The intent here was to do a logical && instead of a bitwise &. The
original condition tests whether they have the some of same bits set.
I have fixed that and rewritten it to be more clear.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
Warning: This is a static analysis bug and I''m not very familiar with
the code. Please review carefully.
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 0b4e2af..0c54027 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2376,8 +2376,8 @@ static int should_balance_chunk(struct btrfs_root *root,
u64 chunk_type = btrfs_chunk_type(leaf, chunk);
/* type filter */
- if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) &
- (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) {
+ if (!(chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) ||
+ !(bctl->flags & BTRFS_BALANCE_TYPE_MASK)) {
return 0;
}
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On Fri, Jan 20, 2012 at 10:54:55AM +0300, Dan Carpenter wrote:> The intent here was to do a logical && instead of a bitwise &. The > original condition tests whether they have the some of same bits set. > I have fixed that and rewritten it to be more clear. > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > --- > Warning: This is a static analysis bug and I''m not very familiar with > the code. Please review carefully. > > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 0b4e2af..0c54027 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -2376,8 +2376,8 @@ static int should_balance_chunk(struct btrfs_root *root, > u64 chunk_type = btrfs_chunk_type(leaf, chunk); > > /* type filter */ > - if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) & > - (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) { > + if (!(chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) || > + !(bctl->flags & BTRFS_BALANCE_TYPE_MASK)) { > return 0; > } >The intent here is definitely bitwise &. The original code tests whether at least one of the bits set in (chunk_type & MASK) is set in (bctl_flags & MASK), and if not returns 0. IOW, u64 mask = chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK; if (((bctl->flags & BTRFS_BALANCE_TYPE_MASK) & mask) == 0) return 0; Your patch does something completely different. However, I think we can strengthen that check (and make it more idiomatic). Can you try the below diff with your checker ? Thanks, Ilya diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 7ffdb15..9c6a074 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -2375,12 +2375,11 @@ static int should_balance_chunk(struct btrfs_root *root, struct btrfs_balance_control *bctl = root->fs_info->balance_ctl; struct btrfs_balance_args *bargs = NULL; u64 chunk_type = btrfs_chunk_type(leaf, chunk); + u64 mask = chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK; /* type filter */ - if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) & - (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) { + if (((bctl->flags & BTRFS_BALANCE_TYPE_MASK) & mask) != mask) return 0; - } if (chunk_type & BTRFS_BLOCK_GROUP_DATA) bargs = &bctl->data; -- 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 Fri, Jan 20, 2012 at 04:24:37PM +0200, Ilya Dryomov wrote:> --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -2375,12 +2375,11 @@ static int should_balance_chunk(struct btrfs_root *root, > struct btrfs_balance_control *bctl = root->fs_info->balance_ctl; > struct btrfs_balance_args *bargs = NULL; > u64 chunk_type = btrfs_chunk_type(leaf, chunk); > + u64 mask = chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK; > > /* type filter */ > - if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) & > - (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) { > + if (((bctl->flags & BTRFS_BALANCE_TYPE_MASK) & mask) != mask)I don''t know if it matters, but semantically this is not equivalent to the original. If mask has no flags set then this will pass. This says that every flag in mask but has to be set in ->flags but in the original code, only one needed to be. The original code was equivalent to: if (!(chunk_type & bctl->flags & BTRFS_BLOCK_GROUP_TYPE_MASK & BTRFS_BALANCE_TYPE_MASK)) {... It''s weird that we have BTRFS_BLOCK_GROUP_TYPE_MASK and BTRFS_BALANCE_TYPE_MASK which are the same except that the bitfields have been renamed. Can''t we just reuse the first definition? But really, if this isn''t a bug, then I don''t care. The original is fine, or whatever you choose. regards, dan carpenter
On Fri, Jan 20, 2012 at 06:21:29PM +0300, Dan Carpenter wrote:> On Fri, Jan 20, 2012 at 04:24:37PM +0200, Ilya Dryomov wrote: > > --- a/fs/btrfs/volumes.c > > +++ b/fs/btrfs/volumes.c > > @@ -2375,12 +2375,11 @@ static int should_balance_chunk(struct btrfs_root *root, > > struct btrfs_balance_control *bctl = root->fs_info->balance_ctl; > > struct btrfs_balance_args *bargs = NULL; > > u64 chunk_type = btrfs_chunk_type(leaf, chunk); > > + u64 mask = chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK; > > > > /* type filter */ > > - if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) & > > - (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) { > > + if (((bctl->flags & BTRFS_BALANCE_TYPE_MASK) & mask) != mask) > > I don''t know if it matters, but semantically this is not > equivalent to the original. If mask has no flags set then this will > pass. This says that every flag in mask but has to be set in > ->flags but in the original code, only one needed to be.Yeah, that''s why I said "we can strengthen that check".> > The original code was equivalent to: > if (!(chunk_type & bctl->flags & BTRFS_BLOCK_GROUP_TYPE_MASK & > BTRFS_BALANCE_TYPE_MASK)) {... > > It''s weird that we have BTRFS_BLOCK_GROUP_TYPE_MASK and > BTRFS_BALANCE_TYPE_MASK which are the same except that the bitfields > have been renamed. Can''t we just reuse the first definition? > > But really, if this isn''t a bug, then I don''t care. The original is > fine, or whatever you choose.This is not a bug. Thanks, Ilya -- 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