Defined option "posix_nlink" to compute a Posix compliant st_nlink

When the mount option "posix_nlink" is used, the number of links
returned by stat complies with Posix : the legacy 8.3 names are not
taken into account, and the subdirectories are taken into account
for directories. This causes some overhead for recomputing the
number of links.

include/ntfs-3g/dir.h

@@ -117,6 +117,7 @@ int ntfs_get_ntfs_dos_name(ntfs_inode *ni, ntfs_inode *dir_ni,
 int ntfs_set_ntfs_dos_name(ntfs_inode *ni, ntfs_inode *dir_ni,
 			const char *value, size_t size,	int flags);
 int ntfs_remove_ntfs_dos_name(ntfs_inode *ni, ntfs_inode *dir_ni);
+int ntfs_dir_link_cnt(ntfs_inode *ni);
 
 #if CACHE_INODE_SIZE
 

libntfs-3g/dir.c

@@ -2792,3 +2792,82 @@ int ntfs_remove_ntfs_dos_name(ntfs_inode *ni, ntfs_inode *dir_ni)
 	}
 	return (res);
 }
+
+/*
+ *		Increment the count of subdirectories
+ *		(excluding entries with a short name)
+ */
+
+static int nlink_increment(void *nlink_ptr,
+			const ntfschar *name __attribute__((unused)),
+			const int len __attribute__((unused)),
+			const int type,
+			const s64 pos __attribute__((unused)),
+			const MFT_REF mref __attribute__((unused)),
+			const unsigned int dt_type)
+{
+	if ((dt_type == NTFS_DT_DIR) && (type != FILE_NAME_DOS))
+		(*((int*)nlink_ptr))++;
+	return (0);
+}
+
+/*
+ *		Compute the number of hard links according to Posix
+ *	For a directory count the subdirectories whose name is not
+ *		a short one, but count "." and ".."
+ *	Otherwise count the names, excluding the short ones.
+ *
+ *	if there is an error, a null count is returned.
+ */
+
+int ntfs_dir_link_cnt(ntfs_inode *ni)
+{
+	ntfs_attr_search_ctx *actx;
+	FILE_NAME_ATTR *fn;
+	s64 pos;
+	int err = 0;
+	int nlink = 0;
+
+	if (!ni) {
+		ntfs_log_error("Invalid argument.\n");
+		errno = EINVAL;
+		goto err_out;
+	}
+	if (ni->nr_extents == -1)
+		ni = ni->base_ni;
+	if (ni->mrec->flags & MFT_RECORD_IS_DIRECTORY) {
+		/*
+		 * Directory : scan the directory and count
+		 * subdirectories whose name is not DOS-only.
+		 * The directory names are ignored, but "." and ".."
+		 * are taken into account.
+		 */
+		pos = 0;
+		err = ntfs_readdir(ni, &pos, &nlink, nlink_increment);
+		if (err)
+			nlink = 0;
+	} else {
+		/*
+		 * Non-directory : search for FILE_NAME attributes,
+		 * and count those which are not DOS-only ones.
+		 */
+		actx = ntfs_attr_get_search_ctx(ni, NULL);
+		if (!actx)
+			goto err_out;
+		while (!(err = ntfs_attr_lookup(AT_FILE_NAME, AT_UNNAMED, 0,
+					CASE_SENSITIVE, 0, NULL, 0, actx))) {
+			fn = (FILE_NAME_ATTR*)((u8*)actx->attr +
+					le16_to_cpu(actx->attr->value_offset));
+			if (fn->file_name_type != FILE_NAME_DOS)
+				nlink++;
+		}
+		if (err && (errno != ENOENT))
+			nlink = 0;
+		ntfs_attr_put_search_ctx(actx);
+	}
+	if (!nlink)
+		ntfs_log_perror("Failed to compute nlink of inode %lld",
+			(long long)ni->mft_no);
+err_out :
+	return (nlink);
+}

