From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:25580 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751908AbaGAJ2z (ORCPT ); Tue, 1 Jul 2014 05:28:55 -0400 Received: from acsinet21.oracle.com (acsinet21.oracle.com [141.146.126.237]) by userp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id s619SsJj026472 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 1 Jul 2014 09:28:55 GMT Received: from aserz7021.oracle.com (aserz7021.oracle.com [141.146.126.230]) by acsinet21.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s619SrwL001307 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Tue, 1 Jul 2014 09:28:54 GMT Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by aserz7021.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id s619Srl2001300 for ; Tue, 1 Jul 2014 09:28:53 GMT From: Liu Bo To: linux-btrfs Subject: [PATCH v3] Btrfs: fix race of using total_bytes_pinned Date: Tue, 1 Jul 2014 17:28:46 +0800 Message-Id: <1404206926-7953-1-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: This percpu counter @total_bytes_pinned is introduced to skip unnecessary operations of 'commit transaction', it accounts for those space we may free but are stuck in delayed refs. And we zero out @space_info->total_bytes_pinned every transaction period so we have a better idea of how much space we'll actually free up by committing this transaction. However, we do the 'zero out' part a little earlier, before we actually unpin space, so we end up returning ENOSPC when we actually have free space that's just unpinned from committing transaction. xfstests/generic/074 complained then. This fixes it by actually accounting the percpu pinned number when 'unpin', and when finding space for writing, if it finds that pinned bytes is less than needed, we first try again to check if we have space now, as someone may have committed transaction, yes means we're good, while no means we really have run out of space. Signed-off-by: Liu Bo --- v3: Really account the percpu pinned number when unpin, instead of zeroing it out, as we set transaction with UNBLOCKED before 'unpin', zeroing it out may end up with messing percpu pinned number(suggested by Miao). v2: Add missing brakets for if statement fs/btrfs/extent-tree.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 99c2539..f36fb13 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -3685,7 +3685,7 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes) struct btrfs_root *root = BTRFS_I(inode)->root; struct btrfs_fs_info *fs_info = root->fs_info; u64 used; - int ret = 0, committed = 0, alloc_chunk = 1; + int ret = 0, committed = 0, alloc_chunk = 1, check_pinned = 0; /* make sure bytes are sectorsize aligned */ bytes = ALIGN(bytes, root->sectorsize); @@ -3756,11 +3756,18 @@ alloc: * allocation don't bother committing the transaction. */ if (percpu_counter_compare(&data_sinfo->total_bytes_pinned, - bytes) < 0) - committed = 1; + bytes) < 0) { + if (check_pinned) { + committed = 1; /* really run out of space. */ + } else { + check_pinned = 1; + spin_unlock(&data_sinfo->lock); + goto again; + } + } spin_unlock(&data_sinfo->lock); - /* commit the current transaction and try again */ + /* commit the current transaction and try again */ commit_trans: if (!committed && !atomic_read(&root->fs_info->open_ioctl_trans)) { @@ -5678,7 +5685,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans, struct btrfs_caching_control *next; struct btrfs_caching_control *caching_ctl; struct btrfs_block_group_cache *cache; - struct btrfs_space_info *space_info; down_write(&fs_info->commit_root_sem); @@ -5701,9 +5707,6 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans, up_write(&fs_info->commit_root_sem); - list_for_each_entry_rcu(space_info, &fs_info->space_info, list) - percpu_counter_set(&space_info->total_bytes_pinned, 0); - update_global_block_rsv(fs_info); } @@ -5741,6 +5744,7 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end) spin_lock(&cache->lock); cache->pinned -= len; space_info->bytes_pinned -= len; + percpu_counter_add(&space_info->total_bytes_pinned, -len); if (cache->ro) { space_info->bytes_readonly += len; readonly = true; -- 1.8.1.4