Subject: [merged] ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread.patch removed from -mm tree
To: jack@xxxxxxx,jlbec@xxxxxxxxxxxx,mfasheh@xxxxxxx,srinivas.eeda@xxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 04 Apr 2014 12:30:15 -0700
The patch titled
Subject: ocfs2: avoid blocking in ocfs2_mark_lockres_freeing() in downconvert thread
has been removed from the -mm tree. Its filename was
ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Jan Kara <jack@xxxxxxx>
Subject: ocfs2: avoid blocking in ocfs2_mark_lockres_freeing() in downconvert thread
If we are dropping last inode reference from downconvert thread, we will
end up calling ocfs2_mark_lockres_freeing() which can block if the lock we
are freeing is queued thus creating an A-A deadlock. Luckily, since we
are the downconvert thread, we can immediately dequeue the lock and thus
avoid waiting in this case.
Signed-off-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Mark Fasheh <mfasheh@xxxxxxx>
Reviewed-by: Srinivas Eeda <srinivas.eeda@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/dlmglue.c | 44 ++++++++++++++++++++++++++++++++++++++++---
fs/ocfs2/dlmglue.h | 3 +-
fs/ocfs2/inode.c | 7 +++---
3 files changed, 47 insertions(+), 7 deletions(-)
diff -puN fs/ocfs2/dlmglue.c~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread fs/ocfs2/dlmglue.c
--- a/fs/ocfs2/dlmglue.c~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread
+++ a/fs/ocfs2/dlmglue.c
@@ -3144,22 +3144,60 @@ out:
return 0;
}
+static void ocfs2_process_blocked_lock(struct ocfs2_super *osb,
+ struct ocfs2_lock_res *lockres);
+
/* Mark the lockres as being dropped. It will no longer be
* queued if blocking, but we still may have to wait on it
* being dequeued from the downconvert thread before we can consider
* it safe to drop.
*
* You can *not* attempt to call cluster_lock on this lockres anymore. */
-void ocfs2_mark_lockres_freeing(struct ocfs2_lock_res *lockres)
+void ocfs2_mark_lockres_freeing(struct ocfs2_super *osb,
+ struct ocfs2_lock_res *lockres)
{
int status;
struct ocfs2_mask_waiter mw;
- unsigned long flags;
+ unsigned long flags, flags2;
ocfs2_init_mask_waiter(&mw);
spin_lock_irqsave(&lockres->l_lock, flags);
lockres->l_flags |= OCFS2_LOCK_FREEING;
+ if (lockres->l_flags & OCFS2_LOCK_QUEUED && current == osb->dc_task) {
+ /*
+ * We know the downconvert is queued but not in progress
+ * because we are the downconvert thread and processing
+ * different lock. So we can just remove the lock from the
+ * queue. This is not only an optimization but also a way
+ * to avoid the following deadlock:
+ * ocfs2_dentry_post_unlock()
+ * ocfs2_dentry_lock_put()
+ * ocfs2_drop_dentry_lock()
+ * iput()
+ * ocfs2_evict_inode()
+ * ocfs2_clear_inode()
+ * ocfs2_mark_lockres_freeing()
+ * ... blocks waiting for OCFS2_LOCK_QUEUED
+ * since we are the downconvert thread which
+ * should clear the flag.
+ */
+ spin_unlock_irqrestore(&lockres->l_lock, flags);
+ spin_lock_irqsave(&osb->dc_task_lock, flags2);
+ list_del_init(&lockres->l_blocked_list);
+ osb->blocked_lock_count--;
+ spin_unlock_irqrestore(&osb->dc_task_lock, flags2);
+ /*
+ * Warn if we recurse into another post_unlock call. Strictly
+ * speaking it isn't a problem but we need to be careful if
+ * that happens (stack overflow, deadlocks, ...) so warn if
+ * ocfs2 grows a path for which this can happen.
+ */
+ WARN_ON_ONCE(lockres->l_ops->post_unlock);
+ /* Since the lock is freeing we don't do much in the fn below */
+ ocfs2_process_blocked_lock(osb, lockres);
+ return;
+ }
while (lockres->l_flags & OCFS2_LOCK_QUEUED) {
lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_QUEUED, 0);
spin_unlock_irqrestore(&lockres->l_lock, flags);
@@ -3180,7 +3218,7 @@ void ocfs2_simple_drop_lockres(struct oc
{
int ret;
- ocfs2_mark_lockres_freeing(lockres);
+ ocfs2_mark_lockres_freeing(osb, lockres);
ret = ocfs2_drop_lock(osb, lockres);
if (ret)
mlog_errno(ret);
diff -puN fs/ocfs2/dlmglue.h~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread fs/ocfs2/dlmglue.h
--- a/fs/ocfs2/dlmglue.h~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread
+++ a/fs/ocfs2/dlmglue.h
@@ -157,7 +157,8 @@ int ocfs2_refcount_lock(struct ocfs2_ref
void ocfs2_refcount_unlock(struct ocfs2_refcount_tree *ref_tree, int ex);
-void ocfs2_mark_lockres_freeing(struct ocfs2_lock_res *lockres);
+void ocfs2_mark_lockres_freeing(struct ocfs2_super *osb,
+ struct ocfs2_lock_res *lockres);
void ocfs2_simple_drop_lockres(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres);
diff -puN fs/ocfs2/inode.c~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread fs/ocfs2/inode.c
--- a/fs/ocfs2/inode.c~ocfs2-avoid-blocking-in-ocfs2_mark_lockres_freeing-in-downconvert-thread
+++ a/fs/ocfs2/inode.c
@@ -1080,6 +1080,7 @@ static void ocfs2_clear_inode(struct ino
{
int status;
struct ocfs2_inode_info *oi = OCFS2_I(inode);
+ struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
clear_inode(inode);
trace_ocfs2_clear_inode((unsigned long long)oi->ip_blkno,
@@ -1096,9 +1097,9 @@ static void ocfs2_clear_inode(struct ino
/* Do these before all the other work so that we don't bounce
* the downconvert thread while waiting to destroy the locks. */
- ocfs2_mark_lockres_freeing(&oi->ip_rw_lockres);
- ocfs2_mark_lockres_freeing(&oi->ip_inode_lockres);
- ocfs2_mark_lockres_freeing(&oi->ip_open_lockres);
+ ocfs2_mark_lockres_freeing(osb, &oi->ip_rw_lockres);
+ ocfs2_mark_lockres_freeing(osb, &oi->ip_inode_lockres);
+ ocfs2_mark_lockres_freeing(osb, &oi->ip_open_lockres);
ocfs2_resv_discard(&OCFS2_SB(inode->i_sb)->osb_la_resmap,
&oi->ip_la_data_resv);
_
Patches currently in -mm which might be from jack@xxxxxxx are
origin.patch
fs-mpagec-forgotten-write_sync-in-case-of-data-integrity-write.patch
linux-next.patch
mm-add-strictlimit-knob-v2.patch
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