reiserfs: use monotonic time for j_trans_start_time

Using CLOCK_REALTIME time_t timestamps breaks on 32-bit systems in 2038,
and gives surprising results with a concurrent settimeofday().

This changes the reiserfs journal timestamps to use ktime_get_seconds()
instead, which makes it use a 64-bit CLOCK_MONOTONIC stamp.

In the procfs output, the monotonic timestamp needs to be converted back
to CLOCK_REALTIME to keep the existing ABI.

Link: http://lkml.kernel.org/r/20180620142522.27639-2-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/reiserfs/journal.c

@@ -2381,7 +2381,7 @@ static int journal_read(struct super_block *sb)
 	struct reiserfs_journal_desc *desc;
 	unsigned int oldest_trans_id = 0;
 	unsigned int oldest_invalid_trans_id = 0;
-	time_t start;
+	time64_t start;
 	unsigned long oldest_start = 0;
 	unsigned long cur_dblock = 0;
 	unsigned long newest_mount_id = 9;
@@ -2395,7 +2395,7 @@ static int journal_read(struct super_block *sb)
 	cur_dblock = SB_ONDISK_JOURNAL_1st_BLOCK(sb);
 	reiserfs_info(sb, "checking transaction log (%pg)\n",
 		      journal->j_dev_bd);
-	start = get_seconds();
+	start = ktime_get_seconds();
 
 	/*
 	 * step 1, read in the journal header block.  Check the transaction
@@ -2556,7 +2556,7 @@ static int journal_read(struct super_block *sb)
 	if (replay_count > 0) {
 		reiserfs_info(sb,
 			      "replayed %d transactions in %lu seconds\n",
-			      replay_count, get_seconds() - start);
+			      replay_count, ktime_get_seconds() - start);
 	}
 	/* needed to satisfy the locking in _update_journal_header_block */
 	reiserfs_write_lock(sb);
@@ -2914,7 +2914,7 @@ int journal_transaction_should_end(struct reiserfs_transaction_handle *th,
 				   int new_alloc)
 {
 	struct reiserfs_journal *journal = SB_JOURNAL(th->t_super);
-	time_t now = get_seconds();
+	time64_t now = ktime_get_seconds();
 	/* cannot restart while nested */
 	BUG_ON(!th->t_trans_id);
 	if (th->t_refcount > 1)
@@ -3023,7 +3023,7 @@ static int do_journal_begin_r(struct reiserfs_transaction_handle *th,
 			      struct super_block *sb, unsigned long nblocks,
 			      int join)
 {
-	time_t now = get_seconds();
+	time64_t now = ktime_get_seconds();
 	unsigned int old_trans_id;
 	struct reiserfs_journal *journal = SB_JOURNAL(sb);
 	struct reiserfs_transaction_handle myth;
@@ -3056,7 +3056,7 @@ static int do_journal_begin_r(struct reiserfs_transaction_handle *th,
 		PROC_INFO_INC(sb, journal.journal_relock_writers);
 		goto relock;
 	}
-	now = get_seconds();
+	now = ktime_get_seconds();
 
 	/*
 	 * if there is no room in the journal OR
@@ -3119,7 +3119,7 @@ static int do_journal_begin_r(struct reiserfs_transaction_handle *th,
 	}
 	/* we are the first writer, set trans_id */
 	if (journal->j_trans_start_time == 0) {
-		journal->j_trans_start_time = get_seconds();
+		journal->j_trans_start_time = ktime_get_seconds();
 	}
 	atomic_inc(&journal->j_wcount);
 	journal->j_len_alloc += nblocks;
@@ -3559,11 +3559,11 @@ static void flush_async_commits(struct work_struct *work)
  */
 void reiserfs_flush_old_commits(struct super_block *sb)
 {
-	time_t now;
+	time64_t now;
 	struct reiserfs_transaction_handle th;
 	struct reiserfs_journal *journal = SB_JOURNAL(sb);
 
-	now = get_seconds();
+	now = ktime_get_seconds();
 	/*
 	 * safety check so we don't flush while we are replaying the log during
 	 * mount
@@ -3613,7 +3613,7 @@ void reiserfs_flush_old_commits(struct super_block *sb)
 static int check_journal_end(struct reiserfs_transaction_handle *th, int flags)
 {
 
-	time_t now;
+	time64_t now;
 	int flush = flags & FLUSH_ALL;
 	int commit_now = flags & COMMIT_NOW;
 	int wait_on_commit = flags & WAIT;
@@ -3694,7 +3694,7 @@ static int check_journal_end(struct reiserfs_transaction_handle *th, int flags)
 	}
 
 	/* deal with old transactions where we are the last writers */
-	now = get_seconds();
+	now = ktime_get_seconds();
 	if ((now - journal->j_trans_start_time) > journal->j_max_trans_age) {
 		commit_now = 1;
 		journal->j_next_async_flush = 1;

fs/reiserfs/procfs.c

@@ -297,6 +297,13 @@ static int show_oidmap(struct seq_file *m, void *unused)
 	return 0;
 }
 
+static time64_t ktime_mono_to_real_seconds(time64_t mono)
+{
+	ktime_t kt = ktime_set(mono, NSEC_PER_SEC/2);
+
+	return ktime_divns(ktime_mono_to_real(kt), NSEC_PER_SEC);
+}
+
 static int show_journal(struct seq_file *m, void *unused)
 {
 	struct super_block *sb = m->private;
@@ -325,7 +332,7 @@ static int show_journal(struct seq_file *m, void *unused)
 		   "j_bcount: \t%lu\n"
 		   "j_first_unflushed_offset: \t%lu\n"
 		   "j_last_flush_trans_id: \t%u\n"
-		   "j_trans_start_time: \t%li\n"
+		   "j_trans_start_time: \t%lli\n"
 		   "j_list_bitmap_index: \t%i\n"
 		   "j_must_wait: \t%i\n"
 		   "j_next_full_flush: \t%i\n"
@@ -366,7 +373,7 @@ static int show_journal(struct seq_file *m, void *unused)
 		   JF(j_bcount),
 		   JF(j_first_unflushed_offset),
 		   JF(j_last_flush_trans_id),
-		   JF(j_trans_start_time),
+		   ktime_mono_to_real_seconds(JF(j_trans_start_time)),
 		   JF(j_list_bitmap_index),
 		   JF(j_must_wait),
 		   JF(j_next_full_flush),

fs/reiserfs/reiserfs.h

@@ -331,7 +331,7 @@ struct reiserfs_journal {
 
 	struct buffer_head *j_header_bh;
 
-	time_t j_trans_start_time;	/* time this transaction started */
+	time64_t j_trans_start_time;	/* time this transaction started */
 	struct mutex j_mutex;
 	struct mutex j_flush_mutex;