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Commit 4b93c602 authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: avoid race between zero_range and background GC 



Thread A				Background GC
- f2fs_zero_range
 - truncate_pagecache_range
					- gc_data_segment
					 - get_read_data_page
					  - move_data_page
					   - set_page_dirty
					   - set_cold_data
 - f2fs_do_zero_range
  - dn->data_blkaddr = NEW_ADDR;
  - f2fs_set_data_blkaddr

Actually, we don't need to set dirty & checked flag on the page, since
all valid data in the page should be zeroed by zero_range().

Use i_gc_rwsem[WRITE] to avoid such race condition.

Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent fe059de4

fs/f2fs/file.c

+9 −2
Original line number Diff line number Diff line
@@ -1314,8 +1314,6 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, 
	if (ret)

		goto out_sem;



	truncate_pagecache_range(inode, offset, offset + len - 1);



	pg_start = ((unsigned long long) offset) >> PAGE_SHIFT;

	pg_end = ((unsigned long long) offset + len) >> PAGE_SHIFT;
@@ -1345,12 +1343,19 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, 
			unsigned int end_offset;

			pgoff_t end;



			down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);



			truncate_pagecache_range(inode,

				(loff_t)index << PAGE_SHIFT,

				((loff_t)pg_end << PAGE_SHIFT) - 1);



			f2fs_lock_op(sbi);



			set_new_dnode(&dn, inode, NULL, NULL, 0);

			ret = f2fs_get_dnode_of_data(&dn, index, ALLOC_NODE);

			if (ret) {

				f2fs_unlock_op(sbi);

				up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);

				goto out;

			}
@@ -1359,7 +1364,9 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, 


			ret = f2fs_do_zero_range(&dn, index, end);

			f2fs_put_dnode(&dn);



			f2fs_unlock_op(sbi);

			up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);



			f2fs_balance_fs(sbi, dn.node_changed);