GFS2: Make resource groups "append only" during life of fs

Since we have ruled out supporting online filesystem shrink,
it is possible to make the resource group list append only
during the life of a super block. This gives several benefits:

Firstly, we only need to read new rindex elements as they are added
rather than needing to reread the whole rindex file each time one
element is added.

Secondly, the rindex glock can be held for much shorter periods of
time, and is completely removed from the fast path for allocations.
The lock is taken in shared mode only when updating the resource
groups when the first allocation occurs, and after a grow has
taken place.

Thirdly, this results in a reduction in code size, and everything
gets a lot simpler to understand in this area.

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

1 files changed, 72 insertions, 96 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 00f6e3d62c2..88d5b75067a 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -332,14 +332,10 @@ struct gfs2_rgrpd *gfs2_blk2rgrpd(struct gfs2_sbd *sdp, u64 blk)
 	struct rb_node **newn, *parent = NULL;
 
 	spin_lock(&sdp->sd_rindex_spin);
-
 	newn = &sdp->sd_rindex_tree.rb_node;
-
-	/* Figure out where to put new node */
 	while (*newn) {
 		struct gfs2_rgrpd *cur = rb_entry(*newn, struct gfs2_rgrpd,
 						  rd_node);
-
 		parent = *newn;
 		if (blk < cur->rd_addr)
 			newn = &((*newn)->rb_left);
@@ -350,7 +346,6 @@ struct gfs2_rgrpd *gfs2_blk2rgrpd(struct gfs2_sbd *sdp, u64 blk)
 			return cur;
 		}
 	}
-
 	spin_unlock(&sdp->sd_rindex_spin);
 
 	return NULL;
@@ -368,8 +363,10 @@ struct gfs2_rgrpd *gfs2_rgrpd_get_first(struct gfs2_sbd *sdp)
 	const struct rb_node *n;
 	struct gfs2_rgrpd *rgd;
 
+	spin_lock(&sdp->sd_rindex_spin);
 	n = rb_first(&sdp->sd_rindex_tree);
 	rgd = rb_entry(n, struct gfs2_rgrpd, rd_node);
+	spin_unlock(&sdp->sd_rindex_spin);
 
 	return rgd;
 }
@@ -400,7 +397,18 @@ struct gfs2_rgrpd *gfs2_rgrpd_get_next(struct gfs2_rgrpd *rgd)
 	return rgd;
 }
 
-static void clear_rgrpdi(struct gfs2_sbd *sdp)
+void gfs2_free_clones(struct gfs2_rgrpd *rgd)
+{
+	int x;
+
+	for (x = 0; x < rgd->rd_length; x++) {
+		struct gfs2_bitmap *bi = rgd->rd_bits + x;
+		kfree(bi->bi_clone);
+		bi->bi_clone = NULL;
+	}
+}
+
+void gfs2_clear_rgrpd(struct gfs2_sbd *sdp)
 {
 	struct rb_node *n;
 	struct gfs2_rgrpd *rgd;
@@ -413,23 +421,19 @@ static void clear_rgrpdi(struct gfs2_sbd *sdp)
 		rb_erase(n, &sdp->sd_rindex_tree);
 
 		if (gl) {
+			spin_lock(&gl->gl_spin);
 			gl->gl_object = NULL;
+			spin_unlock(&gl->gl_spin);
 			gfs2_glock_add_to_lru(gl);
 			gfs2_glock_put(gl);
 		}
 
+		gfs2_free_clones(rgd);
 		kfree(rgd->rd_bits);
 		kmem_cache_free(gfs2_rgrpd_cachep, rgd);
 	}
 }
 
-void gfs2_clear_rgrpd(struct gfs2_sbd *sdp)
-{
-	mutex_lock(&sdp->sd_rindex_mutex);
-	clear_rgrpdi(sdp);
-	mutex_unlock(&sdp->sd_rindex_mutex);
-}
-
 static void gfs2_rindex_print(const struct gfs2_rgrpd *rgd)
 {
 	printk(KERN_INFO "  ri_addr = %llu\n", (unsigned long long)rgd->rd_addr);
@@ -546,17 +550,6 @@ u64 gfs2_ri_total(struct gfs2_sbd *sdp)
 	return total_data;
 }
 
-static void gfs2_rindex_in(struct gfs2_rgrpd *rgd, const void *buf)
-{
-	const struct gfs2_rindex *str = buf;
-
-	rgd->rd_addr = be64_to_cpu(str->ri_addr);
-	rgd->rd_length = be32_to_cpu(str->ri_length);
-	rgd->rd_data0 = be64_to_cpu(str->ri_data0);
-	rgd->rd_data = be32_to_cpu(str->ri_data);
-	rgd->rd_bitbytes = be32_to_cpu(str->ri_bitbytes);
-}
-
 static void rgd_insert(struct gfs2_rgrpd *rgd)
 {
 	struct gfs2_sbd *sdp = rgd->rd_sbd;
@@ -584,7 +577,7 @@ static void rgd_insert(struct gfs2_rgrpd *rgd)
  * read_rindex_entry - Pull in a new resource index entry from the disk
  * @gl: The glock covering the rindex inode
  *
- * Returns: 0 on success, error code otherwise
+ * Returns: 0 on success, > 0 on EOF, error code otherwise
  */
 
 static int read_rindex_entry(struct gfs2_inode *ip,
@@ -592,19 +585,18 @@ static int read_rindex_entry(struct gfs2_inode *ip,
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	loff_t pos = sdp->sd_rgrps * sizeof(struct gfs2_rindex);
-	char buf[sizeof(struct gfs2_rindex)];
+	struct gfs2_rindex buf;
 	int error;
 	struct gfs2_rgrpd *rgd;
 
