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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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