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>
diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 1932810..c541ab8 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -791,7 +791,7 @@
if (final_size > inode->i_size) {
/* Credits for sb + inode write */
- handle = ext4_journal_start(inode, 2);
+ handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
goto out;
@@ -851,7 +851,7 @@
int err;
/* Credits for sb + inode write */
- handle = ext4_journal_start(inode, 2);
+ handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
if (IS_ERR(handle)) {
/* This is really bad luck. We've written the data
* but cannot extend i_size. Bail out and pretend
@@ -950,7 +950,8 @@
{
handle_t *result;
- result = ext4_journal_start(inode, ext4_blocks_for_truncate(inode));
+ result = ext4_journal_start(inode, EXT4_HT_TRUNCATE,
+ ext4_blocks_for_truncate(inode));
if (!IS_ERR(result))
return result;