switch default_file_splice_read() to use of pipe-backed iov_iter
we only use iov_iter_get_pages_alloc() and iov_iter_advance() - pages are filled by kernel_readv() via a kvec array (as we used to do all along), so iov_iter here is used only as a way of arranging for those pages to be in pipe. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
parent
82c156f853
commit
523ac9afc7
111
fs/splice.c
111
fs/splice.c
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@ -361,7 +361,7 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
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};
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EXPORT_SYMBOL(nosteal_pipe_buf_ops);
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static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
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static ssize_t kernel_readv(struct file *file, const struct kvec *vec,
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unsigned long vlen, loff_t offset)
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{
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mm_segment_t old_fs;
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@ -397,96 +397,65 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
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struct pipe_inode_info *pipe, size_t len,
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unsigned int flags)
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{
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struct kvec *vec, __vec[PIPE_DEF_BUFFERS];
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struct iov_iter to;
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struct page **pages;
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unsigned int nr_pages;
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unsigned int nr_freed;
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size_t offset;
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struct page *pages[PIPE_DEF_BUFFERS];
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struct partial_page partial[PIPE_DEF_BUFFERS];
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struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
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size_t offset, dummy, copied = 0;
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ssize_t res;
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size_t this_len;
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int error;
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int i;
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struct splice_pipe_desc spd = {
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.pages = pages,
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.partial = partial,
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.nr_pages_max = PIPE_DEF_BUFFERS,
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.flags = flags,
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.ops = &default_pipe_buf_ops,
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.spd_release = spd_release_page,
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};
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if (splice_grow_spd(pipe, &spd))
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if (pipe->nrbufs == pipe->buffers)
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return -EAGAIN;
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/*
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* Try to keep page boundaries matching to source pagecache ones -
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* it probably won't be much help, but...
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*/
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offset = *ppos & ~PAGE_MASK;
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iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset);
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res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &dummy);
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if (res <= 0)
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return -ENOMEM;
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res = -ENOMEM;
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nr_pages = res / PAGE_SIZE;
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vec = __vec;
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if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
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vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
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if (!vec)
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goto shrink_ret;
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if (nr_pages > PIPE_DEF_BUFFERS) {
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vec = kmalloc(nr_pages * sizeof(struct kvec), GFP_KERNEL);
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if (unlikely(!vec)) {
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res = -ENOMEM;
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goto out;
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}
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}
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offset = *ppos & ~PAGE_MASK;
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nr_pages = (len + offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
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pipe->bufs[to.idx].offset = offset;
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pipe->bufs[to.idx].len -= offset;
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for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
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struct page *page;
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page = alloc_page(GFP_USER);
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error = -ENOMEM;
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if (!page)
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goto err;
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this_len = min_t(size_t, len, PAGE_SIZE - offset);
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vec[i].iov_base = (void __user *) page_address(page);
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for (i = 0; i < nr_pages; i++) {
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size_t this_len = min_t(size_t, len, PAGE_SIZE - offset);
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vec[i].iov_base = page_address(pages[i]) + offset;
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vec[i].iov_len = this_len;
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spd.pages[i] = page;
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spd.nr_pages++;
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len -= this_len;
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offset = 0;
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}
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res = kernel_readv(in, vec, spd.nr_pages, *ppos);
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if (res < 0) {
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error = res;
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goto err;
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}
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error = 0;
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if (!res)
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goto err;
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nr_freed = 0;
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for (i = 0; i < spd.nr_pages; i++) {
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this_len = min_t(size_t, vec[i].iov_len, res);
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spd.partial[i].offset = 0;
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spd.partial[i].len = this_len;
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if (!this_len) {
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__free_page(spd.pages[i]);
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spd.pages[i] = NULL;
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nr_freed++;
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}
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res -= this_len;
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}
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spd.nr_pages -= nr_freed;
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res = splice_to_pipe(pipe, &spd);
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if (res > 0)
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res = kernel_readv(in, vec, nr_pages, *ppos);
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if (res > 0) {
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copied = res;
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*ppos += res;
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}
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shrink_ret:
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if (vec != __vec)
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kfree(vec);
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splice_shrink_spd(&spd);
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out:
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for (i = 0; i < nr_pages; i++)
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put_page(pages[i]);
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kvfree(pages);
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iov_iter_advance(&to, copied); /* truncates and discards */
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return res;
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err:
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for (i = 0; i < spd.nr_pages; i++)
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__free_page(spd.pages[i]);
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res = error;
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goto shrink_ret;
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}
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/*
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