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Date: Sun, 30 Jul 2023 20:53:04 +0800
From: Chao Yu <chao@...nel.org>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>,
linux-erofs@...ts.ozlabs.org
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] erofs: DEFLATE compression support
On 2023/7/16 17:19, Gao Xiang wrote:
> Add DEFLATE compression as the 3rd supported algorithm.
>
> DEFLATE is a popular generic-purpose compression algorithm for quite
> long time (many advanced formats like gzip, zlib, zip, png are all
> based on that) as Apple documentation written "If you require
> interoperability with non-Apple devices, use COMPRESSION_ZLIB. [1]".
>
> Due to its popularity, there are several hardware on-market DEFLATE
> accelerators, such as (s390) DFLTCC, (Intel) IAA/QAT, (HiSilicon) ZIP
> accelerator, etc. In addition, there are also several high-performence
> IP cores and even open-source FPGA approches available for DEFLATE.
> Therefore, it's useful to support DEFLATE compression in order to find
> a way to utilize these accelerators for asynchronous I/Os and get
> benefits from these later.
>
> Besides, it's a good choice to trade off between compression ratios
> and performance compared to LZ4 and LZMA. The DEFLATE core format is
> simple as well as easy to understand, therefore the code size of its
> decompressor is small even for the bootloader use cases. The runtime
> memory consumption is quite limited too (e.g. 32K + ~7K for each zlib
> stream). As usual, EROFS ourperforms similar approaches too.
>
> Alternatively, DEFLATE could still be used for some specific files
> since EROFS supports multiple compression algorithms in one image.
>
> [1] https://developer.apple.com/documentation/compression/compression_algorithm
> ---
> changes since v3:
> - fix 'insz' mis-calculation, which leads to failure on 4k pclusters.
>
> fs/erofs/Kconfig | 15 ++
> fs/erofs/Makefile | 1 +
> fs/erofs/compress.h | 2 +
> fs/erofs/decompressor.c | 6 +
> fs/erofs/decompressor_deflate.c | 250 ++++++++++++++++++++++++++++++++
> fs/erofs/erofs_fs.h | 7 +
> fs/erofs/internal.h | 20 +++
> fs/erofs/super.c | 10 ++
> fs/erofs/zmap.c | 5 +-
> 9 files changed, 314 insertions(+), 2 deletions(-)
> create mode 100644 fs/erofs/decompressor_deflate.c
>
> diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
> index f259d92c9720..56a99ba8ce22 100644
> --- a/fs/erofs/Kconfig
> +++ b/fs/erofs/Kconfig
> @@ -99,6 +99,21 @@ config EROFS_FS_ZIP_LZMA
>
> If unsure, say N.
>
> +config EROFS_FS_ZIP_DEFLATE
> + bool "EROFS DEFLATE compressed data support"
> + depends on EROFS_FS_ZIP
> + select ZLIB_INFLATE
> + help
> + Saying Y here includes support for reading EROFS file systems
> + containing DEFLATE compressed data. It gives better compression
> + ratios than the default LZ4 format, while it costs more CPU
> + overhead.
> +
> + DEFLATE support is an experimental feature for now and so most
> + file systems will be readable without selecting this option.
> +
> + If unsure, say N.
