This is for kernel.org bug:
#13549, Kernel oops while online resizing of an ext4 filesystem
if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
and every other access to this first tests s_log_groups_per_flex;
same thing needs to happen in resize or we'll wander off into
a null pointer.
Thanks to Christoph Biedl, who came up with the trivial testcase:
# truncate --size 128M fsfile
# mkfs.ext3 -F fsfile
# tune2fs -O extents,uninit_bg,dir_index,flex_bg,huge_file,dir_nlink,extra_isize fsfile
# e2fsck -yDf -C0 fsfile
# truncate --size 132M fsfile
# losetup /dev/loop0 fsfile
# mount /dev/loop0 mnt
# resize2fs -p /dev/loop0
Reported-by: Alessandro Polverini <[email protected]>
Test-case-by: Christoph Biedl <[email protected]>
Signed-off-by: Eric Sandeen <[email protected]>
---
Index: linux-2.6/fs/ext4/resize.c
===================================================================
--- linux-2.6.orig/fs/ext4/resize.c
+++ linux-2.6/fs/ext4/resize.c
@@ -930,7 +930,8 @@ int ext4_group_add(struct super_block *s
percpu_counter_add(&sbi->s_freeinodes_counter,
EXT4_INODES_PER_GROUP(sb));
- if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
+ sbi->s_log_groups_per_flex) {
ext4_group_t flex_group;
flex_group = ext4_flex_group(sbi, input->group);
atomic_add(input->free_blocks_count,
On 2010-03-27, at 13:32, Eric Sandeen wrote:
> #13549, Kernel oops while online resizing of an ext4 filesystem
>
> if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
> and every other access to this first tests s_log_groups_per_flex;
> same thing needs to happen in resize or we'll wander off into
> a null pointer.
Does it even make sense to set INCOMPAT_FLEX_BG if we only have a
single group per flexbg? That is just a normal filesystem then. That
would be a separate bug in mke2fs.
> Reported-by: Alessandro Polverini <[email protected]>
> Test-case-by: Christoph Biedl <[email protected]
> >
> Signed-off-by: Eric Sandeen <[email protected]>
> ---
>
> Index: linux-2.6/fs/ext4/resize.c
> ===================================================================
> --- linux-2.6.orig/fs/ext4/resize.c
> +++ linux-2.6/fs/ext4/resize.c
> @@ -930,7 +930,8 @@ int ext4_group_add(struct super_block *s
> percpu_counter_add(&sbi->s_freeinodes_counter,
> EXT4_INODES_PER_GROUP(sb));
>
> - if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
> + if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG) &&
> + sbi->s_log_groups_per_flex) {
> ext4_group_t flex_group;
> flex_group = ext4_flex_group(sbi, input->group);
> atomic_add(input->free_blocks_count,
>
> --
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Cheers, Andreas
--
Andreas Dilger
Principal Engineer, Lustre Group
Oracle Corporation Canada Inc.
Andreas Dilger wrote:
> On 2010-03-27, at 13:32, Eric Sandeen wrote:
>> #13549, Kernel oops while online resizing of an ext4 filesystem
>>
>> if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
>> and every other access to this first tests s_log_groups_per_flex;
>> same thing needs to happen in resize or we'll wander off into
>> a null pointer.
>
> Does it even make sense to set INCOMPAT_FLEX_BG if we only have a single
> group per flexbg? That is just a normal filesystem then. That would be
> a separate bug in mke2fs.
yes, I really wondered about that, but we have this check throughout the
ext4 kernel code right now, so as a quick fix ...
(note in this case it was an ext3 fs converted to ext4, with tune2fs:)
# tune2fs -O extents,uninit_bg,dir_index,flex_bg,huge_file,dir_nlink,extra_isize fsfile
I haven't honestly looked at what it means to "turn on" flex_bg
for a filesystem not originally mkfs'd with it. I'm not sure it does
anything other than setting the flag, leaving flex group size == group size.
Thanks,
-Eric
On Sun, Mar 28, 2010 at 09:14:07AM -0600, Andreas Dilger wrote:
> On 2010-03-27, at 13:32, Eric Sandeen wrote:
> >#13549, Kernel oops while online resizing of an ext4 filesystem
> >
> >if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
> >and every other access to this first tests s_log_groups_per_flex;
> >same thing needs to happen in resize or we'll wander off into
> >a null pointer.
>
> Does it even make sense to set INCOMPAT_FLEX_BG if we only have a
> single group per flexbg? That is just a normal filesystem then.
> That would be a separate bug in mke2fs.
Yes, it does make sense to set flex_bg in this case; it allows the
group metadata to be stored outside of a blockgroup, which is helpful
to e2fsck in some cases when it needs to relocate an inode table and
there's no contiguous free space available in the block group.
- Ted
On Sat, Mar 27, 2010 at 02:32:16PM -0500, Eric Sandeen wrote:
> This is for kernel.org bug:
>
> #13549, Kernel oops while online resizing of an ext4 filesystem
>
> if groups_per_flex < 2, sbi->s_flex_groups[] doesn't get filled out,
> and every other access to this first tests s_log_groups_per_flex;
> same thing needs to happen in resize or we'll wander off into
> a null pointer.
Added to the ext4 patch queue, thanks.
- Ted