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Old 03-18-2009, 11:23 AM
Default GFS2: Fix locking bug in failed shared to exclusive conversion

From: Benjamin Marzinski <bmarzins@redhat.com>

After calling out to the dlm, GFS2 sets the new state of a glock to
gl_target in gdlm_ast(). However, gl_target is not always the lock
state that was requested. If a conversion from shared to exclusive
fails, finish_xmote() will call do_xmote() with LM_ST_UNLOCKED, instead
of gl->gl_target, so that it can reacquire the lock in exlusive the next
time around. In this case, setting the lock to gl_target in gdlm_ast()
will make GFS2 think that it has the glock in exclusive mode, when
really, it doesn't have the glock locked at all. This patch adds a new
field to the gfs2_glock structure, gl_req, to track the mode that was

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 980a086..399d1b9 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -203,6 +203,7 @@ struct gfs2_glock {
unsigned int gl_target;
unsigned int gl_reply;
unsigned int gl_hash;
+ unsigned int gl_req;
unsigned int gl_demote_state; /* state requested by remote node */
unsigned long gl_demote_time; /* time of first demote request */
struct list_head gl_holders;
diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
index a0bb7d2..46df988 100644
--- a/fs/gfs2/lock_dlm.c
+++ b/fs/gfs2/lock_dlm.c
@@ -46,11 +46,11 @@ static void gdlm_ast(void *arg)

- ret = gl->gl_target;
+ ret = gl->gl_req;
if (gl->gl_lksb.sb_flags & DLM_SBF_ALTMODE) {
- if (gl->gl_target == LM_ST_SHARED)
+ if (gl->gl_req == LM_ST_SHARED)
- else if (gl->gl_target == LM_ST_DEFERRED)
+ else if (gl->gl_req == LM_ST_DEFERRED)
@@ -147,6 +147,7 @@ static unsigned int gdlm_lock(struct gfs2_glock *gl,
int req;
u32 lkf;

+ gl->gl_req = req_state;
req = make_mode(req_state);
lkf = make_flags(gl->gl_lksb.sb_lkid, flags, req);


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