linux-kernel - Re: [PATCH v4 2/3] Add preadv and pwritev system calls.

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Date:	Thu, 18 Dec 2008 14:37:57 +0100
From:	Gerd Hoffmann <kraxel@...hat.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-api@...r.kernel.org, aarcange@...hat.com
Subject: Re: [PATCH v4 2/3] Add preadv and pwritev system calls.

  Hi,

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

Done.

>> +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.

Fixed.

>> +	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?

Due to the new syscalls being derived from the readv()/preadv()
versions, which have the same inconsistency.  Dunno why.  I'd suspect
the reason is that the compat syscalls tend to be overlooked when the
code is updated.  Proof: patch #1 in this series ...

I'll switch them all over in a separate followup patch.

>> +	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().

Yes, makes sense.

cheers,
  Gerd


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