| Message ID | 1313806667-30495-1-git-send-email-liubo2009@cn.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, Aug 20, 2011 at 5:21 AM, Josef Bacik <josef@redhat.com> wrote: > > 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, Indeed. A single-bit 64-bit "double shift" may be a few cycles, but it's still pretty damn cheap. Especially when compared to a 64x32 bit divide. We absolutely don't want to do "do_div()" in order to divide by the constant 2. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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); } else if (index == 1) { dev_min = 2; } else if (index == 2) { - min_free *= 2; + min_free *= dup; } else if (index == 3) { dev_min = fs_devices->rw_devices; - min_free /= dev_min; + do_div(min_free, dev_min); } mutex_lock(&root->fs_info->chunk_mutex);
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(-)