Implement bookmark copying

This feature allows copying existing bookmarks using

    zfs bookmark fs#target fs#newbookmark

There are some niche use cases for such functionality,
e.g. when using bookmarks as markers for replication progress.

Copying redaction bookmarks produces a normal bookmark that
cannot be used for redacted send (we are not duplicating
the redaction object).

ZCP support for bookmarking (both creation and copying) will be
implemented in a separate patch based on this work.

Overview:

- Terminology:
    - source = existing snapshot or bookmark
    - new/bmark = new bookmark
- Implement bookmark copying in `dsl_bookmark.c`
  - create new bookmark node
  - copy source's `zbn_phys` to new's `zbn_phys`
  - zero-out redaction object id in copy
- Extend existing bookmark ioctl nvlist schema to accept
  bookmarks as sources
  - => `dsl_bookmark_create_nvl_validate` is authoritative
- use `dsl_dataset_is_before` check for both snapshot
  and bookmark sources
- Adjust CLI
  - refactor shortname expansion logic in `zfs_do_bookmark`
- Update man pages
  - warn about redaction bookmark handling
- Add test cases
  - CLI
  - pyyzfs libzfs_core bindings

Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Christian Schwarz <[email protected]>
Closes #9571

1 files changed, 64 insertions, 35 deletions

diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 20ecb3031..ce8ed880c 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -30,6 +30,7 @@
  * Copyright (c) 2019 Datto Inc.
  * Copyright (c) 2019, loli10K <[email protected]>
  * Copyright 2019 Joyent, Inc.
+ * Copyright (c) 2019, 2020 by Christian Schwarz. All rights reserved.
  */
 
 #include <assert.h>
@@ -383,7 +384,8 @@ get_usage(zfs_help_t idx)
 		return (gettext("\tdiff [-FHt] <snapshot> "
 		    "[snapshot|filesystem]\n"));
 	case HELP_BOOKMARK:
-		return (gettext("\tbookmark <snapshot> <bookmark>\n"));
+		return (gettext("\tbookmark <snapshot|bookmark> "
+		    "<newbookmark>\n"));
 	case HELP_CHANNEL_PROGRAM:
 		return (gettext("\tprogram [-jn] [-t <instruction limit>] "
 		    "[-m <memory limit (b)>]\n"
@@ -7535,16 +7537,17 @@ out:
 }
 
 /*
- * zfs bookmark <fs@snap> <fs#bmark>
+ * zfs bookmark <fs@source>|<fs#source> <fs#bookmark>
  *
- * Creates a bookmark with the given name from the given snapshot.
+ * Creates a bookmark with the given name from the source snapshot
+ * or creates a copy of an existing source bookmark.
  */
 static int
 zfs_do_bookmark(int argc, char **argv)
 {
-	char snapname[ZFS_MAX_DATASET_NAME_LEN];
-	char bookname[ZFS_MAX_DATASET_NAME_LEN];
-	zfs_handle_t *zhp;
+	char *source, *bookname;
+	char expbuf[ZFS_MAX_DATASET_NAME_LEN];
+	int source_type;
 	nvlist_t *nvl;
 	int ret = 0;
 	int c;
@@ -7564,7 +7567,7 @@ zfs_do_bookmark(int argc, char **argv)
 
 	/* check number of arguments */
 	if (argc < 1) {
-		(void) fprintf(stderr, gettext("missing snapshot argument\n"));
+		(void) fprintf(stderr, gettext("missing source argument\n"));
 		goto usage;
 	}
 	if (argc < 2) {
@@ -7572,50 +7575,72 @@ zfs_do_bookmark(int argc, char **argv)
 		goto usage;
 	}
 
