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    SubjectRe: [PATCH v4 2/3] Add preadv and pwritev system calls.
    Date
    On Thursday 18 December 2008, Gerd Hoffmann wrote:
    > This prototype has one problem though: On 32bit archs is the (64bit)
    > offset argument unaligned, which the syscall ABI of several archs
    > doesn't allow to do. At least s390 needs a wrapper in glibc to handle
    > this. As we'll need a wrappers in glibc anyway I've decided to push
    > problem to glibc entriely and use a syscall prototype which works
    > without arch-specific wrappers inside the kernel: The offset argument
    > is explicitly splitted into two 32bit values.

    Obviously, the interface looks good to me now.

    Please remember to add the function prototypes to
    include/linux/syscalls.h.

    > +asmlinkage ssize_t
    > +compat_sys_preadv(unsigned long fd, const struct compat_iovec __user *vec,
    > + unsigned long vlen, u32 pos_high, u32 pos_low)
    > +{
    > + loff_t pos = ((loff_t)pos_high << 32) | pos_low;

    This is whitespace damaged, as are the other four functions in the
    same place.

    > + struct file *file;
    > + ssize_t ret = -EBADF;
    > +
    > + if (pos < 0)
    > + return -EINVAL;
    > +
    > + file = fget(fd);
    > + if (!file)
    > + return -EBADF;

    Any reason for using fget() here, but fget_light() in sys_preadv?

    > + if (!(file->f_mode & FMODE_READ))
    > + goto out;
    > +
    > + ret = -EINVAL;
    > + if (!file->f_op || (!file->f_op->aio_read && !file->f_op->read))
    > + goto out;

    Maybe this logic could get moved into a compat_readv() function,
    similar to vfs_readv(). The advantage would be that we can make
    the native and compat paths more similar.

    Arnd <><


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