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    SubjectRe: [PATCH v2] Btrfs: use do_div to avoid compile errors on 32bit box
    On 08/19/2011 10:17 PM, Liu Bo wrote:
    > When doing div operation of u64 type, we need to be careful and use do_div
    > to avoid compile ERROR on 32bit box:
    >
    > "ERROR: "__udivdi3" [fs/btrfs/btrfs.ko] undefined!
    > make[1]: *** [__modpost] Error 1
    >
    > v1->v2:
    > - fix stupid do_div() with type "signed integer".
    >
    > Signed-off-by: Liu Bo <liubo2009@cn.fujitsu.com>
    > ---
    > fs/btrfs/extent-tree.c | 11 ++++++-----
    > 1 files changed, 6 insertions(+), 5 deletions(-)
    >
    > diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
    > index 80d6148..e43e4f1 100644
    > --- a/fs/btrfs/extent-tree.c
    > +++ b/fs/btrfs/extent-tree.c
    > @@ -6735,9 +6735,10 @@ int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
    > struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
    > struct btrfs_device *device;
    > u64 min_free;
    > + u32 dev_min = 1;
    > + u32 dev_nr = 0;
    > + u32 dup = 2;
    > int index;
    > - int dev_nr = 0;
    > - int dev_min = 1;
    > int full = 0;
    > int ret = 0;
    >
    > @@ -6796,14 +6797,14 @@ int btrfs_can_relocate(struct btrfs_root *root, u64 bytenr)
    > index = get_block_group_index(block_group);
    > if (index == 0) {
    > dev_min = 4;
    > - min_free /= 2;
    > + do_div(min_free, dup);

    I think Linus was less complaining about how you're dividing here and
    more about the fact that you are. A divide by 2 is the same as a >> 1.
    I'll send a patch to fix this. Thanks,

    Josef


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