fs: add dirtytime_expire_seconds sysctl

Add a tuning knob so we can adjust the dirtytime expiration timeout,
which is very useful for testing lazytime.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

3 files changed, 22 insertions, 0 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 2cfcd74faf87..32a8bbd7a9ad 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1188,6 +1188,17 @@ static int __init start_dirtytime_writeback(void)
 }
 __initcall(start_dirtytime_writeback);
 
+int dirtytime_interval_handler(struct ctl_table *table, int write,
+                               void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        int ret;
+
+        ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+        if (ret == 0 && write)
+                mod_delayed_work(system_wq, &dirtytime_work, 0);
+        return ret;
+}
+
 static noinline void block_dump___mark_inode_dirty(struct inode *inode)
 {
         if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 00048339c23e..b2dd371ec0ca 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -130,6 +130,7 @@ extern int vm_dirty_ratio;
 extern unsigned long vm_dirty_bytes;
 extern unsigned int dirty_writeback_interval;
 extern unsigned int dirty_expire_interval;
+extern unsigned int dirtytime_expire_interval;
 extern int vm_highmem_is_dirtyable;
 extern int block_dump;
 extern int laptop_mode;
@@ -146,6 +147,8 @@ extern int dirty_ratio_handler(struct ctl_table *table, int write,
 extern int dirty_bytes_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos);
+int dirtytime_interval_handler(struct ctl_table *table, int write,
+                               void __user *buffer, size_t *lenp, loff_t *ppos);
 
 struct ctl_table;
 int dirty_writeback_centisecs_handler(struct ctl_table *, int,
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 88ea2d6e0031..ce410bb9f2e1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1228,6 +1228,14 @@ static struct ctl_table vm_table[] = {
                 .extra1         = &zero,
         },
         {
+                .procname       = "dirtytime_expire_seconds",
+                .data           = &dirtytime_expire_interval,
+                .maxlen         = sizeof(dirty_expire_interval),
+                .mode           = 0644,
+                .proc_handler   = dirtytime_interval_handler,
+                .extra1         = &zero,
+        },
+        {
                 .procname       = "nr_pdflush_threads",
                 .mode           = 0444 /* read-only */,
                 .proc_handler   = pdflush_proc_obsolete,