> +
> config EROFS_FS_ONDEMAND
> bool "EROFS fscache-based on-demand read support"
> depends on CACHEFILES_ONDEMAND && (EROFS_FS=m && FSCACHE || EROFS_FS=y && FSCACHE=y)
> diff --git a/fs/erofs/Makefile b/fs/erofs/Makefile
> index a3a98fc3e481..994d0b9deddf 100644
> --- a/fs/erofs/Makefile
> +++ b/fs/erofs/Makefile
> @@ -5,4 +5,5 @@ erofs-objs := super.o inode.o data.o namei.o dir.o utils.o sysfs.o
> erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
> erofs-$(CONFIG_EROFS_FS_ZIP) += decompressor.o zmap.o zdata.o pcpubuf.o
> erofs-$(CONFIG_EROFS_FS_ZIP_LZMA) += decompressor_lzma.o
> +erofs-$(CONFIG_EROFS_FS_ZIP_DEFLATE) += decompressor_deflate.o
> erofs-$(CONFIG_EROFS_FS_ONDEMAND) += fscache.o
> diff --git a/fs/erofs/compress.h b/fs/erofs/compress.h
> index b1b846504027..349c3316ae6b 100644
> --- a/fs/erofs/compress.h
> +++ b/fs/erofs/compress.h
> @@ -94,4 +94,6 @@ extern const struct z_erofs_decompressor erofs_decompressors[];
> /* prototypes for specific algorithms */
> int z_erofs_lzma_decompress(struct z_erofs_decompress_req *rq,
> struct page **pagepool);
> +int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,
> + struct page **pagepool);
> #endif
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index cfad1eac7fd9..332ec5f74002 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -379,4 +379,10 @@ const struct z_erofs_decompressor erofs_decompressors[] = {
> .name = "lzma"
> },
> #endif
> +#ifdef CONFIG_EROFS_FS_ZIP_DEFLATE
> + [Z_EROFS_COMPRESSION_DEFLATE] = {
> + .decompress = z_erofs_deflate_decompress,
> + .name = "deflate"
> + },
> +#endif
> };
> diff --git a/fs/erofs/decompressor_deflate.c b/fs/erofs/decompressor_deflate.c
> new file mode 100644
> index 000000000000..c34e29b15465
> --- /dev/null
> +++ b/fs/erofs/decompressor_deflate.c
> @@ -0,0 +1,250 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +#include <linux/module.h>
> +#include <linux/zlib.h>
> +#include "compress.h"
> +
> +struct z_erofs_deflate {
> + struct z_erofs_deflate *next;
> + struct z_stream_s z;
> + u8 bounce[PAGE_SIZE];
> +};
> +
> +static DEFINE_SPINLOCK(z_erofs_deflate_lock);
> +static unsigned int z_erofs_deflate_nstrms, z_erofs_deflate_avail_strms;
> +static struct z_erofs_deflate *z_erofs_deflate_head;
> +static DECLARE_WAIT_QUEUE_HEAD(z_erofs_deflate_wq);
> +
> +module_param_named(deflate_streams, z_erofs_deflate_nstrms, uint, 0444);
> +
> +void z_erofs_deflate_exit(void)
> +{
> + /* there should be no running fs instance */
> + while (z_erofs_deflate_avail_strms) {
> + struct z_erofs_deflate *strm;
> +
> + spin_lock(&z_erofs_deflate_lock);
> + strm = z_erofs_deflate_head;
> + if (!strm) {
> + spin_unlock(&z_erofs_deflate_lock);
> + DBG_BUGON(1);
> + return;
> + }
> + z_erofs_deflate_head = NULL;
> + spin_unlock(&z_erofs_deflate_lock);
> +
> + while (strm) {
> + struct z_erofs_deflate *n = strm->next;
> +
> + vfree(strm->z.workspace);
> + kfree(strm);
> + --z_erofs_deflate_avail_strms;
> + strm = n;
> + }
> + }
> +}
> +
> +int __init z_erofs_deflate_init(void)
> +{
> + /* by default, use # of possible CPUs instead */
> + if (!z_erofs_deflate_nstrms)
> + z_erofs_deflate_nstrms = num_possible_cpus();
> +
> + for (; z_erofs_deflate_avail_strms < z_erofs_deflate_nstrms;
> + ++z_erofs_deflate_avail_strms) {
> + struct z_erofs_deflate *strm;
> +
> + strm = kzalloc(sizeof(*strm), GFP_KERNEL);
> + if (!strm)
> + goto out_failed;
> +
> + /* XXX: in-kernel zlib cannot shrink windowbits currently */
> + strm->z.workspace = vmalloc(zlib_inflate_workspacesize());
> + if (!strm->z.workspace)
kfree(strm)?
Thanks,
> + goto out_failed;
> +
> + spin_lock(&z_erofs_deflate_lock);
> + strm->next = z_erofs_deflate_head;
> + z_erofs_deflate_head = strm;
> + spin_unlock(&z_erofs_deflate_lock);
> + }
> + return 0;
> +
> +out_failed:
> + pr_err("failed to allocate zlib workspace\n");
> + z_erofs_deflate_exit();
> + return -ENOMEM;
> +}
> +
> +int z_erofs_load_deflate_config(struct super_block *sb,
> + struct erofs_super_block *dsb,
> + struct z_erofs_deflate_cfgs *dfl, int size)
> +{
> + if (!dfl || size < sizeof(struct z_erofs_deflate_cfgs)) {
> + erofs_err(sb, "invalid deflate cfgs, size=%u", size);
> + return -EINVAL;
> + }
> +
> + if (dfl->windowbits > MAX_WBITS) {
> + erofs_err(sb, "unsupported windowbits %u", dfl->windowbits);
> + return -EOPNOTSUPP;
> + }
> +
> + erofs_info(sb, "EXPERIMENTAL DEFLATE feature in use. Use at your own risk!");
> + return 0;
> +}
> +
> +int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,
> + struct page **pagepool)
> +{
> + static u8 skipped[PAGE_SIZE];
> + 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;
> + struct super_block *sb = rq->sb;
> + unsigned int insz, outsz, pofs;
> + struct z_erofs_deflate *strm;
> + u8 *kin, *kout = NULL;
> + bool bounced = false;
> + int no = -1, ni = 0, j = 0, zerr, err;
> +
> + /* 1. get the exact DEFLATE compressed size */
> + kin = kmap_local_page(*rq->in);
> + err = z_erofs_fixup_insize(rq, kin + rq->pageofs_in,
> + min_t(unsigned int, rq->inputsize,
> + sb->s_blocksize - rq->pageofs_in));
> + if (err) {
> + kunmap_local(kin);
> + return err;
> + }
> +
> + /* 2. get an available DEFLATE context */
> +again:
> + spin_lock(&z_erofs_deflate_lock);
> + strm = z_erofs_deflate_head;
> + if (!strm) {
> + spin_unlock(&z_erofs_deflate_lock);
> + wait_event(z_erofs_deflate_wq, READ_ONCE(z_erofs_deflate_head));
> + goto again;
> + }
> + z_erofs_deflate_head = strm->next;
> + spin_unlock(&z_erofs_deflate_lock);
> +
> + /* 3. multi-call decompress */
> + insz = rq->inputsize;
> + outsz = rq->outputsize;
> + zerr = zlib_inflateInit2(&strm->z, -MAX_WBITS);
> + if (zerr != Z_OK) {
> + err = -EIO;
> + goto failed_zinit;
> + }
> +
> + pofs = rq->pageofs_out;
> + strm->z.avail_in = min_t(u32, insz, PAGE_SIZE - rq->pageofs_in);
> + insz -= strm->z.avail_in;
> + strm->z.next_in = kin + rq->pageofs_in;
> + strm->z.avail_out = 0;
> +
> + while (1) {
> + if (!strm->z.avail_out) {
> + if (++no >= nrpages_out || !outsz) {
> + erofs_err(sb, "insufficient space for decompressed data");
> + err = -EFSCORRUPTED;
> + break;
> + }
> +
> + if (kout)
> + kunmap_local(kout);
> + strm->z.avail_out = min_t(u32, outsz, PAGE_SIZE - pofs);
> + outsz -= strm->z.avail_out;
> + if (rq->out[no] && rq->fillgaps) /* deduped data */
> + rq->out[no] = erofs_allocpage(pagepool,
> + GFP_KERNEL | __GFP_NOFAIL);
> + if (rq->out[no]) {
> + kout = kmap_local_page(rq->out[no]) + pofs;
> + strm->z.next_out = kout;
