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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: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu 2018-08-05 23:02:22 +08:00 committed by Jaegeuk Kim
parent 91291e9998
commit c7079853c8
1 changed files with 9 additions and 2 deletions
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11
fs/f2fs/file.c
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@ -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);