Now that vfio_pci has been split into two source modules, one focusing on
the "struct pci_driver" (vfio_pci.c) and a toolbox library of code
(vfio_pci_core.c), complete the split and move them into two different
kernel modules.
As before vfio_pci.ko continues to present the same interface under sysfs
and this change will have no functional impact.
Splitting into another module and adding exports allows creating new HW
specific VFIO PCI drivers that can implement device specific
functionality, such as VFIO migration interfaces or specialized device
requirements.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-14-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Expose an 'override_only' helper macro (i.e.
PCI_DRIVER_OVERRIDE_DEVICE_VFIO) for VFIO PCI sub system and add the
required code to prefix its matching entries with "vfio_" in
modules.alias file.
It allows VFIO device drivers to include match entries in the
modules.alias file produced by kbuild that are not used for normal
driver autoprobing and module autoloading. Drivers using these match
entries can be connected to the PCI device manually, by userspace, using
the existing driver_override sysfs.
For example the resulting modules.alias may have:
alias pci:v000015B3d00001021sv*sd*bc*sc*i* mlx5_core
alias vfio_pci:v000015B3d00001021sv*sd*bc*sc*i* mlx5_vfio_pci
alias vfio_pci:v*d*sv*sd*bc*sc*i* vfio_pci
In this example mlx5_core and mlx5_vfio_pci match to the same PCI
device. The kernel will autoload and autobind to mlx5_core but the
kernel and udev mechanisms will ignore mlx5_vfio_pci.
When userspace wants to change a device to the VFIO subsystem it can
implement a generic algorithm:
1) Identify the sysfs path to the device:
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0
2) Get the modalias string from the kernel:
$ cat /sys/bus/pci/devices/0000:01:00.0/modalias
pci:v000015B3d00001021sv000015B3sd00000001bc02sc00i00
3) Prefix it with vfio_:
vfio_pci:v000015B3d00001021sv000015B3sd00000001bc02sc00i00
4) Search modules.alias for the above string and select the entry that
has the fewest *'s:
alias vfio_pci:v000015B3d00001021sv*sd*bc*sc*i* mlx5_vfio_pci
5) modprobe the matched module name:
$ modprobe mlx5_vfio_pci
6) cat the matched module name to driver_override:
echo mlx5_vfio_pci > /sys/bus/pci/devices/0000:01:00.0/driver_override
7) unbind device from original module
echo 0000:01:00.0 > /sys/bus/pci/devices/0000:01:00.0/driver/unbind
8) probe PCI drivers (or explicitly bind to mlx5_vfio_pci)
echo 0000:01:00.0 > /sys/bus/pci/drivers_probe
The algorithm is independent of bus type. In future the other buses with
VFIO device drivers, like platform and ACPI, can use this algorithm as
well.
This patch is the infrastructure to provide the information in the
modules.alias to userspace. Convert the only VFIO pci_driver which results
in one new line in the modules.alias:
alias vfio_pci:v*d*sv*sd*bc*sc*i* vfio_pci
Later series introduce additional HW specific VFIO PCI drivers, such as
mlx5_vfio_pci.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com> # for pci.h
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-11-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Add 'override_only' field to struct pci_device_id to be used as part of
pci_match_device().
When set, a driver only matches the entry when dev->driver_override is
set to that driver.
In addition, add a helper macro named 'PCI_DEVICE_DRIVER_OVERRIDE' to
enable setting some data on it.
Next patch from this series will use the above functionality.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-10-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This is a preparation before splitting vfio_pci.ko to 2 modules.
As module parameters are a kind of uAPI they need to stay on vfio_pci.ko
to avoid a user visible impact.
For now continue to keep the implementation of these options in
vfio_pci_core.c. Arguably they are vfio_pci functionality, but further
splitting of vfio_pci_core.c will be better done in another series
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-9-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Split the vfio_pci driver into two logical parts, the 'struct
pci_driver' (vfio_pci.c) which implements "Generic VFIO support for any
PCI device" and a library of code (vfio_pci_core.c) that helps
implementing a struct vfio_device on top of a PCI device.
vfio_pci.ko continues to present the same interface under sysfs and this
change should have no functional impact.
