2008-02-11 11:30:21

by Aneesh Kumar K.V

Subject: [PATCH] ext4: Don't claim block from group which has corrupt bitmap

In ext4_mb_complex_scan_group, if the extent length of the newly
found extentet is greater than than the total free blocks counted
in group info, break without claiming the block.

Document different ext4_error usage, explaining the state with which we
continue if we mount with errors=continue

Signed-off-by: Aneesh Kumar K.V <[email protected]>
---
fs/ext4/mballoc.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index dd0fcfc..898eefc 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -967,6 +967,10 @@ static void ext4_mb_generate_buddy(struct super_block *sb,
ext4_error(sb, __FUNCTION__,
"EXT4-fs: group %lu: %u blocks in bitmap, %u in gd\n",
group, free, grp->bb_free);
+ /*
+ * If we intent to continue, we consider group descritor
+ * corrupt and update bb_free using bitmap value
+ */
grp->bb_free = free;
}

@@ -1822,7 +1826,7 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
EXT4_BLOCKS_PER_GROUP(sb), i);
if (i >= EXT4_BLOCKS_PER_GROUP(sb)) {
/*
- * IF we corrupt the bitmap we won't find any
+ * IF we have corrupt bitmap, we won't find any
* free blocks even though group info says we
* we have free blocks
*/
@@ -1838,6 +1842,12 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
ext4_error(sb, __FUNCTION__, "%d free blocks as per "
"group info. But got %d blocks\n",
free, ex.fe_len);
+ /*
+ * The number of free blocks differs. This mostly
+ * indicate that the bitmap is corrupt. So exit
+ * without claiming the space.
+ */
+ break;
}

ext4_mb_measure_extent(ac, &ex, e4b);
@@ -3771,6 +3781,10 @@ static int ext4_mb_release_inode_pa(struct ext4_buddy *e4b,
(unsigned long) pa->pa_len);
ext4_error(sb, __FUNCTION__, "free %u, pa_free %u\n",
free, pa->pa_free);
+ /*
+ * pa is already deleted so we use the value obtained
+ * from the bitmap and continue.
+ */
}
atomic_add(free, &sbi->s_mb_discarded);
if (ac)
--
1.5.4.23.gef5b9-dirty

2008-02-11 11:36:59

by Aneesh Kumar K.V

Subject: Re: [PATCH] ext4: Don't claim block from group which has corrupt bitmap

On Mon, Feb 11, 2008 at 05:00:18PM +0530, Aneesh Kumar K.V wrote:
> In ext4_mb_complex_scan_group, if the extent length of the newly
> found extentet is greater than than the total free blocks counted
> in group info, break without claiming the block.
>
> Document different ext4_error usage, explaining the state with which we
> continue if we mount with errors=continue
>
> Signed-off-by: Aneesh Kumar K.V <[email protected]>
> ---
> fs/ext4/mballoc.c | 16 +++++++++++++++-
> 1 files changed, 15 insertions(+), 1 deletions(-)


This was actually part of the version 2 of the patch
ext4_avoid_panic_in_case_of_corrupted_bitmap.patch. But we missed it
in the last update. So sending it as a separate patch.


-aneesh