Pull printk updates from Petr Mladek:
- Add a console_msg_format command line option:
The value "default" keeps the old "[time stamp] text\n" format. The
value "syslog" allows to see the syslog-like "<log
level>[timestamp] text" format.
This feature was requested by people doing regression tests, for
example, 0day robot. They want to have both filtered and full logs
at hands.
- Reduce the risk of softlockup:
Pass the console owner in a busy loop.
This is a new approach to the old problem. It was first proposed by
Steven Rostedt on Kernel Summit 2017. It marks a context in which
the console_lock owner calls console drivers and could not sleep.
On the other side, printk() callers could detect this state and use
a busy wait instead of a simple console_trylock(). Finally, the
console_lock owner checks if there is a busy waiter at the end of
the special context and eventually passes the console_lock to the
waiter.
The hand-off works surprisingly well and helps in many situations.
Well, there is still a possibility of the softlockup, for example,
when the flood of messages stops and the last owner still has too
much to flush.
There is increasing number of people having problems with
printk-related softlockups. We might eventually need to get better
solution. Anyway, this looks like a good start and promising
direction.
- Do not allow to schedule in console_unlock() called from printk():
This reverts an older controversial commit. The reschedule helped
to avoid softlockups. But it also slowed down the console output.
This patch is obsoleted by the new console waiter logic described
above. In fact, the reschedule made the hand-off less effective.
- Deprecate "%pf" and "%pF" format specifier:
It was needed on ia64, ppc64 and parisc64 to dereference function
descriptors and show the real function address. It is done
transparently by "%ps" and "pS" format specifier now.
Sergey Senozhatsky found that all the function descriptors were in
a special elf section and could be easily detected.
- Remove printk_symbol() API:
It has been obsoleted by "%pS" format specifier, and this change
helped to remove few continuous lines and a less intuitive old API.
- Remove redundant memsets:
Sergey removed unnecessary memset when processing printk.devkmsg
command line option.
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
printk: drop redundant devkmsg_log_str memsets
printk: Never set console_may_schedule in console_trylock()
printk: Hide console waiter logic into helpers
printk: Add console owner and waiter logic to load balance console writes
kallsyms: remove print_symbol() function
checkpatch: add pF/pf deprecation warning
symbol lookup: introduce dereference_symbol_descriptor()
parisc64: Add .opd based function descriptor dereference
powerpc64: Add .opd based function descriptor dereference
ia64: Add .opd based function descriptor dereference
sections: split dereference_function_descriptor()
openrisc: Fix conflicting types for _exext and _stext
lib: do not use print_symbol()
irq debug: do not use print_symbol()
sysfs: do not use print_symbol()
drivers: do not use print_symbol()
x86: do not use print_symbol()
unicore32: do not use print_symbol()
sh: do not use print_symbol()
mn10300: do not use print_symbol()
...
Move the license "mark" of the sysfs files to be in SPDX form, instead
of the custom text that it currently is in. This is in a quest to get
rid of the 700+ different ways we say "GPLv2" in the kernel tree.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
print_symbol() is a very old API that has been obsoleted by %pS format
specifier in a normal printk() call.
Replace print_symbol() with a direct printk("%pS") call.
Link: http://lkml.kernel.org/r/20171211125025.2270-11-sergey.senozhatsky@gmail.com
To: Andrew Morton <akpm@linux-foundation.org>
To: Russell King <linux@armlinux.org.uk>
To: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Salter <msalter@redhat.com>
To: Tony Luck <tony.luck@intel.com>
To: David Howells <dhowells@redhat.com>
To: Yoshinori Sato <ysato@users.sourceforge.jp>
To: Guan Xuetao <gxt@mprc.pku.edu.cn>
To: Borislav Petkov <bp@alien8.de>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>
To: Vineet Gupta <vgupta@synopsys.com>
To: Fengguang Wu <fengguang.wu@intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-am33-list@redhat.com
Cc: linux-sh@vger.kernel.org
Cc: linux-edac@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
[pmladek@suse.com: updated commit message]
Signed-off-by: Petr Mladek <pmladek@suse.com>
ops->show() can return a negative error code.
Commit 65da3484d9 ("sysfs: correctly handle short reads on PREALLOC attrs.")
(in v4.4) caused this to be stored in an unsigned 'size_t' variable, so errors
would look like large numbers.
As a result, if an error is returned, sysfs_kf_read() will return the
value of 'count', typically 4096.
Commit 17d0774f80 ("sysfs: correctly handle read offset on PREALLOC attrs")
(in v4.8) extended this error to use the unsigned large 'len' as a size for
memmove().
Consequently, if ->show returns an error, then the first read() on the
sysfs file will return 4096 and could return uninitialized memory to
user-space.
If the application performs a subsequent read, this will trigger a memmove()
with extremely large count, and is likely to crash the machine is bizarre ways.
This bug can currently only be triggered by reading from an md
sysfs attribute declared with __ATTR_PREALLOC() during the
brief period between when mddev_put() deletes an mddev from
the ->all_mddevs list, and when mddev_delayed_delete() - which is
scheduled on a workqueue - completes.
Before this, an error won't be returned by the ->show()
After this, the ->show() won't be called.
