From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:57218 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751617AbcIXEC2 (ORCPT ); Sat, 24 Sep 2016 00:02:28 -0400 Date: Sat, 24 Sep 2016 05:02:26 +0100 From: Al Viro To: Linus Torvalds Cc: Dave Chinner , CAI Qian , linux-xfs , xfs@oss.sgi.com, Jens Axboe , Nick Piggin , linux-fsdevel Subject: [PATCH 12/12] switch default_file_splice_read() to use of pipe-backed iov_iter Message-ID: <20160924040226.GR2356@ZenIV.linux.org.uk> References: <20160914031648.GB2356@ZenIV.linux.org.uk> <20160914042559.GC2356@ZenIV.linux.org.uk> <20160917082007.GA6489@ZenIV.linux.org.uk> <20160917190023.GA8039@ZenIV.linux.org.uk> <20160923190032.GA25771@ZenIV.linux.org.uk> <20160923190326.GB2356@ZenIV.linux.org.uk> <20160923201025.GJ2356@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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 --- fs/splice.c | 111 ++++++++++++++++++++++-------------------------------------- 1 file changed, 40 insertions(+), 71 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index 58c322a..0df907b 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -361,7 +361,7 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = { }; EXPORT_SYMBOL(nosteal_pipe_buf_ops); -static ssize_t kernel_readv(struct file *file, const struct iovec *vec, +static ssize_t kernel_readv(struct file *file, const struct kvec *vec, unsigned long vlen, loff_t offset) { mm_segment_t old_fs; @@ -397,96 +397,65 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { + struct kvec *vec, __vec[PIPE_DEF_BUFFERS]; + struct iov_iter to; + struct page **pages; unsigned int nr_pages; - unsigned int nr_freed; - size_t offset; - struct page *pages[PIPE_DEF_BUFFERS]; - struct partial_page partial[PIPE_DEF_BUFFERS]; - struct iovec *vec, __vec[PIPE_DEF_BUFFERS]; + size_t offset, dummy, copied = 0; ssize_t res; - size_t this_len; - int error; int i; - struct splice_pipe_desc spd = { - .pages = pages, - .partial = partial, - .nr_pages_max = PIPE_DEF_BUFFERS, - .flags = flags, - .ops = &default_pipe_buf_ops, - .spd_release = spd_release_page, - }; - if (splice_grow_spd(pipe, &spd)) + if (pipe->nrbufs == pipe->buffers) + return -EAGAIN; + + /* + * Try to keep page boundaries matching to source pagecache ones - + * it probably won't be much help, but... + */ + offset = *ppos & ~PAGE_MASK; + + iov_iter_pipe(&to, ITER_PIPE | READ, pipe, len + offset); + + res = iov_iter_get_pages_alloc(&to, &pages, len + offset, &dummy); + if (res <= 0) return -ENOMEM; - res = -ENOMEM; + nr_pages = res / PAGE_SIZE; + vec = __vec; - if (spd.nr_pages_max > PIPE_DEF_BUFFERS) { - vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL); - if (!vec) - goto shrink_ret; + if (nr_pages > PIPE_DEF_BUFFERS) { + vec = kmalloc(nr_pages * sizeof(struct kvec), GFP_KERNEL); + if (unlikely(!vec)) { + res = -ENOMEM; + goto out; + } } - offset = *ppos & ~PAGE_MASK; - nr_pages = (len + offset + PAGE_SIZE - 1) >> PAGE_SHIFT; - - for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) { - struct page *page; - - page = alloc_page(GFP_USER); - error = -ENOMEM; - if (!page) - goto err; + pipe->bufs[to.idx].offset = offset; + pipe->bufs[to.idx].len -= offset; - this_len = min_t(size_t, len, PAGE_SIZE - offset); - vec[i].iov_base = (void __user *) page_address(page); + for (i = 0; i < nr_pages; i++) { + size_t this_len = min_t(size_t, len, PAGE_SIZE - offset); + vec[i].iov_base = page_address(pages[i]) + offset; vec[i].iov_len = this_len; - spd.pages[i] = page; - spd.nr_pages++; len -= this_len; offset = 0; } - res = kernel_readv(in, vec, spd.nr_pages, *ppos); - if (res < 0) { - error = res; - goto err; - } - - error = 0; - if (!res) - goto err; - - nr_freed = 0; - for (i = 0; i < spd.nr_pages; i++) { - this_len = min_t(size_t, vec[i].iov_len, res); - spd.partial[i].offset = 0; - spd.partial[i].len = this_len; - if (!this_len) { - __free_page(spd.pages[i]); - spd.pages[i] = NULL; - nr_freed++; - } - res -= this_len; - } - spd.nr_pages -= nr_freed; - - res = splice_to_pipe(pipe, &spd); - if (res > 0) + res = kernel_readv(in, vec, nr_pages, *ppos); + if (res > 0) { + copied = res; *ppos += res; + } -shrink_ret: if (vec != __vec) kfree(vec); - splice_shrink_spd(&spd); +out: + for (i = 0; i < nr_pages; i++) + put_page(pages[i]); + kvfree(pages); + iov_iter_advance(&to, copied); /* truncates and discards */ return res; - -err: - for (i = 0; i < spd.nr_pages; i++) - __free_page(spd.pages[i]); - - res = error; - goto shrink_ret; } /* -- 2.9.3