dont-let-dirty-time-inodes-get-more-than-a-day-stale

   1 vfs: don't let the dirty time inodes get more than a day stale
   2
   3 Guarantee that the on-disk timestamps will be no more than 24 hours
   4 stale.
   5
   6 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   7 ---
   8  fs/fs-writeback.c  |  1 +
   9  fs/inode.c         | 28 +++++++++++++++++++++++-----
  10  include/linux/fs.h |  1 +
  11  3 files changed, 25 insertions(+), 5 deletions(-)
  12
  13 diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
  14 index ce7de22..eb04277 100644
  15 --- a/fs/fs-writeback.c
  16 +++ b/fs/fs-writeback.c
  17 @@ -1141,6 +1141,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
  18         if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
  19                 trace_writeback_dirty_inode_start(inode, flags);
  20
  21 +               inode->i_ts_dirty_day = 0;
  22                 if (sb->s_op->dirty_inode)
  23                         sb->s_op->dirty_inode(inode, flags);
  24
  25 diff --git a/fs/inode.c b/fs/inode.c
  26 index 2093a84..321c7d7 100644
  27 --- a/fs/inode.c
  28 +++ b/fs/inode.c
  29 @@ -1511,6 +1511,8 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
  30   */
  31  static int update_time(struct inode *inode, struct timespec *time, int flags)
  32  {
  33 +       struct timespec uptime;
  34 +       unsigned short days_since_boot;
  35         int ret;
  36
  37         if (inode->i_op->update_time) {
  38 @@ -1525,17 +1527,33 @@ static int update_time(struct inode *inode, struct timespec *time, int flags)
  39                 if (flags & S_CTIME)
  40                         inode->i_ctime = *time;
  41                 if (flags & S_MTIME)
  42 -                       inode->i_mtime = *time;
  43 +               inode->i_mtime = *time;
  44         }
  45 +       /*
  46 +        * If i_ts_dirty_day is zero, then either we have not deferred
  47 +        * timestamp updates, or the system has been up for less than
  48 +        * a day (so days_since_boot is zero), so we defer timestamp
  49 +        * updates in that case and set the I_DIRTY_TIME flag.  If a
  50 +        * day or more has passed, then i_ts_dirty_day will be
  51 +        * different from days_since_boot, and then we should update
  52 +        * the on-disk inode and then we can clear i_ts_dirty_day.
  53 +        */
  54         if ((inode->i_sb->s_flags & MS_LAZYTIME) &&
  55             !(flags & S_VERSION)) {
  56                 if (inode->i_state & I_DIRTY_TIME)
  57                         return 0;
  58 -               spin_lock(&inode->i_lock);
  59 -               inode->i_state |= I_DIRTY_TIME;
  60 -               spin_unlock(&inode->i_lock);
  61 -               return 0;
  62 +               get_monotonic_boottime(&uptime);
  63 +               days_since_boot = div_u64(uptime.tv_sec, 86400);
  64 +               if (!inode->i_ts_dirty_day ||
  65 +                   inode->i_ts_dirty_day == days_since_boot) {
  66 +                       spin_lock(&inode->i_lock);
  67 +                       inode->i_state |= I_DIRTY_TIME;
  68 +                       spin_unlock(&inode->i_lock);
  69 +                       inode->i_ts_dirty_day = days_since_boot;
  70 +                       return 0;
  71 +               }
  72         }
  73 +       inode->i_ts_dirty_day = 0;
  74         if (inode->i_op->write_time)
  75                 return inode->i_op->write_time(inode);
  76         mark_inode_dirty_sync(inode);
  77 diff --git a/include/linux/fs.h b/include/linux/fs.h
  78 index 489b2f2..e3574cd 100644
  79 --- a/include/linux/fs.h
  80 +++ b/include/linux/fs.h
  81 @@ -575,6 +575,7 @@ struct inode {
  82         struct timespec         i_ctime;
  83         spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
  84         unsigned short          i_bytes;
  85 +       unsigned short          i_ts_dirty_day;
  86         unsigned int            i_blkbits;
  87         blkcnt_t                i_blocks;
  88