Merge tag 'erofs-for-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs

Pull erofs updates from Gao Xiang:
 "There are some new features available for this cycle. Firstly, EROFS
  LZMA algorithm support, specifically called MicroLZMA, is available as
  an option for embedded devices, LiveCDs and/or as the secondary
  auxiliary compression algorithm besides the primary algorithm in one
  file.

  In order to better support the LZMA fixed-sized output compression,
  especially for 4KiB pcluster size (which has lowest memory pressure
  thus useful for memory-sensitive scenarios), Lasse introduced a new
  LZMA header/container format called MicroLZMA to minimize the original
  LZMA1 header (for example, we don't need to waste 4-byte dictionary
  size and another 8-byte uncompressed size, which can be calculated by
  fs directly, for each pcluster) and enable EROFS fixed-sized output
  compression.

  Note that MicroLZMA can also be later used by other things in addition
  to EROFS too where wasting minimal amount of space for headers is
  important and it can be only compiled by enabling XZ_DEC_MICROLZMA.
  MicroLZMA has been supported by the latest upstream XZ embedded [1] &
  XZ utils [2], apply the latest related XZ embedded upstream patches by
  the XZ author Lasse here.

  Secondly, multiple device is also supported in this cycle, which is
  designed for multi-layer container images. By working together with
  inter-layer data deduplication and compression, we can achieve the
  next high-performance container image solution. Our team will announce
  the new Nydus container image service [3] implementation with new RAFS
  v6 (EROFS-compatible) format in Open Source Summit 2021 China [4]
  soon.

  Besides, the secondary compression head support and readmore
  decompression strategy are also included in this cycle. There are also
  some minor bugfixes and cleanups, as always.

  Summary:

   - support multiple devices for multi-layer container images;

   - support the secondary compression head;

   - support readmore decompression strategy;

   - support new LZMA algorithm (specifically called MicroLZMA);

   - some bugfixes & cleanups"

* tag 'erofs-for-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs:
  erofs: don't trigger WARN() when decompression fails
  erofs: get rid of ->lru usage
  erofs: lzma compression support
  erofs: rename some generic methods in decompressor
  lib/xz, lib/decompress_unxz.c: Fix spelling in comments
  lib/xz: Add MicroLZMA decoder
  lib/xz: Move s->lzma.len = 0 initialization to lzma_reset()
  lib/xz: Validate the value before assigning it to an enum variable
  lib/xz: Avoid overlapping memcpy() with invalid input with in-place decompression
  erofs: introduce readmore decompression strategy
  erofs: introduce the secondary compression head
  erofs: get compression algorithms directly on mapping
  erofs: add multiple device support
  erofs: decouple basic mount options from fs_context
  erofs: remove the fast path of per-CPU buffer decompression

Documentation/filesystems/erofs.rst

@@ -19,9 +19,10 @@ It is designed as a better filesystem solution for the following scenarios:
    immutable and bit-for-bit identical to the official golden image for
    their releases due to security and other considerations and
 
- - hope to save some extra storage space with guaranteed end-to-end performance
-   by using reduced metadata and transparent file compression, especially
-   for those embedded devices with limited memory (ex, smartphone);
+ - hope to minimize extra storage space with guaranteed end-to-end performance
+   by using compact layout, transparent file compression and direct access,
+   especially for those embedded devices with limited memory and high-density
+   hosts with numerous containers;
 
 Here is the main features of EROFS:
 
@@ -51,7 +52,9 @@ Here is the main features of EROFS:
  - Support POSIX.1e ACLs by using xattrs;
 
  - Support transparent data compression as an option:
-   LZ4 algorithm with the fixed-sized output compression for high performance.
+   LZ4 algorithm with the fixed-sized output compression for high performance;
+
+ - Multiple device support for multi-layer container images.
 
 The following git tree provides the file system user-space tools under
 development (ex, formatting tool mkfs.erofs):
@@ -87,6 +90,7 @@ cache_strategy=%s      Select a strategy for cached decompression from now on:
 dax={always,never}     Use direct access (no page cache).  See
                        Documentation/filesystems/dax.rst.
 dax                    A legacy option which is an alias for ``dax=always``.
+device=%s              Specify a path to an extra device to be used together.
 ===================    =========================================================
 
 On-disk details

fs/erofs/Kconfig

@@ -6,16 +6,22 @@ config EROFS_FS
 	select FS_IOMAP
 	select LIBCRC32C
 	help
-	  EROFS (Enhanced Read-Only File System) is a lightweight
-	  read-only file system with modern designs (eg. page-sized
-	  blocks, inline xattrs/data, etc.) for scenarios which need
-	  high-performance read-only requirements, e.g. Android OS
-	  for mobile phones and LIVECDs.
+	  EROFS (Enhanced Read-Only File System) is a lightweight read-only
+	  file system with modern designs (e.g. no buffer heads, inline
+	  xattrs/data, chunk-based deduplication, multiple devices, etc.) for
+	  scenarios which need high-performance read-only solutions, e.g.
+	  smartphones with Android OS, LiveCDs and high-density hosts with
+	  numerous containers;
 
-	  It also provides fixed-sized output compression support,
-	  which improves storage density, keeps relatively higher
-	  compression ratios, which is more useful to achieve high
-	  performance for embedded devices with limited memory.
+	  It also provides fixed-sized output compression support in order to
+	  improve storage density as well as keep relatively higher compression
+	  ratios and implements in-place decompression to reuse the file page
+	  for compressed data temporarily with proper strategies, which is
+	  quite useful to ensure guaranteed end-to-end runtime decompression
+	  performance under extremely memory pressure without extra cost.
+
+	  See the documentation at <file:Documentation/filesystems/erofs.rst>
+	  for more details.
 
 	  If unsure, say N.
 
@@ -76,3 +82,19 @@ config EROFS_FS_ZIP
 	  Enable fixed-sized output compression for EROFS.
 
 	  If you don't want to enable compression feature, say N.
+
+config EROFS_FS_ZIP_LZMA
+	bool "EROFS LZMA compressed data support"
+	depends on EROFS_FS_ZIP
+	select XZ_DEC
+	select XZ_DEC_MICROLZMA
+	help
+	  Saying Y here includes support for reading EROFS file systems
+	  containing LZMA compressed data, specifically called microLZMA. it
+	  gives better compression ratios than the LZ4 algorithm, at the
+	  expense of more CPU overhead.
+
+	  LZMA support is an experimental feature for now and so most file
+	  systems will be readable without selecting this option.
+
+	  If unsure, say N.

fs/erofs/Makefile

@@ -4,3 +4,4 @@ obj-$(CONFIG_EROFS_FS) += erofs.o
 erofs-objs := super.o inode.o data.o namei.o dir.o utils.o pcpubuf.o
 erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
 erofs-$(CONFIG_EROFS_FS_ZIP) += decompressor.o zmap.o zdata.o
+erofs-$(CONFIG_EROFS_FS_ZIP_LZMA) += decompressor_lzma.o

fs/erofs/compress.h

@@ -8,11 +8,6 @@
 
 #include "internal.h"
 
-enum {
-	Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
-	Z_EROFS_COMPRESSION_RUNTIME_MAX
-};
-
 struct z_erofs_decompress_req {
 	struct super_block *sb;
 	struct page **in, **out;
@@ -25,6 +20,12 @@ struct z_erofs_decompress_req {
 	bool inplace_io, partial_decoding;
 };
 
+struct z_erofs_decompressor {
+	int (*decompress)(struct z_erofs_decompress_req *rq,
+			  struct page **pagepool);
+	char *name;
+};
+
 /* some special page->private (unsigned long, see below) */
 #define Z_EROFS_SHORTLIVED_PAGE		(-1UL << 2)
 #define Z_EROFS_PREALLOCATED_PAGE	(-2UL << 2)
@@ -63,7 +64,7 @@ static inline bool z_erofs_is_shortlived_page(struct page *page)
 	return true;
 }
 
-static inline bool z_erofs_put_shortlivedpage(struct list_head *pagepool,
+static inline bool z_erofs_put_shortlivedpage(struct page **pagepool,
 					      struct page *page)
 {
 	if (!z_erofs_is_shortlived_page(page))
@@ -74,13 +75,22 @@ static inline bool z_erofs_put_shortlivedpage(struct list_head *pagepool,
 		put_page(page);
 	} else {
 		/* follow the pcluster rule above. */
-		set_page_private(page, 0);
-		list_add(&page->lru, pagepool);
+		erofs_pagepool_add(pagepool, page);
 	}
 	return true;
 }
 
+#define MNGD_MAPPING(sbi)	((sbi)->managed_cache->i_mapping)
+static inline bool erofs_page_is_managed(const struct erofs_sb_info *sbi,
+					 struct page *page)
+{
+	return page->mapping == MNGD_MAPPING(sbi);
+}
+
 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
-		       struct list_head *pagepool);
+		       struct page **pagepool);
 
+/* prototypes for specific algorithms */
+int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
+			    struct page **pagepool);
 #endif

fs/erofs/data.c

@@ -89,6 +89,7 @@ static int erofs_map_blocks(struct inode *inode,
 	erofs_off_t pos;
 	int err = 0;
 
+	map->m_deviceid = 0;
 	if (map->m_la >= inode->i_size) {
 		/* leave out-of-bound access unmapped */
 		map->m_flags = 0;
@@ -135,14 +136,8 @@ static int erofs_map_blocks(struct inode *inode,
 		map->m_flags = 0;
 		break;
 	default:
-		/* only one device is supported for now */
-		if (idx->device_id) {
-			erofs_err(sb, "invalid device id %u @ %llu for nid %llu",
-				  le16_to_cpu(idx->device_id),
-				  chunknr, vi->nid);
-			err = -EFSCORRUPTED;
-			goto out_unlock;
-		}
+		map->m_deviceid = le16_to_cpu(idx->device_id) &
+			EROFS_SB(sb)->device_id_mask;
 		map->m_pa = blknr_to_addr(le32_to_cpu(idx->blkaddr));
 		map->m_flags = EROFS_MAP_MAPPED;
 		break;
@@ -155,11 +150,55 @@ static int erofs_map_blocks(struct inode *inode,
 	return err;
 }
 
+int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *map)
+{
+	struct erofs_dev_context *devs = EROFS_SB(sb)->devs;
+	struct erofs_device_info *dif;
+	int id;
+
+	/* primary device by default */
+	map->m_bdev = sb->s_bdev;
+	map->m_daxdev = EROFS_SB(sb)->dax_dev;
+
+	if (map->m_deviceid) {
+		down_read(&devs->rwsem);
+		dif = idr_find(&devs->tree, map->m_deviceid - 1);
+		if (!dif) {
+			up_read(&devs->rwsem);
+			return -ENODEV;
+		}
+		map->m_bdev = dif->bdev;
+		map->m_daxdev = dif->dax_dev;
+		up_read(&devs->rwsem);
+	} else if (devs->extra_devices) {
+		down_read(&devs->rwsem);
+		idr_for_each_entry(&devs->tree, dif, id) {
+			erofs_off_t startoff, length;
+
+			if (!dif->mapped_blkaddr)
+				continue;
+			startoff = blknr_to_addr(dif->mapped_blkaddr);
+			length = blknr_to_addr(dif->blocks);
+
+			if (map->m_pa >= startoff &&
+			    map->m_pa < startoff + length) {
+				map->m_pa -= startoff;
+				map->m_bdev = dif->bdev;
+				map->m_daxdev = dif->dax_dev;
+				break;
+			}
+		}
+		up_read(&devs->rwsem);
+	}
+	return 0;
+}
+
 static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 		unsigned int flags, struct iomap *iomap, struct iomap *srcmap)
 {
 	int ret;
 	struct erofs_map_blocks map;
+	struct erofs_map_dev mdev;
 
 	map.m_la = offset;
 	map.m_llen = length;
@@ -168,8 +207,16 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	if (ret < 0)
 		return ret;
 
-	iomap->bdev = inode->i_sb->s_bdev;
-	iomap->dax_dev = EROFS_I_SB(inode)->dax_dev;
+	mdev = (struct erofs_map_dev) {
+		.m_deviceid = map.m_deviceid,
+		.m_pa = map.m_pa,
+	};
+	ret = erofs_map_dev(inode->i_sb, &mdev);
+	if (ret)
+		return ret;
+
+	iomap->bdev = mdev.m_bdev;
+	iomap->dax_dev = mdev.m_daxdev;
 	iomap->offset = map.m_la;
 	iomap->length = map.m_llen;
 	iomap->flags = 0;
@@ -188,15 +235,15 @@ static int erofs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 
 		iomap->type = IOMAP_INLINE;
 		ipage = erofs_get_meta_page(inode->i_sb,
-					    erofs_blknr(map.m_pa));
+					    erofs_blknr(mdev.m_pa));
 		if (IS_ERR(ipage))
 			return PTR_ERR(ipage);
 		iomap->inline_data = page_address(ipage) +
-					erofs_blkoff(map.m_pa);
+					erofs_blkoff(mdev.m_pa);
 		iomap->private = ipage;
 	} else {
 		iomap->type = IOMAP_MAPPED;
-		iomap->addr = map.m_pa;
+		iomap->addr = mdev.m_pa;
 	}
 	return 0;
 }

fs/erofs/decompressor.c

@@ -16,17 +16,6 @@
 #define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize)  (((srcsize) >> 8) + 32)
 #endif
 
-struct z_erofs_decompressor {
-	/*
-	 * if destpages have sparsed pages, fill them with bounce pages.
-	 * it also check whether destpages indicate continuous physical memory.
-	 */
-	int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
-				 struct list_head *pagepool);
-	int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
-	char *name;
-};
-
 int z_erofs_load_lz4_config(struct super_block *sb,
 			    struct erofs_super_block *dsb,
 			    struct z_erofs_lz4_cfgs *lz4, int size)
@@ -63,8 +52,12 @@ int z_erofs_load_lz4_config(struct super_block *sb,
 	return erofs_pcpubuf_growsize(sbi->lz4.max_pclusterblks);
 }
 
-static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
-					 struct list_head *pagepool)
+/*
+ * Fill all gaps with bounce pages if it's a sparse page list. Also check if
+ * all physical pages are consecutive, which can be seen for moderate CR.
+ */
+static int z_erofs_lz4_prepare_dstpages(struct z_erofs_decompress_req *rq,
+					struct page **pagepool)
 {
 	const unsigned int nr =
 		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
@@ -119,7 +112,7 @@ static int z_erofs_lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
 	return kaddr ? 1 : 0;
 }
 
-static void *z_erofs_handle_inplace_io(struct z_erofs_decompress_req *rq,
+static void *z_erofs_lz4_handle_inplace_io(struct z_erofs_decompress_req *rq,
 			void *inpage, unsigned int *inputmargin, int *maptype,
 			bool support_0padding)
 {
@@ -189,7 +182,8 @@ static void *z_erofs_handle_inplace_io(struct z_erofs_decompress_req *rq,
 	return src;
 }
 
-static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
+static int z_erofs_lz4_decompress_mem(struct z_erofs_decompress_req *rq,
+				      u8 *out)
 {
 	unsigned int inputmargin;
 	u8 *headpage, *src;
@@ -216,8 +210,8 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 	}
 
 	rq->inputsize -= inputmargin;
-	src = z_erofs_handle_inplace_io(rq, headpage, &inputmargin, &maptype,
-					support_0padding);
+	src = z_erofs_lz4_handle_inplace_io(rq, headpage, &inputmargin,
+					    &maptype, support_0padding);
 	if (IS_ERR(src))
 		return PTR_ERR(src);
 
@@ -233,7 +227,6 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 		erofs_err(rq->sb, "failed to decompress %d in[%u, %u] out[%u]",
 			  ret, rq->inputsize, inputmargin, rq->outputsize);
 
-		WARN_ON(1);
 		print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
 			       16, 1, src + inputmargin, rq->inputsize, true);
 		print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
@@ -242,6 +235,8 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 		if (ret >= 0)
 			memset(out + ret, 0, rq->outputsize - ret);
 		ret = -EIO;
+	} else {
+		ret = 0;
 	}
 
 	if (maptype == 0) {
@@ -257,86 +252,25 @@ static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
 	return ret;
 }
 
-static struct z_erofs_decompressor decompressors[] = {
-	[Z_EROFS_COMPRESSION_SHIFTED] = {
-		.name = "shifted"
-	},
-	[Z_EROFS_COMPRESSION_LZ4] = {
-		.prepare_destpages = z_erofs_lz4_prepare_destpages,
-		.decompress = z_erofs_lz4_decompress,
-		.name = "lz4"
-	},
-};
-
-static void copy_from_pcpubuf(struct page **out, const char *dst,
-			      unsigned short pageofs_out,
-			      unsigned int outputsize)
-{
-	const char *end = dst + outputsize;
-	const unsigned int righthalf = PAGE_SIZE - pageofs_out;
-	const char *cur = dst - pageofs_out;
-
-	while (cur < end) {
-		struct page *const page = *out++;
-
-		if (page) {
-			char *buf = kmap_atomic(page);
-
-			if (cur >= dst) {
-				memcpy(buf, cur, min_t(uint, PAGE_SIZE,
-						       end - cur));
-			} else {
-				memcpy(buf + pageofs_out, cur + pageofs_out,
-				       min_t(uint, righthalf, end - cur));
-			}
-			kunmap_atomic(buf);
-		}
-		cur += PAGE_SIZE;
-	}
-}
-
-static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
-				      struct list_head *pagepool)
+static int z_erofs_lz4_decompress(struct z_erofs_decompress_req *rq,
+				  struct page **pagepool)
 {
 	const unsigned int nrpages_out =
 		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
-	const struct z_erofs_decompressor *alg = decompressors + rq->alg;
 	unsigned int dst_maptype;
 	void *dst;
 	int ret;
 
-	/* two optimized fast paths only for non bigpcluster cases yet */
-	if (rq->inputsize <= PAGE_SIZE) {
-		if (nrpages_out == 1 && !rq->inplace_io) {
-			DBG_BUGON(!*rq->out);
-			dst = kmap_atomic(*rq->out);
-			dst_maptype = 0;
-			goto dstmap_out;
-		}
-
-		/*
-		 * For the case of small output size (especially much less
-		 * than PAGE_SIZE), memcpy the decompressed data rather than
-		 * compressed data is preferred.
-		 */
-		if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
-			dst = erofs_get_pcpubuf(1);
-			if (IS_ERR(dst))
-				return PTR_ERR(dst);
-
-			rq->inplace_io = false;
-			ret = alg->decompress(rq, dst);
-			if (!ret)
-				copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
-						  rq->outputsize);
-
-			erofs_put_pcpubuf(dst);
-			return ret;
-		}
+	/* one optimized fast path only for non bigpcluster cases yet */
+	if (rq->inputsize <= PAGE_SIZE && nrpages_out == 1 && !rq->inplace_io) {
+		DBG_BUGON(!*rq->out);
+		dst = kmap_atomic(*rq->out);
+		dst_maptype = 0;
+		goto dstmap_out;
 	}
 
 	/* general decoding path which can be used for all cases */
-	ret = alg->prepare_destpages(rq, pagepool);
+	ret = z_erofs_lz4_prepare_dstpages(rq, pagepool);
 	if (ret < 0)
 		return ret;
 	if (ret) {
@@ -351,7 +285,7 @@ static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 	dst_maptype = 2;
 
 dstmap_out:
-	ret = alg->decompress(rq, dst + rq->pageofs_out);
+	ret = z_erofs_lz4_decompress_mem(rq, dst + rq->pageofs_out);
 
 	if (!dst_maptype)
 		kunmap_atomic(dst);
@@ -360,8 +294,8 @@ static int z_erofs_decompress_generic(struct z_erofs_decompress_req *rq,
 	return ret;
 }
 
-static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
-				     struct list_head *pagepool)
+static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
+				     struct page **pagepool)
 {
 	const unsigned int nrpages_out =
 		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
@@ -399,10 +333,25 @@ static int z_erofs_shifted_transform(const struct z_erofs_decompress_req *rq,
 	return 0;
 }
 
+static struct z_erofs_decompressor decompressors[] = {
+	[Z_EROFS_COMPRESSION_SHIFTED] = {
+		.decompress = z_erofs_shifted_transform,
+		.name = "shifted"
+	},
+	[Z_EROFS_COMPRESSION_LZ4] = {
+		.decompress = z_erofs_lz4_decompress,
+		.name = "lz4"
+	},
+#ifdef CONFIG_EROFS_FS_ZIP_LZMA
+	[Z_EROFS_COMPRESSION_LZMA] = {
+		.decompress = z_erofs_lzma_decompress,
+		.name = "lzma"
+	},
+#endif
+};
+
 int z_erofs_decompress(struct z_erofs_decompress_req *rq,
-		       struct list_head *pagepool)
+		       struct page **pagepool)
 {
-	if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
-		return z_erofs_shifted_transform(rq, pagepool);
-	return z_erofs_decompress_generic(rq, pagepool);
+	return decompressors[rq->alg].decompress(rq, pagepool);
 }

fs/erofs/decompressor_lzma.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/xz.h>
+#include <linux/module.h>
+#include "compress.h"
+
+struct z_erofs_lzma {
+	struct z_erofs_lzma *next;
+	struct xz_dec_microlzma *state;
+	struct xz_buf buf;
+	u8 bounce[PAGE_SIZE];
+};
+
+/* considering the LZMA performance, no need to use a lockless list for now */
+static DEFINE_SPINLOCK(z_erofs_lzma_lock);
+static unsigned int z_erofs_lzma_max_dictsize;
+static unsigned int z_erofs_lzma_nstrms, z_erofs_lzma_avail_strms;
+static struct z_erofs_lzma *z_erofs_lzma_head;
+static DECLARE_WAIT_QUEUE_HEAD(z_erofs_lzma_wq);
+
+module_param_named(lzma_streams, z_erofs_lzma_nstrms, uint, 0444);
+
+void z_erofs_lzma_exit(void)
+{
+	/* there should be no running fs instance */
+	while (z_erofs_lzma_avail_strms) {
+		struct z_erofs_lzma *strm;
+
+		spin_lock(&z_erofs_lzma_lock);
+		strm = z_erofs_lzma_head;
+		if (!strm) {
+			spin_unlock(&z_erofs_lzma_lock);
+			DBG_BUGON(1);
+			return;
+		}
+		z_erofs_lzma_head = NULL;
+		spin_unlock(&z_erofs_lzma_lock);
+
+		while (strm) {
+			struct z_erofs_lzma *n = strm->next;
+
+			if (strm->state)
+				xz_dec_microlzma_end(strm->state);
+			kfree(strm);
+			--z_erofs_lzma_avail_strms;
+			strm = n;
+		}
+	}
+}
+
+int z_erofs_lzma_init(void)
+{
+	unsigned int i;
+
+	/* by default, use # of possible CPUs instead */
+	if (!z_erofs_lzma_nstrms)
+		z_erofs_lzma_nstrms = num_possible_cpus();
+
+	for (i = 0; i < z_erofs_lzma_nstrms; ++i) {
+		struct z_erofs_lzma *strm = kzalloc(sizeof(*strm), GFP_KERNEL);
+
+		if (!strm) {
+			z_erofs_lzma_exit();
+			return -ENOMEM;
+		}
+		spin_lock(&z_erofs_lzma_lock);
+		strm->next = z_erofs_lzma_head;
+		z_erofs_lzma_head = strm;
+		spin_unlock(&z_erofs_lzma_lock);
+		++z_erofs_lzma_avail_strms;
+	}
+	return 0;
+}
+
+int z_erofs_load_lzma_config(struct super_block *sb,
+			     struct erofs_super_block *dsb,
+			     struct z_erofs_lzma_cfgs *lzma, int size)
+{
+	static DEFINE_MUTEX(lzma_resize_mutex);
+	unsigned int dict_size, i;
+	struct z_erofs_lzma *strm, *head = NULL;
+	int err;
+
+	if (!lzma || size < sizeof(struct z_erofs_lzma_cfgs)) {
+		erofs_err(sb, "invalid lzma cfgs, size=%u", size);
+		return -EINVAL;
+	}
+	if (lzma->format) {
+		erofs_err(sb, "unidentified lzma format %x, please check kernel version",
+			  le16_to_cpu(lzma->format));
+		return -EINVAL;
+	}
+	dict_size = le32_to_cpu(lzma->dict_size);
+	if (dict_size > Z_EROFS_LZMA_MAX_DICT_SIZE || dict_size < 4096) {
+		erofs_err(sb, "unsupported lzma dictionary size %u",
+			  dict_size);
+		return -EINVAL;
+	}
+
+	erofs_info(sb, "EXPERIMENTAL MicroLZMA in use. Use at your own risk!");
+
+	/* in case 2 z_erofs_load_lzma_config() race to avoid deadlock */
+	mutex_lock(&lzma_resize_mutex);
+
+	if (z_erofs_lzma_max_dictsize >= dict_size) {
+		mutex_unlock(&lzma_resize_mutex);
+		return 0;
+	}
+
+	/* 1. collect/isolate all streams for the following check */
+	for (i = 0; i < z_erofs_lzma_avail_strms; ++i) {
+		struct z_erofs_lzma *last;
+
+again:
+		spin_lock(&z_erofs_lzma_lock);
+		strm = z_erofs_lzma_head;
+		if (!strm) {
+			spin_unlock(&z_erofs_lzma_lock);
+			wait_event(z_erofs_lzma_wq,
+				   READ_ONCE(z_erofs_lzma_head));
+			goto again;
+		}
+		z_erofs_lzma_head = NULL;
+		spin_unlock(&z_erofs_lzma_lock);
+
+		for (last = strm; last->next; last = last->next)
+			++i;
+		last->next = head;
+		head = strm;
+	}
+
+	err = 0;
+	/* 2. walk each isolated stream and grow max dict_size if needed */
+	for (strm = head; strm; strm = strm->next) {
+		if (strm->state)
+			xz_dec_microlzma_end(strm->state);
+		strm->state = xz_dec_microlzma_alloc(XZ_PREALLOC, dict_size);
+		if (!strm->state)
+			err = -ENOMEM;
+	}
+
+	/* 3. push back all to the global list and update max dict_size */
+	spin_lock(&z_erofs_lzma_lock);
+	DBG_BUGON(z_erofs_lzma_head);
+	z_erofs_lzma_head = head;
+	spin_unlock(&z_erofs_lzma_lock);
+
+	z_erofs_lzma_max_dictsize = dict_size;
+	mutex_unlock(&lzma_resize_mutex);
+	return err;
+}
+
+int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
+			    struct page **pagepool)
+{
+	const unsigned int nrpages_out =
+		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
+	const unsigned int nrpages_in =
+		PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
+	unsigned int inputmargin, inlen, outlen, pageofs;
+	struct z_erofs_lzma *strm;
+	u8 *kin;
+	bool bounced = false;
+	int no, ni, j, err = 0;
+
+	/* 1. get the exact LZMA compressed size */
+	kin = kmap(*rq->in);
+	inputmargin = 0;
+	while (!kin[inputmargin & ~PAGE_MASK])
+		if (!(++inputmargin & ~PAGE_MASK))
+			break;
+
+	if (inputmargin >= PAGE_SIZE) {
+		kunmap(*rq->in);
+		return -EFSCORRUPTED;
+	}
+	rq->inputsize -= inputmargin;
+
+	/* 2. get an available lzma context */
+again:
+	spin_lock(&z_erofs_lzma_lock);
+	strm = z_erofs_lzma_head;
+	if (!strm) {
+		spin_unlock(&z_erofs_lzma_lock);
+		wait_event(z_erofs_lzma_wq, READ_ONCE(z_erofs_lzma_head));
+		goto again;
+	}
+	z_erofs_lzma_head = strm->next;
+	spin_unlock(&z_erofs_lzma_lock);
+
+	/* 3. multi-call decompress */
+	inlen = rq->inputsize;
+	outlen = rq->outputsize;
+	xz_dec_microlzma_reset(strm->state, inlen, outlen,
+			       !rq->partial_decoding);
+	pageofs = rq->pageofs_out;
+	strm->buf.in = kin + inputmargin;
+	strm->buf.in_pos = 0;
+	strm->buf.in_size = min_t(u32, inlen, PAGE_SIZE - inputmargin);
+	inlen -= strm->buf.in_size;
+	strm->buf.out = NULL;
+	strm->buf.out_pos = 0;
+	strm->buf.out_size = 0;
+
+	for (ni = 0, no = -1;;) {
+		enum xz_ret xz_err;
+
+		if (strm->buf.out_pos == strm->buf.out_size) {
+			if (strm->buf.out) {
+				kunmap(rq->out[no]);
+				strm->buf.out = NULL;
+			}
+
+			if (++no >= nrpages_out || !outlen) {
+				erofs_err(rq->sb, "decompressed buf out of bound");
+				err = -EFSCORRUPTED;
+				break;
+			}
+			strm->buf.out_pos = 0;
+			strm->buf.out_size = min_t(u32, outlen,
+						   PAGE_SIZE - pageofs);
+			outlen -= strm->buf.out_size;
+			if (rq->out[no])
+				strm->buf.out = kmap(rq->out[no]) + pageofs;
+			pageofs = 0;
+		} else if (strm->buf.in_pos == strm->buf.in_size) {
+			kunmap(rq->in[ni]);
+
+			if (++ni >= nrpages_in || !inlen) {
+				erofs_err(rq->sb, "compressed buf out of bound");
+				err = -EFSCORRUPTED;
+				break;
+			}
+			strm->buf.in_pos = 0;
+			strm->buf.in_size = min_t(u32, inlen, PAGE_SIZE);
+			inlen -= strm->buf.in_size;
+			kin = kmap(rq->in[ni]);
+			strm->buf.in = kin;
+			bounced = false;
+		}
+
+		/*
+		 * Handle overlapping: Use bounced buffer if the compressed
+		 * data is under processing; Otherwise, Use short-lived pages
+		 * from the on-stack pagepool where pages share with the same
+		 * request.
+		 */
+		if (!bounced && rq->out[no] == rq->in[ni]) {
+			memcpy(strm->bounce, strm->buf.in, strm->buf.in_size);
+			strm->buf.in = strm->bounce;
+			bounced = true;
+		}
+		for (j = ni + 1; j < nrpages_in; ++j) {
+			struct page *tmppage;
+
+			if (rq->out[no] != rq->in[j])
+				continue;
+
+			DBG_BUGON(erofs_page_is_managed(EROFS_SB(rq->sb),
+							rq->in[j]));
+			tmppage = erofs_allocpage(pagepool,
+						  GFP_KERNEL | __GFP_NOFAIL);
+			set_page_private(tmppage, Z_EROFS_SHORTLIVED_PAGE);
+			copy_highpage(tmppage, rq->in[j]);
+			rq->in[j] = tmppage;
+		}
+		xz_err = xz_dec_microlzma_run(strm->state, &strm->buf);
+		DBG_BUGON(strm->buf.out_pos > strm->buf.out_size);
+		DBG_BUGON(strm->buf.in_pos > strm->buf.in_size);
+
+		if (xz_err != XZ_OK) {
+			if (xz_err == XZ_STREAM_END && !outlen)
+				break;
+			erofs_err(rq->sb, "failed to decompress %d in[%u] out[%u]",
+				  xz_err, rq->inputsize, rq->outputsize);
+			err = -EFSCORRUPTED;
+			break;
+		}
+	}
+	if (no < nrpages_out && strm->buf.out)
+		kunmap(rq->in[no]);
+	if (ni < nrpages_in)
+		kunmap(rq->in[ni]);
+	/* 4. push back LZMA stream context to the global list */
+	spin_lock(&z_erofs_lzma_lock);
+	strm->next = z_erofs_lzma_head;
+	z_erofs_lzma_head = strm;
+	spin_unlock(&z_erofs_lzma_lock);
+	wake_up(&z_erofs_lzma_wq);
+	return err;
+}

fs/erofs/erofs_fs.h

@@ -21,14 +21,29 @@
 #define EROFS_FEATURE_INCOMPAT_COMPR_CFGS	0x00000002
 #define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER	0x00000002
 #define EROFS_FEATURE_INCOMPAT_CHUNKED_FILE	0x00000004
+#define EROFS_FEATURE_INCOMPAT_DEVICE_TABLE	0x00000008
+#define EROFS_FEATURE_INCOMPAT_COMPR_HEAD2	0x00000008
 #define EROFS_ALL_FEATURE_INCOMPAT		\
 	(EROFS_FEATURE_INCOMPAT_LZ4_0PADDING | \
 	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
 	 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER | \
-	 EROFS_FEATURE_INCOMPAT_CHUNKED_FILE)
+	 EROFS_FEATURE_INCOMPAT_CHUNKED_FILE | \
+	 EROFS_FEATURE_INCOMPAT_DEVICE_TABLE | \
+	 EROFS_FEATURE_INCOMPAT_COMPR_HEAD2)
 
 #define EROFS_SB_EXTSLOT_SIZE	16
 
+struct erofs_deviceslot {
+	union {
+		u8 uuid[16];		/* used for device manager later */
+		u8 userdata[64];	/* digest(sha256), etc. */
+	} u;
+	__le32 blocks;			/* total fs blocks of this device */
+	__le32 mapped_blkaddr;		/* map starting at mapped_blkaddr */
+	u8 reserved[56];
+};
+#define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)
+
 /* erofs on-disk super block (currently 128 bytes) */
 struct erofs_super_block {
 	__le32 magic;           /* file system magic number */
@@ -54,7 +69,9 @@ struct erofs_super_block {
 		/* customized sliding window size instead of 64k by default */
 		__le16 lz4_max_distance;
 	} __packed u1;
-	__u8 reserved2[42];
+	__le16 extra_devices;	/* # of devices besides the primary device */
+	__le16 devt_slotoff;	/* startoff = devt_slotoff * devt_slotsize */
+	__u8 reserved2[38];
 };
 
 /*
@@ -238,7 +255,7 @@ static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
 /* 8-byte inode chunk indexes */
 struct erofs_inode_chunk_index {
 	__le16 advise;		/* always 0, don't care for now */
-	__le16 device_id;	/* back-end storage id, always 0 for now */
+	__le16 device_id;	/* back-end storage id (with bits masked) */
 	__le32 blkaddr;		/* start block address of this inode chunk */
 };
 
@@ -247,10 +264,11 @@ struct erofs_inode_chunk_index {
 
 /* available compression algorithm types (for h_algorithmtype) */
 enum {
-	Z_EROFS_COMPRESSION_LZ4	= 0,
+	Z_EROFS_COMPRESSION_LZ4		= 0,
+	Z_EROFS_COMPRESSION_LZMA	= 1,
 	Z_EROFS_COMPRESSION_MAX
 };
-#define Z_EROFS_ALL_COMPR_ALGS		(1 << (Z_EROFS_COMPRESSION_MAX - 1))
+#define Z_EROFS_ALL_COMPR_ALGS		((1 << Z_EROFS_COMPRESSION_MAX) - 1)
 
 /* 14 bytes (+ length field = 16 bytes) */
 struct z_erofs_lz4_cfgs {
@@ -259,6 +277,15 @@ struct z_erofs_lz4_cfgs {
 	u8 reserved[10];
 } __packed;
 
+/* 14 bytes (+ length field = 16 bytes) */
+struct z_erofs_lzma_cfgs {
+	__le32 dict_size;
+	__le16 format;
+	u8 reserved[8];
+} __packed;
+
+#define Z_EROFS_LZMA_MAX_DICT_SIZE	(8 * Z_EROFS_PCLUSTER_MAX_SIZE)
+
 /*
  * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
  *  e.g. for 4k logical cluster size,      4B        if compacted 2B is off;
@@ -288,35 +315,34 @@ struct z_erofs_map_header {
 #define Z_EROFS_VLE_LEGACY_HEADER_PADDING       8
 
 /*
- * Fixed-sized output compression ondisk Logical Extent cluster type:
- *    0 - literal (uncompressed) cluster
- *    1 - compressed cluster (for the head logical cluster)
- *    2 - compressed cluster (for the other logical clusters)
+ * Fixed-sized output compression on-disk logical cluster type:
+ *    0   - literal (uncompressed) lcluster
+ *    1,3 - compressed lcluster (for HEAD lclusters)
+ *    2   - compressed lcluster (for NONHEAD lclusters)
  *
  * In detail,
- *    0 - literal (uncompressed) cluster,
+ *    0 - literal (uncompressed) lcluster,
  *        di_advise = 0
- *        di_clusterofs = the literal data offset of the cluster
- *        di_blkaddr = the blkaddr of the literal cluster
+ *        di_clusterofs = the literal data offset of the lcluster
+ *        di_blkaddr = the blkaddr of the literal pcluster
  *
- *    1 - compressed cluster (for the head logical cluster)
- *        di_advise = 1
- *        di_clusterofs = the decompressed data offset of the cluster
- *        di_blkaddr = the blkaddr of the compressed cluster
+ *    1,3 - compressed lcluster (for HEAD lclusters)
+ *        di_advise = 1 or 3
+ *        di_clusterofs = the decompressed data offset of the lcluster
+ *        di_blkaddr = the blkaddr of the compressed pcluster
  *
- *    2 - compressed cluster (for the other logical clusters)
+ *    2 - compressed lcluster (for NONHEAD lclusters)
  *        di_advise = 2
  *        di_clusterofs =
- *           the decompressed data offset in its own head cluster
- *        di_u.delta[0] = distance to its corresponding head cluster
- *        di_u.delta[1] = distance to its corresponding tail cluster
- *                (di_advise could be 0, 1 or 2)
+ *           the decompressed data offset in its own HEAD lcluster
+ *        di_u.delta[0] = distance to this HEAD lcluster
+ *        di_u.delta[1] = distance to the next HEAD lcluster
  */
 enum {
 	Z_EROFS_VLE_CLUSTER_TYPE_PLAIN		= 0,
-	Z_EROFS_VLE_CLUSTER_TYPE_HEAD		= 1,
+	Z_EROFS_VLE_CLUSTER_TYPE_HEAD1		= 1,
 	Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD	= 2,
-	Z_EROFS_VLE_CLUSTER_TYPE_RESERVED	= 3,
+	Z_EROFS_VLE_CLUSTER_TYPE_HEAD2		= 3,
 	Z_EROFS_VLE_CLUSTER_TYPE_MAX
 };
 
@@ -384,6 +410,7 @@ static inline void erofs_check_ondisk_layout_definitions(void)
 	/* keep in sync between 2 index structures for better extendibility */
 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) !=
 		     sizeof(struct z_erofs_vle_decompressed_index));
+	BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);
 
 	BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
 		     Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);

fs/erofs/inode.c

@@ -192,7 +192,7 @@ static struct page *erofs_read_inode(struct inode *inode,
 	inode->i_atime.tv_nsec = inode->i_ctime.tv_nsec;
 
 	inode->i_flags &= ~S_DAX;
-	if (test_opt(&sbi->ctx, DAX_ALWAYS) && S_ISREG(inode->i_mode) &&
+	if (test_opt(&sbi->opt, DAX_ALWAYS) && S_ISREG(inode->i_mode) &&
 	    vi->datalayout == EROFS_INODE_FLAT_PLAIN)
 		inode->i_flags |= S_DAX;
 	if (!nblks)

fs/erofs/internal.h

@@ -47,7 +47,16 @@ typedef u64 erofs_off_t;
 /* data type for filesystem-wide blocks number */
 typedef u32 erofs_blk_t;
 
-struct erofs_fs_context {
+struct erofs_device_info {
+	char *path;
+	struct block_device *bdev;
+	struct dax_device *dax_dev;
+
+	u32 blocks;
+	u32 mapped_blkaddr;
+};
+
+struct erofs_mount_opts {
 #ifdef CONFIG_EROFS_FS_ZIP
 	/* current strategy of how to use managed cache */
 	unsigned char cache_strategy;
@@ -60,6 +69,18 @@ struct erofs_fs_context {
 	unsigned int mount_opt;
 };
 
+struct erofs_dev_context {
+	struct idr tree;
+	struct rw_semaphore rwsem;
+
+	unsigned int extra_devices;
+};
+
+struct erofs_fs_context {
+	struct erofs_mount_opts opt;
+	struct erofs_dev_context *devs;
+};
+
 /* all filesystem-wide lz4 configurations */
 struct erofs_sb_lz4_info {
 	/* # of pages needed for EROFS lz4 rolling decompression */
@@ -69,6 +90,7 @@ struct erofs_sb_lz4_info {
 };
 
 struct erofs_sb_info {
+	struct erofs_mount_opts opt;	/* options */
 #ifdef CONFIG_EROFS_FS_ZIP
 	/* list for all registered superblocks, mainly for shrinker */
 	struct list_head list;
@@ -85,12 +107,16 @@ struct erofs_sb_info {
 
 	struct erofs_sb_lz4_info lz4;
 #endif	/* CONFIG_EROFS_FS_ZIP */
+	struct erofs_dev_context *devs;
 	struct dax_device *dax_dev;
-	u32 blocks;
+	u64 total_blocks;
+	u32 primarydevice_blocks;
+
 	u32 meta_blkaddr;
 #ifdef CONFIG_EROFS_FS_XATTR
 	u32 xattr_blkaddr;
 #endif
+	u16 device_id_mask;	/* valid bits of device id to be used */
 
 	/* inode slot unit size in bit shift */
 	unsigned char islotbits;
@@ -108,8 +134,6 @@ struct erofs_sb_info {
 	u8 volume_name[16];             /* volume name */
 	u32 feature_compat;
 	u32 feature_incompat;
-
-	struct erofs_fs_context ctx;	/* options */
 };
 
 #define EROFS_SB(sb) ((struct erofs_sb_info *)(sb)->s_fs_info)
@@ -121,9 +145,9 @@ struct erofs_sb_info {
 #define EROFS_MOUNT_DAX_ALWAYS		0x00000040
 #define EROFS_MOUNT_DAX_NEVER		0x00000080
 
-#define clear_opt(ctx, option)	((ctx)->mount_opt &= ~EROFS_MOUNT_##option)
-#define set_opt(ctx, option)	((ctx)->mount_opt |= EROFS_MOUNT_##option)
-#define test_opt(ctx, option)	((ctx)->mount_opt & EROFS_MOUNT_##option)
+#define clear_opt(opt, option)	((opt)->mount_opt &= ~EROFS_MOUNT_##option)
+#define set_opt(opt, option)	((opt)->mount_opt |= EROFS_MOUNT_##option)
+#define test_opt(opt, option)	((opt)->mount_opt & EROFS_MOUNT_##option)
 
 enum {
 	EROFS_ZIP_CACHE_DISABLED,
@@ -237,6 +261,7 @@ static inline bool erofs_sb_has_##name(struct erofs_sb_info *sbi) \
 EROFS_FEATURE_FUNCS(lz4_0padding, incompat, INCOMPAT_LZ4_0PADDING)
 EROFS_FEATURE_FUNCS(compr_cfgs, incompat, INCOMPAT_COMPR_CFGS)
 EROFS_FEATURE_FUNCS(big_pcluster, incompat, INCOMPAT_BIG_PCLUSTER)
+EROFS_FEATURE_FUNCS(device_table, incompat, INCOMPAT_DEVICE_TABLE)
 EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
 
 /* atomic flag definitions */
@@ -307,6 +332,19 @@ static inline unsigned int erofs_inode_datalayout(unsigned int value)
 			      EROFS_I_DATALAYOUT_BITS);
 }
 
+/*
+ * Different from grab_cache_page_nowait(), reclaiming is never triggered
+ * when allocating new pages.
+ */
+static inline
+struct page *erofs_grab_cache_page_nowait(struct address_space *mapping,
+					  pgoff_t index)
+{
+	return pagecache_get_page(mapping, index,
+			FGP_LOCK|FGP_CREAT|FGP_NOFS|FGP_NOWAIT,
+			readahead_gfp_mask(mapping) & ~__GFP_RECLAIM);
+}
+
 extern const struct super_operations erofs_sops;
 
 extern const struct address_space_operations erofs_raw_access_aops;
@@ -338,7 +376,7 @@ extern const struct address_space_operations z_erofs_aops;
  * of the corresponding uncompressed data in the file.
  */
 enum {
-	BH_Zipped = BH_PrivateStart,
+	BH_Encoded = BH_PrivateStart,
 	BH_FullMapped,
 };
 
@@ -346,8 +384,8 @@ enum {
 #define EROFS_MAP_MAPPED	(1 << BH_Mapped)
 /* Located in metadata (could be copied from bd_inode) */
 #define EROFS_MAP_META		(1 << BH_Meta)
-/* The extent has been compressed */
-#define EROFS_MAP_ZIPPED	(1 << BH_Zipped)
+/* The extent is encoded */
+#define EROFS_MAP_ENCODED	(1 << BH_Encoded)
 /* The length of extent is full */
 #define EROFS_MAP_FULL_MAPPED	(1 << BH_FullMapped)
 
@@ -355,6 +393,8 @@ struct erofs_map_blocks {
 	erofs_off_t m_pa, m_la;
 	u64 m_plen, m_llen;
 
+	unsigned short m_deviceid;
+	char m_algorithmformat;
 	unsigned int m_flags;
 
 	struct page *mpage;
@@ -367,6 +407,13 @@ struct erofs_map_blocks {
  * approach instead if possible since it's more metadata lightweight.)
  */
 #define EROFS_GET_BLOCKS_FIEMAP	0x0002
+/* Used to map the whole extent if non-negligible data is requested for LZMA */
+#define EROFS_GET_BLOCKS_READMORE	0x0004
+
+enum {
+	Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
+	Z_EROFS_COMPRESSION_RUNTIME_MAX
+};
 
 /* zmap.c */
 extern const struct iomap_ops z_erofs_iomap_report_ops;
@@ -386,9 +433,18 @@ static inline int z_erofs_map_blocks_iter(struct inode *inode,
 }
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
+struct erofs_map_dev {
+	struct block_device *m_bdev;
+	struct dax_device *m_daxdev;
+
+	erofs_off_t m_pa;
+	unsigned int m_deviceid;
+};
+
 /* data.c */
 extern const struct file_operations erofs_file_fops;
 struct page *erofs_get_meta_page(struct super_block *sb, erofs_blk_t blkaddr);
+int erofs_map_dev(struct super_block *sb, struct erofs_map_dev *dev);
 int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		 u64 start, u64 len);
 
@@ -443,7 +499,14 @@ void erofs_pcpubuf_init(void);
 void erofs_pcpubuf_exit(void);
 
 /* utils.c / zdata.c */
-struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp);
+struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp);
+static inline void erofs_pagepool_add(struct page **pagepool,
+		struct page *page)
+{
+	set_page_private(page, (unsigned long)*pagepool);
+	*pagepool = page;
+}
+void erofs_release_pages(struct page **pagepool);
 
 #ifdef CONFIG_EROFS_FS_ZIP
 int erofs_workgroup_put(struct erofs_workgroup *grp);
@@ -483,6 +546,26 @@ static inline int z_erofs_load_lz4_config(struct super_block *sb,
 }
 #endif	/* !CONFIG_EROFS_FS_ZIP */
 
+#ifdef CONFIG_EROFS_FS_ZIP_LZMA
+int z_erofs_lzma_init(void);
+void z_erofs_lzma_exit(void);
+int z_erofs_load_lzma_config(struct super_block *sb,
+			     struct erofs_super_block *dsb,
+			     struct z_erofs_lzma_cfgs *lzma, int size);
+#else
+static inline int z_erofs_lzma_init(void) { return 0; }
+static inline int z_erofs_lzma_exit(void) { return 0; }
+static inline int z_erofs_load_lzma_config(struct super_block *sb,
+			     struct erofs_super_block *dsb,
+			     struct z_erofs_lzma_cfgs *lzma, int size) {
+	if (lzma) {
+		erofs_err(sb, "lzma algorithm isn't enabled");
+		return -EINVAL;
+	}
+	return 0;
+}
+#endif	/* !CONFIG_EROFS_FS_ZIP */
+
 #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
 
 #endif	/* __EROFS_INTERNAL_H */

fs/erofs/pcpubuf.c

@@ -49,7 +49,7 @@ int erofs_pcpubuf_growsize(unsigned int nrpages)
 {
 	static DEFINE_MUTEX(pcb_resize_mutex);
 	static unsigned int pcb_nrpages;
-	LIST_HEAD(pagepool);
+	struct page *pagepool = NULL;
 	int delta, cpu, ret, i;
 
 	mutex_lock(&pcb_resize_mutex);
@@ -102,13 +102,13 @@ int erofs_pcpubuf_growsize(unsigned int nrpages)
 			vunmap(old_ptr);
 free_pagearray:
 		while (i)
-			list_add(&oldpages[--i]->lru, &pagepool);
+			erofs_pagepool_add(&pagepool, oldpages[--i]);
 		kfree(oldpages);
 		if (ret)
 			break;
 	}
 	pcb_nrpages = nrpages;
-	put_pages_list(&pagepool);
+	erofs_release_pages(&pagepool);
 out:
 	mutex_unlock(&pcb_resize_mutex);
 	return ret;

fs/erofs/utils.c

@@ -6,20 +6,29 @@
 #include "internal.h"
 #include <linux/pagevec.h>
 
-struct page *erofs_allocpage(struct list_head *pool, gfp_t gfp)
+struct page *erofs_allocpage(struct page **pagepool, gfp_t gfp)
 {
-	struct page *page;
+	struct page *page = *pagepool;
 
-	if (!list_empty(pool)) {
-		page = lru_to_page(pool);
+	if (page) {
 		DBG_BUGON(page_ref_count(page) != 1);
-		list_del(&page->lru);
+		*pagepool = (struct page *)page_private(page);
 	} else {
 		page = alloc_page(gfp);
 	}
 	return page;
 }
 
+void erofs_release_pages(struct page **pagepool)
+{
+	while (*pagepool) {
+		struct page *page = *pagepool;
+
+		*pagepool = (struct page *)page_private(page);
+		put_page(page);
+	}
+}
+
 #ifdef CONFIG_EROFS_FS_ZIP
 /* global shrink count (for all mounted EROFS instances) */
 static atomic_long_t erofs_global_shrink_cnt;

fs/erofs/xattr.c

@@ -429,7 +429,7 @@ static int shared_getxattr(struct inode *inode, struct getxattr_iter *it)
 
 static bool erofs_xattr_user_list(struct dentry *dentry)
 {
-	return test_opt(&EROFS_SB(dentry->d_sb)->ctx, XATTR_USER);
+	return test_opt(&EROFS_SB(dentry->d_sb)->opt, XATTR_USER);
 }
 
 static bool erofs_xattr_trusted_list(struct dentry *dentry)
@@ -476,7 +476,7 @@ static int erofs_xattr_generic_get(const struct xattr_handler *handler,
 
 	switch (handler->flags) {
 	case EROFS_XATTR_INDEX_USER:
-		if (!test_opt(&sbi->ctx, XATTR_USER))
+		if (!test_opt(&sbi->opt, XATTR_USER))
 			return -EOPNOTSUPP;
 		break;
 	case EROFS_XATTR_INDEX_TRUSTED:

fs/erofs/zdata.h

@@ -94,13 +94,6 @@ struct z_erofs_decompressqueue {
 	} u;
 };
 
-#define MNGD_MAPPING(sbi)	((sbi)->managed_cache->i_mapping)
-static inline bool erofs_page_is_managed(const struct erofs_sb_info *sbi,
-					 struct page *page)
-{
-	return page->mapping == MNGD_MAPPING(sbi);
-}
-
 #define Z_EROFS_ONLINEPAGE_COUNT_BITS   2
 #define Z_EROFS_ONLINEPAGE_COUNT_MASK   ((1 << Z_EROFS_ONLINEPAGE_COUNT_BITS) - 1)
 #define Z_EROFS_ONLINEPAGE_INDEX_SHIFT  (Z_EROFS_ONLINEPAGE_COUNT_BITS)

fs/erofs/zmap.c

@@ -28,7 +28,7 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
 {
 	struct erofs_inode *const vi = EROFS_I(inode);
 	struct super_block *const sb = inode->i_sb;
-	int err;
+	int err, headnr;
 	erofs_off_t pos;
 	struct page *page;
 	void *kaddr;
@@ -68,9 +68,11 @@ static int z_erofs_fill_inode_lazy(struct inode *inode)
 	vi->z_algorithmtype[0] = h->h_algorithmtype & 15;
 	vi->z_algorithmtype[1] = h->h_algorithmtype >> 4;
 
-	if (vi->z_algorithmtype[0] >= Z_EROFS_COMPRESSION_MAX) {
-		erofs_err(sb, "unknown compression format %u for nid %llu, please upgrade kernel",
-			  vi->z_algorithmtype[0], vi->nid);
+	headnr = 0;
+	if (vi->z_algorithmtype[0] >= Z_EROFS_COMPRESSION_MAX ||
+	    vi->z_algorithmtype[++headnr] >= Z_EROFS_COMPRESSION_MAX) {
+		erofs_err(sb, "unknown HEAD%u format %u for nid %llu, please upgrade kernel",
+			  headnr + 1, vi->z_algorithmtype[headnr], vi->nid);
 		err = -EOPNOTSUPP;
 		goto unmap_done;
 	}
@@ -111,7 +113,7 @@ struct z_erofs_maprecorder {
 
 	unsigned long lcn;
 	/* compression extent information gathered */
-	u8  type;
+	u8  type, headtype;
 	u16 clusterofs;
 	u16 delta[2];
 	erofs_blk_t pblk, compressedlcs;
@@ -178,7 +180,8 @@ static int legacy_load_cluster_from_disk(struct z_erofs_maprecorder *m,
 		m->clusterofs = 1 << vi->z_logical_clusterbits;
 		m->delta[0] = le16_to_cpu(di->di_u.delta[0]);
 		if (m->delta[0] & Z_EROFS_VLE_DI_D0_CBLKCNT) {
-			if (!(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) {
+			if (!(vi->z_advise & (Z_EROFS_ADVISE_BIG_PCLUSTER_1 |
+					Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
 				DBG_BUGON(1);
 				return -EFSCORRUPTED;
 			}
@@ -189,7 +192,8 @@ static int legacy_load_cluster_from_disk(struct z_erofs_maprecorder *m,
 		m->delta[1] = le16_to_cpu(di->di_u.delta[1]);
 		break;
 	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
-	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
 		m->clusterofs = le16_to_cpu(di->di_clusterofs);
 		m->pblk = le32_to_cpu(di->di_u.blkaddr);
 		break;
@@ -446,9 +450,9 @@ static int z_erofs_extent_lookback(struct z_erofs_maprecorder *m,
 		}
 		return z_erofs_extent_lookback(m, m->delta[0]);
 	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
-		map->m_flags &= ~EROFS_MAP_ZIPPED;
-		fallthrough;
-	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
+		m->headtype = m->type;
 		map->m_la = (lcn << lclusterbits) | m->clusterofs;
 		break;
 	default:
@@ -471,13 +475,18 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
 	int err;
 
 	DBG_BUGON(m->type != Z_EROFS_VLE_CLUSTER_TYPE_PLAIN &&
-		  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD);
-	if (!(map->m_flags & EROFS_MAP_ZIPPED) ||
-	    !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) {
+		  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD1 &&
+		  m->type != Z_EROFS_VLE_CLUSTER_TYPE_HEAD2);
+	DBG_BUGON(m->type != m->headtype);
+
+	if (m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN ||
+	    ((m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD1) &&
+	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) ||
+	    ((m->headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) &&
+	     !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_2))) {
 		map->m_plen = 1 << lclusterbits;
 		return 0;
 	}
-
 	lcn = m->lcn + 1;
 	if (m->compressedlcs)
 		goto out;
@@ -499,7 +508,8 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m,
 
 	switch (m->type) {
 	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
-	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
 		/*
 		 * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type
 		 * rather than CBLKCNT, it's a 1 lcluster-sized pcluster.
@@ -554,7 +564,8 @@ static int z_erofs_get_extent_decompressedlen(struct z_erofs_maprecorder *m)
 			DBG_BUGON(!m->delta[1] &&
 				  m->clusterofs != 1 << lclusterbits);
 		} else if (m->type == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN ||
-			   m->type == Z_EROFS_VLE_CLUSTER_TYPE_HEAD) {
+			   m->type == Z_EROFS_VLE_CLUSTER_TYPE_HEAD1 ||
+			   m->type == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2) {
 			/* go on until the next HEAD lcluster */
 			if (lcn != headlcn)
 				break;
@@ -609,16 +620,15 @@ int z_erofs_map_blocks_iter(struct inode *inode,
 	if (err)
 		goto unmap_out;
 
-	map->m_flags = EROFS_MAP_ZIPPED;	/* by default, compressed */
+	map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_ENCODED;
 	end = (m.lcn + 1ULL) << lclusterbits;
 
 	switch (m.type) {
 	case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN:
-		if (endoff >= m.clusterofs)
-			map->m_flags &= ~EROFS_MAP_ZIPPED;
-		fallthrough;
-	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD1:
+	case Z_EROFS_VLE_CLUSTER_TYPE_HEAD2:
 		if (endoff >= m.clusterofs) {
+			m.headtype = m.type;
 			map->m_la = (m.lcn << lclusterbits) | m.clusterofs;
 			break;
 		}
@@ -650,13 +660,22 @@ int z_erofs_map_blocks_iter(struct inode *inode,
 
 	map->m_llen = end - map->m_la;
 	map->m_pa = blknr_to_addr(m.pblk);
-	map->m_flags |= EROFS_MAP_MAPPED;
 
 	err = z_erofs_get_extent_compressedlen(&m, initial_lcn);
 	if (err)
 		goto out;
 
