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git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi
Pull EFI updates from Ard Biesheuvel:
- Enable mirrored memory for arm64
- Fix up several abuses of the efivar API
- Refactor the efivar API in preparation for moving the 'business
logic' part of it into efivarfs
- Enable ACPI PRM on arm64
* tag 'efi-next-for-v5.20' of git://git.kernel.org/pub/scm/linux/kernel/git/efi/efi: (24 commits)
ACPI: Move PRM config option under the main ACPI config
ACPI: Enable Platform Runtime Mechanism(PRM) support on ARM64
ACPI: PRM: Change handler_addr type to void pointer
efi: Simplify arch_efi_call_virt() macro
drivers: fix typo in firmware/efi/memmap.c
efi: vars: Drop __efivar_entry_iter() helper which is no longer used
efi: vars: Use locking version to iterate over efivars linked lists
efi: pstore: Omit efivars caching EFI varstore access layer
efi: vars: Add thin wrapper around EFI get/set variable interface
efi: vars: Don't drop lock in the middle of efivar_init()
pstore: Add priv field to pstore_record for backend specific use
Input: applespi - avoid efivars API and invoke EFI services directly
selftests/kexec: remove broken EFI_VARS secure boot fallback check
brcmfmac: Switch to appropriate helper to load EFI variable contents
iwlwifi: Switch to proper EFI variable store interface
media: atomisp_gmin_platform: stop abusing efivar API
efi: efibc: avoid efivar API for setting variables
efi: avoid efivars layer when loading SSDTs from variables
efi: Correct comment on efi_memmap_alloc
memblock: Disable mirror feature if kernelcore is not specified
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Currently PRM(Platform Runtime Mechanism) config option is listed along
with the main ACPI (Advanced Configuration and Power Interface) option
at the same level. On ARM64 platforms unlike x86, ACPI option is listed
at the topmost level of configuration menu. It is rather very confusing
to see PRM option also listed along with ACPI in the topmost level.
Move the same under ACPI config option. No functional change, just changes
the level of visibility of this option under the configuration menu.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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There is interest to make use of PRM(Platform Runtime Mechanism) even on
ARM64 ACPI platforms. Allow PRM to be enabled on ARM64 platforms. It will
be enabled by default as on x86_64.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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handler_addr is a virtual address passed to efi_call_virt_pointer.
While x86 currently type cast it into the pointer in it's arch specific
arch_efi_call_virt() implementation, ARM64 is restrictive for right
reasons.
Convert the handler_addr type from u64 to void pointer.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Currently, the arch_efi_call_virt() assumes all users of it will have
defined a type 'efi_##f##_t' to make use of it.
Simplify the arch_efi_call_virt() macro by eliminating the explicit
need for efi_##f##_t type for every user of this macro.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
[ardb: apply Sudeep's ARM fix to i686, Loongarch and RISC-V too]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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This patch fixes the spelling error in firmware/efi/memmap.c, changing
it to the correct word.
Signed-off-by: Zheng Zhi Yuan <kevinjone25@g.ncu.edu.tw>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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__efivar_entry_iter() uses a list iterator in a dubious way, i.e., it
assumes that the iteration variable always points to an object of the
appropriate type, even if the list traversal exhausts the list
completely, in which case it will point somewhere in the vicinity of the
list's anchor instead.
Fortunately, we no longer use this function so we can just get rid of it
entirely.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Both efivars and efivarfs uses __efivar_entry_iter() to go over the
linked list that shadows the list of EFI variables held by the firmware,
but fail to call the begin/end helpers that are documented as a
prerequisite.
So switch to the proper version, which is efivar_entry_iter(). Given
that in both cases, efivar_entry_remove() is invoked with the lock held
already, don't take the lock there anymore.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Avoid the efivars layer and simply call the newly introduced EFI
varstore helpers instead. This simplifies the code substantially, and
also allows us to remove some hacks in the shared efivars layer that
were added for efi-pstore specifically.
In order to be able to delete the EFI variable associated with a record,
store the UTF-16 name of the variable in the pstore record's priv field.
