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/extents.c b/fs/ext4/extents.c
index db55c62..b6b54d6 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2656,7 +2656,7 @@
ext_debug("truncate since %u to %u\n", start, end);
/* probably first extent we're gonna free will be last in block */
- handle = ext4_journal_start(inode, depth + 1);
+ handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, depth + 1);
if (IS_ERR(handle))
return PTR_ERR(handle);
@@ -4287,7 +4287,7 @@
* probably first extent we're gonna free will be last in block
*/
err = ext4_writepage_trans_blocks(inode);
- handle = ext4_journal_start(inode, err);
+ handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, err);
if (IS_ERR(handle))
return;
@@ -4454,7 +4454,8 @@
while (ret >= 0 && ret < max_blocks) {
map.m_lblk = map.m_lblk + ret;
map.m_len = max_blocks = max_blocks - ret;
- handle = ext4_journal_start(inode, credits);
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
+ credits);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
break;
@@ -4532,7 +4533,7 @@
while (ret >= 0 && ret < max_blocks) {
map.m_lblk += ret;
map.m_len = (max_blocks -= ret);
- handle = ext4_journal_start(inode, credits);
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, credits);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
break;
@@ -4710,7 +4711,7 @@
inode_dio_wait(inode);
credits = ext4_writepage_trans_blocks(inode);
- handle = ext4_journal_start(inode, credits);
+ handle = ext4_journal_start(inode, EXT4_HT_TRUNCATE, credits);
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
goto out_dio;