[Ocfs2-devel] [PATCH] ocfs2: fix a potential 'ABBA' deadlock caused by 'l_lock' and 'dentry_attach_lock'

From: piaojun <piaojun@huawei.com>
To: ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [PATCH] ocfs2: fix a potential 'ABBA' deadlock caused by 'l_lock' and 'dentry_attach_lock'
Date: Thu, 7 Dec 2017 19:28:59 +0800	[thread overview]
Message-ID: <5A2925FB.2060908@huawei.com> (raw)

       CPUA                                      CPUB

ocfs2_dentry_convert_worker
get 'l_lock'

                                    get 'dentry_attach_lock'

                                    interruptted by dio_end_io:
                                      dio_end_io
                                        dio_bio_end_aio
                                          dio_complete
                                            dio->end_io
                                              ocfs2_dio_end_io
                                                ocfs2_rw_unlock
                                                ...
                                                try to get 'l_lock'
                                                but CPUA has got it.

try to get 'dentry_attach_lock',
but CPUB has got 'dentry_attach_lock',
and would not release it.

so we need use spin_lock_irqsave for 'dentry_attach_lock' to prevent
interruptted by softirq.

Signed-off-by: Jun Piao <piaojun@huawei.com>
Reviewed-by: Alex Chen <alex.chen@huawei.com>
---
 fs/ocfs2/dcache.c  | 14 ++++++++------
 fs/ocfs2/dlmglue.c | 14 +++++++-------
 fs/ocfs2/namei.c   |  5 +++--
 3 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/fs/ocfs2/dcache.c b/fs/ocfs2/dcache.c
index 2903730..6555fbf 100644
--- a/fs/ocfs2/dcache.c
+++ b/fs/ocfs2/dcache.c
@@ -230,6 +230,7 @@ int ocfs2_dentry_attach_lock(struct dentry *dentry,
 	int ret;
 	struct dentry *alias;
 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
+	unsigned long flags;

 	trace_ocfs2_dentry_attach_lock(dentry->d_name.len, dentry->d_name.name,
 				       (unsigned long long)parent_blkno, dl);
@@ -309,10 +310,10 @@ int ocfs2_dentry_attach_lock(struct dentry *dentry,
 	ocfs2_dentry_lock_res_init(dl, parent_blkno, inode);

 out_attach:
-	spin_lock(&dentry_attach_lock);
+	spin_lock_irqsave(&dentry_attach_lock, flags);
 	dentry->d_fsdata = dl;
 	dl->dl_count++;
-	spin_unlock(&dentry_attach_lock);
+	spin_unlock_irqrestore(&dentry_attach_lock, flags);

 	/*
 	 * This actually gets us our PRMODE level lock. From now on,
@@ -333,9 +334,9 @@ int ocfs2_dentry_attach_lock(struct dentry *dentry,
 	if (ret < 0 && !alias) {
 		ocfs2_lock_res_free(&dl->dl_lockres);
 		BUG_ON(dl->dl_count != 1);
-		spin_lock(&dentry_attach_lock);
+		spin_lock_irqsave(&dentry_attach_lock, flags);
 		dentry->d_fsdata = NULL;
-		spin_unlock(&dentry_attach_lock);
+		spin_unlock_irqrestore(&dentry_attach_lock, flags);
 		kfree(dl);
 		iput(inode);
 	}
@@ -379,13 +380,14 @@ void ocfs2_dentry_lock_put(struct ocfs2_super *osb,
 			   struct ocfs2_dentry_lock *dl)
 {
 	int unlock = 0;
+	unsigned long flags;

 	BUG_ON(dl->dl_count == 0);

-	spin_lock(&dentry_attach_lock);
+	spin_lock_irqsave(&dentry_attach_lock, flags);
 	dl->dl_count--;
 	unlock = !dl->dl_count;
-	spin_unlock(&dentry_attach_lock);
+	spin_unlock_irqrestore(&dentry_attach_lock, flags);

 	if (unlock)
 		ocfs2_drop_dentry_lock(osb, dl);
diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 4689940..9bff3d2 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -3801,7 +3801,7 @@ static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
 	struct ocfs2_dentry_lock *dl = ocfs2_lock_res_dl(lockres);
 	struct ocfs2_inode_info *oi = OCFS2_I(dl->dl_inode);
 	struct dentry *dentry;
-	unsigned long flags;
+	unsigned long flags, d_flags;
 	int extra_ref = 0;

 	/*
@@ -3831,13 +3831,13 @@ static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
 	 * flag.
 	 */
 	spin_lock_irqsave(&lockres->l_lock, flags);
-	spin_lock(&dentry_attach_lock);
+	spin_lock_irqsave(&dentry_attach_lock, d_flags);
 	if (!(lockres->l_flags & OCFS2_LOCK_FREEING)
 	    && dl->dl_count) {
 		dl->dl_count++;
 		extra_ref = 1;
 	}
-	spin_unlock(&dentry_attach_lock);
+	spin_unlock_irqrestore(&dentry_attach_lock, d_flags);
 	spin_unlock_irqrestore(&lockres->l_lock, flags);

 	mlog(0, "extra_ref = %d\n", extra_ref);
@@ -3850,13 +3850,13 @@ static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
 	if (!extra_ref)
 		return UNBLOCK_CONTINUE;

-	spin_lock(&dentry_attach_lock);
+	spin_lock_irqsave(&dentry_attach_lock, d_flags);
 	while (1) {
 		dentry = ocfs2_find_local_alias(dl->dl_inode,
 						dl->dl_parent_blkno, 1);
 		if (!dentry)
 			break;
-		spin_unlock(&dentry_attach_lock);
+		spin_unlock_irqrestore(&dentry_attach_lock, d_flags);

 		if (S_ISDIR(dl->dl_inode->i_mode))
 			shrink_dcache_parent(dentry);
@@ -3874,9 +3874,9 @@ static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
 		d_delete(dentry);
 		dput(dentry);

-		spin_lock(&dentry_attach_lock);
+		spin_lock_irqsave(&dentry_attach_lock, d_flags);
 	}
-	spin_unlock(&dentry_attach_lock);
+	spin_unlock_irqrestore(&dentry_attach_lock, d_flags);

 	/*
 	 * If we are the last holder of this dentry lock, there is no
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 3b0a10d..a17454e 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -223,13 +223,14 @@ static void ocfs2_cleanup_add_entry_failure(struct ocfs2_super *osb,
 		struct dentry *dentry, struct inode *inode)
 {
 	struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
+	unsigned long flags;

 	ocfs2_simple_drop_lockres(osb, &dl->dl_lockres);
 	ocfs2_lock_res_free(&dl->dl_lockres);
 	BUG_ON(dl->dl_count != 1);
-	spin_lock(&dentry_attach_lock);
+	spin_lock_irqsave(&dentry_attach_lock, flags);
 	dentry->d_fsdata = NULL;
-	spin_unlock(&dentry_attach_lock);
+	spin_unlock_irqrestore(&dentry_attach_lock, flags);
 	kfree(dl);
 	iput(inode);
 }
-- 
