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Commit 729f52c6 authored by Zheng Liu's avatar Zheng Liu Committed by Theodore Ts'o
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ext4: add a new nolock flag in ext4_map_blocks 



EXT4_GET_BLOCKS_NO_LOCK flag is added to indicate that we don't need
to acquire i_data_sem lock in ext4_map_blocks.  Meanwhile, it changes
ext4_get_block() to not start a new journal because when we do a
overwrite dio, there is no any metadata that needs to be modified.

We define a new function called ext4_get_block_write_nolock, which is
used in dio overwrite nolock.  In this function, it doesn't try to
acquire i_data_sem lock and doesn't start a new journal as it does a
lookup.

CC: Tao Ma <tm@tao.ma>
CC: Eric Sandeen <sandeen@redhat.com>
CC: Robin Dong <hao.bigrat@gmail.com>
Signed-off-by: default avatarZheng Liu <wenqing.lz@taobao.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent fbe10494

fs/ext4/ext4.h

+2 −0
Original line number Diff line number Diff line
@@ -571,6 +571,8 @@ enum { 
#define EXT4_GET_BLOCKS_NO_NORMALIZE		0x0040

	/* Request will not result in inode size update (user for fallocate) */

#define EXT4_GET_BLOCKS_KEEP_SIZE		0x0080

	/* Do not take i_data_sem locking in ext4_map_blocks */

#define EXT4_GET_BLOCKS_NO_LOCK			0x0100



/*

 * Flags used by ext4_free_blocks

fs/ext4/inode.c

+49 −10
Original line number Diff line number Diff line
@@ -544,6 +544,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
	 * Try to see if we can get the block without requesting a new

	 * file system block.

	 */

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

		down_read((&EXT4_I(inode)->i_data_sem));

	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {

		retval = ext4_ext_map_blocks(handle, inode, map, flags &
@@ -552,6 +553,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, 
		retval = ext4_ind_map_blocks(handle, inode, map, flags &

					     EXT4_GET_BLOCKS_KEEP_SIZE);

	}

	if (!(flags & EXT4_GET_BLOCKS_NO_LOCK))

		up_read((&EXT4_I(inode)->i_data_sem));



	if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
@@ -2818,6 +2820,32 @@ static int ext4_get_block_write(struct inode *inode, sector_t iblock, 
			       EXT4_GET_BLOCKS_IO_CREATE_EXT);

}



static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock,

		   struct buffer_head *bh_result, int flags)

{

	handle_t *handle = ext4_journal_current_handle();

	struct ext4_map_blocks map;

	int ret = 0;



	ext4_debug("ext4_get_block_write_nolock: inode %lu, flag %d\n",

		   inode->i_ino, flags);



	flags = EXT4_GET_BLOCKS_NO_LOCK;



	map.m_lblk = iblock;

	map.m_len = bh_result->b_size >> inode->i_blkbits;



	ret = ext4_map_blocks(handle, inode, &map, flags);

	if (ret > 0) {

		map_bh(bh_result, inode->i_sb, map.m_pblk);

		bh_result->b_state = (bh_result->b_state & ~EXT4_MAP_FLAGS) |

					map.m_flags;

		bh_result->b_size = inode->i_sb->s_blocksize * map.m_len;

		ret = 0;

	}

	return ret;

}



static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,

			    ssize_t size, void *private, int ret,

			    bool is_async)
@@ -2966,6 +2994,8 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, 


	loff_t final_size = offset + count;

	if (rw == WRITE && final_size <= inode->i_size) {

		int overwrite = 0;



		/*

 		 * We could direct write to holes and fallocate.

		 *
@@ -3005,6 +3035,15 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, 
			EXT4_I(inode)->cur_aio_dio = iocb->private;

		}



		if (overwrite)

			ret = __blockdev_direct_IO(rw, iocb, inode,

						 inode->i_sb->s_bdev, iov,

						 offset, nr_segs,

						 ext4_get_block_write_nolock,

						 ext4_end_io_dio,

						 NULL,

						 0);

		else

			ret = __blockdev_direct_IO(rw, iocb, inode,

						 inode->i_sb->s_bdev, iov,

						 offset, nr_segs,
@@ -3031,7 +3070,7 @@ static ssize_t ext4_ext_direct_IO(int rw, struct kiocb *iocb, 
		if (ret != -EIOCBQUEUED && ret <= 0 && iocb->private) {

			ext4_free_io_end(iocb->private);

			iocb->private = NULL;

		} else if (ret > 0 && ext4_test_inode_state(inode,

		} else if (ret > 0 && !overwrite && ext4_test_inode_state(inode,

						EXT4_STATE_DIO_UNWRITTEN)) {

			int err;

			/*