On Thu, 2008-02-07 at 18:25 +0530, Aneesh Kumar K.V wrote:
> ext4: Don't panic in case of corrupt bitmap
>
> From: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>
> Multiblock allocator was calling BUG_ON in many case if the free and used
> blocks count obtained looking at the bitmap is different from what
> the allocator internally accounted for. Use ext4_error in such case
> and don't panic the system.
>
There seems a lot of BUG_ON() and BUG() in mballoc code, other than this
case. Should it always panic the whole system in those cases? Perhaps
replacing with ext4_error() or some cases just WARN_ON is enough.
Mingming
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> ---
>
> fs/ext4/mballoc.c | 35 +++++++++++++++++++++--------------
> 1 files changed, 21 insertions(+), 14 deletions(-)
>
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 06d1f52..656729b 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -680,7 +680,6 @@ static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
> {
> char *bb;
>
> - /* FIXME!! is this needed */
> BUG_ON(EXT4_MB_BITMAP(e4b) == EXT4_MB_BUDDY(e4b));
> BUG_ON(max == NULL);
>
> @@ -964,7 +963,7 @@ static void ext4_mb_generate_buddy(struct super_block *sb,
> grp->bb_fragments = fragments;
>
> if (free != grp->bb_free) {
> - printk(KERN_DEBUG
> + ext4_error(sb, __FUNCTION__,
> "EXT4-fs: group %lu: %u blocks in bitmap, %u in gd\n",
> group, free, grp->bb_free);
> grp->bb_free = free;
> @@ -1821,13 +1820,24 @@ static void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
> i = ext4_find_next_zero_bit(bitmap,
> EXT4_BLOCKS_PER_GROUP(sb), i);
> if (i >= EXT4_BLOCKS_PER_GROUP(sb)) {
> - BUG_ON(free != 0);
> + /*
> + * IF we corrupt the bitmap we won't find any
> + * free blocks even though group info says we
> + * we have free blocks
> + */
> + ext4_error(sb, __FUNCTION__, "%d free blocks as per "
> + "group info. But bitmap says 0\n",
> + free);
> break;
> }
>
> mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex);
> BUG_ON(ex.fe_len <= 0);
> - BUG_ON(free < ex.fe_len);
> + if (free < ex.fe_len) {
> + ext4_error(sb, __FUNCTION__, "%d free blocks as per "
> + "group info. But got %d blocks\n",
> + free, ex.fe_len);
> + }
>
> ext4_mb_measure_extent(ac, &ex, e4b);
>
> @@ -3354,13 +3364,10 @@ static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
> ac->ac_pa = pa;
>
> /* we don't correct pa_pstart or pa_plen here to avoid
> - * possible race when tte group is being loaded concurrently
> + * possible race when the group is being loaded concurrently
> * instead we correct pa later, after blocks are marked
> - * in on-disk bitmap -- see ext4_mb_release_context() */
> - /*
> - * FIXME!! but the other CPUs can look at this particular
> - * pa and think that it have enought free blocks if we
> - * don't update pa_free here right ?
> + * in on-disk bitmap -- see ext4_mb_release_context()
> + * Other CPUs are prevented from allocating from this pa by lg_mutex
> */
> mb_debug("use %u/%u from group pa %p\n", pa->pa_lstart-len, len, pa);
> }
> @@ -3743,13 +3750,13 @@ static int ext4_mb_release_inode_pa(struct ext4_buddy *e4b,
> bit = next + 1;
> }
> if (free != pa->pa_free) {
> - printk(KERN_ERR "pa %p: logic %lu, phys. %lu, len %lu\n",
> + printk(KERN_CRIT "pa %p: logic %lu, phys. %lu, len %lu\n",
> pa, (unsigned long) pa->pa_lstart,
> (unsigned long) pa->pa_pstart,
> (unsigned long) pa->pa_len);
> - printk(KERN_ERR "free %u, pa_free %u\n", free, pa->pa_free);
> + ext4_error(sb, __FUNCTION__, "free %u, pa_free %u\n",
> + free, pa->pa_free);
> }
> - BUG_ON(free != pa->pa_free);
> atomic_add(free, &sbi->s_mb_discarded);
>
> return err;
> @@ -4405,7 +4412,7 @@ void ext4_mb_free_blocks(handle_t *handle, struct inode *inode,
> unsigned long block, unsigned long count,
> int metadata, unsigned long *freed)
> {
> - struct buffer_head *bitmap_bh = 0;
> + struct buffer_head *bitmap_bh = NULL;
> struct super_block *sb = inode->i_sb;
> struct ext4_allocation_context ac;
> struct ext4_group_desc *gdp;
> -
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