fuse: fix possibly missed wake-up after abort

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commit 2d84a2d19b upstream.

In current fuse_drop_waiting() implementation it's possible that
fuse_wait_aborted() will not be woken up in the unlikely case that
fuse_abort_conn() + fuse_wait_aborted() runs in between checking
fc->connected and calling atomic_dec(&fc->num_waiting).

Do the atomic_dec_and_test() unconditionally, which also provides the
necessary barrier against reordering with the fc->connected check.

The explicit smp_mb() in fuse_wait_aborted() is not actually needed, since
the spin_unlock() in fuse_abort_conn() provides the necessary RELEASE
barrier after resetting fc->connected.  However, this is not a performance
sensitive path, and adding the explicit barrier makes it easier to
document.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: b8f95e5d13 ("fuse: umount should wait for all requests")
Cc: <stable@vger.kernel.org> #v4.19
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Miklos Szeredi 2018-11-09 15:52:16 +01:00 • committed by Greg Kroah-Hartman

parent 280da47603

commit 18cd6106cf

1 changed files with 9 additions and 3 deletions

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fs/fuse/dev.c

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