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gfs2: Use GL_NOBLOCK flag for non-blocking lookups

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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>
This commit is contained in:
Abhi Das 2023-11-10 13:10:08 +01:00 committed by Andreas Gruenbacher
parent f9f229c1f7
commit dd00aaeb34
2 changed files with 18 additions and 13 deletions
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23
fs/gfs2/dentry.c
View File

@ -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;
}

8
fs/gfs2/inode.c
View File

@ -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;
}