linux-ext4 - Re: [PATCH] Ext4: Uninitialized Block Groups

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Date:	Wed, 19 Sep 2007 17:04:39 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Valerie Clement <valerie.clement@...l.net>
CC:	Avantika Mathur <mathur@...ux.vnet.ibm.com>,
	linux-ext4@...r.kernel.org, Andreas Dilger <adilger@...sterfs.com>,
	cmm@...ibm.com
Subject: Re: [PATCH] Ext4: Uninitialized Block Groups



Valerie Clement wrote:
> Hi Avantika,
> I ran some tests with the uninit_groups feature enabled and got error messages
> when running e2fsck on my ext4 partition. e2fsck complains of an "invalid 
> unused inodes count" in some group descriptors.
> These errors occur when checking groups which have only one inode in use. The 
> "free inodes" count has been decremented by one in these groups but not the 
> "unused inodes" count.
> 
> The following patch fixes the problem.
> 
> Andreas, could you check if my patch is correct?
> Thanks a lot,
>   Valérie
> 
> Index: linux-2.6.23-rc6/fs/ext4/ialloc.c
> ===================================================================
> --- linux-2.6.23-rc6.orig/fs/ext4/ialloc.c	2007-09-19 11:31:01.000000000 +0200
> +++ linux-2.6.23-rc6/fs/ext4/ialloc.c	2007-09-19 11:31:41.000000000 +0200
> @@ -633,13 +633,10 @@ got:
>  	/* If we didn't allocate from within the initialized part of the inode
>  	 * table then we need to initialize up to this inode. */
>  	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
> -		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
> +		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT))
>  			gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
> -			free = EXT4_INODES_PER_GROUP(sb);
> -		} else {
> -			free = EXT4_INODES_PER_GROUP(sb) -
> +		free = EXT4_INODES_PER_GROUP(sb) -
>  				le16_to_cpu(gdp->bg_itable_unused);
> -		}
> 
>

the variable free is confusingly named here. It is not the free inode count.
rather it indicate the last used relative inode number in the group. How about
the below ?

-aneesh

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 4250c02..cfe2e09 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -633,17 +633,21 @@ got:
 	/* If we didn't allocate from within the initialized part of the inode
 	 * table then we need to initialize up to this inode. */
 	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
-		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT)) {
+		if (gdp->bg_flags & cpu_to_le16(EXT4_BG_INODE_UNINIT))
 			gdp->bg_flags &= cpu_to_le16(~EXT4_BG_INODE_UNINIT);
-			free = EXT4_INODES_PER_GROUP(sb);
-		} else {
-			free = EXT4_INODES_PER_GROUP(sb) -
-				le16_to_cpu(gdp->bg_itable_unused);
-		}
 
-		if (ino > free)
+		/*
+		 * Check the relative inode number against the last used
+		 * relative inode number in this group. if it is greater
+		 * we need to  update the bg_itable_unused count
+		 *
+		 */
+		if (ino > (EXT4_INODES_PER_GROUP(sb) -
+					le16_to_cpu(gdp->bg_itable_unused))) {
+
 			gdp->bg_itable_unused =
 				cpu_to_le16(EXT4_INODES_PER_GROUP(sb) - ino);
+		}
 	}
 
 	gdp->bg_free_inodes_count =
-
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