Re: [PATCH] btrfs: tree-checker: add btrfs dev extent checks

[David Sterba <dsterba@suse.cz>]

On Thu, Aug 15, 2024 at 01:17:00PM +0800, Anand Jain wrote:
> On 11/8/24 1:50 pm, Qu Wenruo wrote:
> > [REPORT]
> > There is a corruption report that btrfs refuse to mount a fs that has
> > overlapping dev extents:
> > 
> >   BTRFS error (device sdc): dev extent devid 4 physical offset
> > 14263979671552 overlap with previous dev extent end 14263980982272
> >   BTRFS error (device sdc): failed to verify dev extents against chunks: -117
> >   BTRFS error (device sdc): open_ctree failed
> > 
> > [CAUSE]
> > The cause is very obvious, there is a bad dev extent item with incorrect
> > length.
> > Although we are not 100% sure of the cause before getting the dev tree
> > dump, I'm already surprised that we do not have any checks on dev tree.
> > 
> > Currently we only do the dev-extent verification at mount time, but if the
> > corruption is caused by memory bitflip, we really want to catch it before
> > writing the corruption to the storage.
> > 
> > Furthermore the dev extent items has the following key definition:
> > 
> > 	(<device id> DEV_EXTENT <physical offset>)
> > 
> > Thus we can not just rely on the generic key order check to make sure
> > there is no overlapping.
> > 
> > [ENHANCEMENT]
> > Introduce dedicated dev extent checks, including:
> > 
> > - Fixed member checks
> >    * chunk_tree should always be BTRFS_CHUNK_TREE_OBJECTID (3)
> >    * chunk_objectid should always be
> >      BTRFS_FIRST_CHUNK_CHUNK_TREE_OBJECTID (256)
> > 
> > - Alignment checks
> >    * chunk_offset should be aligned to sectorsize
> >    * length should be aligned to sectorsize
> >    * key.offset should be aligned to sectorsize
> > 
> > - Overlap checks
> >    If the previous key is also a dev-extent item, with the same
> >    device id, make sure we do not overlap with the previous dev extent.
> > 
> > Reported: Stefan N <stefannnau@gmail.com>
> > Link: https://lore.kernel.org/linux-btrfs/CA+W5K0rSO3koYTo=nzxxTm1-Pdu1HYgVxEpgJ=aGc7d=E8mGEg@mail.gmail.com/
> > Signed-off-by: Qu Wenruo <wqu@suse.com>
> 
> Looks good.
> 
> Reviewed-by: Anand Jain <anand.jain@oracle.com>

I'm doing some updaets to for-next so I've added the tag.