[Cluster-devel] GFS2: Use kmalloc when possible for ->readdir()

[Steven Whitehouse]

If we don't need a huge amount of memory in ->readdir() then
we can use kmalloc rather than vmalloc to allocate it. This
should cut down on the greater overheads associated with
vmalloc for smaller directories.

We may be able to eliminate vmalloc entirely at some stage,
but this is easy to do right away.

Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Nick Piggin <npiggin at suse.de>
Cc: Prarit Bhargava <prarit at redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho at redhat.com>

diff --git a/fs/gfs2/dir.c b/fs/gfs2/dir.c
index 401deaf..80d9dfb 100644
--- a/fs/gfs2/dir.c
+++ b/fs/gfs2/dir.c
@@ -1248,12 +1248,14 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 	struct gfs2_leaf *lf;
 	unsigned entries = 0, entries2 = 0;
 	unsigned leaves = 0;
+	unsigned alloc_size;
 	const struct gfs2_dirent **darr, *dent;
 	struct dirent_gather g;
-	struct buffer_head **larr;
+	struct buffer_head **larr = NULL;
 	int leaf = 0;
 	int error, i;
 	u64 lfn = leaf_no;
+	int do_vfree = 0;
 
 	do {
 		error = get_leaf(ip, lfn, &bh);
@@ -1278,9 +1280,15 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 	 * 99 is the maximum number of entries that can fit in a single
 	 * leaf block.
 	 */
-	larr = vmalloc((leaves + entries + 99) * sizeof(void *));
-	if (!larr)
-		goto out;
+	alloc_size = (leaves + entries + 99) * sizeof(void *);
+	if (alloc_size < KMALLOC_MAX_SIZE)
+		larr = kmalloc(alloc_size, GFP_NOFS);
+	if (!larr) {
+		larr = vmalloc(alloc_size);
+		if (!larr)
+			goto out;
+		do_vfree = 1;
+	}
 	darr = (const struct gfs2_dirent **)(larr + leaves);
 	g.pdent = darr;
 	g.offset = 0;
@@ -1289,7 +1297,7 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 	do {
 		error = get_leaf(ip, lfn, &bh);
 		if (error)
-			goto out_kfree;
+			goto out_free;
 		lf = (struct gfs2_leaf *)bh->b_data;
 		lfn = be64_to_cpu(lf->lf_next);
 		if (lf->lf_entries) {
@@ -1298,7 +1306,7 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 						gfs2_dirent_gather, NULL, &g);
 			error = PTR_ERR(dent);
 			if (IS_ERR(dent))
-				goto out_kfree;
+				goto out_free;
 			if (entries2 != g.offset) {
 				fs_warn(sdp, "Number of entries corrupt in dir "
 						"leaf %llu, entries2 (%u) != "
@@ -1307,7 +1315,7 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 					entries2, g.offset);
 					
 				error = -EIO;
-				goto out_kfree;
+				goto out_free;
 			}
 			error = 0;
 			larr[leaf++] = bh;
@@ -1319,10 +1327,13 @@ static int gfs2_dir_read_leaf(struct inode *inode, u64 *offset, void *opaque,
 	BUG_ON(entries2 != entries);
 	error = do_filldir_main(ip, offset, opaque, filldir, darr,
 				entries, copied);
-out_kfree:
+out_free:
 	for(i = 0; i < leaf; i++)
 		brelse(larr[i]);
-	vfree(larr);
+	if (do_vfree)
+		vfree(larr);
+	else
+		kfree(larr);
 out:
 	return error;
 }