Commit db5ad6b7f8 ("nvme-tcp: try to send request in queue_rq
context") added a second context that may perform a network send.
This means that now RX and TX are not serialized in nvme_tcp_io_work
and can run concurrently.
While there is correct mutual exclusion in the TX path (where
the send_mutex protect the queue socket send activity) RX activity,
and more specifically request completion may run concurrently.
This means we must guarantee that any mutation of the request state
related to its lifetime, bytes sent must not be accessed when a completion
may have possibly arrived back (and processed).
The race may trigger when a request completion arrives, processed
_and_ reused as a fresh new request, exactly in the (relatively short)
window between the last data payload sent and before the request iov_iter
is advanced.
Consider the following race:
1. 16K write request is queued
2. The nvme command and the data is sent to the controller (in-capsule
or solicited by r2t)
3. After the last payload is sent but before the req.iter is advanced,
the controller sends back a completion.
4. The completion is processed, the request is completed, and reused
to transfer a new request (write or read)
5. The new request is queued, and the driver reset the request parameters
(nvme_tcp_setup_cmd_pdu).
6. Now context in (2) resumes execution and advances the req.iter
==> use-after-completion as this is already a new request.
Fix this by making sure the request is not advanced after the last
data payload send, knowing that a completion may have arrived already.
An alternative solution would have been to delay the request completion
or state change waiting for reference counting on the TX path, but besides
adding atomic operations to the hot-path, it may present challenges in
multi-stage R2T scenarios where a r2t handler needs to be deferred to
an async execution.
Reported-by: Narayan Ayalasomayajula <narayan.ayalasomayajula@wdc.com>
Tested-by: Anil Mishra <anil.mishra@wdc.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Cc: stable@vger.kernel.org # v5.8+
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When creating loop ctrl in nvme_loop_create_ctrl(), if nvme_init_ctrl()
fails, the loop ctrl should be freed before jumping to the "out" label.
Fixes: 3a85a5de29 ("nvme-loop: add a NVMe loopback host driver")
Signed-off-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When creating ctrl in nvmet_alloc_ctrl(), if the cntlid_min is larger
than cntlid_max of the subsystem, and jumps to the
"out_free_changed_ns_list" label, but the ctrl->sqs lack of be freed.
Fix this by jumping to the "out_free_sqs" label.
Fixes: 94a39d61f8 ("nvmet: make ctrl-id configurable")
Signed-off-by: Wu Bo <wubo40@huawei.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reset the ns->file value to NULL also in the error case in
nvmet_file_ns_enable().
The ns->file variable points either to file object or contains the
error code after the filp_open() call. This can lead to following
problem:
When the user first setups an invalid file backend and tries to enable
the ns, it will fail. Then the user switches over to a bdev backend
and enables successfully the ns. The first received I/O will crash the
system because the IO backend is chosen based on the ns->file value:
static u16 nvmet_parse_io_cmd(struct nvmet_req *req)
{
[...]
if (req->ns->file)
return nvmet_file_parse_io_cmd(req);
return nvmet_bdev_parse_io_cmd(req);
}
Reported-by: Enzo Matsumiya <ematsumiya@suse.com>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Host can send invalid commands and flood the target with error messages.
Demote the error message from pr_err() to pr_debug() in
nvmet_parse_fabrics_cmd() and nvmet_parse_connect_cmd().
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Use the helper nvmet_report_invalid_opcode() to report invalid opcode
so we can remove the duplicate code.
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Host can send invalid commands and flood the target with error messages
for the discovery controller. Demote the error message from pr_err() to
pr_debug( in nvmet_parse_discovery_cmd().
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When handling passthru commands, for inline bio allocation we only
consider the transfer size. This works well when req->sg_cnt fits into
the req->inline_bvec, but it will result in the early return from
bio_add_hw_page() when req->sg_cnt > NVMET_MAX_INLINE_BVEC.