That way, we don't have to make guesses regarding which variable the
record may have been loaded from.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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The current efivars layer is a jumble of list iterators, shadow data
structures and safe variable manipulation helpers that really belong in
the efivarfs pseudo file system once the obsolete sysfs access method to
EFI variables is removed.
So split off a minimal efivar get/set variable API that reuses the
existing efivars_lock semaphore to mediate access to the various runtime
services, primarily to ensure that performing a SetVariable() on one CPU
while another is calling GetNextVariable() in a loop to enumerate the
contents of the EFI variable store does not result in surprises.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Even though the efivars_lock lock is documented as protecting the
efivars->ops pointer (among other things), efivar_init() happily
releases and reacquires the lock for every EFI variable that it
enumerates. This used to be needed because the lock was originally a
spinlock, which prevented the callback that is invoked for every
variable from being able to sleep. However, releasing the lock could
potentially invalidate the ops pointer, but more importantly, it might
allow a SetVariable() runtime service call to take place concurrently,
and the UEFI spec does not define how this affects an enumeration that
is running in parallel using the GetNextVariable() runtime service,
which is what efivar_init() uses.
In the meantime, the lock has been converted into a semaphore, and the
only reason we need to drop the lock is because the efivarfs pseudo
filesystem driver will otherwise deadlock when it invokes the efivars
API from the callback to create the efivar_entry items and insert them
into the linked list. (EFI pstore is affected in a similar way)
So let's switch to helpers that can be used while the lock is already
taken. This way, we can hold on to the lock throughout the enumeration.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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The EFI pstore backend will need to store per-record variable name data
when we switch away from the efivars layer. Add a priv field to struct
pstore_record, and document it as holding a backend specific pointer
that is assumed to be a kmalloc()d buffer, and will be kfree()d when the
entire record is freed.
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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This driver abuses the efivar API, by using a few of its helpers on
entries that were not instantiated by the API itself. This is a problem
as future cleanup work on efivars is complicated by this.
So let's just switch to the get/set variable runtime wrappers directly.
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Commit b433a52aa28733e0 ("selftests/kexec: update get_secureboot_mode")
refactored the code that discovers the EFI secure boot mode so it only
depends on either the efivars pseudo filesystem or the efivars sysfs
interface, but never both.
However, the latter version was not implemented correctly, given the
fact that the local 'efi_vars' variable never assumes a value. This
means the fallback has been dead code ever since it was introduced.
So let's drop the fallback altogether. The sysfs interface has been
deprecated for ~10 years now, and is only enabled on x86 to begin with,
so it is time to get rid of it entirely.
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Avoid abusing the efivar layer by invoking it with locally constructed
efivar_entry instances, and instead, just call the EFI routines directly
if available.
Acked-by: Kalle Valo <kvalo@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Using half of the efivar API with locally baked efivar_entry instances
is not the right way to use this API, and these uses impede planned work
on the efivar layer itself.
So switch to direct EFI variable store accesses: we don't need the
efivar layer anyway.
Acked-by: Kalle Valo <kvalo@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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As the code comment already suggests, using the efivar API in this way
is not how it is intended, and so let's switch to the right one, which
is simply to call efi.get_variable() directly after checking whether or
not the GetVariable() runtime service is supported.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Avoid abusing the efivar API by passing locally instantiated
efivar_entry structs into efivar_set_entry_safe(), rather than using the
API as intended. Instead, just call efi.set_variable() directly.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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The efivars intermediate variable access layer provides an abstraction
that permits the EFI variable store to be replaced by something else
that implements a compatible interface, and caches all variables in the
variable store for fast access via the efivarfs pseudo-filesystem.
The SSDT override feature does not take advantage of either feature, as
it is only used when the generic EFI implementation of efivars is used,
and it traverses all variables only once to find the ones it is
interested in, and frees all data structures that the efivars layer
keeps right after.
So in this case, let's just call EFI's code directly, using the function
pointers in struct efi.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Returning zero means success now.
Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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If system have some mirrored memory and mirrored feature is not specified
in boot parameter, the basic mirrored feature will be enabled and this will
lead to the following situations:
- memblock memory allocation prefers mirrored region. This may have some
unexpected influence on numa affinity.
- contiguous memory will be split into several parts if parts of them
is mirrored memory via memblock_mark_mirror().
