staging: erofs: add a generic z_erofs VLE decompressor

Currently, this patch only simply implements LZ4
decompressor due to its development priority.

In the future, erofs will support more compression
algorithm and format other than LZ4, thus a generic
decompressor interface will be needed.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/Kconfig

@@ -87,3 +87,17 @@ config EROFS_FS_ZIP
 
 	  If you don't want to use compression feature, say N.
 
+config EROFS_FS_CLUSTER_PAGE_LIMIT
+	int "EROFS Cluster Pages Hard Limit"
+	depends on EROFS_FS_ZIP
+	range 1 256
+	default "1"
+	help
+	  Indicates VLE compressed pages hard limit of a
+	  compressed cluster.
+
+	  For example, if files of a image are compressed
+	  into 8k-unit, the hard limit should not be less
+	  than 2. Otherwise, the image cannot be mounted
+	  correctly on this kernel.
+

drivers/staging/erofs/Makefile

@@ -9,5 +9,5 @@ obj-$(CONFIG_EROFS_FS) += erofs.o
 ccflags-y += -I$(src)/include
 erofs-objs := super.o inode.o data.o namei.o dir.o utils.o
 erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
-erofs-$(CONFIG_EROFS_FS_ZIP) += unzip_vle.o unzip_lz4.o
+erofs-$(CONFIG_EROFS_FS_ZIP) += unzip_vle.o unzip_lz4.o unzip_vle_lz4.o
 

drivers/staging/erofs/internal.h

@@ -161,6 +161,11 @@ static inline void *erofs_kmalloc(struct erofs_sb_info *sbi,
 
 #define ROOT_NID(sb)		((sb)->root_nid)
 
+#ifdef CONFIG_EROFS_FS_ZIP
+/* hard limit of pages per compressed cluster */
+#define Z_EROFS_CLUSTER_MAX_PAGES       (CONFIG_EROFS_FS_CLUSTER_PAGE_LIMIT)
+#endif
+
 typedef u64 erofs_off_t;
 
 /* data type for filesystem-wide blocks number */

drivers/staging/erofs/unzip_vle.h

@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * linux/drivers/staging/erofs/unzip_vle.h
+ *
+ * Copyright (C) 2018 HUAWEI, Inc.
+ *             http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@huawei.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+#ifndef __EROFS_FS_UNZIP_VLE_H
+#define __EROFS_FS_UNZIP_VLE_H
+
+#include "internal.h"
+
+#define Z_EROFS_VLE_INLINE_PAGEVECS     3
+
+/* unzip_vle_lz4.c */
+extern int z_erofs_vle_plain_copy(struct page **compressed_pages,
+	unsigned clusterpages, struct page **pages,
+	unsigned nr_pages, unsigned short pageofs);
+
+extern int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages,
+	unsigned clusterpages, struct page **pages,
+	unsigned outlen, unsigned short pageofs,
+	void (*endio)(struct page *));
+
+extern int z_erofs_vle_unzip_vmap(struct page **compressed_pages,
+	unsigned clusterpages, void *vaddr, unsigned llen,
+	unsigned short pageofs, bool overlapped);
+
+#endif
+

