[GFS2] Reduce inode size by moving i_alloc out of line

It is possible to reduce the size of GFS2 inodes by taking the i_alloc
structure out of the gfs2_inode. This patch allocates the i_alloc
structure whenever its needed, and frees it afterward. This decreases
the amount of low memory we use at the expense of requiring a memory
allocation for each page or partial page that we write. A quick test
with postmark shows that the overhead is not measurable and I also note
that OCFS2 use the same approach.

In the future I'd like to solve the problem by shrinking down the size
of the members of the i_alloc structure, but for now, this reduces the
immediate problem of using too much low-memory on x86 and doesn't add
too much overhead.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 9949bb746a52..57e2ed932adc 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -1876,7 +1876,7 @@ static int leaf_dealloc(struct gfs2_inode *dip, u32 index, u32 len,
         if (error)
                 goto out;
 
-        error = gfs2_rindex_hold(sdp, &dip->i_alloc.al_ri_gh);
+        error = gfs2_rindex_hold(sdp, &dip->i_alloc->al_ri_gh);
         if (error)
                 goto out_qs;
 
@@ -1949,7 +1949,7 @@ out_rg_gunlock:
         gfs2_glock_dq_m(rlist.rl_rgrps, rlist.rl_ghs);
 out_rlist:
         gfs2_rlist_free(&rlist);
-        gfs2_glock_dq_uninit(&dip->i_alloc.al_ri_gh);
+        gfs2_glock_dq_uninit(&dip->i_alloc->al_ri_gh);
 out_qs:
         gfs2_quota_unhold(dip);
 out: