[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, 4 insertions, 4 deletions

diff --git a/fs/gfs2/ops_inode.c b/fs/gfs2/ops_inode.c
index 8386ab323e33..9f71372c1757 100644
--- a/fs/gfs2/ops_inode.c
+++ b/fs/gfs2/ops_inode.c
@@ -61,7 +61,7 @@ static int gfs2_create(struct inode *dir, struct dentry *dentry,
                 inode = gfs2_createi(ghs, &dentry->d_name, S_IFREG | mode, 0);
                 if (!IS_ERR(inode)) {
                         gfs2_trans_end(sdp);
-                        if (dip->i_alloc.al_rgd)
+                        if (dip->i_alloc->al_rgd)
                                 gfs2_inplace_release(dip);
                         gfs2_quota_unlock(dip);
                         gfs2_alloc_put(dip);
@@ -376,7 +376,7 @@ static int gfs2_symlink(struct inode *dir, struct dentry *dentry,
         }
 
         gfs2_trans_end(sdp);
-        if (dip->i_alloc.al_rgd)
+        if (dip->i_alloc->al_rgd)
                 gfs2_inplace_release(dip);
         gfs2_quota_unlock(dip);
         gfs2_alloc_put(dip);
@@ -452,7 +452,7 @@ static int gfs2_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         gfs2_assert_withdraw(sdp, !error); /* dip already pinned */
 
         gfs2_trans_end(sdp);
-        if (dip->i_alloc.al_rgd)
+        if (dip->i_alloc->al_rgd)
                 gfs2_inplace_release(dip);
         gfs2_quota_unlock(dip);
         gfs2_alloc_put(dip);
@@ -558,7 +558,7 @@ static int gfs2_mknod(struct inode *dir, struct dentry *dentry, int mode,
         }
 
         gfs2_trans_end(sdp);
-        if (dip->i_alloc.al_rgd)
+        if (dip->i_alloc->al_rgd)
                 gfs2_inplace_release(dip);
         gfs2_quota_unlock(dip);
         gfs2_alloc_put(dip);