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Commit 82e0a5aa authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: fix to avoid data update racing between GC and DIO 



Datas in file can be operated by GC and DIO simultaneously, so we will
face race case as below:

For write case:
Thread A				Thread B
- generic_file_direct_write
 - invalidate_inode_pages2_range
 - f2fs_direct_IO
  - do_blockdev_direct_IO
   - do_direct_IO
    - get_more_blocks
					- f2fs_gc
					 - do_garbage_collect
					  - gc_data_segment
					   - move_data_page
					    - do_write_data_page
					    migrate data block to new block address
   - dio_bio_submit
   update user data to old block address

For read case:
Thread A                                Thread B
- generic_file_direct_write
 - invalidate_inode_pages2_range
 - f2fs_direct_IO
  - do_blockdev_direct_IO
   - do_direct_IO
    - get_more_blocks
					- f2fs_balance_fs
					 - f2fs_gc
					  - do_garbage_collect
					   - gc_data_segment
					    - move_data_page
					     - do_write_data_page
					     migrate data block to new block address
					  - write_checkpoint
					   - do_checkpoint
					    - clear_prefree_segments
					     - f2fs_issue_discard
                                             discard old block adress
   - dio_bio_submit
   update user buffer from obsolete block address

In order to fix this, for one file, we should let DIO and GC getting exclusion
against with each other.

Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent 44a83499

fs/f2fs/data.c

+5 −1
Original line number Diff line number Diff line
@@ -1716,6 +1716,7 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 
	struct inode *inode = mapping->host;

	size_t count = iov_iter_count(iter);

	loff_t offset = iocb->ki_pos;

	int rw = iov_iter_rw(iter);

	int err;



	err = check_direct_IO(inode, iter, offset);
@@ -1729,8 +1730,11 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) 


	trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter));



	down_read(&F2FS_I(inode)->dio_rwsem[rw]);

	err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio);

	if (iov_iter_rw(iter) == WRITE) {

	up_read(&F2FS_I(inode)->dio_rwsem[rw]);



	if (rw == WRITE) {

		if (err > 0)

			set_inode_flag(inode, FI_UPDATE_WRITE);

		else if (err < 0)

fs/f2fs/f2fs.h

+1 −0
Original line number Diff line number Diff line
@@ -454,6 +454,7 @@ struct f2fs_inode_info { 
	struct list_head inmem_pages;	/* inmemory pages managed by f2fs */

	struct mutex inmem_lock;	/* lock for inmemory pages */

	struct extent_tree *extent_tree;	/* cached extent_tree entry */

	struct rw_semaphore dio_rwsem[2];/* avoid racing between dio and gc */

};



static inline void get_extent_info(struct extent_info *ext,

fs/f2fs/gc.c

+20 −0
Original line number Diff line number Diff line
@@ -755,12 +755,32 @@ static void gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum, 
		/* phase 3 */

		inode = find_gc_inode(gc_list, dni.ino);

		if (inode) {

			struct f2fs_inode_info *fi = F2FS_I(inode);

			bool locked = false;



			if (S_ISREG(inode->i_mode)) {

				if (!down_write_trylock(&fi->dio_rwsem[READ]))

					continue;

				if (!down_write_trylock(

						&fi->dio_rwsem[WRITE])) {

					up_write(&fi->dio_rwsem[READ]);

					continue;

				}

				locked = true;

			}



			start_bidx = start_bidx_of_node(nofs, inode)

								+ ofs_in_node;

			if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))

				move_encrypted_block(inode, start_bidx);

			else

				move_data_page(inode, start_bidx, gc_type);



			if (locked) {

				up_write(&fi->dio_rwsem[WRITE]);

				up_write(&fi->dio_rwsem[READ]);

			}



			stat_inc_data_blk_count(sbi, 1, gc_type);

		}

	}

fs/f2fs/super.c

+2 −0
Original line number Diff line number Diff line
@@ -579,6 +579,8 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb) 
	INIT_LIST_HEAD(&fi->gdirty_list);

	INIT_LIST_HEAD(&fi->inmem_pages);

	mutex_init(&fi->inmem_lock);

	init_rwsem(&fi->dio_rwsem[READ]);

	init_rwsem(&fi->dio_rwsem[WRITE]);



	/* Will be used by directory only */

	fi->i_dir_level = F2FS_SB(sb)->dir_level;