[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>

12 files changed, 39 insertions, 36 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 224114166529..73dfad70de66 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -683,7 +683,7 @@ static int do_strip(struct gfs2_inode *ip, struct buffer_head *dibh,
         if (metadata)
                 revokes = (height) ? sdp->sd_inptrs : sdp->sd_diptrs;
 
-        error = gfs2_rindex_hold(sdp, &ip->i_alloc.al_ri_gh);
+        error = gfs2_rindex_hold(sdp, &ip->i_alloc->al_ri_gh);
         if (error)
                 return error;
 
@@ -785,7 +785,7 @@ out_rg_gunlock:
 out_rlist:
         gfs2_rlist_free(&rlist);
 out:
-        gfs2_glock_dq_uninit(&ip->i_alloc.al_ri_gh);
+        gfs2_glock_dq_uninit(&ip->i_alloc->al_ri_gh);
         return error;
 }
 
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:
diff --git a/fs/gfs2/eattr.c b/fs/gfs2/eattr.c
index 2a7435b5c4dc..bee99704ea10 100644
--- a/fs/gfs2/eattr.c
+++ b/fs/gfs2/eattr.c
@@ -1418,7 +1418,7 @@ out:
 static int ea_dealloc_block(struct gfs2_inode *ip)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_rgrpd *rgd;
         struct buffer_head *dibh;
         int error;
diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
index 745dada4085c..4cdda1a3e12c 100644
--- a/fs/gfs2/incore.h
+++ b/fs/gfs2/incore.h
@@ -264,7 +264,7 @@ struct gfs2_inode {
         struct gfs2_glock *i_gl; /* Move into i_gh? */
         struct gfs2_holder i_iopen_gh;
         struct gfs2_holder i_gh; /* for prepare/commit_write only */
-        struct gfs2_alloc i_alloc;
+        struct gfs2_alloc *i_alloc;
         u64 i_last_rg_alloc;
 
         spinlock_t i_spin;
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 53bca9978fb5..c84764ad82b3 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -711,9 +711,10 @@ static int alloc_dinode(struct gfs2_inode *dip, u64 *no_addr, u64 *generation)
         struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
         int error;
 
-        gfs2_alloc_get(dip);
+        if (gfs2_alloc_get(dip) == NULL)
+                return -ENOMEM;
 
-        dip->i_alloc.al_requested = RES_DINODE;
+        dip->i_alloc->al_requested = RES_DINODE;
         error = gfs2_inplace_reserve(dip);
         if (error)
                 goto out;
@@ -900,7 +901,7 @@ fail_end_trans:
         gfs2_trans_end(sdp);
 
 fail_ipreserv:
-        if (dip->i_alloc.al_rgd)
+        if (dip->i_alloc->al_rgd)
                 gfs2_inplace_release(dip);
 
 fail_quota_locks:
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 653fd5a6203a..88686fcdfb1b 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -31,6 +31,7 @@ static void gfs2_init_inode_once(struct kmem_cache *cachep, void *foo)
         inode_init_once(&ip->i_inode);
         spin_lock_init(&ip->i_spin);
         init_rwsem(&ip->i_rw_mutex);
+        ip->i_alloc = NULL;
 }
 
 static void gfs2_init_glock_once(struct kmem_cache *cachep, void *foo)
diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 37406a379e7a..38dbe99a30ed 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -646,7 +646,6 @@ static int gfs2_write_begin(struct file *file, struct address_space *mapping,
         if (error)
                 goto out_unlock;
 
-        ip->i_alloc.al_requested = 0;
         if (alloc_required) {
                 al = gfs2_alloc_get(ip);
 
@@ -823,7 +822,7 @@ static int gfs2_write_end(struct file *file, struct address_space *mapping,
         struct gfs2_inode *ip = GFS2_I(inode);
         struct gfs2_sbd *sdp = GFS2_SB(inode);
         struct buffer_head *dibh;
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_dinode *di;
         unsigned int from = pos & (PAGE_CACHE_SIZE - 1);
         unsigned int to = from + len;
@@ -861,7 +860,7 @@ static int gfs2_write_end(struct file *file, struct address_space *mapping,
         brelse(dibh);
         gfs2_trans_end(sdp);
 failed:
-        if (al->al_requested) {
+        if (al) {
                 gfs2_inplace_release(ip);
                 gfs2_quota_unlock(ip);
                 gfs2_alloc_put(ip);
diff --git a/fs/gfs2/ops_file.c b/fs/gfs2/ops_file.c
index 597f7ff2bc11..d7f4726ae0ce 100644
--- a/fs/gfs2/ops_file.c
+++ b/fs/gfs2/ops_file.c
@@ -364,9 +364,11 @@ static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct page *page)
         ret = gfs2_write_alloc_required(ip, pos, PAGE_CACHE_SIZE, &alloc_required);
         if (ret || !alloc_required)
                 goto out_unlock;
-
-        ip->i_alloc.al_requested = 0;
+        ret = -ENOMEM;
         al = gfs2_alloc_get(ip);
+        if (al == NULL)
+                goto out_unlock;
+
         ret = gfs2_quota_lock(ip, NO_QUOTA_CHANGE, NO_QUOTA_CHANGE);
         if (ret)
                 goto out_alloc_put;
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);
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 60cc50fe15b4..a08dabd6ce90 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -453,7 +453,7 @@ static void qdsb_put(struct gfs2_quota_data *qd)
 int gfs2_quota_hold(struct gfs2_inode *ip, u32 uid, u32 gid)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_quota_data **qd = al->al_qd;
         int error;
 
