From: Zheng Liu Subject: Re: [PATCH] Avoid unnecessarily writing back dirty pages before hole punching Date: Fri, 17 May 2013 11:23:28 +0800 Message-ID: <20130517032328.GA14249@gmail.com> References: <1368517494-12472-1-git-send-email-liwang@ubuntukylin.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, Theodore Ts'o , Andreas Dilger , Dmitry Monakhov , Yunchuan Wen To: Li Wang Return-path: Received: from mail-pd0-f182.google.com ([209.85.192.182]:39891 "EHLO mail-pd0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063Ab3EQDFo (ORCPT ); Thu, 16 May 2013 23:05:44 -0400 Received: by mail-pd0-f182.google.com with SMTP id 3so2905883pdj.27 for ; Thu, 16 May 2013 20:05:43 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1368517494-12472-1-git-send-email-liwang@ubuntukylin.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Hello Li, Thanks for fixing this. Some comments below. On Tue, May 14, 2013 at 03:44:54PM +0800, Li Wang wrote: > For hole punching, currently ext4 will synchronously write back the > dirty pages fit into the hole, since the data on the disk responding > to those pages are to be deleted, it is benefical to directly release > those pages, no matter they are dirty or not, except the ordered case. > > Signed-off-by: Li Wang > Signed-off-by: Yunchuan Wen > Reviewed-by: Theodore Ts'o > Reviewed-by: Dmitry Monakhov If I remember correctly, Ted and Dmirty only answer your question about this problem, but they don't review the patch. So don't add "Reviewed-by", please. > --- > fs/ext4/inode.c | 21 ++++++++++------- > fs/jbd2/transaction.c | 62 +++++++++++++++++++++++++++++++------------------ > include/linux/jbd2.h | 2 ++ > 3 files changed, 55 insertions(+), 30 deletions(-) > > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 0723774..3e00360 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3578,6 +3578,16 @@ int ext4_can_truncate(struct inode *inode) > return 0; > } > > +static inline int ext4_begin_ordered_fallocate(struct inode *inode, > + loff_t start, loff_t length) > +{ > + if (!EXT4_I(inode)->jinode) > + return 0; > + return jbd2_journal_begin_ordered_fallocate(EXT4_JOURNAL(inode), > + EXT4_I(inode)->jinode, > + start, length); > +} > + > /* > * ext4_punch_hole: punches a hole in a file by releaseing the blocks > * associated with the given offset and length > @@ -3611,17 +3621,12 @@ int ext4_punch_hole(struct file *file, loff_t offset, loff_t length) > > trace_ext4_punch_hole(inode, offset, length); > > - /* > - * Write out all dirty pages to avoid race conditions > - * Then release them. > - */ > - if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) { > - ret = filemap_write_and_wait_range(mapping, offset, > - offset + length - 1); > + if (ext4_should_order_data(inode)) { > + ret = ext4_begin_ordered_fallocate(inode, offset, length); > if (ret) > return ret; > } > - > + > mutex_lock(&inode->i_mutex); I am wondering if we need to call ext4_begin_ordered_fallocate() after i_mutex is taken. Otherwise we can not prevent other buffered writes to redirty this range of pages. > /* It's not possible punch hole on append only file */ > if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) { > diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c > index 10f524c..1284e1b 100644 > --- a/fs/jbd2/transaction.c > +++ b/fs/jbd2/transaction.c > @@ -2305,6 +2305,36 @@ done: > return 0; > } > > + > +static int jbd2_journal_begin_ordered_discard(journal_t *journal, > + struct jbd2_inode *jinode, > + loff_t start, loff_t end) > +{ > + transaction_t *inode_trans, *commit_trans; > + int ret = 0; > + > + /* This is a quick check to avoid locking if not necessary */ > + if (!jinode->i_transaction) > + goto out; > + /* Locks are here just to force reading of recent values, it is > + * enough that the transaction was not committing before we started > + * a transaction adding the inode to orphan list */ > + read_lock(&journal->j_state_lock); > + commit_trans = journal->j_committing_transaction; > + read_unlock(&journal->j_state_lock); > + spin_lock(&journal->j_list_lock); > + inode_trans = jinode->i_transaction; > + spin_unlock(&journal->j_list_lock); > + if (inode_trans == commit_trans) { > + ret = filemap_fdatawrite_range(jinode->i_vfs_inode->i_mapping, > + start, end); > + if (ret) > + jbd2_journal_abort(journal, ret); > + } > +out: > + return ret; > +} > + > /* > * File truncate and transaction commit interact with each other in a > * non-trivial way. If a transaction writing data block A is > @@ -2329,27 +2359,15 @@ int jbd2_journal_begin_ordered_truncate(journal_t *journal, > struct jbd2_inode *jinode, > loff_t new_size) > { > - transaction_t *inode_trans, *commit_trans; > - int ret = 0; > + return jbd2_journal_begin_ordered_discard(journal, jinode, > + new_size, LLONG_MAX); Coding style problem. Before you submit a patch, you could use $LINUX/scripts/checkpatch.pl to check your patch in order to make sure whether it is ready for submission or not. > +} > > - /* This is a quick check to avoid locking if not necessary */ > - if (!jinode->i_transaction) > - goto out; > - /* Locks are here just to force reading of recent values, it is > - * enough that the transaction was not committing before we started > - * a transaction adding the inode to orphan list */ > - read_lock(&journal->j_state_lock); > - commit_trans = journal->j_committing_transaction; > - read_unlock(&journal->j_state_lock); > - spin_lock(&journal->j_list_lock); > - inode_trans = jinode->i_transaction; > - spin_unlock(&journal->j_list_lock); > - if (inode_trans == commit_trans) { > - ret = filemap_fdatawrite_range(jinode->i_vfs_inode->i_mapping, > - new_size, LLONG_MAX); > - if (ret) > - jbd2_journal_abort(journal, ret); > - } > -out: > - return ret; > +int jbd2_journal_begin_ordered_fallocate(journal_t *journal, > + struct jbd2_inode *jinode, > + loff_t start, loff_t length) > +{ > + return jbd2_journal_begin_ordered_discard(journal, jinode, > + start, start + length - 1); The same as above. Regards, - Zheng > } > + > diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h > index 6e051f4..9940cfb 100644 > --- a/include/linux/jbd2.h > +++ b/include/linux/jbd2.h > @@ -1128,6 +1128,8 @@ extern int jbd2_journal_force_commit(journal_t *); > extern int jbd2_journal_file_inode(handle_t *handle, struct jbd2_inode *inode); > extern int jbd2_journal_begin_ordered_truncate(journal_t *journal, > struct jbd2_inode *inode, loff_t new_size); > +extern int jbd2_journal_begin_ordered_fallocate(journal_t *journal, > + struct jbd2_inode *inode, loff_t start, loff_t length); > extern void jbd2_journal_init_jbd_inode(struct jbd2_inode *jinode, struct inode *inode); > extern void jbd2_journal_release_jbd_inode(journal_t *journal, struct jbd2_inode *jinode); > > -- > 1.7.9.5 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html