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Date: Mon, 23 Oct 2006 14:02:42 -0600
From: Andreas Dilger <adilger@...sterfs.com>
To: Andre Noll <maan@...temlinux.org>, Theodore Ts'o <tytso@....edu>,
linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
Cc: Eric Sandeen <esandeen@...hat.com>
Subject: Re: ext3: bogus i_mode errors with 2.6.18.1
On Oct 23, 2006 10:44 -0600, Andreas Dilger wrote:
> Hmm, this would appear to be a buglet in error handling. If the block just
> allocated above is in the system zone it should be marked in-use in the
> bitmap but otherwise ignored. We definitely should NOT be freeing it on
> error.
>
> Yikes! It seems a patch I submitted to 2.4 that fixed the behaviour
> of ext3_new_block() so that if we detect this block shouldn't be
> allocated it is skipped instead of corrupting the filesystem if it
> is running with errors=continue...
>
> It looks like ext3_free_blocks() needs a similar fix - i.e. report an
> error and don't actually free those blocks.
I found a URL for the 2.4 version of this patch, if some kind soul would
update it for 2.6 it might save someone's data in the future. It looks
at the time I wasn't working on 2.5 kernels and nobody else took it on.
http://lkml.org/lkml/2003/4/7/252
[patch is pasted, may not be free of whitespace munging, but then it will
need to be applied to 2.6 by hand anyways]
======================= ext2-2.4.18-badalloc.diff ===========================
--- linux-2.4.18.orig/fs/ext3/balloc.c Wed Feb 27 10:31:59 2002
+++ linux-2.4.18-aed/fs/ext3/balloc.c Mon Mar 18 17:15:46 2002
@@ -276,7 +273,8 @@ void ext3_free_blocks
}
lock_super (sb);
es = sb->u.ext3_sb.s_es;
- if (block < le32_to_cpu(es->s_first_data_block) ||
+ if (block < le32_to_cpu(es->s_first_data_block) ||
+ block + count < block ||
(block + count) > le32_to_cpu(es->s_blocks_count)) {
ext3_error (sb, "ext3_free_blocks",
"Freeing blocks not in datazone - "
@@ -309,17 +307,6 @@ void ext3_free_blocks
if (!gdp)
goto error_return;
- if (in_range (le32_to_cpu(gdp->bg_block_bitmap), block, count) ||
- in_range (le32_to_cpu(gdp->bg_inode_bitmap), block, count) ||
- in_range (block, le32_to_cpu(gdp->bg_inode_table),
- sb->u.ext3_sb.s_itb_per_group) ||
- in_range (block + count - 1, le32_to_cpu(gdp->bg_inode_table),
- sb->u.ext3_sb.s_itb_per_group))
- ext3_error (sb, "ext3_free_blocks",
- "Freeing blocks in system zones - "
- "Block = %lu, count = %lu",
- block, count);
-
/*
* We are about to start releasing blocks in the bitmap,
* so we need undo access.
@@ -345,14 +332,24 @@ void ext3_free_blocks
if (err)
goto error_return;
- for (i = 0; i < count; i++) {
+ for (i = 0; i < count; i++, block++) {
+ if (block == le32_to_cpu(gdp->bg_block_bitmap) ||
+ block == le32_to_cpu(gdp->bg_inode_bitmap) ||
+ in_range(block, le32_to_cpu(gdp->bg_inode_table),
+ EXT3_SB(sb)->s_itb_per_group)) {
+ ext3_error(sb, __FUNCTION__,
+ "Freeing block in system zone - block =
%lu",
+ block);
+ continue;
+ }
+
/*
* An HJ special. This is expensive...
*/
#ifdef CONFIG_JBD_DEBUG
{
struct buffer_head *debug_bh;
- debug_bh = sb_get_hash_table(sb, block + i);
+ debug_bh = sb_get_hash_table(sb, block);
if (debug_bh) {
BUFFER_TRACE(debug_bh, "Deleted!");
if (!bh2jh(bitmap_bh)->b_committed_data)
@@ -365,9 +362,8 @@ void ext3_free_blocks
#endif
BUFFER_TRACE(bitmap_bh, "clear bit");
if (!ext3_clear_bit (bit + i, bitmap_bh->b_data)) {
- ext3_error (sb, __FUNCTION__,
- "bit already cleared for block %lu",
- block + i);
+ ext3_error(sb, __FUNCTION__,
+ "bit already cleared for block %lu",
block);
BUFFER_TRACE(bitmap_bh, "bit already cleared");
} else {
dquot_freed_blocks++;
@@ -415,7 +411,6 @@ void ext3_free_blocks
if (!err) err = ret;
if (overflow && !err) {
- block += count;
count = overflow;
goto do_more;
}
@@ -575,6 +574,7 @@ int ext3_new_block
ext3_debug ("goal=%lu.\n", goal);
+repeat:
/*
* First, test whether the goal block is free.
*/
@@ -684,10 +684,21 @@ int ext3_new_block
if (tmp == le32_to_cpu(gdp->bg_block_bitmap) ||
tmp == le32_to_cpu(gdp->bg_inode_bitmap) ||
in_range (tmp, le32_to_cpu(gdp->bg_inode_table),
- sb->u.ext3_sb.s_itb_per_group))
- ext3_error (sb, "ext3_new_block",
- "Allocating block in system zone - "
- "block = %u", tmp);
+ EXT3_SB(sb)->s_itb_per_group)) {
+ ext3_error(sb, __FUNCTION__,
+ "Allocating block in system zone - block = %u",
tmp);
+
+ /* Note: This will potentially use up one of the handle's
+ * buffer credits. Normally we have way too many credits,
+ * so that is OK. In _very_ rare cases it might not be OK.
+ * We will trigger an assertion if we run out of credits,
+ * and we will have to do a full fsck of the filesystem -
+ * better than randomly corrupting filesystem metadata.
+ */
+ ext3_set_bit(j, bh->b_data);
+ goto repeat;
+ }
+
/* The superblock lock should guard against anybody else beating
* us to this point! */
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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