[PATCH] btrfs-progs: check: Support precise nlink tracking

[Nikolay Borisov <nborisov@suse.com>]

This commit makes progs compatible with a kernel that has implemented
subdirectory tracking in nlink. To achieve this the logic is modified
such that found_link is incremented for the parent dir for every
DIR_ITEM found which points to a subdirectory. Another change is to
always set found_link to 1 when parsing INODE_ITEM which corresponds to
a subvolume/snapshot root. This is to account for the fact that such
inodes are the root in their respective fs trees so they won't have
their found_link count bumped when parsing their DIR_ITEM in the parent
directory.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 check/main.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/check/main.c b/check/main.c
index c622caa8e04f..eec18132f8e5 100644
--- a/check/main.c
+++ b/check/main.c
@@ -908,6 +908,8 @@ static int process_inode_item(struct extent_buffer *eb,
 	if (S_ISLNK(rec->imode) &&
 	    flags & (BTRFS_INODE_IMMUTABLE | BTRFS_INODE_APPEND))
 		rec->errors |= I_ERR_ODD_INODE_FLAGS;
+	if (S_ISDIR(rec->imode) && rec->ino == BTRFS_FIRST_FREE_OBJECTID)
+		rec->found_link = 1;
 	/*
 	 * We don't have accurate root info to determine the correct
 	 * inode generation uplimit, use super_generation + 1 anyway
@@ -1421,6 +1423,16 @@ static int process_dir_item(struct extent_buffer *eb,
 			goto next;
 		}
 
+		if ((location.type == BTRFS_INODE_ITEM_KEY ||
+			location.type == BTRFS_ROOT_ITEM_KEY) && filetype == BTRFS_FT_DIR &&
+				key->type == BTRFS_DIR_ITEM_KEY) {
+			struct inode_record *dir_rec = get_inode_rec(inode_cache,
+					key->objectid, 1);
+			BUG_ON(IS_ERR(rec));
+			dir_rec->found_link++;
+			maybe_free_inode_rec(inode_cache, dir_rec);
+		}
+
 		if (location.type == BTRFS_INODE_ITEM_KEY) {
 			add_inode_backref(inode_cache, location.objectid,
 					  key->objectid, key->offset, namebuf,
@@ -1893,7 +1905,7 @@ static int check_root_dir(struct inode_record *rec)
 		goto out;
 	}
 
-	if (rec->nlink != 1 || rec->found_link != 0) {
+	if (rec->nlink != rec->found_link) {
 		rec->errors |= I_ERR_LINK_COUNT_WRONG;
 		goto out;
 	}
-- 
2.17.1