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[209.132.180.67]) by mx.google.com with ESMTP id g192si26793348pfc.29.2017.11.27.22.20.51; Mon, 27 Nov 2017 22:21:03 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751206AbdK1GUP (ORCPT + 77 others); Tue, 28 Nov 2017 01:20:15 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:2182 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750753AbdK1GUO (ORCPT ); Tue, 28 Nov 2017 01:20:14 -0500 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id CA42F77940153; Tue, 28 Nov 2017 14:20:09 +0800 (CST) Received: from [127.0.0.1] (10.177.26.59) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.361.1; Tue, 28 Nov 2017 14:20:09 +0800 Message-ID: <5A1D0003.6060605@huawei.com> Date: Tue, 28 Nov 2017 14:19:47 +0800 From: alex chen User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Gang He CC: , , , "Goldwyn Rodrigues" , , Subject: Re: [Ocfs2-devel] [PATCH 2/3] ocfs2: add ocfs2_overwrite_io function References: <1511775987-841-1-git-send-email-ghe@suse.com> <1511775987-841-3-git-send-email-ghe@suse.com> <5A1CC7BC.3060309@huawei.com> <5A1D65C4020000F90009ACE1@prv-mh.provo.novell.com> In-Reply-To: <5A1D65C4020000F90009ACE1@prv-mh.provo.novell.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.26.59] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gang, On 2017/11/28 13:33, Gang He wrote: > Hello Alex, > > >>>> >> Hi Gang, >> >> On 2017/11/27 17:46, Gang He wrote: >>> Add ocfs2_overwrite_io function, which is used to judge if >>> overwrite allocated blocks, otherwise, the write will bring extra >>> block allocation overhead. >>> >>> Signed-off-by: Gang He >>> --- >>> fs/ocfs2/extent_map.c | 67 >> +++++++++++++++++++++++++++++++++++++++++++++++++++ >>> fs/ocfs2/extent_map.h | 3 +++ >>> 2 files changed, 70 insertions(+) >>> >>> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c >>> index e4719e0..98bf325 100644 >>> --- a/fs/ocfs2/extent_map.c >>> +++ b/fs/ocfs2/extent_map.c >>> @@ -832,6 +832,73 @@ int ocfs2_fiemap(struct inode *inode, struct >> fiemap_extent_info *fieinfo, >>> return ret; >>> } >>> >>> +/* Is IO overwriting allocated blocks? */ >>> +int ocfs2_overwrite_io(struct inode *inode, u64 map_start, u64 map_len, >>> + int wait) >>> +{ >>> + int ret = 0, is_last; >>> + u32 mapping_end, cpos; >>> + struct ocfs2_super *osb = OCFS2_SB(inode->i_sb); >>> + struct buffer_head *di_bh = NULL; >>> + struct ocfs2_extent_rec rec; >>> + >>> + if (wait) >>> + ret = ocfs2_inode_lock(inode, &di_bh, 0); >>> + else >>> + ret = ocfs2_try_inode_lock(inode, &di_bh, 0); >>> + if (ret) >>> + goto out; >>> + >>> + if (wait) >>> + down_read(&OCFS2_I(inode)->ip_alloc_sem); >>> + else { >>> + if (!down_read_trylock(&OCFS2_I(inode)->ip_alloc_sem)) { >>> + ret = -EAGAIN; >>> + goto out_unlock1; >>> + } >>> + } >>> + >>> + if ((OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) && >>> + ((map_start + map_len) <= i_size_read(inode))) >>> + goto out_unlock2; >>> + >>> + cpos = map_start >> osb->s_clustersize_bits; >>> + mapping_end = ocfs2_clusters_for_bytes(inode->i_sb, >>> + map_start + map_len); >>> + is_last = 0; >>> + while (cpos < mapping_end && !is_last) { >>> + ret = ocfs2_get_clusters_nocache(inode, di_bh, cpos, >>> + NULL, &rec, &is_last); >>> + if (ret) { >>> + mlog_errno(ret); >>> + goto out_unlock2; >>> + } >>> + >>> + if (rec.e_blkno == 0ULL) >>> + break; >> I think here the blocks is not overwrite, because the hold is found and the >> blocks >> should be allocated. > If the rec.e_blkno == NULL, this means there is a hole. > The file hole means that these blocks are not allocated, it does not like unwritten block. > The unwritten blocks means that these blocks are allocated, but still have not been unwritten. > If we break the loop when we find the hold, out of this function we will allocate the blocks in ocfs2_file_write_iter()->..->ocfs2_direct_IO->__blockdev_direct_IO->..->ocfs2_dio_wr_get_block() ->ocfs2_write_begin_nolock. Does this violate the semantics of 'IOCB_NOWAIT'; BTW, should we consider the down_write() and ocfs2_inode_lock() in ocfs2_dio_wr_get_block() when the flag 'IOCB_NOWAIT' is set; >>> + >>> + if (rec.e_flags & OCFS2_EXT_REFCOUNTED) >>> + break; >>> + >>> + cpos = le32_to_cpu(rec.e_cpos) + >>> + le16_to_cpu(rec.e_leaf_clusters); >>> + } >>> + >>> + if (cpos < mapping_end) >>> + ret = 1; >>> + >>> +out_unlock2: >> >> I think the 'out_up_read' is more readable than the 'out_unlock2' . > Ok, I will use more readable tag here. >> >>> + brelse(di_bh); >>> + >>> + up_read(&OCFS2_I(inode)->ip_alloc_sem); >>> + >>> +out_unlock1: >> >> We should release buffer head here. >> >>> + ocfs2_inode_unlock(inode, 0); >>> + >>> +out: >>> + return (ret ? 0 : 1); >>> +} >>> + >>> int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int >> whence) >>> { >>> struct inode *inode = file->f_mapping->host; >>> diff --git a/fs/ocfs2/extent_map.h b/fs/ocfs2/extent_map.h >>> index 67ea57d..fd9e86a 100644 >>> --- a/fs/ocfs2/extent_map.h >>> +++ b/fs/ocfs2/extent_map.h >>> @@ -53,6 +53,9 @@ int ocfs2_extent_map_get_blocks(struct inode *inode, u64 >> v_blkno, u64 *p_blkno, >>> int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, >>> u64 map_start, u64 map_len); >>> >>> +int ocfs2_overwrite_io(struct inode *inode, u64 map_start, u64 map_len, >>> + int wait); >>> + >>> int ocfs2_seek_data_hole_offset(struct file *file, loff_t *offset, int >> origin); >>> >>> int ocfs2_xattr_get_clusters(struct inode *inode, u32 v_cluster, >>> > > > . > From 1585287195181835940@xxx Tue Nov 28 05:41:22 +0000 2017 X-GM-THRID: 1585212205986077742 X-Gmail-Labels: Inbox,Category Forums,HistoricalUnread