ext4: add fsync batch tuning knobs

Add new mount options, min_batch_time and max_batch_time, which
controls how long the jbd2 layer should wait for additional filesystem
operations to get batched with a synchronous write transaction.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ac8551e0b70a..9ba9fd6d14da 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -328,6 +328,7 @@ struct ext4_mount_options {
         uid_t s_resuid;
         gid_t s_resgid;
         unsigned long s_commit_interval;
+        u32 s_min_batch_time, s_max_batch_time;
 #ifdef CONFIG_QUOTA
         int s_jquota_fmt;
         char *s_qf_names[MAXQUOTAS];
@@ -806,6 +807,12 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 #define EXT4_DEFM_JMODE_WBACK   0x0060
 
 /*
+ * Default journal batch times
+ */
+#define EXT4_DEF_MIN_BATCH_TIME 0
+#define EXT4_DEF_MAX_BATCH_TIME 15000 /* 15ms */
+
+/*
  * Structure of a directory entry
  */
 #define EXT4_NAME_LEN 255