[email protected] (Paul Goyette) writes:
>In any case, if the bp->b_flags access needs to be protected by the
>mutex, a cursory grep shows that there are some other places that might
>need similar treatment, in wapbl_do_io(), wapbl_resize_buf(), and
>wapbl_write_blocks().
Not b_flags, just the B_LOCKED flag which is abused as a "is already
in wl_bufs list" marker.
These are the two operations that need to be protected:
add_buf:
if (B_LOCKED) {
remove from wl_bufs
} else {
do accounting for that buf
}
add to wl_bufs
set B_LOCKED
remove_buf:
remove from wl_bufs
clear B_LOCKED
wapbl_resize_buf apparently assumes that it cannot be
called concurrently with wapbl_remove_buf. That should
be ok since add_buf/remove_buf/resize_buf are just
additions to vfs_bio functions.
bdwrite() -> WAPBL_ADD_BUF
brelsel() -> WAPBL_REMOVE_BUF
allocbuf() -> WAPBL_RESIZE_BUF
I doubt that allocbuf() and brelsel() run concurrently on
the same buffer.
wapbl_doio only initializes the flags in a new buffer. That's
not relevant.
wapbl_write_blocks iterates over the whole wl_bufs list
and uses wl_rwlock to protect it. But is that sufficient?
--
--
Michael van Elst
Internet: [email protected]
"A potential Snark may lurk in every tree."
