From: Abhijith Das <adas@redhat.com>
Subject: [RHEL5.1 PATCH] GFS2 - bz 235299: GFS2 gfs_quota do_list operation 	hangs when you have a large sparse quota file
Date: Thu, 16 Aug 2007 12:28:03 -0500
Bugzilla: 235299
Message-Id: <46C48923.7030203@redhat.com>
Changelog: [gfs2] hang when using a large sparse quota file


Hi,
This is the filesystem part of the patches to fix this bz. There are
additional userland patches (gfs2_quota, libgfs2) for the complete
solution. 
This patch adds a new field qu_ll_next to the gfs2_quota
structure. This field allows us to create linked lists of quotas in the
ondisk quota inode. Instead of scanning through the entire sparse quota
file for valid quotas, we can now simply walk through the user and group
quota linked lists to perform the do_list operation.

Signed-off-by: Abhijith Das <adas@redhat.com>



Index: linux-rhel51-quilt/fs/gfs2/quota.c
===================================================================
--- linux-rhel51-quilt.orig/fs/gfs2/quota.c	2007-08-15 09:48:24.000000000 -0500
+++ linux-rhel51-quilt/fs/gfs2/quota.c	2007-08-15 16:56:57.000000000 -0500
@@ -70,6 +70,7 @@
 	u64 qu_limit;
 	u64 qu_warn;
 	s64 qu_value;
+	u32 qu_ll_next;
 };
 
 struct gfs2_quota_change_host {
@@ -580,6 +581,7 @@
 	qu->qu_limit = be64_to_cpu(str->qu_limit);
 	qu->qu_warn = be64_to_cpu(str->qu_warn);
 	qu->qu_value = be64_to_cpu(str->qu_value);
+	qu->qu_ll_next = be32_to_cpu(str->qu_ll_next);
 }
 
 static void gfs2_quota_out(const struct gfs2_quota_host *qu, void *buf)
@@ -589,6 +591,7 @@
 	str->qu_limit = cpu_to_be64(qu->qu_limit);
 	str->qu_warn = cpu_to_be64(qu->qu_warn);
 	str->qu_value = cpu_to_be64(qu->qu_value);
+	str->qu_ll_next = cpu_to_be32(qu->qu_ll_next);
 	memset(&str->qu_reserved, 0, sizeof(str->qu_reserved));
 }
 
Index: linux-rhel51-quilt/include/linux/gfs2_ondisk.h
===================================================================
--- linux-rhel51-quilt.orig/include/linux/gfs2_ondisk.h	2007-08-15 09:35:52.000000000 -0500
+++ linux-rhel51-quilt/include/linux/gfs2_ondisk.h	2007-08-15 16:56:57.000000000 -0500
@@ -170,6 +170,33 @@
 };
 
 /*
+ * quota linked list: user quotas and group quotas form two separate 
+ * singly linked lists. ll_next stores uids or gids of next quotas in the 
+ * linked list.
+
+Given the uid/gid, how to calculate the quota file offsets for the corresponding
+gfs2_quota structures on disk:
+
+for user quotas, given uid,
+offset = uid * sizeof(struct gfs2_quota);
+
+for group quotas, given gid,
+offset = (gid * sizeof(struct gfs2_quota)) + sizeof(struct gfs2_quota);
+
+
+  uid:0   gid:0       uid:12   gid:12      uid:17   gid:17     uid:5142 gid:5142
++-------+-------+    +-------+-------+    +-------+- - - -+    +- - - -+-------+
+| valid | valid | :: | valid | valid | :: | valid | inval | :: | inval | valid |
++-------+-------+    +-------+-------+    +-------+- - - -+    +- - - -+-------+
+next:12   next:12    next:17 next:5142    next:NULL                    next:NULL
+    |       |            |       |            |<-- user quota list         |
+     \______|___________/ \______|___________/         group quota list -->|
+            |                    |                                         |
+             \__________________/ \_______________________________________/
+
+*/
+
+/*
  * quota structure
  */
 
@@ -177,7 +204,8 @@
 	__be64 qu_limit;
 	__be64 qu_warn;
 	__be64 qu_value;
-	__u8 qu_reserved[64];
+	__be32 qu_ll_next; /* location of next quota in list */
+	__u8 qu_reserved[60];
 };
 
 /*