-	if (flags & EROFS_GET_BLOCKS_FIEMAP) {
+	if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_PLAIN)
+		map->m_algorithmformat = Z_EROFS_COMPRESSION_SHIFTED;
+	else if (m.headtype == Z_EROFS_VLE_CLUSTER_TYPE_HEAD2)
+		map->m_algorithmformat = vi->z_algorithmtype[1];
+	else
+		map->m_algorithmformat = vi->z_algorithmtype[0];
+
+	if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
+	    ((flags & EROFS_GET_BLOCKS_READMORE) &&
+	     map->m_algorithmformat == Z_EROFS_COMPRESSION_LZMA &&
+	     map->m_llen >= EROFS_BLKSIZ)) {
 		err = z_erofs_get_extent_decompressedlen(&m);
 		if (!err)
 			map->m_flags |= EROFS_MAP_FULL_MAPPED;

include/linux/xz.h

@@ -233,6 +233,112 @@ XZ_EXTERN void xz_dec_reset(struct xz_dec *s);
  */
 XZ_EXTERN void xz_dec_end(struct xz_dec *s);
 
+/*
+ * Decompressor for MicroLZMA, an LZMA variant with a very minimal header.
+ * See xz_dec_microlzma_alloc() below for details.
+ *
+ * These functions aren't used or available in preboot code and thus aren't
+ * marked with XZ_EXTERN. This avoids warnings about static functions that
+ * are never defined.
+ */
+/**
+ * struct xz_dec_microlzma - Opaque type to hold the MicroLZMA decoder state
+ */
+struct xz_dec_microlzma;
+
+/**
+ * xz_dec_microlzma_alloc() - Allocate memory for the MicroLZMA decoder
+ * @mode        XZ_SINGLE or XZ_PREALLOC
+ * @dict_size   LZMA dictionary size. This must be at least 4 KiB and
+ *              at most 3 GiB.
+ *
+ * In contrast to xz_dec_init(), this function only allocates the memory
+ * and remembers the dictionary size. xz_dec_microlzma_reset() must be used
+ * before calling xz_dec_microlzma_run().
+ *
+ * The amount of allocated memory is a little less than 30 KiB with XZ_SINGLE.
+ * With XZ_PREALLOC also a dictionary buffer of dict_size bytes is allocated.
+ *
+ * On success, xz_dec_microlzma_alloc() returns a pointer to
+ * struct xz_dec_microlzma. If memory allocation fails or
+ * dict_size is invalid, NULL is returned.
+ *
+ * The compressed format supported by this decoder is a raw LZMA stream
+ * whose first byte (always 0x00) has been replaced with bitwise-negation
+ * of the LZMA properties (lc/lp/pb) byte. For example, if lc/lp/pb is
+ * 3/0/2, the first byte is 0xA2. This way the first byte can never be 0x00.
+ * Just like with LZMA2, lc + lp <= 4 must be true. The LZMA end-of-stream
+ * marker must not be used. The unused values are reserved for future use.
+ * This MicroLZMA header format was created for use in EROFS but may be used
+ * by others too.
+ */
+extern struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode,
+						       uint32_t dict_size);
+
+/**
+ * xz_dec_microlzma_reset() - Reset the MicroLZMA decoder state
+ * @s           Decoder state allocated using xz_dec_microlzma_alloc()
+ * @comp_size   Compressed size of the input stream
+ * @uncomp_size Uncompressed size of the input stream. A value smaller
+ *              than the real uncompressed size of the input stream can
+ *              be specified if uncomp_size_is_exact is set to false.
+ *              uncomp_size can never be set to a value larger than the
+ *              expected real uncompressed size because it would eventually
+ *              result in XZ_DATA_ERROR.
+ * @uncomp_size_is_exact  This is an int instead of bool to avoid
+ *              requiring stdbool.h. This should normally be set to true.
+ *              When this is set to false, error detection is weaker.
+ */
+extern void xz_dec_microlzma_reset(struct xz_dec_microlzma *s,
+				   uint32_t comp_size, uint32_t uncomp_size,
+				   int uncomp_size_is_exact);
+
+/**
+ * xz_dec_microlzma_run() - Run the MicroLZMA decoder
+ * @s           Decoder state initialized using xz_dec_microlzma_reset()
+ * @b:          Input and output buffers
+ *
+ * This works similarly to xz_dec_run() with a few important differences.
+ * Only the differences are documented here.
+ *
+ * The only possible return values are XZ_OK, XZ_STREAM_END, and
+ * XZ_DATA_ERROR. This function cannot return XZ_BUF_ERROR: if no progress
+ * is possible due to lack of input data or output space, this function will
+ * keep returning XZ_OK. Thus, the calling code must be written so that it
+ * will eventually provide input and output space matching (or exceeding)
+ * comp_size and uncomp_size arguments given to xz_dec_microlzma_reset().
+ * If the caller cannot do this (for example, if the input file is truncated
+ * or otherwise corrupt), the caller must detect this error by itself to
+ * avoid an infinite loop.
+ *
+ * If the compressed data seems to be corrupt, XZ_DATA_ERROR is returned.
+ * This can happen also when incorrect dictionary, uncompressed, or
+ * compressed sizes have been specified.
+ *
+ * With XZ_PREALLOC only: As an extra feature, b->out may be NULL to skip over
+ * uncompressed data. This way the caller doesn't need to provide a temporary
+ * output buffer for the bytes that will be ignored.
+ *
+ * With XZ_SINGLE only: In contrast to xz_dec_run(), the return value XZ_OK
+ * is also possible and thus XZ_SINGLE is actually a limited multi-call mode.
+ * After XZ_OK the bytes decoded so far may be read from the output buffer.
+ * It is possible to continue decoding but the variables b->out and b->out_pos
+ * MUST NOT be changed by the caller. Increasing the value of b->out_size is
+ * allowed to make more output space available; one doesn't need to provide
+ * space for the whole uncompressed data on the first call. The input buffer
+ * may be changed normally like with XZ_PREALLOC. This way input data can be
+ * provided from non-contiguous memory.
+ */
+extern enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s,
+					struct xz_buf *b);
+
+/**
+ * xz_dec_microlzma_end() - Free the memory allocated for the decoder state
+ * @s:          Decoder state allocated using xz_dec_microlzma_alloc().
+ *              If s is NULL, this function does nothing.
+ */
+extern void xz_dec_microlzma_end(struct xz_dec_microlzma *s);
+
 /*
  * Standalone build (userspace build or in-kernel build for boot time use)
  * needs a CRC32 implementation. For normal in-kernel use, kernel's own

include/trace/events/erofs.h

@@ -24,7 +24,7 @@ struct erofs_map_blocks;
 #define show_mflags(flags) __print_flags(flags, "",	\
 	{ EROFS_MAP_MAPPED,	"M" },			\
 	{ EROFS_MAP_META,	"I" },			\
-	{ EROFS_MAP_ZIPPED,	"Z" })
+	{ EROFS_MAP_ENCODED,	"E" })
 
 TRACE_EVENT(erofs_lookup,
 

lib/decompress_unxz.c

@@ -20,8 +20,8 @@
  *
  * The worst case for in-place decompression is that the beginning of
  * the file is compressed extremely well, and the rest of the file is
- * uncompressible. Thus, we must look for worst-case expansion when the
- * compressor is encoding uncompressible data.
+ * incompressible. Thus, we must look for worst-case expansion when the
+ * compressor is encoding incompressible data.
  *
  * The structure of the .xz file in case of a compressed kernel is as follows.
  * Sizes (as bytes) of the fields are in parenthesis.
@@ -58,7 +58,7 @@
  * uncompressed size of the payload is in practice never less than the
  * payload size itself. The LZMA2 format would allow uncompressed size
  * to be less than the payload size, but no sane compressor creates such
- * files. LZMA2 supports storing uncompressible data in uncompressed form,
+ * files. LZMA2 supports storing incompressible data in uncompressed form,
  * so there's never a need to create payloads whose uncompressed size is
  * smaller than the compressed size.
  *
@@ -167,8 +167,8 @@
  * memeq and memzero are not used much and any remotely sane implementation
  * is fast enough. memcpy/memmove speed matters in multi-call mode, but
  * the kernel image is decompressed in single-call mode, in which only
- * memcpy speed can matter and only if there is a lot of uncompressible data
- * (LZMA2 stores uncompressible chunks in uncompressed form). Thus, the
+ * memmove speed can matter and only if there is a lot of incompressible data
+ * (LZMA2 stores incompressible chunks in uncompressed form). Thus, the
  * functions below should just be kept small; it's probably not worth
  * optimizing for speed.
  */

lib/xz/Kconfig

@@ -39,6 +39,19 @@ config XZ_DEC_SPARC
 	default y
 	select XZ_DEC_BCJ
 
+config XZ_DEC_MICROLZMA
+	bool "MicroLZMA decoder"
+	default n
+	help
+	  MicroLZMA is a header format variant where the first byte
+	  of a raw LZMA stream (without the end of stream marker) has
+	  been replaced with a bitwise-negation of the lc/lp/pb
+	  properties byte. MicroLZMA was created to be used in EROFS
+	  but can be used by other things too where wasting minimal
+	  amount of space for headers is important.
+
+	  Unless you know that you need this, say N.
+
 endif
 
 config XZ_DEC_BCJ

lib/xz/xz_dec_lzma2.c

@@ -248,6 +248,10 @@ struct lzma2_dec {
 	 * before the first LZMA chunk.
 	 */
 	bool need_props;
+
+#ifdef XZ_DEC_MICROLZMA
+	bool pedantic_microlzma;
+#endif
 };
 
 struct xz_dec_lzma2 {
@@ -387,7 +391,14 @@ static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
 
 		*left -= copy_size;
 
