* potential data race on disk_i_size in two btrfs_endio_writer_helper()
@ 2019-11-28 3:44 Meng Xu
0 siblings, 0 replies; only message in thread
From: Meng Xu @ 2019-11-28 3:44 UTC (permalink / raw)
To: linux-btrfs
Hi Btrfs Developers,
I found a potential data race around the disk_i_size in btrfs inodes.
Following is the call stack in the helper threads.
[Thread 1]
btrfs_endio_write_helper
normal_work_helper
finish_ordered_fn
btrfs_finish_ordered_io
btrfs_ordered_update_i_size
[WRITE] BTRFS_I(inode)->disk_i_size = new_i_size;
[Thread 2]
btrfs_endio_write_helper
normal_work_helper
finish_ordered_fn
btrfs_finish_ordered_io
insert_reserved_file_extent
__btrfs_drop_extents
[READ] if (start >= BTRFS_I(inode)->disk_i_size && !replace_extent)
I can confirm that the read and write may happen in close proximity
(in time) and the READ may get either the old value or the new value
of the disk_i_size. Is this a valid data race or some operation
designed for lock-free accesses?
Best Regards,
Meng
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2019-11-28 3:44 potential data race on disk_i_size in two btrfs_endio_writer_helper() Meng Xu
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