To fix this, variable mirrored_kernelcore will be checked in
memblock_mark_mirror(). Mark mirrored memory with flag MEMBLOCK_MIRROR iff
kernelcore=mirror is added in the kernel parameters.
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220614092156.1972846-6-mawupeng1@huawei.com
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Commit 177e15f0c144 ("arm64: add the initrd region to the linear mapping explicitly")
remove all the flags of the memory used by initrd. This is fine since
MEMBLOCK_MIRROR is not used in arm64.
However with mirrored feature introduced to arm64, this will clear the mirrored
flag used by initrd, which will lead to error log printed by
find_zone_movable_pfns_for_nodes() if the lower 4G range has some non-mirrored
memory.
To solve this problem, only MEMBLOCK_NOMAP flag will be removed via
memblock_clear_nomap().
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220614092156.1972846-5-mawupeng1@huawei.com
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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For a system only have limited mirrored memory or some numa node without
mirrored memory, the per node vmemmap page_structs prefer to allocate
memory from mirrored region, which will lead to vmemmap_verify() in
vmemmap_populate_basepages() report lots of warning message.
This patch change the frequency of "potential offnode page_structs" warning
messages to only once to avoid a very long print during bootup.
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20220614092156.1972846-4-mawupeng1@huawei.com
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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If system has mirrored memory, memblock will try to allocate mirrored
memory firstly and fallback to non-mirrored memory when fails, but if with
limited mirrored memory or some numa node without mirrored memory, lots of
warning message about memblock allocation will occur.
This patch ratelimit the warning message to avoid a very long print during
bootup.
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Link: https://lore.kernel.org/r/20220614092156.1972846-3-mawupeng1@huawei.com
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Commit b05b9f5f9dcf ("x86, mirror: x86 enabling - find mirrored memory
ranges") introduce the efi_find_mirror() function on x86. In order to reuse
the API we make it public.
Arm64 can support mirrored memory too, so function efi_find_mirror() is added to
efi_init() to this support for arm64.
Since efi_init() is shared by ARM, arm64 and riscv, this patch will bring
mirror memory support for these architectures, but this support is only tested
in arm64.
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Link: https://lore.kernel.org/r/20220614092156.1972846-2-mawupeng1@huawei.com
[ardb: fix subject to better reflect the payload]
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull 9p iov_iter fix from Al Viro:
"net/9p abuses iov_iter primitives - it attempts to copy _from_ a
destination-only iov_iter when it handles Rerror arriving in reply to
zero-copy request. Not hard to fix, fortunately.
This is a prereq for the iov_iter_get_pages() work in the second part
of iov_iter series, ended up in a separate branch"
* tag 'pull-work.9p' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
9p: handling Rerror without copy_from_iter_full()
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p9_client_zc_rpc()/p9_check_zc_errors() are playing fast
and loose with copy_from_iter_full().
Reading from file is done by sending Tread request. Response
consists of fixed-sized header (including the amount of data actually
read) followed by the data itself.
For zero-copy case we arrange the things so that the first
11 bytes of reply go into the fixed-sized buffer, with the rest going
straight into the pages we want to read into.
What makes the things inconvenient is that sglist describing
what should go where has to be set *before* the reply arrives. As
the result, if reply is an error, the things get interesting. On success
we get
size[4] Rread tag[2] count[4] data[count]
For error layout varies depending upon the protocol variant -
in original 9P and 9P2000 it's
size[4] Rerror tag[2] len[2] error[len]
in 9P2000.U
size[4] Rerror tag[2] len[2] error[len] errno[4]
in 9P2000.L
size[4] Rlerror tag[2] errno[4]
The last case is nice and simple - we have an 11-byte response
that fits into the fixed-sized buffer we hoped to get an Rread into.
In other two, though, we get a variable-length string spill into the
pages we'd prepared for the data to be read.
Had that been in fixed-sized buffer (which is actually 4K),
we would've dealt with that the same way we handle non-zerocopy case.
However, for zerocopy it doesn't end up there, so we need to copy it
from those pages.
The trouble is, by the time we get around to that, the
references to pages in question are already dropped. As the result,
p9_zc_check_errors() tries to get the data using copy_from_iter_full().
