* [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
@ 2021-02-09 17:33 Marek Behún
2021-02-10 0:09 ` Qu Wenruo
2021-03-02 3:47 ` Tom Rini
0 siblings, 2 replies; 7+ messages in thread
From: Marek Behún @ 2021-02-09 17:33 UTC (permalink / raw)
To: u-boot; +Cc: linux-btrfs, Marek Behún, David Sterba, Qu Wenruo, Tom Rini
When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
location key offset other than -1, it currently fails via BUG_ON.
The offset can have other value than -1, though. This can happen for
example if a subvolume is renamed:
$ btrfs subvolume create X && sync
Create subvolume './X'
$ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
location key (270 ROOT_ITEM 18446744073709551615) type DIR
transid 283 data_len 0 name_len 1
name: X
$ mv X Y && sync
$ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
location key (270 ROOT_ITEM 0) type DIR
transid 285 data_len 0 name_len 1
name: Y
As can be seen the offset changed from -1ULL to 0.
Do not fail in this case.
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Cc: David Sterba <dsterba@suse.com>
Cc: Qu Wenruo <wqu@suse.com>
Cc: Tom Rini <trini@konsulko.com>
---
fs/btrfs/disk-io.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b332ecb796..c6fdec95c1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -732,8 +732,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
return fs_info->chunk_root;
if (location->objectid == BTRFS_CSUM_TREE_OBJECTID)
return fs_info->csum_root;
- BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID ||
- location->offset != (u64)-1);
+ BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID);
node = rb_search(&fs_info->fs_root_tree, (void *)&objectid,
btrfs_fs_roots_compare_objectids, NULL);
--
2.26.2
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-09 17:33 [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1 Marek Behún
@ 2021-02-10 0:09 ` Qu Wenruo
2021-02-10 1:05 ` Marek Behun
2021-03-02 3:47 ` Tom Rini
1 sibling, 1 reply; 7+ messages in thread
From: Qu Wenruo @ 2021-02-10 0:09 UTC (permalink / raw)
To: Marek Behún, u-boot; +Cc: linux-btrfs, David Sterba, Qu Wenruo, Tom Rini
On 2021/2/10 上午1:33, Marek Behún wrote:
> When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
> location key offset other than -1, it currently fails via BUG_ON.
>
> The offset can have other value than -1, though. This can happen for
> example if a subvolume is renamed:
>
> $ btrfs subvolume create X && sync
> Create subvolume './X'
> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
> location key (270 ROOT_ITEM 18446744073709551615) type DIR
> transid 283 data_len 0 name_len 1
> name: X
> $ mv X Y && sync
> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
> location key (270 ROOT_ITEM 0) type DIR
> transid 285 data_len 0 name_len 1
> name: Y
>
> As can be seen the offset changed from -1ULL to 0.
Offset for subvolume ROOT_ITEM can be other values, especially for
snapshot that offset is the transid when it get created.
But the problem is, if we call btrfs_read_fs_root() for subvolume tree,
the offset of the key really doesn't matter, the only important thing is
the objectid.
Thus we use that BUG_ON() to catch careless callers.
Would you please provide a case where we wrongly call
btrfs_read_fs_root() with incorrect offset inside btrfs-progs/uboot?
I believe that would be the proper way to fix.
Thanks,
Qu
>
> Do not fail in this case.
>
> Signed-off-by: Marek Behún <marek.behun@nic.cz>
> Cc: David Sterba <dsterba@suse.com>
> Cc: Qu Wenruo <wqu@suse.com>
> Cc: Tom Rini <trini@konsulko.com>
> ---
> fs/btrfs/disk-io.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index b332ecb796..c6fdec95c1 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -732,8 +732,7 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
> return fs_info->chunk_root;
> if (location->objectid == BTRFS_CSUM_TREE_OBJECTID)
> return fs_info->csum_root;
> - BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID ||
> - location->offset != (u64)-1);
> + BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID);
>
> node = rb_search(&fs_info->fs_root_tree, (void *)&objectid,
> btrfs_fs_roots_compare_objectids, NULL);
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-10 0:09 ` Qu Wenruo
@ 2021-02-10 1:05 ` Marek Behun
2021-02-10 1:20 ` Qu Wenruo
0 siblings, 1 reply; 7+ messages in thread
From: Marek Behun @ 2021-02-10 1:05 UTC (permalink / raw)
To: Qu Wenruo; +Cc: u-boot, linux-btrfs, David Sterba, Qu Wenruo, Tom Rini
On Wed, 10 Feb 2021 08:09:14 +0800
Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
> On 2021/2/10 上午1:33, Marek Behún wrote:
> > When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
> > location key offset other than -1, it currently fails via BUG_ON.
> >
> > The offset can have other value than -1, though. This can happen for
> > example if a subvolume is renamed:
> >
> > $ btrfs subvolume create X && sync
> > Create subvolume './X'
> > $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
> > location key (270 ROOT_ITEM 18446744073709551615) type DIR
> > transid 283 data_len 0 name_len 1
> > name: X
> > $ mv X Y && sync
> > $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
> > location key (270 ROOT_ITEM 0) type DIR
> > transid 285 data_len 0 name_len 1
> > name: Y
> >
> > As can be seen the offset changed from -1ULL to 0.
