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From:   Gao Xiang <xiang@kernel.org>
To:     linux-erofs@lists.ozlabs.org
Cc:     Chao Yu <chao@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Yue Hu <zbestahu@gmail.com>,
        Gao Xiang <hsiangkao@linux.alibaba.com>
Subject: [PATCH v3 2/3] erofs: introduce the secondary compression head
Date:   Sun, 10 Oct 2021 02:12:09 +0800
Message-Id: <20211009181209.23041-1-xiang@kernel.org>
In-Reply-To: <20211008200839.24541-3-xiang@kernel.org>
References: <20211008200839.24541-3-xiang@kernel.org>
MIME-Version: 1.0
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From: Gao Xiang <hsiangkao@linux.alibaba.com>

Previously, for each HEAD lcluster, it can be either HEAD or PLAIN
lcluster to indicate whether the whole pcluster is compressed or not.

In this patch, a new HEAD2 head type is introduced to specify another
compression algorithm other than the primary algorithm for each
compressed file, which can be used for upcoming LZMA compression and
LZ4 range dictionary compression for various data patterns.

It has been stayed in the EROFS roadmap for years. Complete it now!

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
v2: https://lore.kernel.org/r/20211008200839.24541-3-xiang@kernel.org
changes since v2:
 - simplify z_algorithmtype check suggested by Yue.

 fs/erofs/erofs_fs.h |  8 +++++---
 fs/erofs/zmap.c     | 38 ++++++++++++++++++++++++++------------
 2 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
index b0b23f41abc3..f579c8c78fff 100644
--- a/fs/erofs/erofs_fs.h
+++ b/fs/erofs/erofs_fs.h
@@ -21,11 +21,13 @@
 #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_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_COMPR_HEAD2)
 
 #define EROFS_SB_EXTSLOT_SIZE	16
 
@@ -314,9 +316,9 @@ struct z_erofs_map_header {
  */
 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
 };
 
diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c
index 9d9c26343dab..864d9d5474d5 100644
--- a/fs/erofs/zmap.c
+++ b/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;
 	}
@@ -189,7 +191,8 @@ 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;
@@ -446,7 +449,8 @@ 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:
-	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;
@@ -470,13 +474,18 @@ 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);
+		  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 ||
-	    !(vi->z_advise & Z_EROFS_ADVISE_BIG_PCLUSTER_1)) {
+	    ((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;
@@ -498,7 +507,8 @@ 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.
@@ -553,7 +563,8 @@ 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;
@@ -612,7 +623,8 @@ int z_erofs_map_blocks_iter(struct inode *inode,
 
 	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 (endoff >= m.clusterofs) {
 			m.headtype = m.type;
 			map->m_la = (m.lcn << lclusterbits) | m.clusterofs;
@@ -654,6 +666,8 @@ int z_erofs_map_blocks_iter(struct inode *inode,
 
 	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];
 
-- 
2.20.1