Following patches will turn vfio_pci and vfio_pci_core into a separate
module.
This is a preparation for allowing another module to provide the
pci_driver and allow that module to customize how VFIO is setup, inject
its own operations, and easily extend vendor specific functionality.
At this point the vfio_pci_core still contains a lot of vfio_pci
functionality mixed into it. Following patches will move more of the
large scale items out, but another cleanup series will be needed to get
everything.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-7-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This is a preparation patch for separating the vfio_pci driver to a
subsystem driver and a generic pci driver. This patch doesn't change any
logic.
The new vfio_pci_core_device structure will be the main structure of the
core driver and later on vfio_pci_device structure will be the main
structure of the generic vfio_pci driver.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-4-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
It was pointed out during an unrelated patch review that locks should not
be open coded - i.e., writing the algorithm of a standard lock in a
function instead of using a lock from the standard library. The setting and
testing of a busy flag and sleeping on a wait_event is the same thing
a lock does. The open coded locks are invisible to lockdep, so potential
locking problems are not detected.
This patch removes the open coded locks used during
VFIO_GROUP_NOTIFY_SET_KVM notification. The busy flag
and wait queue were introduced to resolve a possible circular locking
dependency reported by lockdep when starting a secure execution guest
configured with AP adapters and domains. Reversing the order in which
the kvm->lock mutex and matrix_dev->lock mutex are locked resolves the
issue reported by lockdep, thus enabling the removal of the open coded
locks.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Acked-by: Halil Pasic <pasic@linux.ibm.com>
Link: https://lore.kernel.org/r/20210823212047.1476436-3-akrowiak@linux.ibm.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The function pointer to the interception handler for the PQAP instruction
can get changed during the interception process. Let's add a
semaphore to struct kvm_s390_crypto to control read/write access to the
function pointer contained therein.
The semaphore must be locked for write access by the vfio_ap device driver
when notified that the KVM pointer has been set or cleared. It must be
locked for read access by the interception framework when the PQAP
instruction is intercepted.
Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lore.kernel.org/r/20210823212047.1476436-2-akrowiak@linux.ibm.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The user can open multiple device FDs if it likes, however the open
function calls vfio_register_notifier() on device global state. Calling
vfio_register_notifier() twice will trigger a WARN_ON from
notifier_chain_register() and the first close will wrongly delete the
notifier and more.
Since these really want the new open/close_device() semantics just change
the function over.
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/13-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
The user can open multiple device FDs if it likes, however these open()
functions call vfio_register_notifier() on some device global
state. Calling vfio_register_notifier() twice in will trigger a WARN_ON
from notifier_chain_register() and the first close will wrongly delete the
notifier and more.
Since these really want the new open/close_device() semantics just change
the functions over.
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/12-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Like vfio_pci_dev_set_try_reset() this code wants to reset all of the
devices in the "reset group" which is the same membership as the device
set.
Instead of trying to reconstruct the device set from the PCI list go
directly from the device set's device list to execute the reset.
The same basic structure as vfio_pci_dev_set_try_reset() is used. The
'vfio_devices' struct is replaced with the device set linked list and we
simply sweep it multiple times under the lock.
This eliminates a memory allocation and get/put traffic and another
improperly locked test of pci_dev_driver().
Reviewed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/10-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
vfio_pci_try_bus_reset() is triggering a reset of the entire_dev set if
any device within it has accumulated a needs_reset. This reset can only be
done once all of the drivers operating the PCI devices to be reset are in
a known safe state.
Make this clearer by directly operating on the dev_set instead of the
vfio_pci_device. Rename the function to vfio_pci_dev_set_try_reset().
Use the device list inside the dev_set to check that all drivers are in a
safe state instead of working backwards from the pci_device.
The dev_set->lock directly prevents devices from joining/leaving the set,
or changing their state, which further implies the pci_device cannot
change drivers or that the vfio_device be freed, eliminating the need for
get/put's.
If a pci_device to be reset is not in the dev_set then the reset cannot be
used as we can't know what the state of that driver is. Directly measure
this by checking that every pci_device is in the dev_set - which
effectively proves that VFIO drivers are attached to everything.
