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[Cluster-devel] Cluster Project branch, RHEL46, updated. cman-kernel_2_6_9_54-6-g0413a20



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      from  c22322ad43d192cdc2de77c6ceca782f5e35412b (commit)

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- Log -----------------------------------------------------------------
commit 0413a207c89b6b4d440b4f8bc27545ec4ee76528
Author: Benjamin Marzinski <bmarzins redhat com>
Date:   Tue Jan 29 22:21:45 2008 +0000

    Fix for bz #419391.  gfs_glock_dq was traversing the gl_holders list without
    holding the gl_spin spinlock, this was causing a problem when the list item
    it was currently looking at got removed from the list.  The solution is to
    not traverse the list, because it is unncessary. Unfortunately, there is also
    a bug in this section of code, where you can't guarantee that you will not
    cache a glock held with GL_NOCACHE.  Fixing this issue requires significantly
    more work.
    
    4.6.z bz#441747

-----------------------------------------------------------------------

Summary of changes:
 gfs-kernel/src/gfs/glock.c |   15 ++++++---------
 1 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/gfs-kernel/src/gfs/glock.c b/gfs-kernel/src/gfs/glock.c
index 570ee8f..1014ea2 100644
--- a/gfs-kernel/src/gfs/glock.c
+++ b/gfs-kernel/src/gfs/glock.c
@@ -1608,8 +1608,6 @@ gfs_glock_dq(struct gfs_holder *gh)
 	struct gfs_sbd *sdp = gl->gl_sbd;
 	struct gfs_glock_operations *glops = gl->gl_ops;
 	struct list_head *pos;
-	struct gfs_holder *tmp_gh = NULL;
-	int count = 0;
 
 	atomic_inc(&gl->gl_sbd->sd_glock_dq_calls);
 
@@ -1620,14 +1618,13 @@ gfs_glock_dq(struct gfs_holder *gh)
 		set_bit(GLF_SYNC, &gl->gl_flags);
 
 	/* Don't cache glock; request demote to unlock at inter-node scope */
-	if (gh->gh_flags & GL_NOCACHE) {
-		list_for_each(pos, &gl->gl_holders) {
-			tmp_gh = list_entry(pos, struct gfs_holder, gh_list);
-			++count;
-		}
-		if (tmp_gh == gh && count == 1)
+	if (gh->gh_flags & GL_NOCACHE && gl->gl_holders.next == &gh->gh_list &&
+	    gl->gl_holders.prev == &gh->gh_list)
+		/* There's a race here.  If there are two holders, and both
+ 		 * are dq'ed at almost the same time, you can't guarantee that
+ 		 * you will call handle_callback. Fixing this will require
+ 		 * some refactoring */
 		handle_callback(gl, LM_ST_UNLOCKED);
-	}
 
 	lock_on_glock(gl);
 


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