>
>
> Offset for subvolume ROOT_ITEM can be other values, especially for
> snapshot that offset is the transid when it get created.
>
> But the problem is, if we call btrfs_read_fs_root() for subvolume tree,
> the offset of the key really doesn't matter, the only important thing is
> the objectid.
>
> Thus we use that BUG_ON() to catch careless callers.
>
> Would you please provide a case where we wrongly call
> btrfs_read_fs_root() with incorrect offset inside btrfs-progs/uboot?
>
> I believe that would be the proper way to fix.
Qu,
this can be triggered in U-Boot when listing a directory containing a
subvolume that was renamed:
- create a subvolume && sync
- rename subvolume && sync
- umount, reboot, list the directory containing the subvolume in
u-boot
It will also break when you want to read a file that has a subvolume in
it's path (e.g. `read mmc 0 0x10000000 /renamed-subvol/file`).
I found out this btrfs-progs commit:
https://github.com/kdave/btrfs-progs/commit/10f1af0fe7de5a0310657993c7c21a1d78087e56
This commit ensures that while searching a directory recursively, when
a ROOT_ITEM is encountered, the offset of its location is changed to -1
before passing the location to btrfs_read_fs_root().
So maybe we could do this in u-boot as well, but why do this? Linux'
btrfs driver does not check whether the offset is -1. So why do it here?
BTW, Qu, I think we have to change the BUG_ON code in U-Boot's btrfs
driver. BUG_ON in U-Boot calls a complete SOC reset. We can't break
whole U-Boot simply because btrfs partition contains broken data.
U-Boot commands must fail in such a case, not reset the SOC.
Marek
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-10 1:05 ` Marek Behun
@ 2021-02-10 1:20 ` Qu Wenruo
2021-02-10 16:21 ` Marek Behun
0 siblings, 1 reply; 7+ messages in thread
From: Qu Wenruo @ 2021-02-10 1:20 UTC (permalink / raw)
To: Marek Behun, Qu Wenruo; +Cc: u-boot, linux-btrfs, David Sterba, Tom Rini
On 2021/2/10 上午9:05, Marek Behun wrote:
> On Wed, 10 Feb 2021 08:09:14 +0800
> Qu Wenruo <quwenruo.btrfs@gmx.com> wrote:
>
>> On 2021/2/10 上午1:33, Marek Behún wrote:
>>> When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
>>> location key offset other than -1, it currently fails via BUG_ON.
>>>
>>> The offset can have other value than -1, though. This can happen for
>>> example if a subvolume is renamed:
>>>
>>> $ btrfs subvolume create X && sync
>>> Create subvolume './X'
>>> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
>>> location key (270 ROOT_ITEM 18446744073709551615) type DIR
>>> transid 283 data_len 0 name_len 1
>>> name: X
>>> $ mv X Y && sync
>>> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
>>> location key (270 ROOT_ITEM 0) type DIR
>>> transid 285 data_len 0 name_len 1
>>> name: Y
>>>
>>> As can be seen the offset changed from -1ULL to 0.
>>
>>
>> Offset for subvolume ROOT_ITEM can be other values, especially for
>> snapshot that offset is the transid when it get created.
>>
>> But the problem is, if we call btrfs_read_fs_root() for subvolume tree,
>> the offset of the key really doesn't matter, the only important thing is
>> the objectid.
>>
>> Thus we use that BUG_ON() to catch careless callers.
>>
>> Would you please provide a case where we wrongly call
>> btrfs_read_fs_root() with incorrect offset inside btrfs-progs/uboot?
>>
>> I believe that would be the proper way to fix.
>
> Qu,
>
> this can be triggered in U-Boot when listing a directory containing a
> subvolume that was renamed:
> - create a subvolume && sync
> - rename subvolume && sync
> - umount, reboot, list the directory containing the subvolume in
> u-boot
> It will also break when you want to read a file that has a subvolume in
> it's path (e.g. `read mmc 0 0x10000000 /renamed-subvol/file`).
>
> I found out this btrfs-progs commit:
> https://github.com/kdave/btrfs-progs/commit/10f1af0fe7de5a0310657993c7c21a1d78087e56
> This commit ensures that while searching a directory recursively, when
> a ROOT_ITEM is encountered, the offset of its location is changed to -1
> before passing the location to btrfs_read_fs_root().
That's what I expect the code to do, but you're right, if kernel is not
doing it anymore, I prefer the kernel behavior.
>
> So maybe we could do this in u-boot as well, but why do this? Linux'
> btrfs driver does not check whether the offset is -1. So why do it here?
You're correct, the kernel is using new schema, btrfs_get_fs_root(),
which only requires root objectid and completely get rid of the
offset/type, which is far less possible to call with wrong parameters.
It would be a good timing to sync the code between kernel and
progs/u-boot now.