src/lowntfs-3g.c

@@ -708,6 +708,9 @@ static int ntfs_fuse_getstat(struct SECURITY_CONTEXT *scx,
 	memset(stbuf, 0, sizeof(struct stat));
 	withusermapping = (scx->mapping[MAPUSERS] != (struct MAPPING*)NULL);
 	stbuf->st_nlink = le16_to_cpu(ni->mrec->link_count);
+	if (ctx->posix_nlink
+	    && !(ni->flags & FILE_ATTR_REPARSE_POINT))
+		stbuf->st_nlink = ntfs_dir_link_cnt(ni);
 	if ((ni->mrec->flags & MFT_RECORD_IS_DIRECTORY)
 	    || (ni->flags & FILE_ATTR_REPARSE_POINT)) {
 		if (ni->flags & FILE_ATTR_REPARSE_POINT) {
@@ -770,6 +773,7 @@ static int ntfs_fuse_getstat(struct SECURITY_CONTEXT *scx,
 			}
 			stbuf->st_size = ni->data_size;
 			stbuf->st_blocks = ni->allocated_size >> 9;
+			if (!ctx->posix_nlink)
 				stbuf->st_nlink = 1;	/* Make find(1) work */
 		}
 	} else {

src/ntfs-3g.8.in

@@ -250,6 +250,13 @@ they do not appear in Windows directory displays either.
 When a file is renamed or linked with a new name, the hidden flag is
 adjusted to the latest name.
 .TP
+.B posix_nlink
+Compute the count of hard links of a file or directory according to
+the Posix specifications. When this option is not set, a count of 1
+is set for directories, and the short name of files is accounted for.
+Using the option entails some penalty as the count is not stored and
+has to be computed.
+.TP
 .B windows_names
 This option prevents files, directories and extended attributes to be
 created with a name not allowed by windows, because

src/ntfs-3g.c

@@ -790,6 +790,9 @@ static int ntfs_fuse_getattr(const char *org_path, struct stat *stbuf)
 	}
 #endif
 	stbuf->st_nlink = le16_to_cpu(ni->mrec->link_count);
+	if (ctx->posix_nlink
+	    && !(ni->flags & FILE_ATTR_REPARSE_POINT))
+		stbuf->st_nlink = ntfs_dir_link_cnt(ni);
 
 	if (((ni->mrec->flags & MFT_RECORD_IS_DIRECTORY)
 		|| (ni->flags & FILE_ATTR_REPARSE_POINT))
@@ -852,6 +855,7 @@ static int ntfs_fuse_getattr(const char *org_path, struct stat *stbuf)
 			}
 			stbuf->st_size = ni->data_size;
 			stbuf->st_blocks = ni->allocated_size >> 9;
+			if (!ctx->posix_nlink)
 				stbuf->st_nlink = 1;	/* Make find(1) work */
 		}
 	} else {

src/ntfs-3g_common.c

@@ -1,7 +1,7 @@
 /**
  * ntfs-3g_common.c - Common definitions for ntfs-3g and lowntfs-3g.
  *
- * Copyright (c) 2010-2019 Jean-Pierre Andre
+ * Copyright (c) 2010-2020 Jean-Pierre Andre
  * Copyright (c) 2010      Erik Larsson
  *
  * This program/include file is free software; you can redistribute it and/or
@@ -126,6 +126,7 @@ const struct DEFOPTION optionlist[] = {
 	{ "usermapping", OPT_USERMAPPING, FLGOPT_STRING },
 	{ "xattrmapping", OPT_XATTRMAPPING, FLGOPT_STRING },
 	{ "efs_raw", OPT_EFS_RAW, FLGOPT_BOGUS },
+	{ "posix_nlink", OPT_POSIX_NLINK, FLGOPT_BOGUS },
 	{ (const char*)NULL, 0, 0 } /* end marker */
 } ;
 
@@ -492,6 +493,9 @@ char *parse_mount_options(ntfs_fuse_context_t *ctx,
 				ctx->efs_raw = TRUE;
 				break;
 #endif /* HAVE_SETXATTR */
+			case OPT_POSIX_NLINK :
+				ctx->posix_nlink = TRUE;
+				break;
 			case OPT_FSNAME : /* Filesystem name. */
 			/*
 			 * We need this to be able to check whether filesystem

src/ntfs-3g_common.h

@@ -92,6 +92,7 @@ enum {
 	OPT_USERMAPPING,
 	OPT_XATTRMAPPING,
 	OPT_EFS_RAW,
+	OPT_POSIX_NLINK,
 } ;
 
 			/* Option flags */
@@ -153,6 +154,7 @@ typedef struct {
 	BOOL no_detach;
 	BOOL blkdev;
 	BOOL mounted;
+	BOOL posix_nlink;
 #ifdef HAVE_SETXATTR	/* extended attributes interface required */
 	BOOL efs_raw;
 #ifdef XATTR_MAPPINGS