From dd00aaeb343255a8a30de671bd27bde79a47c8e5 Mon Sep 17 00:00:00 2001
From: Abhi Das <adas@redhat.com>
Date: Fri, 10 Nov 2023 13:10:08 +0100
Subject: [PATCH] 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>
---
fs/gfs2/dentry.c | 23 ++++++++++++++---------
fs/gfs2/inode.c | 8 ++++----
2 files changed, 18 insertions(+), 13 deletions(-)
diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
index 2e215e8c3c88e..177f1f41f2254 100644
--- 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 1b95db2c3aac3..6bfc9383b7b8e 100644
--- 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;
}
--
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