> + } else {
> + kout = NULL;
> + strm->z.next_out = skipped;
> + }
> + pofs = 0;
> + }
> +
> + if (!strm->z.avail_in && insz) {
> + if (++ni >= nrpages_in) {
> + erofs_err(sb, "compressed data was invalid");
> + err = -EFSCORRUPTED;
> + break;
> + }
> +
> + if (kout) { /* unlike kmap(), take care of the orders */
> + j = strm->z.next_out - kout;
> + kunmap_local(kout);
> + }
> + kunmap_local(kin);
> + strm->z.avail_in = min_t(u32, insz, PAGE_SIZE);
> + insz -= strm->z.avail_in;
> + kin = kmap_local_page(rq->in[ni]);
> + strm->z.next_in = kin;
> + bounced = false;
> + if (kout) {
> + kout = kmap_local_page(rq->out[no]);
> + strm->z.next_out = kout + j;
> + }
> + }
> +
> + /*
> + * Handle overlapping: Use bounced buffer if the compressed
> + * data is under processing; Or use short-lived pages from the
> + * on-stack pagepool where pages share among the same request
> + * and not _all_ inplace I/O pages are needed to be doubled.
> + */
> + if (!bounced && rq->out[no] == rq->in[ni]) {
> + memcpy(strm->bounce, strm->z.next_in, strm->z.avail_in);
> + strm->z.next_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(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;
> + }
> +
> + zerr = zlib_inflate(&strm->z, Z_SYNC_FLUSH);
> + if (zerr != Z_OK || !outsz) {
> + if (zerr == Z_OK && rq->partial_decoding)
> + break;
> + if (zerr == Z_STREAM_END && !outsz)
> + break;
> + erofs_err(sb, "failed to decompress %d in[%u] out[%u]",
> + zerr, rq->inputsize, rq->outputsize);
> + err = -EFSCORRUPTED;
> + break;
> + }
> + }
> +
> + if (zlib_inflateEnd(&strm->z) != Z_OK && !err)
> + err = -EIO;
> + if (kout)
> + kunmap_local(kout);
> +failed_zinit:
> + if (kin)
> + kunmap_local(kin);
> + /* 4. push back DEFLATE stream context to the global list */
> + spin_lock(&z_erofs_deflate_lock);
> + strm->next = z_erofs_deflate_head;
> + z_erofs_deflate_head = strm;
> + spin_unlock(&z_erofs_deflate_lock);
> + wake_up(&z_erofs_deflate_wq);
> + return err;
> +}
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 2c7b16e340fe..364f51171c13 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -289,6 +289,7 @@ struct erofs_dirent {
> enum {
> Z_EROFS_COMPRESSION_LZ4 = 0,
> Z_EROFS_COMPRESSION_LZMA = 1,
> + Z_EROFS_COMPRESSION_DEFLATE = 2,
> Z_EROFS_COMPRESSION_MAX
> };
> #define Z_EROFS_ALL_COMPR_ALGS ((1 << Z_EROFS_COMPRESSION_MAX) - 1)
> @@ -309,6 +310,12 @@ struct z_erofs_lzma_cfgs {
>
> #define Z_EROFS_LZMA_MAX_DICT_SIZE (8 * Z_EROFS_PCLUSTER_MAX_SIZE)
>
> +/* 6 bytes (+ length field = 8 bytes) */
> +struct z_erofs_deflate_cfgs {
> + u8 windowbits; /* 8..15 for DEFLATE */
> + u8 reserved[5];
> +} __packed;
> +
> /*
> * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
> * e.g. for 4k logical cluster size, 4B if compacted 2B is off;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 36e32fa542f0..fb45855cfd5d 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -519,6 +519,26 @@ static inline int z_erofs_load_lzma_config(struct super_block *sb,
