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    SubjectRe: 2.1.118 Tons of oopes (arms waving violently!!!)
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    > Potentially. I've thought about it on and off, but it's painful to add the
    > entries to every single driver, and the win has never been very big.
    >

    Did you see my message on this? You can do auto initialization in register_blkdev.
    Additionally, my suggestion changes the device arrays to simply hardwire invalid
    devices to a fops which simply returns 0 (or NULL or whatever) when it hits a bad
    device.

    The math is pretty simple:

    right now, we're loading the struct from the device array, checking a pointer in
    the structure, then we're executing that or returning NULL.

    My method was to simply preset all the NULL entries in register_blkdev to point
    to the generic case equivelent and blindly call the function with a simple inline
    macro:

    #define function(dev) do { \
    device_array[MAJOR(dev)]->function(dev); \
    } while(0)

    It's simple, it's elegant and it leverages precomputed tables all over the place.
    I would reckon that we could gain a usec or more in benchmarks with this optimization.

    > Also note that many of the current NULL checks (not the ones for the fops
    > thing, but for other things) are superfluous: we check for NULL not
    > because we need to, but often because it's just an almost automatic thing
    > for me.
    >
    > For example, there is sometimes code essentially like this (see
    > sys_lseek(), for example)
    >
    > struct dentry * dentry;
    > struct inode * inode;
    > struct file * filp = fget(fd);
    >
    > if (!filp)
    > return -EBADF;
    >
    > dentry = filp->f_dentry;
    > if (!dentry)
    > return -EBADF;
    >
    > inode = dentry->d_inode;
    > if (!inode)
    > return -BADF;
    >
    > and the only check that needs to be done is really the filp one: if you
    > get a filp that is active, then the dentry and inode had better be there,
    > because it would be a major error (worthy of a kernel oops) if they
    > weren't, so checking for dentry/inode being non-NULL is unnecessary, but
    > often done simply because I and others have been anal about it.
    >
    > Personally, I would suggest against changing all the file and inode
    > operations unless somebody can show cases where it makes a real-world
    > difference in performance..
    >
    > Linus
    >
    >
    > -
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    --
    Perry Harrington Linux rules all OSes. APSoft ()
    email: perry@apsoft.com Think Blue. /\

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