-		memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
+		/*
+		 * If doing in-place decompression in single-call mode and the
+		 * uncompressed size of the file is larger than the caller
+		 * thought (i.e. it is invalid input!), the buffers below may
+		 * overlap and cause undefined behavior with memcpy().
+		 * With valid inputs memcpy() would be fine here.
+		 */
+		memmove(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
 		dict->pos += copy_size;
 
 		if (dict->full < dict->pos)
@@ -397,7 +408,11 @@ static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
 			if (dict->pos == dict->end)
 				dict->pos = 0;
 
-			memcpy(b->out + b->out_pos, b->in + b->in_pos,
+			/*
+			 * Like above but for multi-call mode: use memmove()
+			 * to avoid undefined behavior with invalid input.
+			 */
+			memmove(b->out + b->out_pos, b->in + b->in_pos,
 					copy_size);
 		}
 
@@ -408,6 +423,12 @@ static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
 	}
 }
 
+#ifdef XZ_DEC_MICROLZMA
+#	define DICT_FLUSH_SUPPORTS_SKIPPING true
+#else
+#	define DICT_FLUSH_SUPPORTS_SKIPPING false
+#endif
+
 /*
  * Flush pending data from dictionary to b->out. It is assumed that there is
  * enough space in b->out. This is guaranteed because caller uses dict_limit()
@@ -421,8 +442,19 @@ static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
 		if (dict->pos == dict->end)
 			dict->pos = 0;
 
-		memcpy(b->out + b->out_pos, dict->buf + dict->start,
-				copy_size);
+		/*
+		 * These buffers cannot overlap even if doing in-place
+		 * decompression because in multi-call mode dict->buf
+		 * has been allocated by us in this file; it's not
+		 * provided by the caller like in single-call mode.
+		 *
+		 * With MicroLZMA, b->out can be NULL to skip bytes that
+		 * the caller doesn't need. This cannot be done with XZ
+		 * because it would break BCJ filters.
+		 */
+		if (!DICT_FLUSH_SUPPORTS_SKIPPING || b->out != NULL)
+			memcpy(b->out + b->out_pos, dict->buf + dict->start,
+					copy_size);
 	}
 
 	dict->start = dict->pos;
@@ -488,7 +520,7 @@ static __always_inline void rc_normalize(struct rc_dec *rc)
  * functions so that the compiler is supposed to be able to more easily avoid
  * an extra branch. In this particular version of the LZMA decoder, this
  * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
- * on x86). Using a non-splitted version results in nicer looking code too.
+ * on x86). Using a non-split version results in nicer looking code too.
  *
  * NOTE: This must return an int. Do not make it return a bool or the speed
  * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
@@ -774,6 +806,7 @@ static void lzma_reset(struct xz_dec_lzma2 *s)
 	s->lzma.rep1 = 0;
 	s->lzma.rep2 = 0;
 	s->lzma.rep3 = 0;
+	s->lzma.len = 0;
 
 	/*
 	 * All probabilities are initialized to the same value. This hack
@@ -1157,8 +1190,6 @@ XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
 		}
 	}
 
-	s->lzma.len = 0;
-
 	s->lzma2.sequence = SEQ_CONTROL;
 	s->lzma2.need_dict_reset = true;
 
@@ -1174,3 +1205,140 @@ XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
 
 	kfree(s);
 }
+
+#ifdef XZ_DEC_MICROLZMA
+/* This is a wrapper struct to have a nice struct name in the public API. */
+struct xz_dec_microlzma {
+	struct xz_dec_lzma2 s;
+};
+
+enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s_ptr,
+				 struct xz_buf *b)
+{
+	struct xz_dec_lzma2 *s = &s_ptr->s;
+
+	/*
+	 * sequence is SEQ_PROPERTIES before the first input byte,
+	 * SEQ_LZMA_PREPARE until a total of five bytes have been read,
+	 * and SEQ_LZMA_RUN for the rest of the input stream.
+	 */
+	if (s->lzma2.sequence != SEQ_LZMA_RUN) {
+		if (s->lzma2.sequence == SEQ_PROPERTIES) {
+			/* One byte is needed for the props. */
+			if (b->in_pos >= b->in_size)
+				return XZ_OK;
+
+			/*
+			 * Don't increment b->in_pos here. The same byte is
+			 * also passed to rc_read_init() which will ignore it.
+			 */
+			if (!lzma_props(s, ~b->in[b->in_pos]))
+				return XZ_DATA_ERROR;
+
+			s->lzma2.sequence = SEQ_LZMA_PREPARE;
+		}
+
+		/*
+		 * xz_dec_microlzma_reset() doesn't validate the compressed
+		 * size so we do it here. We have to limit the maximum size
+		 * to avoid integer overflows in lzma2_lzma(). 3 GiB is a nice
+		 * round number and much more than users of this code should
+		 * ever need.
+		 */
+		if (s->lzma2.compressed < RC_INIT_BYTES
+				|| s->lzma2.compressed > (3U << 30))
+			return XZ_DATA_ERROR;
+
+		if (!rc_read_init(&s->rc, b))
+			return XZ_OK;
+
+		s->lzma2.compressed -= RC_INIT_BYTES;
+		s->lzma2.sequence = SEQ_LZMA_RUN;
+
+		dict_reset(&s->dict, b);
+	}
+
+	/* This is to allow increasing b->out_size between calls. */
+	if (DEC_IS_SINGLE(s->dict.mode))
+		s->dict.end = b->out_size - b->out_pos;
+
+	while (true) {
+		dict_limit(&s->dict, min_t(size_t, b->out_size - b->out_pos,
+					   s->lzma2.uncompressed));
+
+		if (!lzma2_lzma(s, b))
+			return XZ_DATA_ERROR;
+
+		s->lzma2.uncompressed -= dict_flush(&s->dict, b);
+
+		if (s->lzma2.uncompressed == 0) {
+			if (s->lzma2.pedantic_microlzma) {
+				if (s->lzma2.compressed > 0 || s->lzma.len > 0
+						|| !rc_is_finished(&s->rc))
+					return XZ_DATA_ERROR;
+			}
+
+			return XZ_STREAM_END;
+		}
+
+		if (b->out_pos == b->out_size)
+			return XZ_OK;
+
+		if (b->in_pos == b->in_size
+				&& s->temp.size < s->lzma2.compressed)
+			return XZ_OK;
+	}
+}
+
+struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode,
+						uint32_t dict_size)
+{
+	struct xz_dec_microlzma *s;
+
+	/* Restrict dict_size to the same range as in the LZMA2 code. */
+	if (dict_size < 4096 || dict_size > (3U << 30))
+		return NULL;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s == NULL)
+		return NULL;
+
+	s->s.dict.mode = mode;
+	s->s.dict.size = dict_size;
+
+	if (DEC_IS_MULTI(mode)) {
+		s->s.dict.end = dict_size;
+
+		s->s.dict.buf = vmalloc(dict_size);
+		if (s->s.dict.buf == NULL) {
+			kfree(s);
+			return NULL;
+		}
+	}
+
+	return s;
+}
+
+void xz_dec_microlzma_reset(struct xz_dec_microlzma *s, uint32_t comp_size,
+			    uint32_t uncomp_size, int uncomp_size_is_exact)
+{
+	/*
+	 * comp_size is validated in xz_dec_microlzma_run().
+	 * uncomp_size can safely be anything.
+	 */
+	s->s.lzma2.compressed = comp_size;
+	s->s.lzma2.uncompressed = uncomp_size;
+	s->s.lzma2.pedantic_microlzma = uncomp_size_is_exact;
+
+	s->s.lzma2.sequence = SEQ_PROPERTIES;
+	s->s.temp.size = 0;
+}
+
+void xz_dec_microlzma_end(struct xz_dec_microlzma *s)
+{
+	if (DEC_IS_MULTI(s->s.dict.mode))
+		vfree(s->s.dict.buf);
+
+	kfree(s);
+}
+#endif

lib/xz/xz_dec_stream.c

@@ -402,12 +402,12 @@ static enum xz_ret dec_stream_header(struct xz_dec *s)
 	 * we will accept other check types too, but then the check won't
 	 * be verified and a warning (XZ_UNSUPPORTED_CHECK) will be given.
 	 */
+	if (s->temp.buf[HEADER_MAGIC_SIZE + 1] > XZ_CHECK_MAX)
+		return XZ_OPTIONS_ERROR;
+
 	s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
 
 #ifdef XZ_DEC_ANY_CHECK
-	if (s->check_type > XZ_CHECK_MAX)
-		return XZ_OPTIONS_ERROR;
-
 	if (s->check_type > XZ_CHECK_CRC32)
 		return XZ_UNSUPPORTED_CHECK;
 #else

lib/xz/xz_dec_syms.c

@@ -15,8 +15,15 @@ EXPORT_SYMBOL(xz_dec_reset);
 EXPORT_SYMBOL(xz_dec_run);
 EXPORT_SYMBOL(xz_dec_end);
 
+#ifdef CONFIG_XZ_DEC_MICROLZMA
+EXPORT_SYMBOL(xz_dec_microlzma_alloc);
+EXPORT_SYMBOL(xz_dec_microlzma_reset);
+EXPORT_SYMBOL(xz_dec_microlzma_run);
+EXPORT_SYMBOL(xz_dec_microlzma_end);
+#endif
+
 MODULE_DESCRIPTION("XZ decompressor");
-MODULE_VERSION("1.0");
+MODULE_VERSION("1.1");
 MODULE_AUTHOR("Lasse Collin <lasse.collin@tukaani.org> and Igor Pavlov");
 
 /*

lib/xz/xz_private.h

@@ -37,6 +37,9 @@
 #		ifdef CONFIG_XZ_DEC_SPARC
 #			define XZ_DEC_SPARC
 #		endif
+#		ifdef CONFIG_XZ_DEC_MICROLZMA
+#			define XZ_DEC_MICROLZMA
+#		endif
 #		define memeq(a, b, size) (memcmp(a, b, size) == 0)
 #		define memzero(buf, size) memset(buf, 0, size)
 #	endif