-        return rv;
+        getboottime(&boot);
+        return rv - boot.tv_sec;
 }
 
 static inline void sunrpc_invalidate(struct cache_head *h,
                                      struct cache_detail *detail)
 {
-        h->expiry_time = get_seconds() - 1;
-        detail->nextcheck = get_seconds();
+        h->expiry_time = seconds_since_boot() - 1;
+        detail->nextcheck = seconds_since_boot();
 }
 #endif /*  _LINUX_SUNRPC_CACHE_H_ */
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 2b06410e584e..8dc121955fdc 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -42,7 +42,7 @@ static void cache_revisit_request(struct cache_head *item);
 
 static void cache_init(struct cache_head *h)
 {
-        time_t now = get_seconds();
+        time_t now = seconds_since_boot();
         h->next = NULL;
         h->flags = 0;
         kref_init(&h->ref);
@@ -52,7 +52,7 @@ static void cache_init(struct cache_head *h)
 
 static inline int cache_is_expired(struct cache_detail *detail, struct cache_head *h)
 {
-        return  (h->expiry_time < get_seconds()) ||
+        return  (h->expiry_time < seconds_since_boot()) ||
                 (detail->flush_time > h->last_refresh);
 }
 
@@ -127,7 +127,7 @@ static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch);
 static void cache_fresh_locked(struct cache_head *head, time_t expiry)
 {
         head->expiry_time = expiry;
-        head->last_refresh = get_seconds();
+        head->last_refresh = seconds_since_boot();
         set_bit(CACHE_VALID, &head->flags);
 }
 
@@ -238,7 +238,7 @@ int cache_check(struct cache_detail *detail,
 
         /* now see if we want to start an upcall */
         refresh_age = (h->expiry_time - h->last_refresh);
-        age = get_seconds() - h->last_refresh;
+        age = seconds_since_boot() - h->last_refresh;
 
         if (rqstp == NULL) {
                 if (rv == -EAGAIN)
@@ -253,7 +253,7 @@ int cache_check(struct cache_detail *detail,
                                 cache_revisit_request(h);
                                 if (rv == -EAGAIN) {
                                         set_bit(CACHE_NEGATIVE, &h->flags);
-                                        cache_fresh_locked(h, get_seconds()+CACHE_NEW_EXPIRY);
+                                        cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
                                         cache_fresh_unlocked(h, detail);
                                         rv = -ENOENT;
                                 }
@@ -388,11 +388,11 @@ static int cache_clean(void)
                         return -1;
                 }
                 current_detail = list_entry(next, struct cache_detail, others);
-                if (current_detail->nextcheck > get_seconds())
+                if (current_detail->nextcheck > seconds_since_boot())
                         current_index = current_detail->hash_size;
                 else {
                         current_index = 0;
-                        current_detail->nextcheck = get_seconds()+30*60;
+                        current_detail->nextcheck = seconds_since_boot()+30*60;
                 }
         }
 
@@ -477,7 +477,7 @@ EXPORT_SYMBOL_GPL(cache_flush);
 void cache_purge(struct cache_detail *detail)
 {
         detail->flush_time = LONG_MAX;
-        detail->nextcheck = get_seconds();
+        detail->nextcheck = seconds_since_boot();
         cache_flush();
         detail->flush_time = 1;
 }
@@ -902,7 +902,7 @@ static int cache_release(struct inode *inode, struct file *filp,
                 filp->private_data = NULL;
                 kfree(rp);
 
-                cd->last_close = get_seconds();
+                cd->last_close = seconds_since_boot();
                 atomic_dec(&cd->readers);
         }
         module_put(cd->owner);
@@ -1034,7 +1034,7 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h,
         int len;
 
         if (atomic_read(&detail->readers) == 0 &&
-            detail->last_close < get_seconds() - 30) {
+            detail->last_close < seconds_since_boot() - 30) {
                         warn_no_listener(detail);
                         return -EINVAL;
         }
@@ -1219,7 +1219,8 @@ static int c_show(struct seq_file *m, void *p)
 
         ifdebug(CACHE)
                 seq_printf(m, "# expiry=%ld refcnt=%d flags=%lx\n",
-                           cp->expiry_time, atomic_read(&cp->ref.refcount), cp->flags);
+                           convert_to_wallclock(cp->expiry_time),
+                           atomic_read(&cp->ref.refcount), cp->flags);
         cache_get(cp);
         if (cache_check(cd, cp, NULL))
                 /* cache_check does a cache_put on failure */
@@ -1285,7 +1286,7 @@ static ssize_t read_flush(struct file *file, char __user *buf,
         unsigned long p = *ppos;
         size_t len;
 
-        sprintf(tbuf, "%lu\n", cd->flush_time);
+        sprintf(tbuf, "%lu\n", convert_to_wallclock(cd->flush_time));
         len = strlen(tbuf);
         if (p >= len)
                 return 0;
@@ -1303,19 +1304,20 @@ static ssize_t write_flush(struct file *file, const char __user *buf,
                            struct cache_detail *cd)
 {
         char tbuf[20];
-        char *ep;
-        long flushtime;
+        char *bp, *ep;
+
         if (*ppos || count > sizeof(tbuf)-1)
                 return -EINVAL;
         if (copy_from_user(tbuf, buf, count))
                 return -EFAULT;
         tbuf[count] = 0;
-        flushtime = simple_strtoul(tbuf, &ep, 0);
+        simple_strtoul(tbuf, &ep, 0);
         if (*ep && *ep != '\n')
                 return -EINVAL;
 
-        cd->flush_time = flushtime;
-        cd->nextcheck = get_seconds();
+        bp = tbuf;
+        cd->flush_time = get_expiry(&bp);
+        cd->nextcheck = seconds_since_boot();
         cache_flush();
 
         *ppos += count;