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On 7/25/07, Al Viro <viro@ftp.linux.org.uk> wrote: > On Wed, Jul 25, 2007 at 11:48:35AM +0800, rae l wrote: > > Why alloc_super use a static variable default_op? > > the static struct super_operations default_op is just all zeros, and > > just referenced as the initial value of a new allocated super_block, > > what does it for? > > So that we would not have to care about ->s_op *ever* being NULL. But is it valuable? Compared to a waste of sizeof(struct super_block) bytes memory. When some code want to refer fs_type->s_op, it almost always want to refer some function pointer in s_op with fs_type->s_op->***, but all pointers in default_op are all NULLs, what about this scenario? and if you do grep s_op in the source code, you will found nowhere will want to test s_op or dependent on s_op not NULL. So my opinion is to remove default_ops, just keep new allocated s_op NULL. > -- Denis Cheng Linux Application Developer "One of my most productive days was throwing away 1000 lines of code." - Ken Thompson. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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