Remove the odd interaction around vfio_pci_set_power_state() - have the
only caller avoid its redundant vfio_pci_set_power_state() instead of
avoiding it inside vfio_pci_dev_set_try_reset().
This restructuring corrects a call to pci_dev_driver() without holding the
device_lock() and removes a hard wiring to &vfio_pci_driver.
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/9-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
PCI wants to have the usual open/close_device() logic with the slight
twist that the open/close_device() must be done under a singelton lock
shared by all of the vfio_devices that are in the PCI "reset group".
The reset group, and thus the device set, is determined by what devices
pci_reset_bus() touches, which is either the entire bus or only the slot.
Rely on the core code to do everything reflck was doing and delete reflck
entirely.
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/8-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
FSL uses the internal reflck to implement the open_device() functionality,
conversion to the core code is straightforward.
The decision on which set to be part of is trivially based on the
is_fsl_mc_bus_dprc() and we use a 'struct device *' pointer as the set_id.
The dev_set lock is protecting the interrupts setup. The FSL MC devices
are using MSIs and only the DPRC device is allocating the MSIs from the
MSI domain. The other devices just take interrupts from a pool. The lock
is protecting the access to this pool.
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Tested-by: Diana Craciun OSS <diana.craciun@oss.nxp.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/6-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Currently the driver ops have an open/release pair that is called once
each time a device FD is opened or closed. Add an additional set of
open/close_device() ops which are called when the device FD is opened for
the first time and closed for the last time.
An analysis shows that all of the drivers require this semantic. Some are
open coding it as part of their reflck implementation, and some are just
buggy and miss it completely.
To retain the current semantics PCI and FSL depend on, introduce the idea
of a "device set" which is a grouping of vfio_device's that share the same
lock around opening.
The device set is established by providing a 'set_id' pointer. All
vfio_device's that provide the same pointer will be joined to the same
singleton memory and lock across the whole set. This effectively replaces
the oddly named reflck.
After conversion the set_id will be sourced from:
- A struct device from a fsl_mc_device (fsl)
- A struct pci_slot (pci)
- A struct pci_bus (pci)
- The struct vfio_device (everything)
The design ensures that the above pointers are live as long as the
vfio_device is registered, so they form reliable unique keys to group
vfio_devices into sets.
This implementation uses xarray instead of searching through the driver
core structures, which simplifies the somewhat tricky locking in this
area.
Following patches convert all the drivers.
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/4-v4-9ea22c5e6afb+1adf-vfio_reflck_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Pull perf tools fixes from Arnaldo Carvalho de Melo:
- Revert "perf map: Fix dso->nsinfo refcounting", this makes 'perf top'
abort, uncovering a design flaw on how namespace information is kept.
The fix for that is more than we can do right now, leave it for the
next merge window.
- Split --dump-raw-trace by AUX records for ARM's CoreSight, fixing up
the decoding of some records.
- Fix PMU alias matching.
Thanks to James Clark and John Garry for these fixes.
* tag 'perf-tools-fixes-for-v5.14-2021-08-01' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
Revert "perf map: Fix dso->nsinfo refcounting"
perf pmu: Fix alias matching
perf cs-etm: Split --dump-raw-trace by AUX records
Pull powerpc fixes from Michael Ellerman:
- Don't use r30 in VDSO code, to avoid breaking existing Go lang
programs.
- Change an export symbol to allow non-GPL modules to use spinlocks
again.
Thanks to Paul Menzel, and Srikar Dronamraju.
* tag 'powerpc-5.14-4' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/vdso: Don't use r30 to avoid breaking Go lang
powerpc/pseries: Fix regression while building external modules
Pull xfs fixes from Darrick Wong:
"This contains a bunch of bug fixes in XFS.
