Re: [syzbot] Re: [syzbot] [jfs?] possible deadlock in diFree (2)

[syzbot <syzbot+355da3b3a74881008e8f@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

Subject: Re: [syzbot] [jfs?] possible deadlock in diFree (2)
Author: lizhi.xu@windriver.com

In following calltrace, diAlloc and diFree need to hold same ag lock,
so before calling duplicateIXtree(), we maybe unlock it, and relock it after.

 diAlloc()->
   diAllocAG()->
     diAllocExt()->
       diNewIAG()->
         duplicateIXtree()->
	   diFreeSpecial()->
	     evict()->
	       jfs_evict_inode()->
	         diFree()

#syz test

diff --git a/fs/jfs/jfs_imap.c b/fs/jfs/jfs_imap.c
index a360b24ed320..1f47c6e5456b 100644
--- a/fs/jfs/jfs_imap.c
+++ b/fs/jfs/jfs_imap.c
@@ -2594,7 +2594,9 @@ diNewIAG(struct inomap * imap, int *iagnop, int agno, struct metapage ** mpp)
 		txEnd(tid);
 		mutex_unlock(&JFS_IP(ipimap)->commit_mutex);
 
+		AG_UNLOCK(imap, agno);
 		duplicateIXtree(sb, blkno, xlen, &xaddr);
+		AG_LOCK(imap, agno);
 
 		/* update the next available iag number */
 		imap->im_nextiag += 1;