@@ -501,7 +501,7 @@ out:
 void gfs2_quota_unhold(struct gfs2_inode *ip)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         unsigned int x;
 
         gfs2_assert_warn(sdp, !test_bit(GIF_QD_LOCKED, &ip->i_flags));
@@ -853,7 +853,7 @@ fail:
 int gfs2_quota_lock(struct gfs2_inode *ip, u32 uid, u32 gid)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         unsigned int x;
         int error = 0;
 
@@ -921,7 +921,7 @@ static int need_sync(struct gfs2_quota_data *qd)
 
 void gfs2_quota_unlock(struct gfs2_inode *ip)
 {
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_quota_data *qda[4];
         unsigned int count = 0;
         unsigned int x;
@@ -969,7 +969,7 @@ static int print_message(struct gfs2_quota_data *qd, char *type)
 int gfs2_quota_check(struct gfs2_inode *ip, u32 uid, u32 gid)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_quota_data *qd;
         s64 value;
         unsigned int x;
@@ -1013,7 +1013,7 @@ int gfs2_quota_check(struct gfs2_inode *ip, u32 uid, u32 gid)
 void gfs2_quota_change(struct gfs2_inode *ip, s64 change,
                        u32 uid, u32 gid)
 {
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_quota_data *qd;
         unsigned int x;
 
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 68c4bf363c46..3552110b2e5f 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -819,11 +819,9 @@ void gfs2_rgrp_repolish_clones(struct gfs2_rgrpd *rgd)
 
 struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip)
 {
-        struct gfs2_alloc *al = &ip->i_alloc;
-
-        /* FIXME: Should assert that the correct locks are held here... */
-        memset(al, 0, sizeof(*al));
-        return al;
+        BUG_ON(ip->i_alloc != NULL);
+        ip->i_alloc = kzalloc(sizeof(struct gfs2_alloc), GFP_KERNEL);
+        return ip->i_alloc;
 }
 
 /**
@@ -1061,7 +1059,7 @@ static struct inode *get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
         struct inode *inode = NULL;
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
         struct gfs2_rgrpd *rgd, *begin = NULL;
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         int flags = LM_FLAG_TRY;
         int skipped = 0;
         int loops = 0;
@@ -1176,7 +1174,7 @@ out:
 int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct inode *inode;
         int error = 0;
         u64 last_unlinked = NO_BLOCK;
@@ -1222,7 +1220,7 @@ try_again:
 void gfs2_inplace_release(struct gfs2_inode *ip)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
 
         if (gfs2_assert_warn(sdp, al->al_alloced <= al->al_requested) == -1)
                 fs_warn(sdp, "al_alloced = %u, al_requested = %u "
@@ -1412,7 +1410,7 @@ static struct gfs2_rgrpd *rgblk_free(struct gfs2_sbd *sdp, u64 bstart,
 u64 gfs2_alloc_data(struct gfs2_inode *ip)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_rgrpd *rgd = al->al_rgd;
         u32 goal, blk;
         u64 block;
@@ -1457,7 +1455,7 @@ u64 gfs2_alloc_data(struct gfs2_inode *ip)
 u64 gfs2_alloc_meta(struct gfs2_inode *ip)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_alloc *al = &ip->i_alloc;
+        struct gfs2_alloc *al = ip->i_alloc;
         struct gfs2_rgrpd *rgd = al->al_rgd;
         u32 goal, blk;
         u64 block;
@@ -1503,7 +1501,7 @@ u64 gfs2_alloc_meta(struct gfs2_inode *ip)
 u64 gfs2_alloc_di(struct gfs2_inode *dip, u64 *generation)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&dip->i_inode);
-        struct gfs2_alloc *al = &dip->i_alloc;
+        struct gfs2_alloc *al = dip->i_alloc;
         struct gfs2_rgrpd *rgd = al->al_rgd;
         u32 blk;
         u64 block;
diff --git a/fs/gfs2/rgrp.h b/fs/gfs2/rgrp.h
index b4c6adfc6f2e..149bb161f4b6 100644
--- a/fs/gfs2/rgrp.h
+++ b/fs/gfs2/rgrp.h
@@ -32,7 +32,9 @@ void gfs2_rgrp_repolish_clones(struct gfs2_rgrpd *rgd);
 struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip);
 static inline void gfs2_alloc_put(struct gfs2_inode *ip)
 {
-        return; /* So we can see where ip->i_alloc is used */
+        BUG_ON(ip->i_alloc == NULL);
+        kfree(ip->i_alloc);
+        ip->i_alloc = NULL;
 }
 
 int gfs2_inplace_reserve_i(struct gfs2_inode *ip,