linux-ext4 - [PATCH] e2fsprogs: allocate inode table wholly within group

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Date:	Tue, 02 Jul 2013 15:14:35 -0400
From:	Eric Sandeen <sandeen@...hat.com>
To:	ext4 development <linux-ext4@...r.kernel.org>
Subject: [PATCH] e2fsprogs: allocate inode table wholly within group

Building e2fsprogs 1.42.8 on ppc, I got this:

r_1024_small_bg: ext2 1024 blocksize with small block groups: failed

Because during the resize step it did this:

Itable move group 1 block 1030->1092 (diff 62)

but during e2fsck it found:

/tmp/e2fsprogs-tmp.uiFhgP: Inode table for group 1 is not in group.  (block 1092)

i.e. from dumpe2fs we can see:

Group 1: (Blocks 1025-1110)
  Backup superblock at 1025, Group descriptors at 1026-1026
  Block bitmap at 1090 (+65), Inode bitmap at 1091 (+66)
  Inode table at 1092-1123 (+67)
                      ^^^^ beyond end of block group

ext2fs_allocate_group_table() currently sends the last block of the
group as an acceptable *starting* point for the inode table allocation.

Because the inode table may be several blocks, and must reside wholly
within the group, move the last acceptable starting block back by this
amount so that the allocated range cannot extend past the end of the
group.

Signed-off-by: Eric Sandeen <sandeen@...hat.com>
---

p.s. I *think* this fixes it; I've not convinced myself that the failure
is 100% deterministic, so extra eyeballs on the patch are welcome.

Thanks,
-Eric

Index: e2fsprogs-1.42.8/lib/ext2fs/alloc_tables.c
===================================================================
--- e2fsprogs-1.42.8.orig/lib/ext2fs/alloc_tables.c
+++ e2fsprogs-1.42.8/lib/ext2fs/alloc_tables.c
@@ -200,6 +200,9 @@ errcode_t ext2fs_allocate_group_table(ex
 	}

 	if (!ext2fs_inode_table_loc(fs, group)) {
+		/* Inode table must fit within group, so adjust last blk */
+		last_blk -= (fs->inode_blocks_per_group - 1);
+
 		retval = ext2fs_get_free_blocks2(fs, group_blk, last_blk,
 						fs->inode_blocks_per_group,
 						bmap, &new_blk);

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