-	if (strchr(argv[0], '@') == NULL) {
+	source = argv[0];
+	bookname = argv[1];
+
+	if (strchr(source, '@') == NULL && strchr(source, '#') == NULL) {
 		(void) fprintf(stderr,
-		    gettext("invalid snapshot name '%s': "
-		    "must contain a '@'\n"), argv[0]);
+		    gettext("invalid source name '%s': "
+		    "must contain a '@' or '#'\n"), source);
 		goto usage;
 	}
-	if (strchr(argv[1], '#') == NULL) {
+	if (strchr(bookname, '#') == NULL) {
 		(void) fprintf(stderr,
 		    gettext("invalid bookmark name '%s': "
-		    "must contain a '#'\n"), argv[1]);
+		    "must contain a '#'\n"), bookname);
 		goto usage;
 	}
 
-	if (argv[0][0] == '@') {
-		/*
-		 * Snapshot name begins with @.
-		 * Default to same fs as bookmark.
-		 */
-		(void) strlcpy(snapname, argv[1], sizeof (snapname));
-		*strchr(snapname, '#') = '\0';
-		(void) strlcat(snapname, argv[0], sizeof (snapname));
-	} else {
-		(void) strlcpy(snapname, argv[0], sizeof (snapname));
+	/*
+	 * expand source or bookname to full path:
+	 * one of them may be specified as short name
+	 */
+	{
+		char **expand;
+		char *source_short, *bookname_short;
+		source_short = strpbrk(source, "@#");
+		bookname_short = strpbrk(bookname, "#");
+		if (source_short == source &&
+		    bookname_short == bookname) {
+			(void) fprintf(stderr, gettext(
+			    "either source or bookmark must be specified as "
+			    "full dataset paths"));
+			goto usage;
+		} else if (source_short != source &&
+		    bookname_short != bookname) {
+			expand = NULL;
+		} else if (source_short != source) {
+			strlcpy(expbuf, source, sizeof (expbuf));
+			expand = &bookname;
+		} else if (bookname_short != bookname) {
+			strlcpy(expbuf, bookname, sizeof (expbuf));
+			expand = &source;
+		} else {
+			abort();
+		}
+		if (expand != NULL) {
+			*strpbrk(expbuf, "@#") = '\0'; /* dataset name in buf */
+			(void) strlcat(expbuf, *expand, sizeof (expbuf));
+			*expand = expbuf;
+		}
 	}
-	if (argv[1][0] == '#') {
-		/*
-		 * Bookmark name begins with #.
-		 * Default to same fs as snapshot.
-		 */
-		(void) strlcpy(bookname, argv[0], sizeof (bookname));
-		*strchr(bookname, '@') = '\0';
-		(void) strlcat(bookname, argv[1], sizeof (bookname));
-	} else {
-		(void) strlcpy(bookname, argv[1], sizeof (bookname));
+
+	/* determine source type */
+	switch (*strpbrk(source, "@#")) {
+		case '@': source_type = ZFS_TYPE_SNAPSHOT; break;
+		case '#': source_type = ZFS_TYPE_BOOKMARK; break;
+		default: abort();
 	}
 
-	zhp = zfs_open(g_zfs, snapname, ZFS_TYPE_SNAPSHOT);
+	/* test the source exists */
+	zfs_handle_t *zhp;
+	zhp = zfs_open(g_zfs, source, source_type);
 	if (zhp == NULL)
 		goto usage;
 	zfs_close(zhp);
 
-
 	nvl = fnvlist_alloc();
-	fnvlist_add_string(nvl, bookname, snapname);
+	fnvlist_add_string(nvl, bookname, source);
 	ret = lzc_bookmark(nvl, NULL);
 	fnvlist_free(nvl);
 
@@ -7631,6 +7656,10 @@ zfs_do_bookmark(int argc, char **argv)
 		case EXDEV:
 			err_msg = "bookmark is in a different pool";
 			break;
+		case ZFS_ERR_BOOKMARK_SOURCE_NOT_ANCESTOR:
+			err_msg = "source is not an ancestor of the "
+			    "new bookmark's dataset";
+			break;
 		case EEXIST:
 			err_msg = "bookmark exists";
 			break;