From: Wendy Cheng <wcheng@redhat.com>
Subject: [RHEL5 PATCH] GFS2 change nlink panic
Date: Wed, 20 Dec 2006 03:05:59 -0500
Bugzilla: 215088
Message-Id: <4588EEE7.8060102@redhat.com>
Changelog: GFS2 change nlink panic


GFS2 rename will panic if resource group locks are taken by the block 
allocation logic (adding filename to the directory) and the replaced 
(and/or deleted) file is the last reference of the file. It will BUG() 
in gfs2_change_nlink() where the delete logic tries to free on-disk 
inode back to resource group (recursive locking is not allowed)  This 
patch fixes the panic seen by the bugzilla while installing RHEL on gfs2 
partitions. It is verified by a stand-alone test program.

Two un-finished issues:
1. We still can't run thru anaconda installation (with RHEL on GFS2 
partitions) - other issues have been worked on.
2. There are few other gfs2_change_nlink() hidden layers under other 
calls (gfs2_rmdiri() for example) in rename code path that may cause 
similar panic. Haven't had chances to examine the scope yet - if we 
eventually find too many of these, we may need to re-think whether we 
should free on-disk inode back to RG as part of the file deletion logic.

In any case, this is more of a (normal) gfs2 rename issue, not so much 
of an installation issue.

-- Wendy

--- linux-2.6.18/fs/gfs2/inode.h	2006-11-27 15:34:45.000000000 -0500
+++ linux/fs/gfs2/inode.h	2006-12-15 02:45:16.000000000 -0500
@@ -34,6 +34,7 @@ int gfs2_inode_refresh(struct gfs2_inode
 
 int gfs2_dinode_dealloc(struct gfs2_inode *inode);
 int gfs2_change_nlink(struct gfs2_inode *ip, int diff);
+int gfs2_change_nlink_i(struct gfs2_inode *ip, int diff);
 struct inode *gfs2_lookupi(struct inode *dir, const struct qstr *name,
 			   int is_root, struct nameidata *nd);
 struct inode *gfs2_createi(struct gfs2_holder *ghs, const struct qstr *name,
--- linux-2.6.18/fs/gfs2/inode.c	2006-11-27 15:34:45.000000000 -0500
+++ linux/fs/gfs2/inode.c	2006-12-15 02:59:54.000000000 -0500
@@ -300,16 +300,14 @@ out:
 }
 
 /**
- * gfs2_change_nlink - Change nlink count on inode
+ * gfs2_change_nlink_i - Change nlink count on inode
  * @ip: The GFS2 inode
  * @diff: The change in the nlink count required
  *
  * Returns: errno
  */
-
-int gfs2_change_nlink(struct gfs2_inode *ip, int diff)
+int gfs2_change_nlink_i(struct gfs2_inode *ip, int diff)
 {
-	struct gfs2_sbd *sdp = ip->i_inode.i_sb->s_fs_info;
 	struct buffer_head *dibh;
 	u32 nlink;
 	int error;
@@ -338,6 +336,20 @@ int gfs2_change_nlink(struct gfs2_inode 
 	brelse(dibh);
 	mark_inode_dirty(&ip->i_inode);
 
+	return error;
+}
+
+int gfs2_change_nlink(struct gfs2_inode *ip, int diff)
+{
+	struct gfs2_sbd *sdp = ip->i_inode.i_sb->s_fs_info;
+	int error;
+
+	/* update the nlink */
+	error = gfs2_change_nlink_i(ip, diff);
+	if (error)
+		return error;
+
+	/* return meta data block back to rg */
 	if (ip->i_di.di_nlink == 0) {
 		struct gfs2_rgrpd *rgd;
 		struct gfs2_holder ri_gh, rg_gh;
--- linux-2.6.18/fs/gfs2/ops_inode.c	2006-11-27 15:34:45.000000000 -0500
+++ linux/fs/gfs2/ops_inode.c	2006-12-15 13:29:13.000000000 -0500
@@ -583,6 +583,7 @@ static int gfs2_rename(struct inode *odi
 	int alloc_required;
 	unsigned int x;
 	int error;
+	struct gfs2_rgrpd *rgd;
 
 	if (ndentry->d_inode) {
 		nip = GFS2_I(ndentry->d_inode);
@@ -716,12 +717,12 @@ static int gfs2_rename(struct inode *odi
 		error = gfs2_trans_begin(sdp, sdp->sd_max_dirres +
 					 al->al_rgd->rd_ri.ri_length +
 					 4 * RES_DINODE + 4 * RES_LEAF +
-					 RES_STATFS + RES_QUOTA, 0);
+					 RES_STATFS + RES_QUOTA + 1, 0);
 		if (error)
 			goto out_ipreserv;
 	} else {
 		error = gfs2_trans_begin(sdp, 4 * RES_DINODE +
-					 5 * RES_LEAF, 0);
+					 5 * RES_LEAF + 1, 0);
 		if (error)
 			goto out_gunlock;
 	}
@@ -735,7 +736,25 @@ static int gfs2_rename(struct inode *odi
 			error = gfs2_dir_del(ndip, &ndentry->d_name);
 			if (error)
 				goto out_end_trans;
-			error = gfs2_change_nlink(nip, -1);
+			error = gfs2_change_nlink_i(nip, -1);
+			if ((!error) && (nip->i_di.di_nlink == 0)) {
+				error = -EIO;
+				rgd = gfs2_blk2rgrpd(sdp, nip->i_num.no_addr);
+				if (rgd) {
+					struct gfs2_holder nlink_rg_gh;
+					if (rgd != nip->i_alloc.al_rgd) 
+						error = gfs2_glock_nq_init(
+						rgd->rd_gl, LM_ST_EXCLUSIVE, 
+						0, &nlink_rg_gh);
+					else 
+						error = 0;
+                			if (!error) {
+						gfs2_unlink_di(&nip->i_inode);
+						if (rgd != nip->i_alloc.al_rgd) 
+							gfs2_glock_dq_uninit(&nlink_rg_gh);
+					}
+				}
+			}
 		}
 		if (error)
 			goto out_end_trans;