drivers/staging/erofs/unzip_vle_lz4.c

@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/drivers/staging/erofs/unzip_vle_lz4.c
+ *
+ * Copyright (C) 2018 HUAWEI, Inc.
+ *             http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@huawei.com>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+#include "unzip_vle.h"
+
+#if Z_EROFS_CLUSTER_MAX_PAGES > Z_EROFS_VLE_INLINE_PAGEVECS
+#define EROFS_PERCPU_NR_PAGES   Z_EROFS_CLUSTER_MAX_PAGES
+#else
+#define EROFS_PERCPU_NR_PAGES   Z_EROFS_VLE_INLINE_PAGEVECS
+#endif
+
+static struct {
+	char data[PAGE_SIZE * EROFS_PERCPU_NR_PAGES];
+} erofs_pcpubuf[NR_CPUS];
+
+int z_erofs_vle_plain_copy(struct page **compressed_pages,
+			   unsigned clusterpages,
+			   struct page **pages,
+			   unsigned nr_pages,
+			   unsigned short pageofs)
+{
+	unsigned i, j;
+	void *src = NULL;
+	const unsigned righthalf = PAGE_SIZE - pageofs;
+	char *percpu_data;
+	bool mirrored[Z_EROFS_CLUSTER_MAX_PAGES] = { 0 };
+
+	preempt_disable();
+	percpu_data = erofs_pcpubuf[smp_processor_id()].data;
+
+	j = 0;
+	for (i = 0; i < nr_pages; j = i++) {
+		struct page *page = pages[i];
+		void *dst;
+
+		if (page == NULL) {
+			if (src != NULL) {
+				if (!mirrored[j])
+					kunmap_atomic(src);
+				src = NULL;
+			}
+			continue;
+		}
+
+		dst = kmap_atomic(page);
+
+		for (; j < clusterpages; ++j) {
+			if (compressed_pages[j] != page)
+				continue;
+
+			BUG_ON(mirrored[j]);
+			memcpy(percpu_data + j * PAGE_SIZE, dst, PAGE_SIZE);
+			mirrored[j] = true;
+			break;
+		}
+
+		if (i) {
+			if (src == NULL)
+				src = mirrored[i-1] ?
+					percpu_data + (i-1) * PAGE_SIZE :
+					kmap_atomic(compressed_pages[i-1]);
+
+			memcpy(dst, src + righthalf, pageofs);
+
+			if (!mirrored[i-1])
+				kunmap_atomic(src);
+
+			if (unlikely(i >= clusterpages)) {
+				kunmap_atomic(dst);
+				break;
+			}
+		}
+
+		if (!righthalf)
+			src = NULL;
+		else {
+			src = mirrored[i] ? percpu_data + i * PAGE_SIZE :
+				kmap_atomic(compressed_pages[i]);
+
+			memcpy(dst + pageofs, src, righthalf);
+		}
+
+		kunmap_atomic(dst);
+	}
+
+	if (src != NULL && !mirrored[j])
+		kunmap_atomic(src);
+
+	preempt_enable();
+	return 0;
+}
+
+extern int z_erofs_unzip_lz4(void *in, void *out, size_t inlen, size_t outlen);
+
+int z_erofs_vle_unzip_fast_percpu(struct page **compressed_pages,
+				  unsigned clusterpages,
+				  struct page **pages,
+				  unsigned outlen,
+				  unsigned short pageofs,
+				  void (*endio)(struct page *))
+{
+	void *vin, *vout;
+	unsigned nr_pages, i, j;
+	int ret;
+
+	if (outlen + pageofs > EROFS_PERCPU_NR_PAGES * PAGE_SIZE)
+		return -ENOTSUPP;
+
+	nr_pages = DIV_ROUND_UP(outlen + pageofs, PAGE_SIZE);
+
+	if (clusterpages == 1)
+		vin = kmap_atomic(compressed_pages[0]);
+	else
+		vin = erofs_vmap(compressed_pages, clusterpages);
+
+	preempt_disable();
+	vout = erofs_pcpubuf[smp_processor_id()].data;
+
+	ret = z_erofs_unzip_lz4(vin, vout + pageofs,
+		clusterpages * PAGE_SIZE, outlen);
+
+	if (ret >= 0) {
+		outlen = ret;
+		ret = 0;
+	}
+
+	for (i = 0; i < nr_pages; ++i) {
+		j = min((unsigned)PAGE_SIZE - pageofs, outlen);
+
+		if (pages[i] != NULL) {
+			if (ret < 0)
+				SetPageError(pages[i]);
+			else if (clusterpages == 1 && pages[i] == compressed_pages[0])
+				memcpy(vin + pageofs, vout + pageofs, j);
+			else {
+				void *dst = kmap_atomic(pages[i]);
+
+				memcpy(dst + pageofs, vout + pageofs, j);
+				kunmap_atomic(dst);
+			}
+			endio(pages[i]);
+		}
+		vout += PAGE_SIZE;
+		outlen -= j;
+		pageofs = 0;
+	}
+	preempt_enable();
+
+	if (clusterpages == 1)
+		kunmap_atomic(vin);
+	else
+		erofs_vunmap(vin, clusterpages);
+
+	return ret;
+}
+
+int z_erofs_vle_unzip_vmap(struct page **compressed_pages,
+			   unsigned clusterpages,
+			   void *vout,
+			   unsigned llen,
+			   unsigned short pageofs,
+			   bool overlapped)
+{
+	void *vin;
+	unsigned i;
+	int ret;
+
+	if (overlapped) {
+		preempt_disable();
+		vin = erofs_pcpubuf[smp_processor_id()].data;
+
+		for (i = 0; i < clusterpages; ++i) {
+			void *t = kmap_atomic(compressed_pages[i]);
+
+			memcpy(vin + PAGE_SIZE *i, t, PAGE_SIZE);
+			kunmap_atomic(t);
+		}
+	} else if (clusterpages == 1)
+		vin = kmap_atomic(compressed_pages[0]);
+	else {
+		vin = erofs_vmap(compressed_pages, clusterpages);
+	}
+
+	ret = z_erofs_unzip_lz4(vin, vout + pageofs,
+		clusterpages * PAGE_SIZE, llen);
+	if (ret > 0)
+		ret = 0;
+
+	if (!overlapped) {
+		if (clusterpages == 1)
+			kunmap_atomic(vin);
+		else {
+			erofs_vunmap(vin, clusterpages);
+		}
+	} else
+		preempt_enable();
+
+	return ret;
+}
+