Hello list, Here is the second version of dio overwrite nolock. In this version, I rework the stuff as Eric said in order to avoid to copy almost all of __generic_file_aio_write back into ext4. Meanwhile, I fix some problems according to Tao's reply. This patch set can improve the performance of ext4 when the user does a dio overwrite because, when a dio overwrite occurs, we don't need to take i_mutex lock in some conditons. The condition includes the size of file doesn't be changed, no buffered I/O and align aio. So dio write can be parallelized in these conditions. In patch 1, ext4_file_dio_write is defined to split buffered I/O and direct I/O in ext4_file_write so that some code can be added to check whether we can do a dio overwrite without i_mutex lock later. In patch 2, a new flag called EXT4_GET_BLOCKS_NOLOCK and a new get_block function that is named ext4_get_block_write_nolock are defined to do a lookup to let me know whether the extent of the file at this offset has been initialized because we need to know whether a dio overwrite needs to modify the metadata of the file or not. In patch 3, we implement dio overwrite nolock. In ext4_file_dio_write, we check whether we can do a dio overwrite without lock. Then we use 'iocb->private' to store this flag to tell ext4_ext_direct_IO to handle it because file_update_time will start a new journal and it will cause a deadlock. So we need to finish to update file time with i_mutex lock, and release lock in ext4_ext_direct_IO. v2 <- v1: * rebase to 3.5 * rework ext4_file_dio_write to avoid to copy vfs's code back into ext4 * add some comments to explain how to determine whether we can do a nolocking overwrite dio In this thread [1], it is the first version of patchset. 1. http://www.spinics.net/lists/linux-ext4/msg31859.html Regards, Zheng Zheng Liu (3): ext4: split ext4_file_write into buffered IO and direct IO ext4: add a new flag for ext4_map_blocks ext4: add dio overwrite nolock fs/ext4/ext4.h | 2 + fs/ext4/file.c | 109 ++++++++++++++++++++++++++++++++++++++++++++----------- fs/ext4/inode.c | 86 ++++++++++++++++++++++++++++++++++++++----- 3 files changed, 165 insertions(+), 32 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
