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Message-Id: <1341152506-32649-4-git-send-email-wenqing.lz@taobao.com> Date: Sun, 1 Jul 2012 22:21:46 +0800 From: Zheng Liu <gnehzuil.liu@...il.com> To: linux-ext4@...r.kernel.org Cc: Tao Ma <tm@....ma>, Eric Sandeen <sandeen@...hat.com>, Robin Dong <hao.bigrat@...il.com>, Zheng Liu <wenqing.lz@...bao.com> Subject: [PATCH 3/3 v3] ext4: add dio overwrite nolock From: Zheng Liu <wenqing.lz@...bao.com> 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 <tm@....ma> CC: Eric Sandeen <sandeen@...hat.com> CC: Robin Dong <hao.bigrat@...il.com> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com> --- fs/ext4/file.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++++-- fs/ext4/inode.c | 17 +++++++++++++++++ 2 files changed, 66 insertions(+), 2 deletions(-) diff --git a/fs/ext4/file.c b/fs/ext4/file.c index a10dc77..1c81509 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 +119,50 @@ 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; + 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 & 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 76cb3b1..8c84070 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2996,6 +2996,16 @@ 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); + } + /* * We could direct write to holes and fallocate. * @@ -3083,6 +3093,13 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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