Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Mon, 18 Sep 2023 20:31:19 +0200 | Subject | Re: [PATCH 1/4] btrfs: fix 64bit division in btrfs_insert_striped_mirrored_raid_extents |
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Hi David,
On Mon, Sep 18, 2023 at 6:31 PM David Sterba <dsterba@suse.cz> wrote: > On Mon, Sep 18, 2023 at 03:03:10PM +0000, Johannes Thumshirn wrote: > > On 18.09.23 16:19, Geert Uytterhoeven wrote: > > > Hi Johannes, > > > > > > On Mon, Sep 18, 2023 at 4:14 PM Johannes Thumshirn > > > <johannes.thumshirn@wdc.com> wrote: > > >> Fix modpost error due to 64bit division on 32bit systems in > > >> btrfs_insert_striped_mirrored_raid_extents. > > >> > > >> Cc: Geert Uytterhoeven <geert@linux-m68k.org> > > >> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> > > > > > > Thanks for your patch! > > > > > >> --- a/fs/btrfs/raid-stripe-tree.c > > >> +++ b/fs/btrfs/raid-stripe-tree.c > > >> @@ -148,10 +148,10 @@ static int btrfs_insert_striped_mirrored_raid_extents( > > >> { > > >> struct btrfs_io_context *bioc; > > >> struct btrfs_io_context *rbioc; > > >> - const int nstripes = list_count_nodes(&ordered->bioc_list); > > >> - const int index = btrfs_bg_flags_to_raid_index(map_type); > > >> - const int substripes = btrfs_raid_array[index].sub_stripes; > > >> - const int max_stripes = trans->fs_info->fs_devices->rw_devices / substripes; > > >> + const size_t nstripes = list_count_nodes(&ordered->bioc_list); > > >> + const enum btrfs_raid_types index = btrfs_bg_flags_to_raid_index(map_type); > > >> + const u8 substripes = btrfs_raid_array[index].sub_stripes; > > >> + const int max_stripes = div_u64(trans->fs_info->fs_devices->rw_devices, substripes); > > > > > > What if the quotient does not fit in a signed 32-bit value? > > > > Then you've bought a lot of HDDs ;-) > > > > Jokes aside, yes this is theoretically correct. Dave can you fix > > max_stripes up to be u64 when applying? > > I think we can keep it int, or unsigned int if needed, we can't hit such > huge values for rw_devices. The 'theoretically' would fit for a machine > with infinite resources, otherwise the maximum number of devices I'd > expect is a few thousand.
rw_devices and various other *_devices are u64. Is there a good reason they are that big? With the fs fuzzing threads in mind, is any validation done on their values?
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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