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Date: Fri, 3 Aug 2007 17:50:13 -0600
From: Andreas Dilger <adilger@...sterfs.com>
To: linux-ext4@...r.kernel.org
Subject: [PATCH] (unfinished) don't alloc/free in system zones
It seems there is a long-standing defect in ext2/ext3/ext4 in the 2.6
kernels that hasn't been fixed, even though I thought it was.
There are checks in ext[234]_{new,free}_blocks() to see if the block(s)
being allocated or freed overlap with the bitmaps or inode tables, but
if the filesystem is mounted with "errors=continue" (the default), then
even though an error is printed the allocation or free will succeed and
this will lead to filesystem corruption.
There was a patch posted in
http://marc.info/?l=linux-ext4&m=116360109620982&w=2
that should be added to the ext[234] patch queue that fixes this problem.
We might also consider making "errors=remount-ro" the default for ext4,
this has long been the default for Debian users of ext[23].
Signed-Off-By: Andreas Dilger <adilger@...sterfs.com>
Signed-Off-By: Andre Noll <maan@...temlinux.org>
---
fs/ext3/balloc.c | 102 +++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 75 insertions(+), 27 deletions(-)
diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index 063d994..763b7a0 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -359,17 +359,6 @@ do_more:
if (!desc)
goto error_return;
- if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
- in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
- in_range (block, le32_to_cpu(desc->bg_inode_table),
- sbi->s_itb_per_group) ||
- in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
- sbi->s_itb_per_group))
- ext3_error (sb, "ext3_free_blocks",
- "Freeing blocks in system zones - "
- "Block = "E3FSBLK", count = %lu",
- block, count);
-
/*
* We are about to start releasing blocks in the bitmap,
* so we need undo access.
@@ -392,7 +381,17 @@ do_more:
jbd_lock_bh_state(bitmap_bh);
- for (i = 0, group_freed = 0; i < count; i++) {
+ for (i = 0, group_freed = 0; i < count; i++, block++) {
+ struct ext3_group_desc *gdp = ext3_get_group_desc(sb, i, NULL);
+ 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...
*/
@@ -400,7 +399,7 @@ do_more:
jbd_unlock_bh_state(bitmap_bh);
{
struct buffer_head *debug_bh;
- debug_bh = sb_find_get_block(sb, block + i);
+ debug_bh = sb_find_get_block(sb, block);
if (debug_bh) {
BUFFER_TRACE(debug_bh, "Deleted!");
if (!bh2jh(bitmap_bh)->b_committed_data)
@@ -452,7 +451,7 @@ do_more:
jbd_unlock_bh_state(bitmap_bh);
ext3_error(sb, __FUNCTION__,
"bit already cleared for block "E3FSBLK,
- block + i);
+ block);
jbd_lock_bh_state(bitmap_bh);
BUFFER_TRACE(bitmap_bh, "bit already cleared");
} else {
@@ -479,7 +478,6 @@ do_more:
*pdquot_freed_blocks += group_freed;
if (overflow && !err) {
- block += count;
count = overflow;
goto do_more;
}
@@ -1192,6 +1190,63 @@ int ext3_should_retry_alloc(struct super
}
/*
+ * Check if given blocks are metadata blocks.
+ *
+ * We should also check the backup group descriptors and the superblock,
+ * but it is too expensive to do so for each allocated/freed block. So,
+ * let's defer that check until we have per-group data structs.
+ */
+static inline int ext3_blocks_are_metadata(ext3_fsblk_t block,
+ unsigned long num,
+ struct ext3_group_desc *gdp,
+ struct super_block *sb)
+{
+ if (in_range(le32_to_cpu(gdp->bg_block_bitmap), block, num))
+ return 1;
+ if (in_range(le32_to_cpu(gdp->bg_inode_bitmap), block, num))
+ return 1;
+ if (in_range(block, le32_to_cpu(gdp->bg_inode_table),
+ EXT3_SB(sb)->s_itb_per_group))
+ return 1;
+ if (in_range(block + num - 1, le32_to_cpu(gdp->bg_inode_table),
+ EXT3_SB(sb)->s_itb_per_group))
+ return 1;
+ return 0;
+}
+
+/*
+ *
+ * set the bits for all of the metadata blocks in the group
+ *
+ * Note: This will potentially use up some 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.
+ */
+static void fix_group(int group, struct super_block *sb)
+{
+ int i;
+ ext3_fsblk_t bit;
+ unsigned long gdblocks;
+ struct buffer_head *gdp_bh;
+ struct ext3_group_desc *gdp = ext3_get_group_desc(sb, group, &gdp_bh);
+
+ if (ext3_bg_has_super(sb, group))
+ ext3_set_bit(0, gdp_bh->b_data);
+ gdblocks = ext3_bg_num_gdb(sb, group);
+ for (i = 0, bit = 1; i < gdblocks; i++, bit++)
+ ext3_set_bit(i, gdp_bh->b_data);
+ ext3_set_bit(gdp->bg_inode_bitmap % EXT3_BLOCKS_PER_GROUP(sb),
+ gdp_bh->b_data);
+ ext3_set_bit(gdp->bg_block_bitmap % EXT3_BLOCKS_PER_GROUP(sb),
+ gdp_bh->b_data);
+ for (i = 0, bit = gdp->bg_inode_table % EXT3_BLOCKS_PER_GROUP(sb);
+ i < EXT3_SB(sb)->s_itb_per_group; i++, bit++)
+ ext3_set_bit(i, gdp_bh->b_data);
+}
+
+/*
* ext3_new_block uses a goal block to assist allocation. If the goal is
* free, or there is a free block within 32 blocks of the goal, that block
* is allocated. Otherwise a forward search is made for a free block; within
@@ -1260,7 +1315,7 @@ ext3_fsblk_t ext3_new_blocks(handle_t *h
*errp = -ENOSPC;
goto out;
}
-
+repeat:
/*
* First, test whether the goal block is free.
*/
@@ -1367,17 +1422,10 @@ allocated:
ret_block = grp_alloc_blk + ext3_group_first_block_no(sb, group_no);
- if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
- in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
- in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
- EXT3_SB(sb)->s_itb_per_group) ||
- in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
- EXT3_SB(sb)->s_itb_per_group))
- ext3_error(sb, "ext3_new_block",
- "Allocating block in system zone - "
- "blocks from "E3FSBLK", length %lu",
- ret_block, num);
-
+ if (ext3_blocks_are_metadata(ret_block, num, gdp, sb)) {
+ fix_group(group_no, sb);
+ goto repeat;
+ }
performed_allocation = 1;
#ifdef CONFIG_JBD_DEBUG
Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.
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