ext4: pass context information to jbd2__journal_start()

So we can better understand what bits of ext4 are responsible for
long-running jbd2 handles, use jbd2__journal_start() so we can pass
context information for logging purposes.

The recommended way for finding the longer-running handles is:

   T=/sys/kernel/debug/tracing
   EVENT=$T/events/jbd2/jbd2_handle_stats
   echo "interval > 5" > $EVENT/filter
   echo 1 > $EVENT/enable

   ./run-my-fs-benchmark

   cat $T/trace > /tmp/problem-handles

This will list handles that were active for longer than 20ms.  Having
longer-running handles is bad, because a commit started at the wrong
time could stall for those 20+ milliseconds, which could delay an
fsync() or an O_SYNC operation.  Here is an example line from the
trace file describing a handle which lived on for 311 jiffies, or over
1.2 seconds:

postmark-2917  [000] ....   196.435786: jbd2_handle_stats: dev 254,32 
   tid 570 type 2 line_no 2541 interval 311 sync 0 requested_blocks 1
   dirtied_blocks 0

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

1 files changed, 5 insertions, 5 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index cb9d67fbc8f0..ef6ac59e4961 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4762,7 +4762,7 @@ static int ext4_write_dquot(struct dquot *dquot)
         struct inode *inode;
 
         inode = dquot_to_inode(dquot);
-        handle = ext4_journal_start(inode,
+        handle = ext4_journal_start(inode, EXT4_HT_QUOTA,
                                     EXT4_QUOTA_TRANS_BLOCKS(dquot->dq_sb));
         if (IS_ERR(handle))
                 return PTR_ERR(handle);
@@ -4778,7 +4778,7 @@ static int ext4_acquire_dquot(struct dquot *dquot)
         int ret, err;
         handle_t *handle;
 
-        handle = ext4_journal_start(dquot_to_inode(dquot),
+        handle = ext4_journal_start(dquot_to_inode(dquot), EXT4_HT_QUOTA,
                                     EXT4_QUOTA_INIT_BLOCKS(dquot->dq_sb));
         if (IS_ERR(handle))
                 return PTR_ERR(handle);
@@ -4794,7 +4794,7 @@ static int ext4_release_dquot(struct dquot *dquot)
         int ret, err;
         handle_t *handle;
 
-        handle = ext4_journal_start(dquot_to_inode(dquot),
+        handle = ext4_journal_start(dquot_to_inode(dquot), EXT4_HT_QUOTA,
                                     EXT4_QUOTA_DEL_BLOCKS(dquot->dq_sb));
         if (IS_ERR(handle)) {
                 /* Release dquot anyway to avoid endless cycle in dqput() */
@@ -4826,7 +4826,7 @@ static int ext4_write_info(struct super_block *sb, int type)
         handle_t *handle;
 
         /* Data block + inode block */
-        handle = ext4_journal_start(sb->s_root->d_inode, 2);
+        handle = ext4_journal_start(sb->s_root->d_inode, EXT4_HT_QUOTA, 2);
         if (IS_ERR(handle))
                 return PTR_ERR(handle);
         ret = dquot_commit_info(sb, type);
@@ -4972,7 +4972,7 @@ static int ext4_quota_off(struct super_block *sb, int type)
 
         /* Update modification times of quota files when userspace can
          * start looking at them */
-        handle = ext4_journal_start(inode, 1);
+        handle = ext4_journal_start(inode, EXT4_HT_QUOTA, 1);
         if (IS_ERR(handle))
                 goto out;
         inode->i_mtime = inode->i_ctime = CURRENT_TIME;