Dave and I have been busy the last couple of weeks to find and fix as
many log recovery bugs as we can find; here are the results so far. Go
fstests -g recoveryloop! ;)
- Fix a number of coordination bugs relating to cache flushes for
metadata writeback, cache flushes for multi-buffer log writes, and
FUA writes for single-buffer log writes
- Fix a bug with incorrect replay of attr3 blocks
- Fix unnecessary stalls when flushing logs to disk
- Fix spoofing problems when recovering realtime bitmap blocks"
* tag 'xfs-5.14-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: prevent spoofing of rtbitmap blocks when recovering buffers
xfs: limit iclog tail updates
xfs: need to see iclog flags in tracing
xfs: Enforce attr3 buffer recovery order
xfs: logging the on disk inode LSN can make it go backwards
xfs: avoid unnecessary waits in xfs_log_force_lsn()
xfs: log forces imply data device cache flushes
xfs: factor out forced iclog flushes
xfs: fix ordering violation between cache flushes and tail updates
xfs: fold __xlog_state_release_iclog into xlog_state_release_iclog
xfs: external logs need to flush data device
xfs: flush data dev on external log write
Pull cifs fixes from Steve French:
"Three cifs/smb3 fixes, including two for stable, and a fix for an
fallocate problem noticed by Clang"
* tag '5.14-rc3-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6:
cifs: add missing parsing of backupuid
smb3: rc uninitialized in one fallocate path
SMB3: fix readpage for large swap cache
Pull networking fixes from Jakub Kicinski:
"Networking fixes for 5.14-rc4, including fixes from bpf, can, WiFi
(mac80211) and netfilter trees.
Current release - regressions:
- mac80211: fix starting aggregation sessions on mesh interfaces
Current release - new code bugs:
- sctp: send pmtu probe only if packet loss in Search Complete state
- bnxt_en: add missing periodic PHC overflow check
- devlink: fix phys_port_name of virtual port and merge error
- hns3: change the method of obtaining default ptp cycle
- can: mcba_usb_start(): add missing urb->transfer_dma initialization
Previous releases - regressions:
- set true network header for ECN decapsulation
- mlx5e: RX, avoid possible data corruption w/ relaxed ordering and
LRO
- phy: re-add check for PHY_BRCM_DIS_TXCRXC_NOENRGY on the BCM54811
PHY
- sctp: fix return value check in __sctp_rcv_asconf_lookup
Previous releases - always broken:
- bpf:
- more spectre corner case fixes, introduce a BPF nospec
instruction for mitigating Spectre v4
- fix OOB read when printing XDP link fdinfo
- sockmap: fix cleanup related races
- mac80211: fix enabling 4-address mode on a sta vif after assoc
- can:
- raw: raw_setsockopt(): fix raw_rcv panic for sock UAF
- j1939: j1939_session_deactivate(): clarify lifetime of session
object, avoid UAF
- fix number of identical memory leaks in USB drivers
- tipc:
- do not blindly write skb_shinfo frags when doing decryption
- fix sleeping in tipc accept routine"
* tag 'net-5.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (91 commits)
gve: Update MAINTAINERS list
can: esd_usb2: fix memory leak
can: ems_usb: fix memory leak
can: usb_8dev: fix memory leak
can: mcba_usb_start(): add missing urb->transfer_dma initialization
can: hi311x: fix a signedness bug in hi3110_cmd()
MAINTAINERS: add Yasushi SHOJI as reviewer for the Microchip CAN BUS Analyzer Tool driver
bpf: Fix leakage due to insufficient speculative store bypass mitigation
bpf: Introduce BPF nospec instruction for mitigating Spectre v4
sis900: Fix missing pci_disable_device() in probe and remove
net: let flow have same hash in two directions
nfc: nfcsim: fix use after free during module unload
tulip: windbond-840: Fix missing pci_disable_device() in probe and remove
sctp: fix return value check in __sctp_rcv_asconf_lookup
nfc: s3fwrn5: fix undefined parameter values in dev_err()
net/mlx5: Fix mlx5_vport_tbl_attr chain from u16 to u32
net/mlx5e: Fix nullptr in mlx5e_hairpin_get_mdev()
net/mlx5: Unload device upon firmware fatal error
net/mlx5e: Fix page allocation failure for ptp-RQ over SF
net/mlx5e: Fix page allocation failure for trap-RQ over SF
...
Pull ACPI fixes from Rafael Wysocki:
"These revert a recent IRQ resources handling modification that turned
out to be problematic, fix suspend-to-idle handling on AMD platforms
to take upcoming systems into account properly and fix the retrieval
of the DPTF attributes of the PCH FIVR.
