All of lore.kernel.org
 help / color / mirror / Atom feed
* [PATCHv3 1/1] jbd2: Fix I/O hang in jbd2_journal_release_jbd_inode
@ 2010-08-31 14:07 Brian King
  2010-09-02  8:21 ` Ted Ts'o
  0 siblings, 1 reply; 2+ messages in thread
From: Brian King @ 2010-08-31 14:07 UTC (permalink / raw)
  To: tytso; +Cc: josef, linux-ext4, cmm, pmac, brking


This fixes a hang seen in jbd2_journal_release_jbd_inode
on a lot of Power 6 systems running with ext4. When we get
in the hung state, all I/O to the disk in question gets blocked
where we stay indefinitely. Looking at the task list, I can see
we are stuck in jbd2_journal_release_jbd_inode waiting on a
wake up. I added some debug code to detect this scenario and
dump additional data if we were stuck in jbd2_journal_release_jbd_inode
for longer than 30 minutes. When it hit, I was able to see that
i_flags was 0, suggesting we missed the wake up.

This patch changes i_flags to be an unsigned long, uses bit operators
to access it, and adds barriers around the accesses. Prior to applying
this patch, we were regularly hitting this hang on numerous systems
in our test environment. After applying the patch, the hangs no longer
occur.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
---

 fs/jbd2/commit.c     |   12 ++++++++----
 fs/jbd2/journal.c    |    4 +++-
 include/linux/jbd2.h |    2 +-
 3 files changed, 12 insertions(+), 6 deletions(-)

diff -puN include/linux/jbd2.h~jbd2_ji_commit_barrier_patch include/linux/jbd2.h
--- linux-2.6/include/linux/jbd2.h~jbd2_ji_commit_barrier_patch	2010-08-30 08:45:04.000000000 -0500
+++ linux-2.6-bjking1/include/linux/jbd2.h	2010-08-30 08:45:04.000000000 -0500
@@ -395,7 +395,7 @@ struct jbd2_inode {
 	struct inode *i_vfs_inode;
 
 	/* Flags of inode [j_list_lock] */
-	unsigned int i_flags;
+	unsigned long i_flags;
 };
 
 struct jbd2_revoke_table_s;
diff -puN fs/jbd2/commit.c~jbd2_ji_commit_barrier_patch fs/jbd2/commit.c
--- linux-2.6/fs/jbd2/commit.c~jbd2_ji_commit_barrier_patch	2010-08-30 08:45:04.000000000 -0500
+++ linux-2.6-bjking1/fs/jbd2/commit.c	2010-08-30 08:45:04.000000000 -0500
@@ -26,7 +26,9 @@
 #include <linux/backing-dev.h>
 #include <linux/bio.h>
 #include <linux/blkdev.h>
+#include <linux/bitops.h>
 #include <trace/events/jbd2.h>
+#include <asm/system.h>
 
 /*
  * Default IO end handler for temporary BJ_IO buffer_heads.
@@ -236,7 +238,7 @@ static int journal_submit_data_buffers(j
 	spin_lock(&journal->j_list_lock);
 	list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 		mapping = jinode->i_vfs_inode->i_mapping;
-		jinode->i_flags |= JI_COMMIT_RUNNING;
+		set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 		spin_unlock(&journal->j_list_lock);
 		/*
 		 * submit the inode data buffers. We use writepage
@@ -251,7 +253,8 @@ static int journal_submit_data_buffers(j
 		spin_lock(&journal->j_list_lock);
 		J_ASSERT(jinode->i_transaction == commit_transaction);
 		commit_transaction->t_flushed_data_blocks = 1;
-		jinode->i_flags &= ~JI_COMMIT_RUNNING;
+		clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
+		smp_mb__after_clear_bit();
 		wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 	}
 	spin_unlock(&journal->j_list_lock);
@@ -272,7 +275,7 @@ static int journal_finish_inode_data_buf
 	/* For locking, see the comment in journal_submit_data_buffers() */
 	spin_lock(&journal->j_list_lock);
 	list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
-		jinode->i_flags |= JI_COMMIT_RUNNING;
+		set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 		spin_unlock(&journal->j_list_lock);
 		err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 		if (err) {
@@ -288,7 +291,8 @@ static int journal_finish_inode_data_buf
 				ret = err;
 		}
 		spin_lock(&journal->j_list_lock);
-		jinode->i_flags &= ~JI_COMMIT_RUNNING;
+		clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
+		smp_mb__after_clear_bit();
 		wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 	}
 
diff -puN fs/jbd2/journal.c~jbd2_ji_commit_barrier_patch fs/jbd2/journal.c
--- linux-2.6/fs/jbd2/journal.c~jbd2_ji_commit_barrier_patch	2010-08-30 08:45:04.000000000 -0500
+++ linux-2.6-bjking1/fs/jbd2/journal.c	2010-08-31 08:58:24.000000000 -0500
@@ -42,12 +42,14 @@
 #include <linux/log2.h>
 #include <linux/vmalloc.h>
 #include <linux/backing-dev.h>
+#include <linux/bitops.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/jbd2.h>
 
 #include <asm/uaccess.h>
 #include <asm/page.h>
+#include <asm/system.h>
 
 EXPORT_SYMBOL(jbd2_journal_extend);
 EXPORT_SYMBOL(jbd2_journal_stop);
@@ -2206,7 +2208,7 @@ void jbd2_journal_release_jbd_inode(jour
 restart:
 	spin_lock(&journal->j_list_lock);
 	/* Is commit writing out inode - we have to wait */
-	if (jinode->i_flags & JI_COMMIT_RUNNING) {
+	if (test_bit(__JI_COMMIT_RUNNING, &jinode->i_flags)) {
 		wait_queue_head_t *wq;
 		DEFINE_WAIT_BIT(wait, &jinode->i_flags, __JI_COMMIT_RUNNING);
 		wq = bit_waitqueue(&jinode->i_flags, __JI_COMMIT_RUNNING);
_

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2010-09-02 10:15 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2010-08-31 14:07 [PATCHv3 1/1] jbd2: Fix I/O hang in jbd2_journal_release_jbd_inode Brian King
2010-09-02  8:21 ` Ted Ts'o

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.