> }
> #endif /* !CONFIG_EROFS_FS_ZIP_LZMA */
>
> +#ifdef CONFIG_EROFS_FS_ZIP_DEFLATE
> +int __init z_erofs_deflate_init(void);
> +void z_erofs_deflate_exit(void);
> +int z_erofs_load_deflate_config(struct super_block *sb,
> + struct erofs_super_block *dsb,
> + struct z_erofs_deflate_cfgs *dfl, int size);
> +#else
> +static inline int z_erofs_deflate_init(void) { return 0; }
> +static inline int z_erofs_deflate_exit(void) { return 0; }
> +static inline int z_erofs_load_deflate_config(struct super_block *sb,
> + struct erofs_super_block *dsb,
> + struct z_erofs_deflate_cfgs *dfl, int size) {
> + if (dfl) {
> + erofs_err(sb, "deflate algorithm isn't enabled");
> + return -EINVAL;
> + }
> + return 0;
> +}
> +#endif /* !CONFIG_EROFS_FS_ZIP_DEFLATE */
> +
> #ifdef CONFIG_EROFS_FS_ONDEMAND
> int erofs_fscache_register_fs(struct super_block *sb);
> void erofs_fscache_unregister_fs(struct super_block *sb);
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 9d6a3c6158bd..832f9fdef712 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -201,6 +201,9 @@ static int erofs_load_compr_cfgs(struct super_block *sb,
> case Z_EROFS_COMPRESSION_LZMA:
> ret = z_erofs_load_lzma_config(sb, dsb, data, size);
> break;
> + case Z_EROFS_COMPRESSION_DEFLATE:
> + ret = z_erofs_load_deflate_config(sb, dsb, data, size);
> + break;
> default:
> DBG_BUGON(1);
> ret = -EFAULT;
> @@ -966,6 +969,10 @@ static int __init erofs_module_init(void)
> if (err)
> goto lzma_err;
>
> + err = z_erofs_deflate_init();
> + if (err)
> + goto deflate_err;
> +
> erofs_pcpubuf_init();
> err = z_erofs_init_zip_subsystem();
> if (err)
> @@ -986,6 +993,8 @@ static int __init erofs_module_init(void)
> sysfs_err:
> z_erofs_exit_zip_subsystem();
> zip_err:
> + z_erofs_deflate_exit();
> +deflate_err:
> z_erofs_lzma_exit();
> lzma_err:
> erofs_exit_shrinker();
> @@ -1003,6 +1012,7 @@ static void __exit erofs_module_exit(void)
>
> erofs_exit_sysfs();
> z_erofs_exit_zip_subsystem();
> + z_erofs_deflate_exit();
> z_erofs_lzma_exit();
> erofs_exit_shrinker();
> kmem_cache_destroy(erofs_inode_cachep);
> diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
> index 1909ddafd9c7..7b55111fd533 100644
> --- a/fs/erofs/zmap.c
> +++ b/fs/erofs/zmap.c
> @@ -561,8 +561,9 @@ static int z_erofs_do_map_blocks(struct inode *inode,
>
> if ((flags & EROFS_GET_BLOCKS_FIEMAP) ||
> ((flags & EROFS_GET_BLOCKS_READMORE) &&
> - map->m_algorithmformat == Z_EROFS_COMPRESSION_LZMA &&
> - map->m_llen >= i_blocksize(inode))) {
> + (map->m_algorithmformat == Z_EROFS_COMPRESSION_LZMA ||
> + map->m_algorithmformat == Z_EROFS_COMPRESSION_DEFLATE) &&
> + map->m_llen >= i_blocksize(inode))) {
> err = z_erofs_get_extent_decompressedlen(&m);
> if (!err)
> map->m_flags |= EROFS_MAP_FULL_MAPPED;
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