Consider an I/O of size 32768 and first buffer is not aligned to the
page boundary, then I/O is split in following manner :-
[ 2206.256140] nvmet: sg->length 3440 sg->offset 656
[ 2206.256144] nvmet: sg->length 4096 sg->offset 0
[ 2206.256148] nvmet: sg->length 4096 sg->offset 0
[ 2206.256152] nvmet: sg->length 4096 sg->offset 0
[ 2206.256155] nvmet: sg->length 4096 sg->offset 0
[ 2206.256159] nvmet: sg->length 4096 sg->offset 0
[ 2206.256163] nvmet: sg->length 4096 sg->offset 0
[ 2206.256166] nvmet: sg->length 4096 sg->offset 0
[ 2206.256170] nvmet: sg->length 656 sg->offset 0
Now the req->transfer_size == NVMET_MAX_INLINE_DATA_LEN i.e. 32768, but
the req->sg_cnt is (9) > NVMET_MAX_INLINE_BIOVEC which is (8).
This will result in early return in the following code path :-
nvmet_bdev_execute_rw()
bio_add_pc_page()
bio_add_hw_page()
if (bio_full(bio, len))
return 0;
Use previously introduced helper nvmet_use_inline_bvec() to consider
req->sg_cnt when using inline bio. This only affects nvme-loop
transport.
Fixes: dab3902b19 ("nvmet: use inline bio for passthru fast path")
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When handling rw commands, for inline bio case we only consider
transfer size. This works well when req->sg_cnt fits into the
req->inline_bvec, but it will result in the warning in
__bio_add_page() when req->sg_cnt > NVMET_MAX_INLINE_BVEC.
Consider an I/O size 32768 and first page is not aligned to the page
boundary, then I/O is split in following manner :-
[ 2206.256140] nvmet: sg->length 3440 sg->offset 656
[ 2206.256144] nvmet: sg->length 4096 sg->offset 0
[ 2206.256148] nvmet: sg->length 4096 sg->offset 0
[ 2206.256152] nvmet: sg->length 4096 sg->offset 0
[ 2206.256155] nvmet: sg->length 4096 sg->offset 0
[ 2206.256159] nvmet: sg->length 4096 sg->offset 0
[ 2206.256163] nvmet: sg->length 4096 sg->offset 0
[ 2206.256166] nvmet: sg->length 4096 sg->offset 0
[ 2206.256170] nvmet: sg->length 656 sg->offset 0
Now the req->transfer_size == NVMET_MAX_INLINE_DATA_LEN i.e. 32768, but
the req->sg_cnt is (9) > NVMET_MAX_INLINE_BIOVEC which is (8).
This will result in the following warning message :-
nvmet_bdev_execute_rw()
bio_add_page()
__bio_add_page()
WARN_ON_ONCE(bio_full(bio, len));
This scenario is very hard to reproduce on the nvme-loop transport only
with rw commands issued with the passthru IOCTL interface from the host
application and the data buffer is allocated with the malloc() and not
the posix_memalign().
Fixes: 73383adfad ("nvmet: don't split large I/Os unconditionally")
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
nvme_init_identify and thus nvme_mpath_init can be called multiple
times and thus must not overwrite potentially initialized or in-use
fields. Split out a helper for the basic initialization when the
controller is initialized and make sure the init_identify path does
not blindly change in-use data structures.
Fixes: 0d0b660f21 ("nvme: add ANA support")
Reported-by: Martin Wilck <mwilck@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Nothing can stop a host from submitting invalid commands. The target
just needs to respond with an appropriate status, but that's not a
target error. Demote invalid command messages to the debug level so
these events don't spam the kernel logs.
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
When a request finally completes in end_io() after it has failed over,
the bdev pointer can be stale and thus the system can crash. Set the
bdev back to ns head, so the request is map to an active path when
resubmitted.
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
reset_work() in nvme-pci may hang forever in the following scenario:
1) A reset caused by a command timeout occurs due to a controller being
temporarily irresponsive.
2) nvme_reset_work() restarts admin queue at nvme_alloc_admin_tags(). At
the same time, a user-submitted admin command is queued and waiting
for completion. Then, reset_work() changes its state to CONNECTING,
and submits an identify command.
3) However, the controller does still not respond to any command,
causing a timeout being fired at the user-submitted command.
Unfortunately, nvme_timeout() does not see the completion on cq, and
any timeout that takes place under CONNECTING state causes a
controller shutdown.
