[PATCH 1/6] gfs2: Avoid ip->i_gl dereferences in gfs2_inode_lookup and gfs2_create_inode

[Andreas Gruenbacher <agruenba@redhat.com>]

Store the inode glock in a separate variable instead of repeatedly retrieving
it as ip->i_gl.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---
 fs/gfs2/inode.c | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index f361876c5583..438519bc06d4 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -130,6 +130,7 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 {
 	struct inode *inode;
 	struct gfs2_inode *ip;
+	struct gfs2_glock *gl = NULL;
 	struct gfs2_holder i_gh;
 	int error;
 
@@ -147,9 +148,10 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 
 		gfs2_setup_inode(inode);
 		error = gfs2_glock_get(sdp, no_addr, &gfs2_inode_glops, CREATE,
-				       &ip->i_gl);
+				       &gl);
 		if (unlikely(error))
 			goto fail;
+		ip->i_gl = gl;
 
 		error = gfs2_glock_get(sdp, no_addr, &gfs2_iopen_glops, CREATE,
 				       &io_gl);
@@ -178,14 +180,14 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 			 * block.  We read the inode when instantiating it
 			 * after possibly checking the block type.
 			 */
-			error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE,
+			error = gfs2_glock_nq_init(gl, LM_ST_EXCLUSIVE,
 						   GL_SKIP, &i_gh);
 			if (error)
 				goto fail;
 
 			error = -ESTALE;
 			if (no_formal_ino &&
-			    gfs2_inode_already_deleted(ip->i_gl, no_formal_ino))
+			    gfs2_inode_already_deleted(gl, no_formal_ino))
 				goto fail;
 
 			if (blktype != GFS2_BLKST_FREE) {
@@ -196,20 +198,20 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 			}
 		}
 
-		set_bit(GLF_INSTANTIATE_NEEDED, &ip->i_gl->gl_flags);
+		set_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
 
 		/* Lowest possible timestamp; will be overwritten in gfs2_dinode_in. */
 		inode_set_atime(inode,
 				1LL << (8 * sizeof(inode_get_atime_sec(inode)) - 1),
 				0);
 
-		glock_set_object(ip->i_gl, ip);
+		glock_set_object(gl, ip);
 
 		if (type == DT_UNKNOWN) {
 			/* Inode glock must be locked already */
 			error = gfs2_instantiate(&i_gh);
 			if (error) {
-				glock_clear_object(ip->i_gl, ip);
+				glock_clear_object(gl, ip);
 				goto fail;
 			}
 		} else {
@@ -240,8 +242,8 @@ struct inode *gfs2_inode_lookup(struct super_block *sb, unsigned int type,
 		gfs2_glock_dq_uninit(&ip->i_iopen_gh);
 	if (gfs2_holder_initialized(&i_gh))
 		gfs2_glock_dq_uninit(&i_gh);
-	if (ip->i_gl) {
-		gfs2_glock_put(ip->i_gl);
+	if (gl) {
+		gfs2_glock_put(gl);
 		ip->i_gl = NULL;
 	}
 	iget_failed(inode);
@@ -708,7 +710,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	struct inode *inode = NULL;
 	struct gfs2_inode *dip = GFS2_I(dir), *ip;
 	struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
-	struct gfs2_glock *io_gl;
+	struct gfs2_glock *gl = NULL, *io_gl;
 	int error, dealloc_error;
 	u32 aflags = 0;
 	unsigned blocks = 1;
@@ -832,9 +834,10 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 
 	gfs2_set_inode_blocks(inode, blocks);
 
-	error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_inode_glops, CREATE, &ip->i_gl);
+	error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_inode_glops, CREATE, &gl);
 	if (error)
 		goto fail_dealloc_inode;
+	ip->i_gl = gl;
 
 	error = gfs2_glock_get(sdp, ip->i_no_addr, &gfs2_iopen_glops, CREATE, &io_gl);
 	if (error)
@@ -854,10 +857,10 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	if (error)
 		goto fail_gunlock2;
 
-	error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, GL_SKIP, &gh);
+	error = gfs2_glock_nq_init(gl, LM_ST_EXCLUSIVE, GL_SKIP, &gh);
 	if (error)
 		goto fail_gunlock3;
-	clear_bit(GLF_INSTANTIATE_NEEDED, &ip->i_gl->gl_flags);
+	clear_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
 
 	error = gfs2_trans_begin(sdp, blocks, 0);
 	if (error)
@@ -870,7 +873,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	init_dinode(dip, ip, symname);
 	gfs2_trans_end(sdp);
 
-	glock_set_object(ip->i_gl, ip);
+	glock_set_object(gl, ip);
 	glock_set_object(io_gl, ip);
 	gfs2_set_iop(inode);
 
@@ -914,7 +917,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 	return error;
 
 fail_gunlock4:
-	glock_clear_object(ip->i_gl, ip);
+	glock_clear_object(gl, ip);
 	glock_clear_object(io_gl, ip);
 fail_gunlock3:
 	gfs2_glock_dq_uninit(&ip->i_iopen_gh);
@@ -932,8 +935,8 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
 		fs_warn(sdp, "%s: %d\n", __func__, dealloc_error);
 	ip->i_no_addr = 0;
 fail_free_inode:
-	if (ip->i_gl) {
-		gfs2_glock_put(ip->i_gl);
+	if (gl) {
+		gfs2_glock_put(gl);
 		ip->i_gl = NULL;
 	}
 	gfs2_rs_deltree(&ip->i_res);
-- 
2.55.0