Unfortunately, the iov_iter it's trying to read from might *NOT* be
capable of that. It is, after all, a data destination, not data source.
In particular, if it's an ITER_PIPE one, copy_from_iter_full() will
simply fail.
In ->zc_request() itself we do have those pages and dealing with
the problem in there would be a simple matter of memcpy_from_page()
into the fixed-sized buffer. Moreover, it isn't hard to recognize
the (rare) case when such copying is needed. That way we get rid of
p9_zc_check_errors() entirely - p9_check_errors() can be used instead
both for zero-copy and non-zero-copy cases.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Pull copy_to_iter_mc fix from Al Viro:
"Backportable fix for copy_to_iter_mc() - the second part of iov_iter
work will pretty much overwrite this, but would be much harder to
backport"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fix short copy handling in copy_mc_pipe_to_iter()
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Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
result in a short copy. In that case we need to trim the unused
buffers, as well as the length of partially filled one - it's not
enough to set ->head, ->iov_offset and ->count to reflect how
much had we copied. Not hard to fix, fortunately...
I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h,
rather than iov_iter.c - it has nothing to do with iov_iter and
having it will allow us to avoid an ugly kludge in fs/splice.c.
We could put it into lib/iov_iter.c for now and move it later,
but I don't see the point going that way...
Cc: stable@kernel.org # 4.19+
Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()"
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs iov_iter updates from Al Viro:
"Part 1 - isolated cleanups and optimizations.
One of the goals is to reduce the overhead of using ->read_iter() and
->write_iter() instead of ->read()/->write().
new_sync_{read,write}() has a surprising amount of overhead, in
particular inside iocb_flags(). That's the explanation for the
beginning of the series is in this pile; it's not directly
iov_iter-related, but it's a part of the same work..."
* tag 'pull-work.iov_iter-base' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
first_iovec_segment(): just return address
iov_iter: massage calling conventions for first_{iovec,bvec}_segment()
iov_iter: first_{iovec,bvec}_segment() - simplify a bit
iov_iter: lift dealing with maxpages out of first_{iovec,bvec}_segment()
iov_iter_get_pages{,_alloc}(): cap the maxsize with MAX_RW_COUNT
iov_iter_bvec_advance(): don't bother with bvec_iter
copy_page_{to,from}_iter(): switch iovec variants to generic
keep iocb_flags() result cached in struct file
iocb: delay evaluation of IS_SYNC(...) until we want to check IOCB_DSYNC
struct file: use anonymous union member for rcuhead and llist
btrfs: use IOMAP_DIO_NOSYNC
teach iomap_dio_rw() to suppress dsync
No need of likely/unlikely on calls of check_copy_size()
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... and calculate the offset in the caller
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Pass maxsize by reference, return length via the same.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We return length + offset in page via *size. Don't bother - the caller
can do that arithmetics just as well; just report the length to it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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caller can do that just as easily
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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All callers can and should handle iov_iter_get_pages() returning
fewer pages than requested. All in-kernel ones do. And it makes
the arithmetical overflow analysis much simpler...
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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do what we do for iovec/kvec; that ends up generating better code,
AFAICS.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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we can do copyin/copyout under kmap_local_page(); it shouldn't overflow
the kmap stack - the maximal footprint increase only by one here.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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* calculate at the time we set FMODE_OPENED (do_dentry_open() for normal
opens, alloc_file() for pipe()/socket()/etc.)
* update when handling F_SETFL
* keep in a new field - file->f_iocb_flags; since that thing is needed only
before the refcount reaches zero, we can put it into the same anon union
where ->f_rcuhead and ->f_llist live - those are used only after refcount
reaches zero.
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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New helper to be used instead of direct checks for IOCB_DSYNC:
iocb_is_dsync(iocb). Checks converted, which allows to avoid
the IS_SYNC(iocb->ki_filp->f_mapping->host) part (4 cache lines)
from iocb_flags() - it's checked in iocb_is_dsync() instead
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Once upon a time we couldn't afford anon unions; these days minimal
gcc version had been raised enough to take care of that.
