add-dirtytime-sysctl-tuning-knob

   1 fs: add dirtytime_expire_seconds sysctl
   2
   3 Add a tuning knob so we can adjust the dirtytime expiration timeout,
   4 which is very useful for testing lazytime.
   5
   6 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   7 Reviewed-by: Jan Kara <jack@suse.cz>
   8 ---
   9  fs/fs-writeback.c         | 11 +++++++++++
  10  include/linux/writeback.h |  3 +++
  11  kernel/sysctl.c           |  8 ++++++++
  12  3 files changed, 22 insertions(+)
  13
  14 diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
  15 index 2cfcd74..32a8bbd 100644
  16 --- a/fs/fs-writeback.c
  17 +++ b/fs/fs-writeback.c
  18 @@ -1188,6 +1188,17 @@ static int __init start_dirtytime_writeback(void)
  19  }
  20  __initcall(start_dirtytime_writeback);
  21
  22 +int dirtytime_interval_handler(struct ctl_table *table, int write,
  23 +                              void __user *buffer, size_t *lenp, loff_t *ppos)
  24 +{
  25 +       int ret;
  26 +
  27 +       ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
  28 +       if (ret == 0 && write)
  29 +               mod_delayed_work(system_wq, &dirtytime_work, 0);
  30 +       return ret;
  31 +}
  32 +
  33  static noinline void block_dump___mark_inode_dirty(struct inode *inode)
  34  {
  35         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
  36 diff --git a/include/linux/writeback.h b/include/linux/writeback.h
  37 index 0004833..b2dd371e 100644
  38 --- a/include/linux/writeback.h
  39 +++ b/include/linux/writeback.h
  40 @@ -130,6 +130,7 @@ extern int vm_dirty_ratio;
  41  extern unsigned long vm_dirty_bytes;
  42  extern unsigned int dirty_writeback_interval;
  43  extern unsigned int dirty_expire_interval;
  44 +extern unsigned int dirtytime_expire_interval;
  45  extern int vm_highmem_is_dirtyable;
  46  extern int block_dump;
  47  extern int laptop_mode;
  48 @@ -146,6 +147,8 @@ extern int dirty_ratio_handler(struct ctl_table *table, int write,
  49  extern int dirty_bytes_handler(struct ctl_table *table, int write,
  50                 void __user *buffer, size_t *lenp,
  51                 loff_t *ppos);
  52 +int dirtytime_interval_handler(struct ctl_table *table, int write,
  53 +                              void __user *buffer, size_t *lenp, loff_t *ppos);
  54
  55  struct ctl_table;
  56  int dirty_writeback_centisecs_handler(struct ctl_table *, int,
  57 diff --git a/kernel/sysctl.c b/kernel/sysctl.c
  58 index 88ea2d6..ce410bb 100644
  59 --- a/kernel/sysctl.c
  60 +++ b/kernel/sysctl.c
  61 @@ -1228,6 +1228,14 @@ static struct ctl_table vm_table[] = {
  62                 .extra1         = &zero,
  63         },
  64         {
  65 +               .procname       = "dirtytime_expire_seconds",
  66 +               .data           = &dirtytime_expire_interval,
  67 +               .maxlen         = sizeof(dirty_expire_interval),
  68 +               .mode           = 0644,
  69 +               .proc_handler   = dirtytime_interval_handler,
  70 +               .extra1         = &zero,
  71 +       },
  72 +       {
  73                 .procname       = "nr_pdflush_threads",
  74                 .mode           = 0444 /* read-only */,
  75                 .proc_handler   = pdflush_proc_obsolete,