4) Normally, the identify command in reset_work() would be canceled with
SC_HOST_ABORTED by nvme_dev_disable(), then reset_work can tear down
the controller accordingly. But the controller happens to return
online and respond the identify command before nvme_dev_disable()
should have been reaped it off.
5) reset_work() continues to setup_io_queues() as it observes no error
in init_identify(). However, the admin queue has already been
quiesced in dev_disable(). Thus, any following commands would be
blocked forever in blk_execute_rq().
This can be fixed by restricting usercmd commands when controller is not
in a LIVE state in nvme_queue_rq(), as what has been done previously in
fabrics.
```
nvme_reset_work(): |
nvme_alloc_admin_tags() |
| nvme_submit_user_cmd():
nvme_init_identify(): | ...
__nvme_submit_sync_cmd(): |
... | ...
---------------------------------------> nvme_timeout():
(Controller starts reponding commands) | nvme_dev_disable(, true):
nvme_setup_io_queues(): |
__nvme_submit_sync_cmd(): |
(hung in blk_execute_rq |
since run_hw_queue sees |
queue quiesced) |
```
Signed-off-by: Tao Chiu <taochiu@synology.com>
Signed-off-by: Cody Wong <codywong@synology.com>
Reviewed-by: Leon Chien <leonchien@synology.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
queue_rq() in pci only checks if the dispatched queue (nvmeq) is ready,
e.g. not being suspended. Since nvme_alloc_admin_tags() in reset flow
restarts the admin queue, users are able to submit admin commands to a
controller before reset_work() completes. Commands submitted under this
condition may interfere with commands that performs identify, IO queue
setup in reset_work(), and may result in a hang described in the
following patch.
As seen in the fabrics, user commands are prevented from being executed
under inproper controller states. We may reuse this logic to maintain a
clear admin queue during reset_work().
Signed-off-by: Tao Chiu <taochiu@synology.com>
Signed-off-by: Cody Wong <codywong@synology.com>
Reviewed-by: Leon Chien <leonchien@synology.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
nvme_clear_nvme_request() clears the nvme_command, which is unncessary
for passthrough requests as nvme_command is overwritten immediately.
Move clearing part from this helper to the caller, so that double memset
for passthrough requests is avoided.
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
In multipath case, we should consider namespace attachment with
controllers in a subsystem when we find out the live controller for the
namespace. This patch manually reverted the commit 3557a44097
("nvme: don't bother to look up a namespace for controller ioctls") with
few more updates to nvme_ns_head_chr_ioctl which has been newly updated.
Fixes: 3557a44097 ("nvme: don't bother to look up a namespace for
controller ioctls")
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Userspace has not been allowed to I/O to device that's failed to
be initialized. This patch introduces generic per-namespace character
device to allow userspace to I/O regardless the block device is there or
not.
The chardev naming convention will similar to the existing blkdev naming,
using a ng prefix instead of nvme, i.e.
- /dev/ngXnY
It also supports multipath which means it will not expose chardev for the
hidden namespace blkdevs (e.g., nvmeXcYnZ). If /dev/ngXnY is created for
a ns_head, then I/O request will be routed to a specific controller
selected by the iopolicy of the subsystem.
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Tested-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Remove a level of indentation from the main code implementating the table
search by using a goto for the APST not supported case. Also move the
main comment above the function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Do not call nvme_configure_apst when the controller is not live, given
that nvme_configure_apst will fail due the lack of an admin queue when
the controller is being torn down and nvme_set_latency_tolerance is
called from dev_pm_qos_hide_latency_tolerance.
Fixes: 510a405d945b("nvme: fix memory leak for power latency tolerance")
Reported-by: Peng Liu <liupeng17@lenovo.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Add a 'kato' controller sysfs attribute to display the current
keep-alive timeout value (if any). This allows userspace to identify
persistent discovery controllers, as these will have a non-zero
KATO value.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
According to the NVMe base spec the KATO commands should be sent
at half of the KATO interval, to properly account for round-trip
times.
As we now will only ever send one KATO command per connection we
can easily use the recommended values.
