[Cluster-devel] [GFS2] Don't hold page lock when starting transaction

[Steven Whitehouse <swhiteho@redhat.com>]

For those of you following the bugzilla, this is the long awaited patch-6b. If you don't
know what that means, don't worry its not important, its just the final patch in the 
series.

From 260cee85730c7ae74f1feb9a40ac5fb651589178 Mon Sep 17 00:00:00 2001
From: Steven Whitehouse <swhiteho@redhat.com>
Date: Wed, 17 Oct 2007 14:05:41 +0100
Subject: [PATCH] [GFS2] Don't hold page lock when starting transaction

This is an addendum to the new AOPs work which moves the point
at which we take the page lock so that we don't get it until
the last possible moment. This resolves a conflict between
starting transactions and the page lock.

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

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 48913e5..ae782d2 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -657,18 +657,10 @@ static int gfs2_write_begin(struct file *file, struct address_space *mapping,
 	if (unlikely(error))
 		goto out_uninit;
 
-	error = -ENOMEM;
-	page = __grab_cache_page(mapping, index);
-	*pagep = page;
-	if (!page)
-		goto out_unlock;
-
 	gfs2_write_calc_reserv(ip, len, &data_blocks, &ind_blocks);
-
 	error = gfs2_write_alloc_required(ip, pos, len, &alloc_required);
 	if (error)
-		goto out_putpage;
-
+		goto out_unlock;
 
 	ip->i_alloc.al_requested = 0;
 	if (alloc_required) {
@@ -699,40 +691,47 @@ static int gfs2_write_begin(struct file *file, struct address_space *mapping,
 	if (error)
 		goto out_trans_fail;
 
+	error = -ENOMEM;
+	page = __grab_cache_page(mapping, index);
+	*pagep = page;
+	if (unlikely(!page))
+		goto out_endtrans;
+
 	if (gfs2_is_stuffed(ip)) {
+		error = 0;
 		if (pos + len > sdp->sd_sb.sb_bsize - sizeof(struct gfs2_dinode)) {
 			error = gfs2_unstuff_dinode(ip, page);
 			if (error == 0)
 				goto prepare_write;
-		} else if (!PageUptodate(page))
+		} else if (!PageUptodate(page)) {
 			error = stuffed_readpage(ip, page);
+		}
 		goto out;
 	}
 
 prepare_write:
 	error = block_prepare_write(page, from, to, gfs2_get_block);
-
 out:
-	if (error) {
-		gfs2_trans_end(sdp);
+	if (error == 0)
+		return 0;
+
+	page_cache_release(page);
+	if (pos + len > ip->i_inode.i_size)
+		vmtruncate(&ip->i_inode, ip->i_inode.i_size);
+out_endtrans:
+	gfs2_trans_end(sdp);
 out_trans_fail:
-		if (alloc_required) {
-			gfs2_inplace_release(ip);
+	if (alloc_required) {
+		gfs2_inplace_release(ip);
 out_qunlock:
-			gfs2_quota_unlock(ip);
+		gfs2_quota_unlock(ip);
 out_alloc_put:
-			gfs2_alloc_put(ip);
-		}
-out_putpage:
-		page_cache_release(page);
-		if (pos + len > ip->i_inode.i_size)
-			vmtruncate(&ip->i_inode, ip->i_inode.i_size);
+		gfs2_alloc_put(ip);
+	}
 out_unlock:
-		gfs2_glock_dq_m(1, &ip->i_gh);
+	gfs2_glock_dq(&ip->i_gh);
 out_uninit:
-		gfs2_holder_uninit(&ip->i_gh);
-	}
-
+	gfs2_holder_uninit(&ip->i_gh);
 	return error;
 }
 
-- 
1.5.1.2