erofs-utils: lib: add API to get pathname of EROFS inode

* General-purpose erofs_get_pathname function utilizing erofs_iterate_dir,
  with recursion and a reused context to avoid overflowing the stack.
  Recommended buffer size is PATH_MAX. Zero-filling the buffer is not
  necessary.
* dump: PATH_MAX+1 is not required since the definition of PATH_MAX is
  "chars in a path name including nul".
* Return err from erofs_iterate_dir instead of hardcoded 0, to allow
  breaking the iteration by the callback using a non-zero return code.

Link: https://lore.kernel.org/r/CABjEcnE84FNBgiHFk6Q+V3d-4L-93bUFDkdfN4ftPX19kpC=ww@mail.gmail.com
Signed-off-by: Igor Ostapenko <igoreisberg@gmail.com>
[ Gao Xiang: let's use NID instead of (struct erofs_inode *). ]
Signed-off-by: Gao Xiang <xiang@kernel.org>

1 files changed, 3 insertions, 69 deletions

diff --git a/dump/main.c b/dump/main.c
index 7f3f743..997460c 100644
--- a/dump/main.c
+++ b/dump/main.c
@@ -328,71 +328,6 @@ static inline int erofs_checkdirent(struct erofs_dirent *de,
 	return dname_len;
 }
 
-static int erofs_get_pathname(erofs_nid_t nid, erofs_nid_t parent_nid,
-		erofs_nid_t target, char *path, unsigned int pos)
-{
-	int err;
-	erofs_off_t offset;
-	char buf[EROFS_BLKSIZ];
-	struct erofs_inode inode = { .nid = nid };
-
-	path[pos++] = '/';
-	if (target == sbi.root_nid)
-		return 0;
-
-	err = erofs_read_inode_from_disk(&inode);
-	if (err) {
-		erofs_err("read inode failed @ nid %llu", nid | 0ULL);
-		return err;
-	}
-
-	offset = 0;
-	while (offset < inode.i_size) {
-		erofs_off_t maxsize = min_t(erofs_off_t,
-					inode.i_size - offset, EROFS_BLKSIZ);
-		struct erofs_dirent *de = (void *)buf;
-		struct erofs_dirent *end;
-		unsigned int nameoff;
-
-		err = erofs_pread(&inode, buf, maxsize, offset);
-		if (err)
-			return err;
-
-		nameoff = le16_to_cpu(de->nameoff);
-		end = (void *)buf + nameoff;
-		while (de < end) {
-			const char *dname;
-			int len;
-
-			nameoff = le16_to_cpu(de->nameoff);
-			dname = (char *)buf + nameoff;
-			len = erofs_checkdirent(de, end, maxsize, dname);
-			if (len < 0)
-				return len;
-
-			if (le64_to_cpu(de->nid) == target) {
-				memcpy(path + pos, dname, len);
-				path[pos + len] = '\0';
-				return 0;
-			}
-
-			if (de->file_type == EROFS_FT_DIR &&
-			    le64_to_cpu(de->nid) != parent_nid &&
-			    le64_to_cpu(de->nid) != nid) {
-				memcpy(path + pos, dname, len);
-				err = erofs_get_pathname(le64_to_cpu(de->nid),
-						nid, target, path, pos + len);
-				if (!err)
-					return 0;
-				memset(path + pos, 0, len);
-			}
-			++de;
-		}
-		offset += maxsize;
-	}
-	return -1;
-}
-
 static int erofsdump_map_blocks(struct erofs_inode *inode,
 		struct erofs_map_blocks *map, int flags)
 {
@@ -411,7 +346,7 @@ static void erofsdump_show_fileinfo(bool show_extent)
 	erofs_off_t size;
 	u16 access_mode;
 	struct erofs_inode inode = { .nid = dumpcfg.nid };
-	char path[PATH_MAX + 1] = {0};
+	char path[PATH_MAX];
 	char access_mode_str[] = "rwxrwxrwx";
 	char timebuf[128] = {0};
 	unsigned int extent_count = 0;
@@ -441,8 +376,7 @@ static void erofsdump_show_fileinfo(bool show_extent)
 		return;
 	}
 
-	err = erofs_get_pathname(sbi.root_nid, sbi.root_nid,
-				 inode.nid, path, 0);
+	err = erofs_get_pathname(dumpcfg.nid, path, sizeof(path));
 	if (err < 0) {
 		erofs_err("file path not found @ nid %llu", inode.nid | 0ULL);
 		return;
@@ -598,7 +532,7 @@ static void erofsdump_print_statistic(void)
 		.cb = erofsdump_dirent_iter,
 		.de_nid = sbi.root_nid,
 		.dname = "",
-		.de_namelen = 0
+		.de_namelen = 0,
 	};
 
 	err = erofsdump_readdir(&ctx);