>
> BTW, Qu, I think we have to change the BUG_ON code in U-Boot's btrfs
> driver. BUG_ON in U-Boot calls a complete SOC reset. We can't break
> whole U-Boot simply because btrfs partition contains broken data.
> U-Boot commands must fail in such a case, not reset the SOC.
Well, progs (and even kernel) is a mine-field for BUG_ON()s.
But at least for kernel, it's protected by tree-checker which rejects
invalid on-disk data before it reaches btrfs code, thus mostly kernel
BUG_ON()s are really hard to hit (a lot of them are even impossible to
hit after the introduction of tree-checker), and indicate real problems.
For now, the BUG_ON()s in U-boot still indicates problems that we can't
really solve or doesn't expect at all in btrfs realm, e.g. the BUG_ON()
you're hitting (call sites problem).
I admit it's a pain in the ass for full SoC reset, but I don't have any
better alternatives yet.
The mid to long term solution would be introducing tree-checker to
U-boot, so that the remaining BUG_ON()s are really code bugs.
Thanks,
Qu
>
> Marek
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-10 1:20 ` Qu Wenruo
@ 2021-02-10 16:21 ` Marek Behun
2021-02-10 23:24 ` Qu Wenruo
0 siblings, 1 reply; 7+ messages in thread
From: Marek Behun @ 2021-02-10 16:21 UTC (permalink / raw)
To: Qu Wenruo; +Cc: Qu Wenruo, u-boot, linux-btrfs, David Sterba, Tom Rini
On Wed, 10 Feb 2021 09:20:11 +0800
Qu Wenruo <wqu@suse.com> wrote:
> You're correct, the kernel is using new schema, btrfs_get_fs_root(),
> which only requires root objectid and completely get rid of the
> offset/type, which is far less possible to call with wrong parameters.
>
> It would be a good timing to sync the code between kernel and
> progs/u-boot now.
So do you agree with this patch? If so, can you add Reviewed-by? Thanks.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-10 16:21 ` Marek Behun
@ 2021-02-10 23:24 ` Qu Wenruo
0 siblings, 0 replies; 7+ messages in thread
From: Qu Wenruo @ 2021-02-10 23:24 UTC (permalink / raw)
To: Marek Behun, Qu Wenruo; +Cc: u-boot, linux-btrfs, David Sterba, Tom Rini
On 2021/2/11 上午12:21, Marek Behun wrote:
> On Wed, 10 Feb 2021 09:20:11 +0800
> Qu Wenruo <wqu@suse.com> wrote:
>
>> You're correct, the kernel is using new schema, btrfs_get_fs_root(),
>> which only requires root objectid and completely get rid of the
>> offset/type, which is far less possible to call with wrong parameters.
>>
>> It would be a good timing to sync the code between kernel and
>> progs/u-boot now.
>
> So do you agree with this patch? If so, can you add Reviewed-by? Thanks.
>
I mean, to change btrfs-progs interface to follow kernel
btrfs_get_fs_root() schema, just pass objectid, without the need for
btrfs_key.
Thanks,
Qu
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1
2021-02-09 17:33 [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1 Marek Behún
2021-02-10 0:09 ` Qu Wenruo
@ 2021-03-02 3:47 ` Tom Rini
1 sibling, 0 replies; 7+ messages in thread
From: Tom Rini @ 2021-03-02 3:47 UTC (permalink / raw)
To: Marek Behún; +Cc: u-boot, linux-btrfs, David Sterba, Qu Wenruo
[-- Attachment #1: Type: text/plain, Size: 1109 bytes --]
On Tue, Feb 09, 2021 at 06:33:37PM +0100, Marek Behún wrote:
> When the btrfs_read_fs_root() function is searching a ROOT_ITEM with
> location key offset other than -1, it currently fails via BUG_ON.
>
> The offset can have other value than -1, though. This can happen for
> example if a subvolume is renamed:
>
> $ btrfs subvolume create X && sync
> Create subvolume './X'
> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: X$
> location key (270 ROOT_ITEM 18446744073709551615) type DIR
> transid 283 data_len 0 name_len 1
> name: X
> $ mv X Y && sync
> $ btrfs inspect-internal dump-tree /dev/root | grep -B 2 'name: Y$
> location key (270 ROOT_ITEM 0) type DIR
> transid 285 data_len 0 name_len 1
> name: Y
>
> As can be seen the offset changed from -1ULL to 0.
>
> Do not fail in this case.
>
> Signed-off-by: Marek Behún <marek.behun@nic.cz>
> Cc: David Sterba <dsterba@suse.com>
> Cc: Qu Wenruo <wqu@suse.com>
> Cc: Tom Rini <trini@konsulko.com>
Applied to u-boot/master, thanks!
--
Tom
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^ permalink raw reply [flat|nested] 7+ messages in thread
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2021-02-09 17:33 [PATCH u-boot] fs: btrfs: do not fail when offset of a ROOT_ITEM is not -1 Marek Behún
2021-02-10 0:09 ` Qu Wenruo
2021-02-10 1:05 ` Marek Behun
2021-02-10 1:20 ` Qu Wenruo
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