f2fs: compress: fix to cover {reserve,release}_compress_blocks() w/ cp_rwsem lock

It needs to cover {reserve,release}_compress_blocks() w/ cp_rwsem lock
to avoid racing with checkpoint, otherwise, filesystem metadata including
blkaddr in dnode, inode fields and .total_valid_block_count may be
corrupted after SPO case.

Fixes: ef8d563f ("f2fs: introduce F2FS_IOC_RELEASE_COMPRESS_BLOCKS")
Fixes: c75488fb ("f2fs: introduce F2FS_IOC_RESERVE_COMPRESS_BLOCKS")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -3593,9 +3593,12 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
 		struct dnode_of_data dn;
 		pgoff_t end_offset, count;
 
+		f2fs_lock_op(sbi);
+
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
 		ret = f2fs_get_dnode_of_data(&dn, page_idx, LOOKUP_NODE);
 		if (ret) {
+			f2fs_unlock_op(sbi);
 			if (ret == -ENOENT) {
 				page_idx = f2fs_get_next_page_offset(&dn,
 								page_idx);
@@ -3613,6 +3616,8 @@ static int f2fs_release_compress_blocks(struct file *filp, unsigned long arg)
 
 		f2fs_put_dnode(&dn);
 
+		f2fs_unlock_op(sbi);
+
 		if (ret < 0)
 			break;
 
@@ -3765,9 +3770,12 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
 		struct dnode_of_data dn;
 		pgoff_t end_offset, count;
 
+		f2fs_lock_op(sbi);
+
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
 		ret = f2fs_get_dnode_of_data(&dn, page_idx, LOOKUP_NODE);
 		if (ret) {
+			f2fs_unlock_op(sbi);
 			if (ret == -ENOENT) {
 				page_idx = f2fs_get_next_page_offset(&dn,
 								page_idx);
@@ -3785,6 +3793,8 @@ static int f2fs_reserve_compress_blocks(struct file *filp, unsigned long arg)
 
 		f2fs_put_dnode(&dn);
 
+		f2fs_unlock_op(sbi);
+
 		if (ret < 0)
 			break;