Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758272AbZIPRWt (ORCPT ); Wed, 16 Sep 2009 13:22:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753882AbZIPRWs (ORCPT ); Wed, 16 Sep 2009 13:22:48 -0400 Received: from cantor.suse.de ([195.135.220.2]:57218 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753732AbZIPRWr (ORCPT ); Wed, 16 Sep 2009 13:22:47 -0400 From: Jan Kara To: jens.axboe@oracle.com Cc: LKML , Jan Kara , Wu Fengguang Subject: [PATCH] fs: Fix busyloop in wb_writeback() Date: Wed, 16 Sep 2009 19:22:48 +0200 Message-Id: <1253121768-20673-1-git-send-email-jack@suse.cz> X-Mailer: git-send-email 1.6.0.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1868 Lines: 58 If all inodes are under writeback (e.g. in case when there's only one inode with dirty pages), wb_writeback() with WB_SYNC_NONE work basically degrades to busylooping until I_SYNC flags of the inode is cleared. Fix the problem by waiting on I_SYNC flags of an inode on b_more_io list in case we failed to write anything. CC: Wu Fengguang Signed-off-by: Jan Kara --- fs/fs-writeback.c | 19 ++++++++++++++++++- 1 files changed, 18 insertions(+), 1 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 8e1e5e1..c59d673 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -706,6 +706,7 @@ static long wb_writeback(struct bdi_writeback *wb, }; unsigned long oldest_jif; long wrote = 0; + struct inode *inode; if (wbc.for_kupdate) { wbc.older_than_this = &oldest_jif; @@ -747,8 +748,24 @@ static long wb_writeback(struct bdi_writeback *wb, * If we ran out of stuff to write, bail unless more_io got set */ if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { - if (wbc.more_io && !wbc.for_kupdate) + if (wbc.more_io && !wbc.for_kupdate) { + if (wbc.nr_to_write < MAX_WRITEBACK_PAGES) + continue; + /* + * Nothing written. Wait for some inode to + * become available for writeback. Otherwise + * we'll just busyloop. + */ + spin_lock(&inode_lock); + if (!list_empty(&wb->b_more_io)) { + inode = list_entry( + wb->b_more_io.prev, + struct inode, i_list); + inode_wait_for_writeback(inode); + } + spin_unlock(&inode_lock); continue; + } break; } } -- 1.6.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/