f2fs: fix to update mtime correctly

If we change system time to the past, get_mtime() will return a
overflowed time, and SIT_I(sbi)->max_mtime will be udpated
incorrectly, this patch fixes the two issues.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

3 files changed, 19 insertions, 7 deletions

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index 8eb184c3de84..40b39db317ea 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1233,7 +1233,7 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
          * modify checkpoint
          * version number is already updated
          */
-        ckpt->elapsed_time = cpu_to_le64(get_mtime(sbi));
+        ckpt->elapsed_time = cpu_to_le64(get_mtime(sbi, true));
         ckpt->free_segment_count = cpu_to_le32(free_segments(sbi));
         for (i = 0; i < NR_CURSEG_NODE_TYPE; i++) {
                 ckpt->cur_node_segno[i] =
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index f0f9593185a7..6dbdf2c48fba 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1822,8 +1822,9 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
                                 (new_vblocks > sbi->blocks_per_seg)));
 
         se->valid_blocks = new_vblocks;
-        se->mtime = get_mtime(sbi);
-        SIT_I(sbi)->max_mtime = se->mtime;
+        se->mtime = get_mtime(sbi, false);
+        if (se->mtime > SIT_I(sbi)->max_mtime)
+                SIT_I(sbi)->max_mtime = se->mtime;
 
         /* Update valid block bitmap */
         if (del > 0) {
@@ -3884,7 +3885,7 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
                 if (sit_i->min_mtime > mtime)
                         sit_i->min_mtime = mtime;
         }
-        sit_i->max_mtime = get_mtime(sbi);
+        sit_i->max_mtime = get_mtime(sbi, false);
         up_write(&sit_i->sentry_lock);
 }
 
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index c574131ac7e1..f18fc82fbe99 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -745,12 +745,23 @@ static inline void set_to_next_sit(struct sit_info *sit_i, unsigned int start)
 #endif
 }
 
-static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi)
+static inline unsigned long long get_mtime(struct f2fs_sb_info *sbi,
+                                                bool base_time)
 {
         struct sit_info *sit_i = SIT_I(sbi);
-        time64_t now = ktime_get_real_seconds();
+        time64_t diff, now = ktime_get_real_seconds();
 
-        return sit_i->elapsed_time + now - sit_i->mounted_time;
+        if (now >= sit_i->mounted_time)
+                return sit_i->elapsed_time + now - sit_i->mounted_time;
+
+        /* system time is set to the past */
+        if (!base_time) {
+                diff = sit_i->mounted_time - now;
+                if (sit_i->elapsed_time >= diff)
+                        return sit_i->elapsed_time - diff;
+                return 0;
+        }
+        return sit_i->elapsed_time;
 }
 
 static inline void set_summary(struct f2fs_summary *sum, nid_t nid,