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The following scenario results in an IO hang: 1) ctrl completes a request with NVME_SC_ANA_TRANSITION. NVME_NS_ANA_PENDING bit in ns->flags is set and ana_work is triggered. 2) ana_work: nvme_read_ana_log() tries to get the ANA log page from the ctrl. This fails because ctrl disconnects. Therefore nvme_update_ns_ana_state() is not called and NVME_NS_ANA_PENDING bit in ns->flags is not cleared. 3) ctrl reconnects: nvme_mpath_init(ctrl,...) calls nvme_read_ana_log(ctrl, groups_only=true). However, nvme_update_ana_state() does not update namespaces because nr_nsids = 0 (due to groups_only mode). 4) scan_work calls nvme_validate_ns() finds the ns and re-validates OK. Result: The ctrl is now live but NVME_NS_ANA_PENDING bit in ns->flags is still set. Consequently ctrl will never be considered a viable path by __nvme_find_path(). IO will hang if ctrl is the only or the last path to the namespace. More generally, while ctrl is reconnecting, its ANA state may change. And because nvme_mpath_init() requests ANA log in groups_only mode, these changes are not propagated to the existing ctrl namespaces. This may result in a mal-function or an IO hang. Solution: nvme_mpath_init() will nvme_read_ana_log() with groups_only set to false. This will not harm the new ctrl case (no namespaces present), and will make sure the ANA state of namespaces gets updated after reconnect. Note: Another option would be for nvme_mpath_init() to invoke nvme_parse_ana_log(..., nvme_set_ns_ana_state) for each existing namespace. Reviewed-by: Sagi Grimberg <sagi@grimberg.me> Signed-off-by: Anton Eidelman <anton@lightbitslabs.com> Signed-off-by: Keith Busch <kbusch@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.