[28/64] xfs: create libxfs helper to remove an existing inode/name from a directory

Commit Message

Darrick J. Wong Oct. 2, 2024, 1:15 a.m. UTC

From: Darrick J. Wong <[e-mail]>

Source kernel commit: 90636e4531a8bfb5ef37d38a76eb97e5f5793deb

Create a new libxfs function to remove a (name, inode) entry from a
directory.  The upcoming metadata directory feature will need this to
create a metadata directory tree.

Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
---
 libxfs/xfs_dir2.c |   81 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 libxfs/xfs_dir2.h |    2 +
 2 files changed, 83 insertions(+)

Patch

diff --git a/libxfs/xfs_dir2.c b/libxfs/xfs_dir2.c
index 802b9a1b3..e46f7f489 100644
--- a/libxfs/xfs_dir2.c
+++ b/libxfs/xfs_dir2.c
@@ -873,3 +873,84 @@  xfs_dir_add_child(
 
 	return 0;
 }
+
+/*
+ * Given a directory @dp, a child @ip, and a @name, remove the (@name, @ip)
+ * entry from the directory.  Both inodes must have the ILOCK held.
+ */
+int
+xfs_dir_remove_child(
+	struct xfs_trans	*tp,
+	unsigned int		resblks,
+	struct xfs_dir_update	*du)
+{
+	struct xfs_inode	*dp = du->dp;
+	const struct xfs_name	*name = du->name;
+	struct xfs_inode	*ip = du->ip;
+	int			error;
+
+	xfs_assert_ilocked(ip, XFS_ILOCK_EXCL);
+	xfs_assert_ilocked(dp, XFS_ILOCK_EXCL);
+
+	/*
+	 * If we're removing a directory perform some additional validation.
+	 */
+	if (S_ISDIR(VFS_I(ip)->i_mode)) {
+		ASSERT(VFS_I(ip)->i_nlink >= 2);
+		if (VFS_I(ip)->i_nlink != 2)
+			return -ENOTEMPTY;
+		if (!xfs_dir_isempty(ip))
+			return -ENOTEMPTY;
+
+		/* Drop the link from ip's "..".  */
+		error = xfs_droplink(tp, dp);
+		if (error)
+			return error;
+
+		/* Drop the "." link from ip to self.  */
+		error = xfs_droplink(tp, ip);
+		if (error)
+			return error;
+
+		/*
+		 * Point the unlinked child directory's ".." entry to the root
+		 * directory to eliminate back-references to inodes that may
+		 * get freed before the child directory is closed.  If the fs
+		 * gets shrunk, this can lead to dirent inode validation errors.
+		 */
+		if (dp->i_ino != tp->t_mountp->m_sb.sb_rootino) {
+			error = xfs_dir_replace(tp, ip, &xfs_name_dotdot,
+					tp->t_mountp->m_sb.sb_rootino, 0);
+			if (error)
+				return error;
+		}
+	} else {
+		/*
+		 * When removing a non-directory we need to log the parent
+		 * inode here.  For a directory this is done implicitly
+		 * by the xfs_droplink call for the ".." entry.
+		 */
+		xfs_trans_log_inode(tp, dp, XFS_ILOG_CORE);
+	}
+	xfs_trans_ichgtime(tp, dp, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
+
+	/* Drop the link from dp to ip. */
+	error = xfs_droplink(tp, ip);
+	if (error)
+		return error;
+
+	error = xfs_dir_removename(tp, dp, name, ip->i_ino, resblks);
+	if (error) {
+		ASSERT(error != -ENOENT);
+		return error;
+	}
+
+	/* Remove parent pointer. */
+	if (du->ppargs) {
+		error = xfs_parent_removename(tp, du->ppargs, dp, name, ip);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
diff --git a/libxfs/xfs_dir2.h b/libxfs/xfs_dir2.h
index 4f9711509..c89916d1c 100644
--- a/libxfs/xfs_dir2.h
+++ b/libxfs/xfs_dir2.h
@@ -322,5 +322,7 @@  int xfs_dir_create_child(struct xfs_trans *tp, unsigned int resblks,
 		struct xfs_dir_update *du);
 int xfs_dir_add_child(struct xfs_trans *tp, unsigned int resblks,
 		struct xfs_dir_update *du);
+int xfs_dir_remove_child(struct xfs_trans *tp, unsigned int resblks,
+		struct xfs_dir_update *du);
 
 #endif	/* __XFS_DIR2_H__ */