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... instead of messing with iocb flags
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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New flag, equivalent to removal of IOCB_DSYNC from iocb flags.
This mimics what btrfs is doing (and that's what btrfs will
switch to). However, I'm not at all sure that we want to
suppress REQ_FUA for those - all btrfs hack really cares about
is suppression of generic_write_sync(). For now let's keep
the existing behaviour, but I really want to hear more detailed
arguments pro or contra.
[folded brain fix from willy]
Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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it's inline and unlikely() inside of it (including the implicit one
in WARN_ON_ONCE()) suffice to convince the compiler that getting
false from check_copy_size() is unlikely.
Spotted-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs dcache updates from Al Viro:
"The main part here is making parallel lookups safe for RT - making
sure preemption is disabled in start_dir_add()/ end_dir_add() sections
(on non-RT it's automatic, on RT it needs to to be done explicitly)
and moving wakeups from __d_lookup_done() inside of such to the end of
those sections.
Wakeups can be safely delayed for as long as ->d_lock on in-lookup
dentry is held; proving that has caught a bug in d_add_ci() that
allows memory corruption when sufficiently bogus ntfs (or
case-insensitive xfs) image is mounted. Easily fixed, fortunately"
* tag 'pull-work.dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs/dcache: Move wakeup out of i_seq_dir write held region.
fs/dcache: Move the wakeup from __d_lookup_done() to the caller.
fs/dcache: Disable preemption on i_dir_seq write side on PREEMPT_RT
d_add_ci(): make sure we don't miss d_lookup_done()
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__d_add() and __d_move() wake up waiters on dentry::d_wait from within
the i_seq_dir write held region. This violates the PREEMPT_RT
constraints as the wake up acquires wait_queue_head::lock which is a
"sleeping" spinlock on RT.
There is no requirement to do so. __d_lookup_unhash() has cleared
DCACHE_PAR_LOOKUP and dentry::d_wait and returned the now unreachable wait
queue head pointer to the caller, so the actual wake up can be postponed
until the i_dir_seq write side critical section is left. The only
requirement is that dentry::lock is held across the whole sequence
including the wake up. The previous commit includes an analysis why this
is considered safe.
Move the wake up past end_dir_add() which leaves the i_dir_seq write side
critical section and enables preemption.
For non RT kernels there is no difference because preemption is still
disabled due to dentry::lock being held, but it shortens the time between
wake up and unlocking dentry::lock, which reduces the contention for the
woken up waiter.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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__d_lookup_done() wakes waiters on dentry->d_wait. On PREEMPT_RT we are
not allowed to do that with preemption disabled, since the wakeup
acquired wait_queue_head::lock, which is a "sleeping" spinlock on RT.
Calling it under dentry->d_lock is not a problem, since that is also a
"sleeping" spinlock on the same configs. Unfortunately, two of its
callers (__d_add() and __d_move()) are holding more than just ->d_lock
and that needs to be dealt with.
The key observation is that wakeup can be moved to any point before
dropping ->d_lock.
As a first step to solve this, move the wake up outside of the
hlist_bl_lock() held section.
This is safe because:
Waiters get inserted into ->d_wait only after they'd taken ->d_lock
and observed DCACHE_PAR_LOOKUP in flags. As long as they are
woken up (and evicted from the queue) between the moment __d_lookup_done()
has removed DCACHE_PAR_LOOKUP and dropping ->d_lock, we are safe,
since the waitqueue ->d_wait points to won't get destroyed without
having __d_lookup_done(dentry) called (under ->d_lock).
->d_wait is set only by d_alloc_parallel() and only in case when
it returns a freshly allocated in-lookup dentry. Whenever that happens,
we are guaranteed that __d_lookup_done() will be called for resulting
dentry (under ->d_lock) before the wq in question gets destroyed.
With two exceptions wq lives in call frame of the caller of
d_alloc_parallel() and we have an explicit d_lookup_done() on the
resulting in-lookup dentry before we leave that frame.
One of those exceptions is nfs_call_unlink(), where wq is embedded into
(dynamically allocated) struct nfs_unlinkdata. It is destroyed in
nfs_async_unlink_release() after an explicit d_lookup_done() on the
dentry wq went into.
