GFS2: Fall back to vmalloc if kmalloc fails for dir hash tables

This version has one more correction: the vmalloc calls are replaced
by __vmalloc calls to preserve the GFP_NOFS flag.

When GFS2's directory management code allocates buffers for a
directory hash table, if it can't get the memory it needs, it
currently gives a bad return code. Rather than giving an error,
this patch allows it to use virtual memory rather than kernel
memory for the hash table. This should make it possible for
directories to function properly, even when kernel memory becomes
very fragmented.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/dir.c

@@ -354,22 +354,31 @@ static __be64 *gfs2_dir_get_hash_table(struct gfs2_inode *ip)
 		return ERR_PTR(-EIO);
 	}
 
-	hc = kmalloc(hsize, GFP_NOFS);
-	ret = -ENOMEM;
+	hc = kmalloc(hsize, GFP_NOFS | __GFP_NOWARN);
+	if (hc == NULL)
+		hc = __vmalloc(hsize, GFP_NOFS, PAGE_KERNEL);
+
 	if (hc == NULL)
 		return ERR_PTR(-ENOMEM);
 
 	ret = gfs2_dir_read_data(ip, hc, hsize);
 	if (ret < 0) {
+		if (is_vmalloc_addr(hc))
+			vfree(hc);
+		else
 			kfree(hc);
 		return ERR_PTR(ret);
 	}
 
 	spin_lock(&inode->i_lock);
-	if (ip->i_hash_cache)
-		kfree(hc);
+	if (ip->i_hash_cache) {
+		if (is_vmalloc_addr(hc))
+			vfree(hc);
 		else
+			kfree(hc);
+	} else {
 		ip->i_hash_cache = hc;
+	}
 	spin_unlock(&inode->i_lock);
 
 	return ip->i_hash_cache;
@@ -385,6 +394,9 @@ void gfs2_dir_hash_inval(struct gfs2_inode *ip)
 {
 	__be64 *hc = ip->i_hash_cache;
 	ip->i_hash_cache = NULL;
+	if (is_vmalloc_addr(hc))
+		vfree(hc);
+	else
 		kfree(hc);
 }
 
@@ -1113,7 +1125,10 @@ static int dir_double_exhash(struct gfs2_inode *dip)
 	if (IS_ERR(hc))
 		return PTR_ERR(hc);
 
-	h = hc2 = kmalloc(hsize_bytes * 2, GFP_NOFS);
+	h = hc2 = kmalloc(hsize_bytes * 2, GFP_NOFS | __GFP_NOWARN);
+	if (hc2 == NULL)
+		hc2 = __vmalloc(hsize_bytes * 2, GFP_NOFS, PAGE_KERNEL);
+
 	if (!hc2)
 		return -ENOMEM;
 
@@ -1145,6 +1160,9 @@ static int dir_double_exhash(struct gfs2_inode *dip)
 	gfs2_dinode_out(dip, dibh->b_data);
 	brelse(dibh);
 out_kfree:
+	if (is_vmalloc_addr(hc2))
+		vfree(hc2);
+	else
 		kfree(hc2);
 	return error;
 }
@@ -1846,6 +1864,8 @@ static int leaf_dealloc(struct gfs2_inode *dip, u32 index, u32 len,
 	memset(&rlist, 0, sizeof(struct gfs2_rgrp_list));
 
 	ht = kzalloc(size, GFP_NOFS);
+	if (ht == NULL)
+		ht = vzalloc(size);
 	if (!ht)
 		return -ENOMEM;
 
@@ -1933,6 +1953,9 @@ static int leaf_dealloc(struct gfs2_inode *dip, u32 index, u32 len,
 	gfs2_rlist_free(&rlist);
 	gfs2_quota_unhold(dip);
 out:
+	if (is_vmalloc_addr(ht))
+		vfree(ht);
+	else
 		kfree(ht);
 	return error;
 }