-	error = gfs2_internal_read(ip, ra_state, buf, &pos,
+	if (pos >= i_size_read(&ip->i_inode))
+		return 1;
+
+	error = gfs2_internal_read(ip, ra_state, (char *)&buf, &pos,
 				   sizeof(struct gfs2_rindex));
-	if (!error)
-		return 0;
-	if (error != sizeof(struct gfs2_rindex)) {
-		if (error > 0)
-			error = -EIO;
-		return error;
-	}
+
+	if (error != sizeof(struct gfs2_rindex))
+		return (error == 0) ? 1 : error;
 
 	rgd = kmem_cache_zalloc(gfs2_rgrpd_cachep, GFP_NOFS);
 	error = -ENOMEM;
@@ -612,23 +604,34 @@ static int read_rindex_entry(struct gfs2_inode *ip,
 		return error;
 
 	rgd->rd_sbd = sdp;
-
-	gfs2_rindex_in(rgd, buf);
-	rgd_insert(rgd);
+	rgd->rd_addr = be64_to_cpu(buf.ri_addr);
+	rgd->rd_length = be32_to_cpu(buf.ri_length);
+	rgd->rd_data0 = be64_to_cpu(buf.ri_data0);
+	rgd->rd_data = be32_to_cpu(buf.ri_data);
+	rgd->rd_bitbytes = be32_to_cpu(buf.ri_bitbytes);
 
 	error = compute_bitstructs(rgd);
 	if (error)
-		return error;
+		goto fail;
 
 	error = gfs2_glock_get(sdp, rgd->rd_addr,
 			       &gfs2_rgrp_glops, CREATE, &rgd->rd_gl);
 	if (error)
-		return error;
+		goto fail;
 
 	rgd->rd_gl->gl_object = rgd;
 	rgd->rd_flags &= ~GFS2_RDF_UPTODATE;
 	if (rgd->rd_data > sdp->sd_max_rg_data)
 		sdp->sd_max_rg_data = rgd->rd_data;
+	spin_lock(&sdp->sd_rindex_spin);
+	rgd_insert(rgd);
+	sdp->sd_rgrps++;
+	spin_unlock(&sdp->sd_rindex_spin);
+	return error;
+
+fail:
+	kfree(rgd->rd_bits);
+	kmem_cache_free(gfs2_rgrpd_cachep, rgd);
 	return error;
 }
 
@@ -639,34 +642,28 @@ static int read_rindex_entry(struct gfs2_inode *ip,
  * Returns: 0 on successful update, error code otherwise
  */
 
-int gfs2_ri_update(struct gfs2_inode *ip)
+static int gfs2_ri_update(struct gfs2_inode *ip)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
 	struct inode *inode = &ip->i_inode;
 	struct file_ra_state ra_state;
-	u64 rgrp_count = i_size_read(inode);
 	int error;
 
-	do_div(rgrp_count, sizeof(struct gfs2_rindex));
-	clear_rgrpdi(sdp);
-
 	file_ra_state_init(&ra_state, inode->i_mapping);
-	for (sdp->sd_rgrps = 0; sdp->sd_rgrps < rgrp_count; sdp->sd_rgrps++) {
+	do {
 		error = read_rindex_entry(ip, &ra_state);
-		if (error) {
-			clear_rgrpdi(sdp);
-			return error;
-		}
-	}
+	} while (error == 0);
+
+	if (error < 0)
+		return error;
 
 	sdp->sd_rindex_uptodate = 1;
 	return 0;
 }
 
 /**
- * gfs2_rindex_hold - Grab a lock on the rindex
+ * gfs2_rindex_update - Update the rindex if required
  * @sdp: The GFS2 superblock
- * @ri_gh: the glock holder
  *
  * We grab a lock on the rindex inode to make sure that it doesn't
  * change whilst we are performing an operation. We keep this lock
@@ -678,30 +675,29 @@ int gfs2_ri_update(struct gfs2_inode *ip)
  * special file, which might have been updated if someone expanded the
  * filesystem (via gfs2_grow utility), which adds new resource groups.
  *
- * Returns: 0 on success, error code otherwise
+ * Returns: 0 on succeess, error code otherwise
  */
 