Remaining exception is d_add_ci(). There wq is what we'd found in
->d_wait of d_add_ci() argument. Callers of d_add_ci() are two
instances of ->d_lookup() and they must have been given an in-lookup
dentry. Which means that they'd been called by __lookup_slow() or
lookup_open(), with wq in the call frame of one of those.
Result of d_alloc_parallel() in d_add_ci() is fed to
d_splice_alias(), which either returns non-NULL (and d_add_ci() does
d_lookup_done()) or feeds dentry to __d_add() that will do
__d_lookup_done() under ->d_lock. That concludes the analysis.
Let __d_lookup_unhash():
1) Lock the lookup hash and clear DCACHE_PAR_LOOKUP
2) Unhash the dentry
3) Retrieve and clear dentry::d_wait
4) Unlock the hash and return the retrieved waitqueue head pointer
5) Let the caller handle the wake up.
6) Rename __d_lookup_done() to __d_lookup_unhash_wake() to enforce
build failures for OOT code that used __d_lookup_done() and is not
aware of the new return value.
This does not yet solve the PREEMPT_RT problem completely because
preemption is still disabled due to i_dir_seq being held for write. This
will be addressed in subsequent steps.
An alternative solution would be to switch the waitqueue to a simple
waitqueue, but aside of Linus not being a fan of them, moving the wake up
closer to the place where dentry::lock is unlocked reduces lock contention
time for the woken up waiter.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/20220613140712.77932-3-bigeasy@linutronix.de
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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i_dir_seq is a sequence counter with a lock which is represented by the
lowest bit. The writer atomically updates the counter which ensures that it
can be modified by only one writer at a time. This requires preemption to
be disabled across the write side critical section.
On !PREEMPT_RT kernels this is implicit by the caller acquiring
dentry::lock. On PREEMPT_RT kernels spin_lock() does not disable preemption
which means that a preempting writer or reader would live lock. It's
therefore required to disable preemption explicitly.
An alternative solution would be to replace i_dir_seq with a seqlock_t for
PREEMPT_RT, but that comes with its own set of problems due to arbitrary
lock nesting. A pure sequence count with an associated spinlock is not
possible because the locks held by the caller are not necessarily related.
As the critical section is small, disabling preemption is a sensible
solution.
Reported-by: Oleg.Karfich@wago.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/20220613140712.77932-2-bigeasy@linutronix.de
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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All callers of d_alloc_parallel() must make sure that resulting
in-lookup dentry (if any) will encounter __d_lookup_done() before
the final dput(). d_add_ci() might end up creating in-lookup
dentries; they are fed to d_splice_alias(), which will normally
make sure they meet __d_lookup_done(). However, it is possible
to end up with d_splice_alias() failing with ERR_PTR(-ELOOP)
without having done so. It takes a corrupted ntfs or case-insensitive
xfs image, but neither should end up with memory corruption...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs lseek updates from Al Viro:
"Jason's lseek series.
Saner handling of 'lseek should fail with ESPIPE' - this gets rid of
the magical no_llseek thing and makes checks consistent.
In particular, the ad-hoc "can we do splice via internal pipe" checks
got saner (and somewhat more permissive, which is what Jason had been
after, AFAICT)"
* tag 'pull-work.lseek' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
fs: remove no_llseek
fs: check FMODE_LSEEK to control internal pipe splicing
vfio: do not set FMODE_LSEEK flag
dma-buf: remove useless FMODE_LSEEK flag
fs: do not compare against ->llseek
fs: clear or set FMODE_LSEEK based on llseek function
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Now that all callers of ->llseek are going through vfs_llseek(), we
don't gain anything by keeping no_llseek around. Nothing actually calls
it and setting ->llseek to no_lseek is completely equivalent to
leaving it NULL.
Longer term (== by the end of merge window) we want to remove all such
intializations. To simplify the merge window this commit does *not*
touch initializers - it only defines no_llseek as NULL (and simplifies
the tests on file opening).
At -rc1 we'll need do a mechanical removal of no_llseek -
git grep -l -w no_llseek | grep -v porting.rst | while read i; do
sed -i '/\<no_llseek\>/d' $i
done
would do it.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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