Specifics:
- Revert recent change of the ACPI IRQ resources handling that
attempted to improve the ACPI IRQ override selection logic, but
introduced serious regressions on some systems (Hui Wang).
- Fix up quirks for AMD platforms in the suspend-to-idle support code
so as to take upcoming systems using uPEP HID AMDI007 into account
as appropriate (Mario Limonciello).
- Fix the code retrieving DPTF attributes of the PCH FIVR so that it
agrees on the return data type with the ACPI control method
evaluated for this purpose (Srinivas Pandruvada)"
* tag 'acpi-5.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI: DPTF: Fix reading of attributes
Revert "ACPI: resources: Add checks for ACPI IRQ override"
ACPI: PM: Add support for upcoming AMD uPEP HID AMDI007
Since commit 1b6b26ae70 ("pipe: fix and clarify pipe write wakeup
logic") we have sanitized the pipe write logic, and would only try to
wake up readers if they needed it.
In particular, if the pipe already had data in it before the write,
there was no point in trying to wake up a reader, since any existing
readers must have been aware of the pre-existing data already. Doing
extraneous wakeups will only cause potential thundering herd problems.
However, it turns out that some Android libraries have misused the EPOLL
interface, and expected "edge triggered" be to "any new write will
trigger it". Even if there was no edge in sight.
Quoting Sandeep Patil:
"The commit 1b6b26ae70 ('pipe: fix and clarify pipe write wakeup
logic') changed pipe write logic to wakeup readers only if the pipe
was empty at the time of write. However, there are libraries that
relied upon the older behavior for notification scheme similar to
what's described in [1]
One such library 'realm-core'[2] is used by numerous Android
applications. The library uses a similar notification mechanism as GNU
Make but it never drains the pipe until it is full. When Android moved
to v5.10 kernel, all applications using this library stopped working.
The library has since been fixed[3] but it will be a while before all
applications incorporate the updated library"
Our regression rule for the kernel is that if applications break from
new behavior, it's a regression, even if it was because the application
did something patently wrong. Also note the original report [4] by
Michal Kerrisk about a test for this epoll behavior - but at that point
we didn't know of any actual broken use case.
So add the extraneous wakeup, to approximate the old behavior.
[ I say "approximate", because the exact old behavior was to do a wakeup
not for each write(), but for each pipe buffer chunk that was filled
in. The behavior introduced by this change is not that - this is just
"every write will cause a wakeup, whether necessary or not", which
seems to be sufficient for the broken library use. ]
It's worth noting that this adds the extraneous wakeup only for the
write side, while the read side still considers the "edge" to be purely
about reading enough from the pipe to allow further writes.
See commit f467a6a664 ("pipe: fix and clarify pipe read wakeup logic")
for the pipe read case, which remains that "only wake up if the pipe was
full, and we read something from it".
Link: https://lore.kernel.org/lkml/CAHk-=wjeG0q1vgzu4iJhW5juPkTsjTYmiqiMUYAebWW+0bam6w@mail.gmail.com/ [1]
Link: https://github.com/realm/realm-core [2]
Link: https://github.com/realm/realm-core/issues/4666 [3]
Link: https://lore.kernel.org/lkml/CAKgNAkjMBGeAwF=2MKK758BhxvW58wYTgYKB2V-gY1PwXxrH+Q@mail.gmail.com/ [4]
Link: https://lore.kernel.org/lkml/20210729222635.2937453-1-sspatil@android.com/
Reported-by: Sandeep Patil <sspatil@android.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull block fixes from Jens Axboe:
- gendisk freeing fix (Christoph)
- blk-iocost wake ordering fix (Tejun)
- tag allocation error handling fix (John)
- loop locking fix. While this isn't the prettiest fix in the world,
nobody has any good alternatives for 5.14. Something to likely
revisit for 5.15. (Tetsuo)
* tag 'block-5.14-2021-07-30' of git://git.kernel.dk/linux-block:
block: delay freeing the gendisk
blk-iocost: fix operation ordering in iocg_wake_fn()
blk-mq-sched: Fix blk_mq_sched_alloc_tags() error handling
loop: reintroduce global lock for safe loop_validate_file() traversal
