Jan Blunck <[email protected]> wrote:
>
> This is a generic sendpage() for regular files.
>
> +static inline size_t
> +filemap_copy_from_kernel(struct page *page, unsigned long offset,
> + const char *buf, unsigned bytes)
> +{
> + char *kaddr;
> +
> + kaddr = kmap(page);
> + memcpy(kaddr + offset, buf, bytes);
> + kunmap(page);
Use kmap_atomic().
Move the flush_dcache_page() into here.
> +static ssize_t
> +__generic_kernel_file_write(struct file *file, const char *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct address_space * mapping = file->f_mapping;
> + struct address_space_operations *a_ops = mapping->a_ops;
> + struct inode *inode = mapping->host;
> + long status = 0;
> + loff_t pos;
> + struct page *page;
> + struct page *cached_page = NULL;
> + const int isblk = S_ISBLK(inode->i_mode);
> + ssize_t written;
> + ssize_t err;
> + size_t bytes;
> + struct pagevec lru_pvec;
> +
> + /* There is no sane reason to use O_DIRECT */
> + BUG_ON(file->f_flags & O_DIRECT);
err, this seems like an easy way for people to make the kernel go BUG.
> + if (unlikely(signal_pending(current)))
> + return -EINTR;
This doesn't help. The reason we've avoided file-to-file sendfile() is
that it can cause applications to get uninterruptibly stuck in the kernel
for ages. This code doesn't solve that problem. It needs to handle
signal_pending() inside the main loop.
And it probably needs to return a sane value (number of bytes copied)
rather than -EINTR.
I don't know if we want to add this feature, really. It's such a
specialised thing.
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