Commit 21020812 authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: fix lock dependency in between dio_rwsem & i_mmap_sem 



test/generic/208 reports a potential deadlock as below:

Chain exists of:
  &mm->mmap_sem --> &fi->i_mmap_sem --> &fi->dio_rwsem[WRITE]

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&fi->dio_rwsem[WRITE]);
                               lock(&fi->i_mmap_sem);
                               lock(&fi->dio_rwsem[WRITE]);
  lock(&mm->mmap_sem);

This patch changes the lock dependency as below in fallocate() to
fix this issue:
- dio_rwsem
 - i_mmap_sem

Fixes: bb06664a ("f2fs: avoid race in between GC and block exchange")
Signed-off-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent e17d488b

fs/f2fs/file.c

+9 −11
Original line number Diff line number Diff line
@@ -1186,14 +1186,14 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len) 
	pg_start = offset >> PAGE_SHIFT;

	pg_end = (offset + len) >> PAGE_SHIFT;



	/* avoid gc operation during block exchange */

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



	down_write(&F2FS_I(inode)->i_mmap_sem);

	/* write out all dirty pages from offset */

	ret = filemap_write_and_wait_range(inode->i_mapping, offset, LLONG_MAX);

	if (ret)

		goto out;



	/* avoid gc operation during block exchange */

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

		goto out_unlock;



	truncate_pagecache(inode, offset);
@@ -1212,9 +1212,8 @@ static int f2fs_collapse_range(struct inode *inode, loff_t offset, loff_t len) 
	if (!ret)

		f2fs_i_size_write(inode, new_size);

out_unlock:

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

out:

	up_write(&F2FS_I(inode)->i_mmap_sem);

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

	return ret;

}
@@ -1385,6 +1384,9 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len) 


	f2fs_balance_fs(sbi, true);



	/* avoid gc operation during block exchange */

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



	down_write(&F2FS_I(inode)->i_mmap_sem);

	ret = truncate_blocks(inode, i_size_read(inode), true);

	if (ret)
@@ -1395,9 +1397,6 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len) 
	if (ret)

		goto out;



	/* avoid gc operation during block exchange */

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



	truncate_pagecache(inode, offset);



	pg_start = offset >> PAGE_SHIFT;
@@ -1425,10 +1424,9 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len) 


	if (!ret)

		f2fs_i_size_write(inode, new_size);



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

out:

	up_write(&F2FS_I(inode)->i_mmap_sem);

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

	return ret;

}

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