commit a37fbe666c016fd89e4460d0ebfcea05baba46dc upstream.
The number of times yet another open coded
`BITS_TO_LONGS(nbits) * sizeof(long)` can be spotted is huge.
Some generic helper is long overdue.
Add one, bitmap_size(), but with one detail.
BITS_TO_LONGS() uses DIV_ROUND_UP(). The latter works well when both
divident and divisor are compile-time constants or when the divisor
is not a pow-of-2. When it is however, the compilers sometimes tend
to generate suboptimal code (GCC 13):
48 83 c0 3f add $0x3f,%rax
48 c1 e8 06 shr $0x6,%rax
48 8d 14 c5 00 00 00 00 lea 0x0(,%rax,8),%rdx
%BITS_PER_LONG is always a pow-2 (either 32 or 64), but GCC still does
full division of `nbits + 63` by it and then multiplication by 8.
Instead of BITS_TO_LONGS(), use ALIGN() and then divide by 8. GCC:
8d 50 3f lea 0x3f(%rax),%edx
c1 ea 03 shr $0x3,%edx
81 e2 f8 ff ff 1f and $0x1ffffff8,%edx
Now it shifts `nbits + 63` by 3 positions (IOW performs fast division
by 8) and then masks bits[2:0]. bloat-o-meter:
add/remove: 0/0 grow/shrink: 20/133 up/down: 156/-773 (-617)
Clang does it better and generates the same code before/after starting
from -O1, except that with the ALIGN() approach it uses %edx and thus
still saves some bytes:
add/remove: 0/0 grow/shrink: 9/133 up/down: 18/-538 (-520)
Note that we can't expand DIV_ROUND_UP() by adding a check and using
this approach there, as it's used in array declarations where
expressions are not allowed.
Add this helper to tools/ as well.
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Acked-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 8692a24d0fae19f674d51726d179ad04ba95d958 ]
The subchannel-type field "st" of s390_cio_stsch and s390_cio_msch
tracepoints is incorrectly filled with the subchannel-enabled SCHIB
value "ena". Fix this by assigning the correct value.
Fixes: d1de8633d96a ("s390 cio: Rewrite trace point class s390_class_schib")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit 5ef1dc40ffa6a6cb968b0fdc43c3a61727a9e950 upstream.
The s390 common I/O layer (CIO) returns an unexpected -EBUSY return code
when drivers try to start I/O while a path-verification (PV) process is
pending. This can lead to failed device initialization attempts with
symptoms like broken network connectivity after boot.
Fix this by replacing the -EBUSY return code with a deferred condition
code 1 reply to make path-verification handling consistent from a
driver's point of view.
The problem can be reproduced semi-regularly using the following process,
while repeating steps 2-3 as necessary (example assumes an OSA device
with bus-IDs 0.0.a000-0.0.a002 on CHPID 0.02):
1. echo 0.0.a000,0.0.a001,0.0.a002 >/sys/bus/ccwgroup/drivers/qeth/group
2. echo 0 > /sys/bus/ccwgroup/devices/0.0.a000/online
3. echo 1 > /sys/bus/ccwgroup/devices/0.0.a000/online ; \
echo on > /sys/devices/css0/chp0.02/status
Background information:
The common I/O layer starts path-verification I/Os when it receives
indications about changes in a device path's availability. This occurs
for example when hardware events indicate a change in channel-path
status, or when a manual operation such as a CHPID vary or configure
operation is performed.
If a driver attempts to start I/O while a PV is running, CIO reports a
successful I/O start (ccw_device_start() return code 0). Then, after
completion of PV, CIO synthesizes an interrupt response that indicates
an asynchronous status condition that prevented the start of the I/O
(deferred condition code 1).
If a PV indication arrives while a device is busy with driver-owned I/O,
PV is delayed until after I/O completion was reported to the driver's
interrupt handler. To ensure that PV can be started eventually, CIO
reports a device busy condition (ccw_device_start() return code -EBUSY)
if a driver tries to start another I/O while PV is pending.
In some cases this -EBUSY return code causes device drivers to consider
a device not operational, resulting in failed device initialization.
Note: The code that introduced the problem was added in 2003. Symptoms
started appearing with the following CIO commit that causes a PV
indication when a device is removed from the cio_ignore list after the
associated parent subchannel device was probed, but before online
processing of the CCW device has started:
2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
During boot, the cio_ignore list is modified by the cio_ignore dracut
module [1] as well as Linux vendor-specific systemd service scripts[2].
When combined, this commit and boot scripts cause a frequent occurrence
of the problem during boot.
[1] https://github.com/dracutdevs/dracut/tree/master/modules.d/81cio_ignore
[2] https://github.com/SUSE/s390-tools/blob/master/cio_ignore.service
Cc: stable@vger.kernel.org # v5.15+
Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
Tested-By: Thorsten Winkler <twinkler@linux.ibm.com>
Reviewed-by: Thorsten Winkler <twinkler@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