-int gfs2_rindex_hold(struct gfs2_sbd *sdp, struct gfs2_holder *ri_gh)
+int gfs2_rindex_update(struct gfs2_sbd *sdp)
 {
 	struct gfs2_inode *ip = GFS2_I(sdp->sd_rindex);
 	struct gfs2_glock *gl = ip->i_gl;
-	int error;
-
-	error = gfs2_glock_nq_init(gl, LM_ST_SHARED, 0, ri_gh);
-	if (error)
-		return error;
+	struct gfs2_holder ri_gh;
+	int error = 0;
 
 	/* Read new copy from disk if we don't have the latest */
 	if (!sdp->sd_rindex_uptodate) {
 		mutex_lock(&sdp->sd_rindex_mutex);
-		if (!sdp->sd_rindex_uptodate) {
+		error = gfs2_glock_nq_init(gl, LM_ST_SHARED, 0, &ri_gh);
+		if (error)
+			return error;
+		if (!sdp->sd_rindex_uptodate)
 			error = gfs2_ri_update(ip);
-			if (error)
-				gfs2_glock_dq_uninit(ri_gh);
-		}
+		gfs2_glock_dq_uninit(&ri_gh);
 		mutex_unlock(&sdp->sd_rindex_mutex);
 	}
 
+
 	return error;
 }
 
@@ -873,8 +869,13 @@ fail:
 
 struct gfs2_alloc *gfs2_alloc_get(struct gfs2_inode *ip)
 {
+	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+	int error;
 	BUG_ON(ip->i_alloc != NULL);
 	ip->i_alloc = kzalloc(sizeof(struct gfs2_alloc), GFP_NOFS);
+	error = gfs2_rindex_update(sdp);
+	if (error)
+		fs_warn(sdp, "rindex update returns %d\n", error);
 	return ip->i_alloc;
 }
 
@@ -1029,7 +1030,7 @@ static int get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
  * Returns: errno
  */
 
-int gfs2_inplace_reserve_i(struct gfs2_inode *ip, int hold_rindex,
+int gfs2_inplace_reserve_i(struct gfs2_inode *ip,
 			   char *file, unsigned int line)
 {
 	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
@@ -1041,18 +1042,6 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, int hold_rindex,
 	if (gfs2_assert_warn(sdp, al->al_requested))
 		return -EINVAL;
 
-	if (hold_rindex) {
-		/* We need to hold the rindex unless the inode we're using is
-		   the rindex itself, in which case it's already held. */
-		if (ip != GFS2_I(sdp->sd_rindex))
-			error = gfs2_rindex_hold(sdp, &al->al_ri_gh);
-		else if (!sdp->sd_rgrps) /* We may not have the rindex read
-					    in, so: */
-			error = gfs2_ri_update(ip);
-		if (error)
-			return error;
-	}
-
 try_again:
 	do {
 		error = get_local_rgrp(ip, &last_unlinked);
@@ -1069,11 +1058,8 @@ try_again:
 		}
 	} while (error && tries++ < 3);
 
-	if (error) {
-		if (hold_rindex && ip != GFS2_I(sdp->sd_rindex))
-			gfs2_glock_dq_uninit(&al->al_ri_gh);
+	if (error)
 		return error;
-	}
 
 	/* no error, so we have the rgrp set in the inode's allocation. */
 	al->al_file = file;
@@ -1103,8 +1089,6 @@ void gfs2_inplace_release(struct gfs2_inode *ip)
 	al->al_rgd = NULL;
 	if (al->al_rgd_gh.gh_gl)
 		gfs2_glock_dq_uninit(&al->al_rgd_gh);
-	if (ip != GFS2_I(sdp->sd_rindex) && al->al_ri_gh.gh_gl)
-		gfs2_glock_dq_uninit(&al->al_ri_gh);
 }
 
 /**
@@ -1558,34 +1542,26 @@ void gfs2_free_di(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip)
 int gfs2_check_blk_type(struct gfs2_sbd *sdp, u64 no_addr, unsigned int type)
 {
 	struct gfs2_rgrpd *rgd;
-	struct gfs2_holder ri_gh, rgd_gh;
-	struct gfs2_inode *ip = GFS2_I(sdp->sd_rindex);
-	int ri_locked = 0;
+	struct gfs2_holder rgd_gh;
 	int error;
 
-	if (!gfs2_glock_is_locked_by_me(ip->i_gl)) {
-		error = gfs2_rindex_hold(sdp, &ri_gh);
-		if (error)
-			goto fail;
-		ri_locked = 1;
-	}
+	error = gfs2_rindex_update(sdp);
+	if (error)
+		return error;
 
 	error = -EINVAL;
 	rgd = gfs2_blk2rgrpd(sdp, no_addr);
 	if (!rgd)
-		goto fail_rindex;
+		goto fail;
 
 	error = gfs2_glock_nq_init(rgd->rd_gl, LM_ST_SHARED, 0, &rgd_gh);
 	if (error)
-		goto fail_rindex;
+		goto fail;
 
 	if (gfs2_get_block_type(rgd, no_addr) != type)
 		error = -ESTALE;
 
 	gfs2_glock_dq_uninit(&rgd_gh);
-fail_rindex:
-	if (ri_locked)
-		gfs2_glock_dq_uninit(&ri_gh);
 fail:
 	return error;
 }