[GFS2] Clean up the glock core

This patch implements a number of cleanups to the core of the
GFS2 glock code. As a result a lot of code is removed. It looks
like a really big change, but actually a large part of this patch
is either removing or moving existing code.

There are some new bits too though, such as the new run_queue()
function which is considerably streamlined. Highlights of this
patch include:

 o Fixes a cluster coherency bug during SH -> EX lock conversions
 o Removes the "glmutex" code in favour of a single bit lock
 o Removes the ->go_xmote_bh() for inodes since it was duplicating
   ->go_lock()
 o We now only use the ->lm_lock() function for both locks and
   unlocks (i.e. unlock is a lock with target mode LM_ST_UNLOCKED)
 o The fast path is considerably shortly, giving performance gains
   especially with lock_nolock
 o The glock_workqueue is now used for all the callbacks from the DLM
   which allows us to simplify the lock_dlm module (see following patch)
 o The way is now open to make further changes such as eliminating the two
   threads (gfs2_glockd and gfs2_scand) in favour of a more efficient
   scheme.

This patch has undergone extensive testing with various test suites
so it should be pretty stable by now.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Bob Peterson <rpeterso@redhat.com>

1 files changed, 11 insertions, 14 deletions

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index f55394e57cb2..2b556dd034bb 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -507,26 +507,23 @@ static int __gfs2_readpage(void *file, struct page *page)
 static int gfs2_readpage(struct file *file, struct page *page)
 {
         struct gfs2_inode *ip = GFS2_I(page->mapping->host);
-        struct gfs2_holder *gh;
+        struct gfs2_holder gh;
         int error;
 
-        gh = gfs2_glock_is_locked_by_me(ip->i_gl);
-        if (!gh) {
-                gh = kmalloc(sizeof(struct gfs2_holder), GFP_NOFS);
-                if (!gh)
-                        return -ENOBUFS;
-                gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME, gh);
+        gfs2_holder_init(ip->i_gl, LM_ST_SHARED, GL_ATIME|LM_FLAG_TRY_1CB, &gh);
+        error = gfs2_glock_nq_atime(&gh);
+        if (unlikely(error)) {
                 unlock_page(page);
-                error = gfs2_glock_nq_atime(gh);
-                if (likely(error != 0))
-                        goto out;
-                return AOP_TRUNCATED_PAGE;
+                goto out;
         }
         error = __gfs2_readpage(file, page);
-        gfs2_glock_dq(gh);
+        gfs2_glock_dq(&gh);
 out:
-        gfs2_holder_uninit(gh);
-        kfree(gh);
+        gfs2_holder_uninit(&gh);
+        if (error == GLR_TRYFAILED) {
+                yield();
+                return AOP_TRUNCATED_PAGE;
+        }
         return error;
 }