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SubjectRe: reiserfs and SCSI oops seen in 2.6.9-rc2 with local SCSI disk IO
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On Fri, 2004-09-24 at 11:03 -0400, David Wysochanski wrote:
> I can reproduce this pretty easily with local disk.
>
> Here's some details about my setup (attached is the
> full kernel config):
> - dell 2650 (dual xeon, hyperthreading disabled)
> - 1 local SCSI disk (root volume)
> - 2 local SCSI disks (data), each with 10 partitions
> of 100MB each, 6 of them reiserfs filesystems, 3 of them
> ext3, and 3 of them ext2 (total of 20 unique filesystems)
> - one instance of test program running on each of the
> 20 filesystems
>
> Sorry, but at this time I can't share the test program itself
> (I'm working on that). Let me try to describe it though.

I think this is a bug in how reiserfs deals with small filesystems.
There are a few different cases where it will try to use bitmap #2 even
when there is only 1 bitmap. Each of your test filesystems will need
only 1 bitmap for reiserfs, so while it is a valid bug, it's not the one
you were originally trying to reproduce.

This patch should do it (against 2.6.9-rc3). Thanks to Jan Kara for
finding this bug.

-chris

On small filesystems (<128M), make sure not to reference bitmap blocks that
don't exist.

Index: linux.269rc3/fs/reiserfs/bitmap.c
===================================================================
--- linux.269rc3.orig/fs/reiserfs/bitmap.c 2004-08-18 09:38:50.000000000 -0400
+++ linux.269rc3/fs/reiserfs/bitmap.c 2004-10-04 20:19:42.000000000 -0400
@@ -236,6 +236,9 @@ static int bmap_hash_id(struct super_blo
if (!bm)
bm = 1;
}
+ /* this can only be true when SB_BMAP_NR = 1 */
+ if (bm >= SB_BMAP_NR(s))
+ bm = 0;
return bm;
}

@@ -293,6 +296,10 @@ static int scan_bitmap (struct reiserfs_

get_bit_address (s, *start, &bm, &off);
get_bit_address (s, finish, &end_bm, &end_off);
+ if (bm > SB_BMAP_NR(s))
+ return 0;
+ if (end_bm > SB_BMAP_NR(s))
+ end_bm = SB_BMAP_NR(s);

/* When the bitmap is more than 10% free, anyone can allocate.
* When it's less than 10% free, only files that already use the
@@ -313,6 +320,7 @@ static int scan_bitmap (struct reiserfs_
if (nr_allocated)
goto ret;
}
+ /* we know from above that start is a reasonable number */
get_bit_address (s, *start, &bm, &off);
}

@@ -1050,9 +1058,10 @@ int reiserfs_allocate_blocknrs(reiserfs_
{
int initial_amount_needed = amount_needed;
int ret;
+ struct super_block *s = hint->th->t_super;

/* Check if there is enough space, taking into account reserved space */
- if ( SB_FREE_BLOCKS(hint->th->t_super) - REISERFS_SB(hint->th->t_super)->reserved_blocks <
+ if ( SB_FREE_BLOCKS(s) - REISERFS_SB(s)->reserved_blocks <
amount_needed - reserved_by_us)
return NO_DISK_SPACE;
/* should this be if !hint->inode && hint->preallocate? */
@@ -1072,6 +1081,8 @@ int reiserfs_allocate_blocknrs(reiserfs_

/* find search start and save it in hint structure */
determine_search_start(hint, amount_needed);
+ if (hint->search_start >= SB_BLOCK_COUNT(s))
+ hint->search_start = SB_BLOCK_COUNT(s) - 1;

/* allocation itself; fill new_blocknrs and preallocation arrays */
ret = blocknrs_and_prealloc_arrays_from_search_start



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