[PATCH] erofs-utils: mkfs: support `-Efragdedupe=inode`

[Gao Xiang]

If the entire inode can be deduplicated against an existing fragment,
simply reuse it.

Multi-threading can still be applied for `-Efragdedupe=inode` with
the current codebase:

Fedora Linux 39 (Workstation Edition) LiveCD results:
 -zlzma,level=6,dictsize=131072 -C65536 -Eall-fragments

   `-E^fragdedupe`         2,003,587,072 bytes (1880 MiB)
   `-Efragdedupe=inode`    1,970,577,408 bytes (1911 MiB)

Signed-off-by: Gao Xiang <hsiangkao at linux.alibaba.com>
---
 include/erofs/config.h |  8 +++++++-
 lib/compress.c         |  9 +++++++--
 mkfs/main.c            | 14 +++++++++++---
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/erofs/config.h b/include/erofs/config.h
index 47e4d00..92c1467 100644
--- a/include/erofs/config.h
+++ b/include/erofs/config.h
@@ -33,6 +33,12 @@ enum {
 	TIMESTAMP_CLAMPING,
 };
 
+enum {
+	FRAGDEDUPE_FULL,
+	FRAGDEDUPE_INODE,
+	FRAGDEDUPE_OFF,
+};
+
 #define EROFS_MAX_COMPR_CFGS		64
 
 struct erofs_compr_opts {
@@ -53,7 +59,7 @@ struct erofs_configure {
 	bool c_fragments;
 	bool c_all_fragments;
 	bool c_dedupe;
-	bool c_nofragdedupe;
+	char c_fragdedupe;
 	bool c_ignore_mtime;
 	bool c_showprogress;
 	bool c_extra_ea_name_prefixes;
diff --git a/lib/compress.c b/lib/compress.c
index fd4c241..b038156 100644
--- a/lib/compress.c
+++ b/lib/compress.c
@@ -1527,12 +1527,17 @@ void *erofs_begin_compressed_file(struct erofs_inode *inode, int fd, u64 fpos)
 	 * parts into the packed inode.
 	 */
 	if (cfg.c_fragments && !erofs_is_packed_inode(inode) &&
-	    !cfg.c_nofragdedupe) {
+	    cfg.c_fragdedupe != FRAGDEDUPE_OFF) {
 		ret = z_erofs_fragments_dedupe(inode, fd, &ictx->tof_chksum);
 		if (ret < 0)
 			goto err_free_ictx;
-	}
 
+		if (cfg.c_fragdedupe == FRAGDEDUPE_INODE &&
+		    inode->fragment_size < inode->i_size) {
+			erofs_dbg("Discard the sub-inode tail fragment @ nid %llu", inode->nid);
+			inode->fragment_size = 0;
+		}
+	}
 	ictx->inode = inode;
 	ictx->fpos = fpos;
 	init_list_head(&ictx->extents);
diff --git a/mkfs/main.c b/mkfs/main.c
index 27c333c..7fbbc7e 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -309,9 +309,17 @@ static int erofs_mkfs_feat_set_dedupe(bool en, const char *val,
 static int erofs_mkfs_feat_set_fragdedupe(bool en, const char *val,
 					  unsigned int vallen)
 {
-	if (vallen)
-		return -EINVAL;
-	cfg.c_nofragdedupe = !en;
+	if (!en) {
+		if (vallen)
+			return -EINVAL;
+		cfg.c_fragdedupe = FRAGDEDUPE_OFF;
+	} else if (vallen == sizeof("inode") - 1 &&
+		   !memcmp(val, "inode", vallen)) {
+		cfg.c_fragdedupe = FRAGDEDUPE_INODE;
+	} else {
+		cfg.c_fragdedupe = FRAGDEDUPE_FULL;
+
+	}
 	return 0;
 }
 
-- 
2.43.5