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/resize.c b/fs/ext4/resize.c
index 8eefb63..c7f4d758 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -466,7 +466,7 @@
meta_bg = EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG);
/* This transaction may be extended/restarted along the way */
- handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, EXT4_MAX_TRANS_DATA);
if (IS_ERR(handle))
return PTR_ERR(handle);
@@ -1031,7 +1031,7 @@
handle_t *handle;
int err = 0, err2;
- handle = ext4_journal_start_sb(sb, EXT4_MAX_TRANS_DATA);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, EXT4_MAX_TRANS_DATA);
if (IS_ERR(handle)) {
group = 1;
err = PTR_ERR(handle);
@@ -1412,7 +1412,7 @@
* modify each of the reserved GDT dindirect blocks.
*/
credit = flex_gd->count * 4 + reserved_gdb;
- handle = ext4_journal_start_sb(sb, credit);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, credit);
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
goto exit;
@@ -1624,7 +1624,7 @@
/* We will update the superblock, one block bitmap, and
* one group descriptor via ext4_group_add_blocks().
*/
- handle = ext4_journal_start_sb(sb, 3);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, 3);
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
ext4_warning(sb, "error %d on journal start", err);
@@ -1788,7 +1788,7 @@
credits += 3; /* block bitmap, bg descriptor, resize inode */
}
- handle = ext4_journal_start_sb(sb, credits);
+ handle = ext4_journal_start_sb(sb, EXT4_HT_RESIZE, credits);
if (IS_ERR(handle))
return PTR_ERR(handle);