This also fixes a potential issue where the request timeout for
the KATO command does not match the value in the connect command,
which might be causing spurious connection drops from the target.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Issue following command:
nvme set-feature -f 0xf -v 0 /dev/nvme1n1 # disable keep-alive timer
nvme admin-passthru -o 0x18 /dev/nvme1n1 # send keep-alive command
will make keep-alive timer fired and thus delete the controller like
below:
[247459.907635] nvmet: ctrl 1 keep-alive timer (0 seconds) expired!
[247459.930294] nvmet: ctrl 1 fatal error occurred!
Avoid this by not queuing delayed keep-alive if it is disabled when
keep-alive command is received from the admin queue.
Signed-off-by: Hou Pu <houpu.main@gmail.com>
Tested-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Adding entry for dev_attr_fast_io_fail_tmo to avoid the kernel crash
while reading and writing the fast_io_fail_tmo.
Fixes: 09fbed6363 (nvme: export fast_io_fail_tmo to sysfs)
Signed-off-by: Gopal Tiwari <gtiwari@redhat.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Instead of failing to scan the namespace entirely when unsupported
features are detected, just mark the gendisk hidden but allow other
access like the upcoming per-namespace character device.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
These will be reused for the per-namespace character devices.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Move the multipath block_device_operations to multipath.c, where they
belong.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Split out the ioctl code from core.c into a new file. Also update
copyrights while we're at it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Don't bother to look up a namespace just to drop if after retreiving the
controller for the multipath case. Just look up a live controller for
the subsystem directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Only use the existing ioctl handler for the multipath case, and add a
simpler one that reverts to the pre-multipath case for not shared
use case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Don't bother defining a separate compat_ioctl handler, and just handle
the NVME_IOCTL_SUBMIT_IO32 case inline. Also only defined it for those
ABIs (currently just i386 vs x86_64) that are affected.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Factor out a helper for the namespace based ioctls.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Pass the proper user pointer instead of the not all that useful integer
representation.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Return false from nvme_set_disk_name and let the caller set the
non-multipath name instead of duplicating the naming information in two
places. Also remove the pointless local variables for the disk name
and flags and the not needed ctrl argument.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Move the multipath gendisk out of #ifdef CONFIG_NVME_MULTIPATH and add
a new nvme_ns_head_multipath that uses it to check if a ns_head has
a multipath device associated with it.
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
[hch: added the IS_ENABLED, converted a few existing users]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
There is a single trailing whitespace in core.c.
Since this is just a single whitespace, the chances of this affecting
backports to stable should be quite low, so let's just remove it.
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
There is a single trailing whitespace in multipath.c.
Since this is just a single whitespace, the chances of this affecting
backports to stable should be quite low, so let's just remove it.
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
There is a single trailing whitespace in pci.c.
Since this is just a single whitespace, the chances of this affecting
backports to stable should be quite low, so let's just remove it.
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
According to the module parameter description for sgl_threshold,
a value of 0 means that SGLs are disabled.
If SGLs are disabled, we should respect that, even for the case
where the request is made up of a single physical segment.
Fixes: 297910571f ("nvme-pci: optimize mapping single segment requests using SGLs")
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
There is a spelling mistake in a pr_err error message. Fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Once a host is already created, avoid allocate additional hostports that
will be thrown away. add an helper function to handle host search.
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Amit Engel <amit.engel@dell.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
In case there is an io that contains inline data and it goes to
parsing error flow, command response will free command and iov
before clearing the data on the socket buffer.
This will delay the command response until receive flow is completed.
Fixes: 872d26a391 ("nvmet-tcp: add NVMe over TCP target driver")
Signed-off-by: Elad Grupi <elad.grupi@dell.com>
Signed-off-by: Hou Pu <houpu.main@gmail.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
list_sort() internally casts the comparison function passed to it
to a different type with constant struct list_head pointers, and
uses this pointer to call the functions, which trips indirect call
Control-Flow Integrity (CFI) checking.
Instead of removing the consts, this change defines the
list_cmp_func_t type and changes the comparison function types of
all list_sort() callers to use const pointers, thus avoiding type
mismatches.
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210408182843.1754385-10-samitolvanen@google.com
Instead of overloading the passthrough fast path with the deprecated
block layer bounce buffering let the users that combine an old
undermaintained driver with a highmem system pay the price by always
falling back to copies in that case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210331073001.46776-9-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
