nvmet: defer setting ns->enabled to false in nvmet_ns_disable()

nvmet_ns_disable() currently clears ns->enabled before draining
in-flight I/O references. This allows namespace configuration to be
changed while existing I/O requests can still hold a reference to the
namespace.

This can race with configuration of namespace attributes such as the
device path, UUID, NGUID etc. These attributes can be accessed by I/O
requests without holding subsys->lock and must not be modified while
such requests are still using the namespace.

In nvmet_ns_disable(), keep ns->enabled set while existing namespace
references are being drained, so namespace configuration remains blocked
until all in-flight I/O has completed. Set ns->enabled to false only
after the namespace references have been drained and the namespace
device has been disabled.

Introduce the NVMET_NS_IO_LIVE flag, which is set after the namespace
is successfully enabled in nvmet_ns_enable(). When nvmet_ns_disable()
starts, clear NVMET_NS_IO_LIVE so that the I/O path stops admitting new
I/O once the flag is cleared. Using test_and_clear_bit() in
nvmet_ns_disable() also prevents concurrent callers from starting a
second disable operation.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

0 files changed, 0 insertions, 0 deletions