gfs2: Fix deadlock between gfs2_{create_inode,inode_lookup} and delete_work_func

In gfs2_create_inode and gfs2_inode_lookup, make sure to cancel any pending
delete work before taking the inode glock.  Otherwise, gfs2_cancel_delete_work
may block waiting for delete_work_func to complete, and delete_work_func may
block trying to acquire the inode glock in gfs2_inode_lookup.
Reported-by: Alexander Aring <aahringo@redhat.com>
Fixes: a0e3cc65 ("gfs2: Turn gl_delete into a delayed work")
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/inode.c

@@ -150,6 +150,8 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 		error = gfs2_glock_get(sdp, no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
 		if (unlikely(error))
 			goto fail;
+		if (blktype != GFS2_BLKST_UNLINKED)
+			gfs2_cancel_delete_work(io_gl);
 
 		if (type == DT_UNKNOWN || blktype != GFS2_BLKST_FREE) {
 			/*
@@ -180,8 +182,6 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 		error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT, &ip->i_iopen_gh);
 		if (unlikely(error))
 			goto fail;
-		if (blktype != GFS2_BLKST_UNLINKED)
-			gfs2_cancel_delete_work(ip->i_iopen_gh.gh_gl);
 		glock_set_object(ip->i_iopen_gh.gh_gl, ip);
 		gfs2_glock_put(io_gl);
 		io_gl = NULL;
@@ -725,13 +725,19 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	flush_delayed_work(&ip->i_gl->gl_work);
 	glock_set_object(ip->i_gl, ip);
 
-	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, ghs + 1);
+	error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
 	if (error)
 		goto fail_free_inode;
+	gfs2_cancel_delete_work(io_gl);
+	glock_set_object(io_gl, ip);
+
+	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, ghs + 1);
+	if (error)
+		goto fail_gunlock2;
 
 	error = gfs2_trans_begin(sdp, blocks, 0);
 	if (error)
-		goto fail_free_inode;
+		goto fail_gunlock2;
 
 	if (blocks > 1) {
 		ip->i_eattr = ip->i_no_addr + 1;
@@ -740,18 +746,12 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	init_dinode(dip, ip, symname);
 	gfs2_trans_end(sdp);
 
-	error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
-	if (error)
-		goto fail_free_inode;
-
 	BUG_ON(test_and_set_bit(GLF_INODE_CREATING, &io_gl->gl_flags));
 
 	error = gfs2_glock_nq_init(io_gl, LM_ST_SHARED, GL_EXACT, &ip->i_iopen_gh);
 	if (error)
 		goto fail_gunlock2;
 
-	gfs2_cancel_delete_work(ip->i_iopen_gh.gh_gl);
-	glock_set_object(ip->i_iopen_gh.gh_gl, ip);
 	gfs2_set_iop(inode);
 	insert_inode_hash(inode);
 
@@ -803,6 +803,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	gfs2_glock_dq_uninit(&ip->i_iopen_gh);
 fail_gunlock2:
 	clear_bit(GLF_INODE_CREATING, &io_gl->gl_flags);
+	glock_clear_object(io_gl, ip);
 	gfs2_glock_put(io_gl);
 fail_free_inode:
 	if (ip->i_gl) {