Possibly at fs/buffer.c:end_buffer_io_async?
We need to flush the cache when I/O was READ or READA. Is there any
way for end_buffer_io_async to distinguish which I/O (READ or WRITE)
has been done?
--------------------------------------
Problem with write-back cache.
(1) Page got swapped out
Swap out
[ Disk ] <---- P [ Page ]
(2) Page got swapped in asynchronously, possibly by read-ahead
Swap in
[ Disk ] ----> P [ Page ]
K
The I/O from disk goes through kernel virtual address K.
We have cache entries indexed by K.
(3) Page fault occurs at user space U
[ Disk ] P [ Page ] <----- U
K
The control goes to do_swap_page, found the page at
lookup_swap_cache.
If K and U indexes differently, we have cache alias issues,
we need to flush the entries indexed by K.
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