From patchwork Fri Feb 3 20:59:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13128377 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0A7EC61DA4 for ; Fri, 3 Feb 2023 21:01:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232736AbjBCVBN (ORCPT ); Fri, 3 Feb 2023 16:01:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232699AbjBCVBK (ORCPT ); Fri, 3 Feb 2023 16:01:10 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3BF420D03 for ; Fri, 3 Feb 2023 12:59:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675457986; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1A6ZB3Yy8mK1H2diytJlOZUelVQn8YZ/aJwc/khkLhs=; b=HhRXwGDWPtInidox4C7aLQw7lIKxzYUBg2BfmSDKD+qXSKXk5M/28/mqxAhWi2ySXFMceH M7cKXEvFjLi4StMy975vx0OAiB5I5S1WMxopSfVljiTQSUqhJ1ZMhvLtg/Rb6Mr+1/98DL 5IKDx+GhL0bsk/jC2mVHUA0syuy5mds= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-554-U-RZ4GVOMV6HO3xiyrYlTw-1; Fri, 03 Feb 2023 15:59:42 -0500 X-MC-Unique: U-RZ4GVOMV6HO3xiyrYlTw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6E462280BCAF; Fri, 3 Feb 2023 20:59:41 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id CD729492B15; Fri, 3 Feb 2023 20:59:39 +0000 (UTC) From: David Howells To: Steve French Cc: David Howells , Al Viro , Shyam Prasad N , Rohith Surabattula , Tom Talpey , Stefan Metzmacher , Christoph Hellwig , Matthew Wilcox , Jeff Layton , linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Steve French Subject: [PATCH 03/11] cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE Date: Fri, 3 Feb 2023 20:59:21 +0000 Message-Id: <20230203205929.2126634-4-dhowells@redhat.com> In-Reply-To: <20230203205929.2126634-1-dhowells@redhat.com> References: <20230203205929.2126634-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Provide cifs_splice_read() to use a bvec rather than an pipe iterator as the latter cannot so easily be split and advanced, which is necessary to pass an iterator down to the bottom levels. Upstream cifs gets around this problem by using iov_iter_get_pages() to prefill the pipe and then passing the list of pages down. This is done by: (1) Bulk-allocate a bunch of pages to carry as much of the requested amount of data as possible, but without overrunning the available slots in the pipe and add them to an ITER_BVEC. (2) Synchronously call ->read_iter() to read into the buffer. (3) Discard any unused pages. (4) Load the remaining pages into the pipe in order and advance the head pointer. Signed-off-by: David Howells cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: Jeff Layton cc: Al Viro cc: linux-cifs@vger.kernel.org Link: https://lore.kernel.org/r/166732028113.3186319.1793644937097301358.stgit@warthog.procyon.org.uk/ # rfc --- fs/cifs/cifsfs.c | 12 +++---- fs/cifs/cifsfs.h | 3 ++ fs/cifs/file.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++ fs/splice.c | 1 + 4 files changed, 102 insertions(+), 6 deletions(-) diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c index 10e00c624922..3c57e8b11692 100644 --- a/fs/cifs/cifsfs.c +++ b/fs/cifs/cifsfs.c @@ -1358,7 +1358,7 @@ const struct file_operations cifs_file_ops = { .fsync = cifs_fsync, .flush = cifs_flush, .mmap = cifs_file_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .llseek = cifs_llseek, .unlocked_ioctl = cifs_ioctl, @@ -1378,7 +1378,7 @@ const struct file_operations cifs_file_strict_ops = { .fsync = cifs_strict_fsync, .flush = cifs_flush, .mmap = cifs_file_strict_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .llseek = cifs_llseek, .unlocked_ioctl = cifs_ioctl, @@ -1398,7 +1398,7 @@ const struct file_operations cifs_file_direct_ops = { .fsync = cifs_fsync, .flush = cifs_flush, .mmap = cifs_file_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .unlocked_ioctl = cifs_ioctl, .copy_file_range = cifs_copy_file_range, @@ -1416,7 +1416,7 @@ const struct file_operations cifs_file_nobrl_ops = { .fsync = cifs_fsync, .flush = cifs_flush, .mmap = cifs_file_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .llseek = cifs_llseek, .unlocked_ioctl = cifs_ioctl, @@ -1434,7 +1434,7 @@ const struct file_operations cifs_file_strict_nobrl_ops = { .fsync = cifs_strict_fsync, .flush = cifs_flush, .mmap = cifs_file_strict_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .llseek = cifs_llseek, .unlocked_ioctl = cifs_ioctl, @@ -1452,7 +1452,7 @@ const struct file_operations cifs_file_direct_nobrl_ops = { .fsync = cifs_fsync, .flush = cifs_flush, .mmap = cifs_file_mmap, - .splice_read = generic_file_splice_read, + .splice_read = cifs_splice_read, .splice_write = iter_file_splice_write, .unlocked_ioctl = cifs_ioctl, .copy_file_range = cifs_copy_file_range, diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h index 63a0ac2b9355..25decebbc478 100644 --- a/fs/cifs/cifsfs.h +++ b/fs/cifs/cifsfs.h @@ -100,6 +100,9 @@ extern ssize_t cifs_strict_readv(struct kiocb *iocb, struct iov_iter *to); extern ssize_t cifs_user_writev(struct kiocb *iocb, struct iov_iter *from); extern ssize_t cifs_direct_writev(struct kiocb *iocb, struct iov_iter *from); extern ssize_t cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from); +extern ssize_t cifs_splice_read(struct file *in, loff_t *ppos, + struct pipe_inode_info *pipe, size_t len, + unsigned int flags); extern int cifs_flock(struct file *pfile, int cmd, struct file_lock *plock); extern int cifs_lock(struct file *, int, struct file_lock *); extern int cifs_fsync(struct file *, loff_t, loff_t, int); diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 22dfc1f8b4f1..30d01b236f77 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -5273,3 +5273,95 @@ const struct address_space_operations cifs_addr_ops_smallbuf = { .launder_folio = cifs_launder_folio, .migrate_folio = filemap_migrate_folio, }; + +/* + * Splice data from a file into a pipe. + */ +ssize_t cifs_splice_read(struct file *file, loff_t *ppos, + struct pipe_inode_info *pipe, size_t len, + unsigned int flags) +{ + LIST_HEAD(pages); + struct iov_iter to; + struct bio_vec *bv; + struct kiocb kiocb; + struct page *page; + unsigned int head; + ssize_t ret; + size_t used, npages, chunk, remain, reclaim; + int i; + + /* Work out how much data we can actually add into the pipe */ + used = pipe_occupancy(pipe->head, pipe->tail); + npages = max_t(ssize_t, pipe->max_usage - used, 0); + len = min_t(size_t, len, npages * PAGE_SIZE); + npages = DIV_ROUND_UP(len, PAGE_SIZE); + + bv = kmalloc(array_size(npages, sizeof(bv[0])), GFP_KERNEL); + if (!bv) + return -ENOMEM; + + npages = alloc_pages_bulk_list(GFP_USER, npages, &pages); + if (!npages) { + kfree(bv); + return -ENOMEM; + } + + remain = len = min_t(size_t, len, npages * PAGE_SIZE); + + for (i = 0; i < npages; i++) { + chunk = min_t(size_t, PAGE_SIZE, remain); + page = list_first_entry(&pages, struct page, lru); + list_del_init(&page->lru); + bv[i].bv_page = page; + bv[i].bv_offset = 0; + bv[i].bv_len = chunk; + remain -= chunk; + } + + /* Do the I/O */ + iov_iter_bvec(&to, READ, bv, npages, len); + init_sync_kiocb(&kiocb, file); + kiocb.ki_pos = *ppos; + ret = call_read_iter(file, &kiocb, &to); + + reclaim = npages * PAGE_SIZE; + remain = 0; + if (ret > 0) { + reclaim -= ret; + remain = ret; + *ppos = kiocb.ki_pos; + file_accessed(file); + } else if (ret < 0) { + /* + * callers of ->splice_read() expect -EAGAIN on + * "can't put anything in there", rather than -EFAULT. + */ + if (ret == -EFAULT) + ret = -EAGAIN; + } + + /* Free any pages that didn't get touched at all. */ + for (; reclaim >= PAGE_SIZE; reclaim -= PAGE_SIZE) + __free_page(bv[--npages].bv_page); + + /* Push the remaining pages into the pipe. */ + head = pipe->head; + for (i = 0; i < npages; i++) { + struct pipe_buffer *buf = &pipe->bufs[head & (pipe->ring_size - 1)]; + + chunk = min_t(size_t, remain, PAGE_SIZE); + *buf = (struct pipe_buffer) { + .ops = &default_pipe_buf_ops, + .page = bv[i].bv_page, + .offset = 0, + .len = chunk, + }; + head++; + remain -= chunk; + } + pipe->head = head; + + kfree(bv); + return ret; +} diff --git a/fs/splice.c b/fs/splice.c index 5969b7a1d353..95435b5cca2a 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -330,6 +330,7 @@ const struct pipe_buf_operations default_pipe_buf_ops = { .try_steal = generic_pipe_buf_try_steal, .get = generic_pipe_buf_get, }; +EXPORT_SYMBOL(default_pipe_buf_ops); /* Pipe buffer operations for a socket and similar. */ const struct pipe_buf_operations nosteal_pipe_buf_ops = {