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

PATCH Superseded Chao Yu 1 participant 1 message Jul 3, 2016 F2FS file system

v2 of 3 Superseded Latest is v3 →

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Chao Yu

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PATCH v2 2/2 f2fs: fix to avoid data update racing between GC and DIO

From: Chao Yu <[email protected]>

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 Chao Yu <[email protected]>
---
 fs/f2fs/data.c  | 11 +++++++++++
 fs/f2fs/f2fs.h  |  2 ++
 fs/f2fs/gc.c    | 19 +++++++++++++++++++
 fs/f2fs/super.c |  2 ++
 4 files changed, 34 insertions(+)
fs/f2fs/data.c +11 -0
index ba4963f..3a03285 100644
@@ -1701,8 +1701,10 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct address_space *mapping = iocb->ki_filp->f_mapping;
 	struct inode *inode = mapping->host;
+	struct f2fs_inode_info *fi = F2FS_I(inode);
 	size_t count = iov_iter_count(iter);
 	loff_t offset = iocb->ki_pos;
+	bool is_write = (iov_iter_rw(iter) == WRITE);
 	int err;
 
 	err = check_direct_IO(inode, iter, offset);

@@ -1716,7 +1718,16 @@ 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));
 
+	if (is_write)
+		mutex_lock(&fi->dio_mutex);
+	else
+		down_read(&fi->dio_rwsem);
 	err = blockdev_direct_IO(iocb, inode, iter, get_data_block_dio);
+	if (is_write)
+		mutex_unlock(&fi->dio_mutex);
+	else
+		up_read(&fi->dio_rwsem);
+
 	if (iov_iter_rw(iter) == WRITE) {
 		if (err > 0)
 			set_inode_flag(inode, FI_UPDATE_WRITE);
fs/f2fs/f2fs.h +2 -0
index bd82b6d..ac3410a 100644
@@ -474,6 +474,8 @@ 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 mutex dio_mutex;		/* avoid racing between write dio and gc */
+	struct rw_semaphore dio_rwsem;	/* avoid racing between read dio and gc */
 };
 
 static inline void get_extent_info(struct extent_info *ext,
fs/f2fs/gc.c +19 -0
index c2c4ac3..a15ae8a 100644
@@ -744,12 +744,31 @@ next_step:
 		/* 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 (!mutex_trylock(&fi->dio_mutex))
+					continue;
+				if (!down_write_trylock(&fi->dio_rwsem)) {
+					mutex_unlock(&fi->dio_mutex);
+					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) {
+				mutex_unlock(&fi->dio_mutex);
+				up_write(&fi->dio_rwsem);
+			}
+
 			stat_inc_data_blk_count(sbi, 1, gc_type);
 		}
 	}
fs/f2fs/super.c +2 -0
index 8c698e1..512bbb4 100644
@@ -575,6 +575,8 @@ 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);
+	mutex_init(&fi->dio_mutex);
+	init_rwsem(&fi->dio_rwsem);
 
 	/* Will be used by directory only */
 	fi->i_dir_level = F2FS_SB(sb)->dir_level;
Signature · 1 line
2.7.2