gfs2: Use GL_NOBLOCK flag for non-blocking lookups

Add the GL_NOBLOCK flag to the locking requests in gfs2_permission() and
gfs2_drevalidate() when called with the MAY_NOT_BLOCK flag and
LOOKUP_RCU flag, respectively.  This will cause the locking requests to
be handled without sleeping if possible.  We bail out with -ECHILD if we
can't grant the glock immediately.

Make sure not to dget() + dput() the parent dentry in gfs2_drevalidate()
in LOOKUP_RCU mode; dput() is a sleeping operation.

Signed-off-by: Abhi Das <adas@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
index 2e215e8c3c88e57d6ed17ba6cc5cb22420e99af6..177f1f41f225458344cd000147d71079c19689ab 100644 (file)
--- a/fs/gfs2/dentry.c
+++ b/fs/gfs2/dentry.c
@@ -32,21 +32,25 @@
 
 static int gfs2_drevalidate(struct dentry *dentry, unsigned int flags)
 {
-       struct dentry *parent;
+       struct dentry *parent = NULL;
        struct gfs2_sbd *sdp;
        struct gfs2_inode *dip;
-       struct inode *inode;
+       struct inode *dinode, *inode;
        struct gfs2_holder d_gh;
        struct gfs2_inode *ip = NULL;
        int error, valid = 0;
        int had_lock = 0;
 
-       if (flags & LOOKUP_RCU)
-               return -ECHILD;
-
-       parent = dget_parent(dentry);
-       sdp = GFS2_SB(d_inode(parent));
-       dip = GFS2_I(d_inode(parent));
+       if (flags & LOOKUP_RCU) {
+               dinode = d_inode_rcu(READ_ONCE(dentry->d_parent));
+               if (!dinode)
+                       return -ECHILD;
+       } else {
+               parent = dget_parent(dentry);
+               dinode = d_inode(parent);
+       }
+       sdp = GFS2_SB(dinode);
+       dip = GFS2_I(dinode);
        inode = d_inode(dentry);
 
        if (inode) {
@@ -62,7 +66,8 @@ static int gfs2_drevalidate(struct dentry *dentry, unsigned int flags)
 
        had_lock = (gfs2_glock_is_locked_by_me(dip->i_gl) != NULL);
        if (!had_lock) {
-               error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
+               error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED,
+                                          flags & LOOKUP_RCU ? GL_NOBLOCK : 0, &d_gh);
                if (error)
                        goto out;
        }

diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 1b95db2c3aac3c9a9d5d881985e70622342b52ab..6bfc9383b7b8eca60aad0d88c341904b572681bb 100644 (file)
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -1882,10 +1882,10 @@ int gfs2_permission(struct mnt_idmap *idmap, struct inode *inode,
                WARN_ON_ONCE(!may_not_block);
                return -ECHILD;
         }
-       if (gfs2_glock_is_locked_by_me(gl) == NULL) {
-               if (may_not_block)
-                       return -ECHILD;
-               error = gfs2_glock_nq_init(gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
+       if (gfs2_glock_is_locked_by_me(ip->i_gl) == NULL) {
+               int noblock = may_not_block ? GL_NOBLOCK : 0;
+               error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED,
+                                          LM_FLAG_ANY | noblock, &i_gh);
                if (error)
                        return error;
        }