From patchwork Wed Aug 16 08:51:57 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 9903285 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 0599560231 for ; Wed, 16 Aug 2017 08:52:09 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EEB8F2898F for ; Wed, 16 Aug 2017 08:52:08 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E39B3289A5; Wed, 16 Aug 2017 08:52:08 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 612BB2898F for ; Wed, 16 Aug 2017 08:52:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751617AbdHPIwE (ORCPT ); Wed, 16 Aug 2017 04:52:04 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:49510 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751767AbdHPIwD (ORCPT ); Wed, 16 Aug 2017 04:52:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Message-Id:Date:Subject:Cc:To:From: Sender:Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=jNJLhk0naVvNRl6XVdp+jDvsKfR+gIm6ceKQD4ESzyc=; b=SGDHDdBWMmriXSd9B4OxvHerO GYQD7fUNRU1yAnjGt/VwFQG5OE4kmF6/lU+j8oHQd/Sm1JuJfLgBVX7TSqsEKsz/Kswq2HQiJ4Azn 0zyUCGMToSqT16ITGFqtyveyNqTws4jO0NF3zWxeaXqhk9LuyhQwVpb+gaNgummYsm/jBFdh6xCs8 C9E13GIatdlt+x+lotgwU7DUpAN+7fE2UtvRXlZMNjStkA2Lk2T7MKfDfOfRPVh+xRT2qQJfpHmFr kchqxUgb30cs87XcTZMGGk9RGh2K70UD5emnu0mwypHQaX/L89BzmasItbkTW4ckKx6816Vb8aUiG 1cMSrKArQ==; Received: from 80-109-164-210.cable.dynamic.surfer.at ([80.109.164.210] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.87 #1 (Red Hat Linux)) id 1dhu3W-0008CE-H1; Wed, 16 Aug 2017 08:52:02 +0000 From: Christoph Hellwig To: linux-xfs@vger.kernel.org Cc: bfoster@redhat.com Subject: [PATCH v3] xfs: open code end_buffer_async_write in xfs_finish_page_writeback Date: Wed, 16 Aug 2017 10:51:57 +0200 Message-Id: <20170816085157.24074-1-hch@lst.de> X-Mailer: git-send-email 2.11.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Our loop in xfs_finish_page_writeback, which iterates over all buffer heads in a page and then calls end_buffer_async_write, which also iterates over all buffers in the page to check if any I/O is in flight is not only inefficient, but also potentially dangerous as end_buffer_async_write can cause the page and all buffers to be freed. Replace it with a single loop that does the work of end_buffer_async_write on a per-page basis. Signed-off-by: Christoph Hellwig Reviewed-by: Brian Foster Reviewed-by: Darrick J. Wong --- Changes since V2: - set b_end_io to NULL fs/xfs/xfs_aops.c | 71 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 47 insertions(+), 24 deletions(-) diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 6bf120bb1a17..f9efd67f6fa1 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -85,11 +85,11 @@ xfs_find_bdev_for_inode( * associated buffer_heads, paying attention to the start and end offsets that * we need to process on the page. * - * Landmine Warning: bh->b_end_io() will call end_page_writeback() on the last - * buffer in the IO. Once it does this, it is unsafe to access the bufferhead or - * the page at all, as we may be racing with memory reclaim and it can free both - * the bufferhead chain and the page as it will see the page as clean and - * unused. + * Note that we open code the action in end_buffer_async_write here so that we + * only have to iterate over the buffers attached to the page once. This is not + * only more efficient, but also ensures that we only calls end_page_writeback + * at the end of the iteration, and thus avoids the pitfall of having the page + * and buffers potentially freed after every call to end_buffer_async_write. */ static void xfs_finish_page_writeback( @@ -97,29 +97,44 @@ xfs_finish_page_writeback( struct bio_vec *bvec, int error) { - unsigned int end = bvec->bv_offset + bvec->bv_len - 1; - struct buffer_head *head, *bh, *next; + struct buffer_head *head = page_buffers(bvec->bv_page), *bh = head; + bool busy = false; unsigned int off = 0; - unsigned int bsize; + unsigned long flags; ASSERT(bvec->bv_offset < PAGE_SIZE); ASSERT((bvec->bv_offset & (i_blocksize(inode) - 1)) == 0); - ASSERT(end < PAGE_SIZE); + ASSERT(bvec->bv_offset + bvec->bv_len <= PAGE_SIZE); ASSERT((bvec->bv_len & (i_blocksize(inode) - 1)) == 0); - bh = head = page_buffers(bvec->bv_page); - - bsize = bh->b_size; + local_irq_save(flags); + bit_spin_lock(BH_Uptodate_Lock, &head->b_state); do { - if (off > end) - break; - next = bh->b_this_page; - if (off < bvec->bv_offset) - goto next_bh; - bh->b_end_io(bh, !error); -next_bh: - off += bsize; - } while ((bh = next) != head); + if (off >= bvec->bv_offset && + off < bvec->bv_offset + bvec->bv_len) { + ASSERT(buffer_async_write(bh)); + ASSERT(bh->b_end_io == NULL); + + if (error) { + mark_buffer_write_io_error(bh); + clear_buffer_uptodate(bh); + SetPageError(bvec->bv_page); + } else { + set_buffer_uptodate(bh); + } + clear_buffer_async_write(bh); + unlock_buffer(bh); + } else if (buffer_async_write(bh)) { + ASSERT(buffer_locked(bh)); + busy = true; + } + off += bh->b_size; + } while ((bh = bh->b_this_page) != head); + bit_spin_unlock(BH_Uptodate_Lock, &head->b_state); + local_irq_restore(flags); + + if (!busy) + end_page_writeback(bvec->bv_page); } /* @@ -133,8 +148,10 @@ xfs_destroy_ioend( int error) { struct inode *inode = ioend->io_inode; - struct bio *last = ioend->io_bio; - struct bio *bio, *next; + struct bio *bio = &ioend->io_inline_bio; + struct bio *last = ioend->io_bio, *next; + u64 start = bio->bi_iter.bi_sector; + bool quiet = bio_flagged(bio, BIO_QUIET); for (bio = &ioend->io_inline_bio; bio; bio = next) { struct bio_vec *bvec; @@ -155,6 +172,11 @@ xfs_destroy_ioend( bio_put(bio); } + + if (unlikely(error && !quiet)) { + xfs_err_ratelimited(XFS_I(inode)->i_mount, + "writeback error on sector %llu", start); + } } /* @@ -423,7 +445,8 @@ xfs_start_buffer_writeback( ASSERT(!buffer_delay(bh)); ASSERT(!buffer_unwritten(bh)); - mark_buffer_async_write(bh); + bh->b_end_io = NULL; + set_buffer_async_write(bh); set_buffer_uptodate(bh); clear_buffer_dirty(bh); }