gfs2: fix GL_SKIP node_scope problems
Before this patch, when a glock was locked, the very first holder on the
queue would unlock the lockref and call the go_instantiate glops function
(if one existed), unless GL_SKIP was specified. When we introduced the new
node-scope concept, we allowed multiple holders to lock glocks in EX mode
and share the lock.
But node-scope introduced a new problem: if the first holder has GL_SKIP
and the next one does NOT, since it is not the first holder on the queue,
the go_instantiate op was not called. Eventually the GL_SKIP holder may
call the instantiate sub-function (e.g. gfs2_rgrp_bh_get) but there was
still a window of time in which another non-GL_SKIP holder assumes the
instantiate function had been called by the first holder. In the case of
rgrp glocks, this led to a NULL pointer dereference on the buffer_heads.
This patch tries to fix the problem by introducing two new glock flags:
GLF_INSTANTIATE_NEEDED, which keeps track of when the instantiate function
needs to be called to "fill in" or "read in" the object before it is
referenced.
GLF_INSTANTIATE_IN_PROG which is used to determine when a process is
in the process of reading in the object. Whenever a function needs to
reference the object, it checks the GLF_INSTANTIATE_NEEDED flag, and if
set, it sets GLF_INSTANTIATE_IN_PROG and calls the glops "go_instantiate"
function.
As before, the gl_lockref spin_lock is unlocked during the IO operation,
which may take a relatively long amount of time to complete. While
unlocked, if another process determines go_instantiate is still needed,
it sees GLF_INSTANTIATE_IN_PROG is set, and waits for the go_instantiate
glop operation to be completed. Once GLF_INSTANTIATE_IN_PROG is cleared,
it needs to check GLF_INSTANTIATE_NEEDED again because the other process's
go_instantiate operation may not have been successful.
Functions that previously called the instantiate sub-functions now call
directly into gfs2_instantiate so the new bits are managed properly.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index cdcbc82..5ee7da3 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1238,8 +1238,7 @@ static int gfs2_rgrp_bh_get(struct gfs2_rgrpd *rgd)
rgd->rd_rgl->rl_unlinked = cpu_to_be32(count_unlinked(rgd));
gfs2_rgrp_ondisk2lvb(rgd->rd_rgl,
rgd->rd_bits[0].bi_bh->b_data);
- }
- else if (sdp->sd_args.ar_rgrplvb) {
+ } else if (sdp->sd_args.ar_rgrplvb) {
if (!gfs2_rgrp_lvb_valid(rgd)){
gfs2_consist_rgrpd(rgd);
error = -EIO;
@@ -1257,11 +1256,10 @@ static int gfs2_rgrp_bh_get(struct gfs2_rgrpd *rgd)
bi->bi_bh = NULL;
gfs2_assert_warn(sdp, !bi->bi_clone);
}
-
return error;
}
-static int update_rgrp_lvb(struct gfs2_rgrpd *rgd)
+static int update_rgrp_lvb(struct gfs2_rgrpd *rgd, struct gfs2_holder *gh)
{
u32 rl_flags;
@@ -1269,7 +1267,7 @@ static int update_rgrp_lvb(struct gfs2_rgrpd *rgd)
return 0;
if (cpu_to_be32(GFS2_MAGIC) != rgd->rd_rgl->rl_magic)
- return gfs2_rgrp_bh_get(rgd);
+ return gfs2_instantiate(gh);
rl_flags = be32_to_cpu(rgd->rd_rgl->rl_flags);
rl_flags &= ~GFS2_RDF_MASK;
@@ -1312,6 +1310,7 @@ void gfs2_rgrp_brelse(struct gfs2_rgrpd *rgd)
bi->bi_bh = NULL;
}
}
+ set_bit(GLF_INSTANTIATE_NEEDED, &rgd->rd_gl->gl_flags);
}
int gfs2_rgrp_send_discards(struct gfs2_sbd *sdp, u64 offset,
@@ -2110,7 +2109,8 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, struct gfs2_alloc_parms *ap)
gfs2_rgrp_congested(rs->rs_rgd, loops))
goto skip_rgrp;
if (sdp->sd_args.ar_rgrplvb) {
- error = update_rgrp_lvb(rs->rs_rgd);
+ error = update_rgrp_lvb(rs->rs_rgd,
+ &ip->i_rgd_gh);
if (unlikely(error)) {
rgrp_unlock_local(rs->rs_rgd);
gfs2_glock_dq_uninit(&ip->i_rgd_gh);
@@ -2125,8 +2125,11 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, struct gfs2_alloc_parms *ap)
(loops == 0 && target > rs->rs_rgd->rd_extfail_pt))
goto skip_rgrp;
- if (sdp->sd_args.ar_rgrplvb)
- gfs2_rgrp_bh_get(rs->rs_rgd);
+ if (sdp->sd_args.ar_rgrplvb) {
+ error = gfs2_instantiate(&ip->i_rgd_gh);
+ if (error)
+ goto skip_rgrp;
+ }
/* Get a reservation if we don't already have one */
if (!gfs2_rs_active(rs))
@@ -2762,8 +2765,6 @@ void gfs2_rlist_free(struct gfs2_rgrp_list *rlist)
void rgrp_lock_local(struct gfs2_rgrpd *rgd)
{
- GLOCK_BUG_ON(rgd->rd_gl, !gfs2_glock_is_held_excl(rgd->rd_gl) &&
- !test_bit(SDF_NORECOVERY, &rgd->rd_sbd->sd_flags));
mutex_lock(&rgd->rd_mutex);
}
