[RFC 3/4] squashfs: use percpu for xz decompression

[Stephen Hemminger <shemminger@vyatta.com>]

[-- Attachment #1: squashfs-xz-percpu.patch --]
[-- Type: text/plain, Size: 2689 bytes --]

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

--- a/fs/squashfs/xz_wrapper.c	2011-04-22 13:55:21.251194626 -0700
+++ b/fs/squashfs/xz_wrapper.c	2011-04-22 13:55:35.779665142 -0700
@@ -47,9 +47,11 @@ static void *squashfs_xz_init(struct squ
 	int len)
 {
 	struct comp_opts *comp_opts = buff;
+	struct squashfs_xz __percpu *percpu;
 	struct squashfs_xz *stream;
 	int dict_size = msblk->block_size;
 	int err, n;
+	int cpu, cpu0;
 
 	if (comp_opts) {
 		/* check compressor options are the expected length */
@@ -71,47 +73,58 @@ static void *squashfs_xz_init(struct squ
 
 	dict_size = max_t(int, dict_size, SQUASHFS_METADATA_SIZE);
 
-	stream = kmalloc(sizeof(*stream), GFP_KERNEL);
-	if (stream == NULL) {
-		err = -ENOMEM;
-		goto failed;
-	}
+	percpu = alloc_percpu(struct squashfs_xz);
+	if (!percpu)
+		goto nomem;
+
+	for_each_possible_cpu(cpu) {
+		stream = per_cpu_ptr(percpu, cpu);
 
-	stream->state = xz_dec_init(XZ_PREALLOC, dict_size);
-	if (stream->state == NULL) {
-		kfree(stream);
-		err = -ENOMEM;
-		goto failed;
+		stream->state = xz_dec_init(XZ_PREALLOC, dict_size);
+		if (stream->state == NULL)
+			goto cleanup_cpu;
 	}
 
-	return stream;
+	return (__force void *) percpu;
 
+cleanup_cpu:
+	for_each_possible_cpu(cpu0) {
+		if (cpu0 == cpu)
+			break;
+
+		stream = per_cpu_ptr(percpu, cpu);
+		xz_dec_end(stream->state);
+	}
+	free_percpu(percpu);
+nomem:
+	err = -ENOMEM;
 failed:
 	ERROR("Failed to initialise xz decompressor\n");
 	return ERR_PTR(err);
 }
 
-
 static void squashfs_xz_free(void *strm)
 {
-	struct squashfs_xz *stream = strm;
+	struct squashfs_xz __percpu *percpu
+		= (struct squashfs_xz __percpu *) strm;
+	int cpu;
 
-	if (stream) {
+	for_each_possible_cpu(cpu) {
+		struct squashfs_xz *stream = per_cpu_ptr(percpu, cpu);
 		xz_dec_end(stream->state);
-		kfree(stream);
 	}
+	free_percpu(percpu);
 }
 
-
 static int squashfs_xz_uncompress(struct squashfs_sb_info *msblk, void **buffer,
 	struct buffer_head **bh, int b, int offset, int length, int srclength,
 	int pages)
 {
 	enum xz_ret xz_err;
 	int avail, total = 0, k = 0, page = 0;
-	struct squashfs_xz *stream = msblk->stream;
-
-	mutex_lock(&msblk->read_data_mutex);
+	struct squashfs_xz __percpu *percpu
+		= (struct squashfs_xz __percpu *)msblk->stream;
+	struct squashfs_xz *stream = get_cpu_ptr(percpu);
 
 	xz_dec_reset(stream->state);
 	stream->buf.in_pos = 0;
@@ -158,11 +171,11 @@ static int squashfs_xz_uncompress(struct
 	}
 
 	total += stream->buf.out_pos;
-	mutex_unlock(&msblk->read_data_mutex);
+	put_cpu_ptr(stream);
 	return total;
 
 release_mutex:
-	mutex_unlock(&msblk->read_data_mutex);
+	put_cpu_ptr(stream);
 
 	for (; k < b; k++)
 		put_bh(bh[k]);