xfs: move dirent update hooks to xfs_dir2.c

Move the directory entry update hook code to xfs_dir2 so that it is
mostly consolidated with the higher level directory functions.  Retain
the exports so that online fsck can still send notifications through the
hooks.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

2 files changed, 129 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_dir2.c b/fs/xfs/libxfs/xfs_dir2.c
index 34b63ba2e4f7..202468223bf9 100644
--- a/fs/xfs/libxfs/xfs_dir2.c
+++ b/fs/xfs/libxfs/xfs_dir2.c
@@ -762,6 +762,81 @@ xfs_dir2_compname(
 	return xfs_da_compname(args, name, len);
 }
 
+#ifdef CONFIG_XFS_LIVE_HOOKS
+/*
+ * Use a static key here to reduce the overhead of directory live update hooks.
+ * If the compiler supports jump labels, the static branch will be replaced by
+ * a nop sled when there are no hook users.  Online fsck is currently the only
+ * caller, so this is a reasonable tradeoff.
+ *
+ * Note: Patching the kernel code requires taking the cpu hotplug lock.  Other
+ * parts of the kernel allocate memory with that lock held, which means that
+ * XFS callers cannot hold any locks that might be used by memory reclaim or
+ * writeback when calling the static_branch_{inc,dec} functions.
+ */
+DEFINE_STATIC_XFS_HOOK_SWITCH(xfs_dir_hooks_switch);
+
+void
+xfs_dir_hook_disable(void)
+{
+	xfs_hooks_switch_off(&xfs_dir_hooks_switch);
+}
+
+void
+xfs_dir_hook_enable(void)
+{
+	xfs_hooks_switch_on(&xfs_dir_hooks_switch);
+}
+
+/* Call hooks for a directory update relating to a child dirent update. */
+inline void
+xfs_dir_update_hook(
+	struct xfs_inode		*dp,
+	struct xfs_inode		*ip,
+	int				delta,
+	const struct xfs_name		*name)
+{
+	if (xfs_hooks_switched_on(&xfs_dir_hooks_switch)) {
+		struct xfs_dir_update_params	p = {
+			.dp		= dp,
+			.ip		= ip,
+			.delta		= delta,
+			.name		= name,
+		};
+		struct xfs_mount	*mp = ip->i_mount;
+
+		xfs_hooks_call(&mp->m_dir_update_hooks, 0, &p);
+	}
+}
+
+/* Call the specified function during a directory update. */
+int
+xfs_dir_hook_add(
+	struct xfs_mount	*mp,
+	struct xfs_dir_hook	*hook)
+{
+	return xfs_hooks_add(&mp->m_dir_update_hooks, &hook->dirent_hook);
+}
+
+/* Stop calling the specified function during a directory update. */
+void
+xfs_dir_hook_del(
+	struct xfs_mount	*mp,
+	struct xfs_dir_hook	*hook)
+{
+	xfs_hooks_del(&mp->m_dir_update_hooks, &hook->dirent_hook);
+}
+
+/* Configure directory update hook functions. */
+void
+xfs_dir_hook_setup(
+	struct xfs_dir_hook	*hook,
+	notifier_fn_t		mod_fn)
+{
+	xfs_hook_setup(&hook->dirent_hook, mod_fn);
+}
+#endif /* CONFIG_XFS_LIVE_HOOKS */
+
 /*
  * Given a directory @dp, a newly allocated inode @ip, and a @name, link @ip
  * into @dp under the given @name.  If @ip is a directory, it will be
@@ -809,6 +884,7 @@ xfs_dir_create_child(
 			return error;
 	}
 
+	xfs_dir_update_hook(dp, ip, 1, name);
 	return 0;
 }
 
@@ -873,6 +949,7 @@ xfs_dir_add_child(
 			return error;
 	}
 
+	xfs_dir_update_hook(dp, ip, 1, name);
 	return 0;
 }
 
@@ -954,6 +1031,7 @@ xfs_dir_remove_child(
 			return error;
 	}
 
+	xfs_dir_update_hook(dp, ip, -1, name);
 	return 0;
 }
 
@@ -1079,6 +1157,18 @@ xfs_dir_exchange_children(
 			return error;
 	}
 
+	/*
+	 * Inform our hook clients that we've finished an exchange operation as
+	 * follows: removed the source and target files from their directories;
+	 * added the target to the source directory; and added the source to
+	 * the target directory.  All inodes are locked, so it's ok to model a
+	 * rename this way so long as we say we deleted entries before we add
+	 * new ones.
+	 */
+	xfs_dir_update_hook(dp1, ip1, -1, name1);
+	xfs_dir_update_hook(dp2, ip2, -1, name2);
+	xfs_dir_update_hook(dp1, ip2, 1, name1);
+	xfs_dir_update_hook(dp2, ip1, 1, name2);
 	return 0;
 }
 
@@ -1305,5 +1395,19 @@ xfs_dir_rename_children(
 			return error;
 	}
 
+	/*
+	 * Inform our hook clients that we've finished a rename operation as
+	 * follows: removed the source and target files from their directories;
+	 * that we've added the source to the target directory; and finally
+	 * that we've added the whiteout, if there was one.  All inodes are
+	 * locked, so it's ok to model a rename this way so long as we say we
+	 * deleted entries before we add new ones.
+	 */
+	if (target_ip)
+		xfs_dir_update_hook(target_dp, target_ip, -1, target_name);
+	xfs_dir_update_hook(src_dp, src_ip, -1, src_name);
+	xfs_dir_update_hook(target_dp, src_ip, 1, target_name);
+	if (du_wip->ip)
+		xfs_dir_update_hook(src_dp, du_wip->ip, 1, src_name);
 	return 0;
 }
diff --git a/fs/xfs/libxfs/xfs_dir2.h b/fs/xfs/libxfs/xfs_dir2.h
index df6d4bbe3d6f..576068ed81fa 100644
--- a/fs/xfs/libxfs/xfs_dir2.h
+++ b/fs/xfs/libxfs/xfs_dir2.h
@@ -309,6 +309,31 @@ static inline unsigned char xfs_ascii_ci_xfrm(unsigned char c)
 	return c;
 }
 
+struct xfs_dir_update_params {
+	const struct xfs_inode	*dp;
+	const struct xfs_inode	*ip;
+	const struct xfs_name	*name;
+	int			delta;
+};
+
+#ifdef CONFIG_XFS_LIVE_HOOKS
+void xfs_dir_update_hook(struct xfs_inode *dp, struct xfs_inode *ip,
+		int delta, const struct xfs_name *name);
+
+struct xfs_dir_hook {
+	struct xfs_hook		dirent_hook;
+};
+
+void xfs_dir_hook_disable(void);
+void xfs_dir_hook_enable(void);
+
+int xfs_dir_hook_add(struct xfs_mount *mp, struct xfs_dir_hook *hook);
+void xfs_dir_hook_del(struct xfs_mount *mp, struct xfs_dir_hook *hook);
+void xfs_dir_hook_setup(struct xfs_dir_hook *hook, notifier_fn_t mod_fn);
+#else
+# define xfs_dir_update_hook(dp, ip, delta, name)	((void)0)
+#endif /* CONFIG_XFS_LIVE_HOOKS */
+
 struct xfs_parent_args;
 
 struct xfs_dir_update {