From: Zheng Liu Subject: [RFC][PATCH v2 3/3] ext4: add dio overwrite nolock Date: Thu, 14 Jun 2012 11:32:10 +0800 Message-ID: <1339644730-6204-4-git-send-email-wenqing.lz@taobao.com> References: <1339644730-6204-1-git-send-email-wenqing.lz@taobao.com> Cc: Tao Ma , Eric Sandeen , Zheng Liu To: linux-ext4@vger.kernel.org Return-path: Received: from mail-pb0-f46.google.com ([209.85.160.46]:37650 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755096Ab2FNDYe (ORCPT ); Wed, 13 Jun 2012 23:24:34 -0400 Received: by mail-pb0-f46.google.com with SMTP id rp8so3174066pbb.19 for ; Wed, 13 Jun 2012 20:24:34 -0700 (PDT) In-Reply-To: <1339644730-6204-1-git-send-email-wenqing.lz@taobao.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Zheng Liu Aligned and overwrite direct I/O can be parallelized. In ext4_file_dio_write, we first check whether these conditions are satisfied or not. If so, we take i_data_sem and release i_mutex lock directly. Meanwhile iocb->private is set to indicate that this is a dio overwrite, and it will be handled in ext4_ext_direct_IO. CC: Tao Ma CC: Eric Sandeen Signed-off-by: Zheng Liu --- fs/ext4/file.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++-- fs/ext4/inode.c | 27 +++++++++++++++++++++++++++ 2 files changed, 78 insertions(+), 2 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index a10dc77..812358f 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -93,9 +93,13 @@ static ssize_t ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov, unsigned long nr_segs, loff_t pos) { - struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode; + struct file *file = iocb->ki_filp; + struct inode *inode = file->f_mapping->host; + struct blk_plug plug; int unaligned_aio = 0; ssize_t ret; + int overwrite = 0; + size_t length = iov_length(iov, nr_segs); if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS) && !is_sync_kiocb(iocb)) @@ -115,7 +119,52 @@ ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov, ext4_aiodio_wait(inode); } - ret = generic_file_aio_write(iocb, iov, nr_segs, pos); + BUG_ON(iocb->ki_pos != pos); + + mutex_lock(&inode->i_mutex); + blk_start_plug(&plug); + + iocb->private = &overwrite; + + /* check whether we do a DIO overwrite or not */ + if (ext4_should_dioread_nolock(inode) && !unaligned_aio && + !file->f_mapping->nrpages && pos + length <= i_size_read(inode)) { + struct ext4_map_blocks map; + unsigned int blkbits = inode->i_blkbits; + int err, len; + + map.m_lblk = pos >> blkbits; + map.m_len = (EXT4_BLOCK_ALIGN(pos + length, blkbits) >> blkbits) + - map.m_lblk; + map.m_flags &= ~EXT4_MAP_FLAGS; + len = map.m_len; + + err = ext4_map_blocks(NULL, inode, &map, 0); + /* + * 'err==len' means that all of blocks has been preallocated no + * matter they are initialized or not. For excluding + * uninitialized extents, we need to check m_flags. There are + * two conditions that indicate for initialized extents. + * 1) If we hit extent cache, EXT4_MAP_MAPPED flag is returned; + * 2) If we do a real lookup, non-flags are returned. + * So we should check these two conditions. + */ + if (err == len && (!map.m_flags || + map.m_flags & EXT4_MAP_MAPPED)) + overwrite = 1; + } + + ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); + mutex_unlock(&inode->i_mutex); + + if (ret > 0 || ret == -EIOCBQUEUED) { + ssize_t err; + + err = generic_write_sync(file, pos, ret); + if (err < 0 && ret > 0) + ret = err; + } + blk_finish_plug(&plug); if (unaligned_aio) mutex_unlock(ext4_aio_mutex(inode)); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 9a714ff..98e9096 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2996,6 +2996,26 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, if (rw == WRITE && final_size <= inode->i_size) { int overwrite = 0; + BUG_ON(iocb->private == NULL); + + /* If we do a overwrite dio, i_mutex locking can be released */ + overwrite = *((int *)iocb->private); + + if (overwrite) { + down_read(&EXT4_I(inode)->i_data_sem); + mutex_unlock(&inode->i_mutex); + } + + /* + * If there are still some buffered I/O, we should fall back + * to take i_mutex locking. + */ + if (overwrite && file->f_mapping->nrpages) { + overwrite = 0; + up_read(&EXT4_I(inode)->i_data_sem); + mutex_lock(&inode->i_mutex); + } + /* * We could direct write to holes and fallocate. * @@ -3083,6 +3103,13 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, ret = err; ext4_clear_inode_state(inode, EXT4_STATE_DIO_UNWRITTEN); } + + /* take i_mutex locking again if we do a ovewrite dio */ + if (overwrite) { + up_read(&EXT4_I(inode)->i_data_sem); + mutex_lock(&inode->i_mutex); + } + return ret; } -- 1.7.4.1