I can reproduce it reliably only by putting delay like
usleep_range(500000,700000);
early in mddev_delayed_delete(). Then after creating an
md device md0 run
echo clear > /sys/block/md0/md/array_state; cat /sys/block/md0/md/array_state
The bug can be triggered without the usleep.
Fixes: 65da3484d9 ("sysfs: correctly handle short reads on PREALLOC attrs.")
Fixes: 17d0774f80 ("sysfs: correctly handle read offset on PREALLOC attrs")
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reported-and-tested-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Attributes declared with __ATTR_PREALLOC use sysfs_kf_read() which returns
zero bytes for non-zero offset. This breaks script checkarray in mdadm tool
in debian where /bin/sh is 'dash' because its builtin 'read' reads only one
byte at a time. Script gets 'i' instead of 'idle' when reads current action
from /sys/block/$dev/md/sync_action and as a result does nothing.
This patch adds trivial implementation of partial read: generate whole
string and move required part into buffer head.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Fixes: 4ef67a8c95 ("sysfs/kernfs: make read requests on pre-alloc files use the buffer.")
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=787950
Cc: Stable <stable@vger.kernel.org> # v3.19+
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
attributes declared with __ATTR_PREALLOC use sysfs_kf_read()
which ignores the 'count' arg.
So a 1-byte read request can return more bytes than that.
This is seen with the 'dash' shell when 'read' is used on
some 'md' sysfs attributes.
So only return the 'min' of count and the attribute length.
Signed-off-by: NeilBrown <neilb@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If count == 0 bytes are requested by a reader, sysfs_kf_bin_read()
deliberately returns 0 without passing a potentially harmful value to
some externally defined underlying battr->read() function.
However in case of (pos == size && count) the next clause always sets
count to 0 and this value is handed over to battr->read().
The change intends to make obsolete (and remove later) a redundant
sanity check in battr->read(), if it is present, or add more
protection to struct bin_attribute users, who does not care about
input arguments.
Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
When a new kernfs node is created, KERNFS_STATIC_NAME is used to avoid
making a separate copy of its name. It's currently only used for sysfs
attributes whose filenames are required to stay accessible and unchanged.
There are rare exceptions where these names are allocated and formatted
dynamically but for the vast majority of cases they're consts in the
rodata section.
Now that kernfs is converted to use kstrdup_const() and kfree_const(),
there's little point in keeping KERNFS_STATIC_NAME around. Remove it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
To match the previous patch which used the pre-alloc buffer for
writes, this patch causes reads to use the same buffer.
This is not strictly necessary as the current seq_read() will allocate
on first read, so user-space can trigger the required pre-alloc. But
consistency is valuable.
The read function is somewhat simpler than seq_read() and, for example,
does not support reading from an offset into the file: reads must be
at the start of the file.
As seq_read() does not use the prealloc buffer, ->seq_show is
incompatible with ->prealloc and caused an EINVAL return from open().
sysfs code which calls into kernfs always chooses the correct function.
As the buffer is shared with writes and other reads, the mutex is
extended to cover the copy_to_user.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
md/raid allows metadata management to be performed in user-space.
A various times, particularly on device failure, the metadata needs
to be updated before further writes can be permitted.
This means that the user-space program which updates metadata much
not block on writeout, and so must not allocate memory.
mlockall(MCL_CURRENT|MCL_FUTURE) and pre-allocation can avoid all
memory allocation issues for user-memory, but that does not help
kernel memory.
Several kernel objects can be pre-allocated. e.g. files opened before
any writes to the array are permitted.
However some kernel allocation happens in places that cannot be
pre-allocated.
In particular, writes to sysfs files (to tell md that it can now
allow writes to the array) allocate a buffer using GFP_KERNEL.
This patch allows attributes to be marked as "PREALLOC". In that case
the maximal buffer is allocated when the file is opened, and then used
on each write instead of allocating a new buffer.
As the same buffer is now shared for all writes on the same file
description, the mutex is extended to cover full use of the buffer
including the copy_from_user().
The new __ATTR_PREALLOC() 'or's a new flag in to the 'mode', which is
inspected by sysfs_add_file_mode_ns() to determine if the file should be
marked as requiring prealloc.
Despite the comment, we *do* use ->seq_show together with ->prealloc
in this patch. The next patch fixes that.
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
According to the user expectations common utilities like dd or sh
redirection operator > should work correctly over binary files from
sysfs. At the moment doing excessive write can not be completed:
write(1, "\0\0\0\0\0\0\0\0", 8) = 4
write(1, "\0\0\0\0", 4) = 0
write(1, "\0\0\0\0", 4) = 0
write(1, "\0\0\0\0", 4) = 0
...
Fix the problem by returning EFBIG described in man 2 write.
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
13c589d5b0 ("sysfs: use seq_file when reading regular files")
switched sysfs from custom read implementation to seq_file to enable
later transition to kernfs. After the change, the buffer passed to
->show() is acquired through seq_get_buf(); unfortunately, this
introduces a subtle behavior change. Before the commit, the buffer
passed to ->show() was always zero as it was allocated using
get_zeroed_page(). Because seq_file doesn't clear buffers on
allocation and neither does seq_get_buf(), after the commit, depending
on the behavior of ->show(), we may end up exposing uninitialized data
to userland thus possibly altering userland visible behavior and
leaking information.
Fix it by explicitly clearing the buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ron <ron@debian.org>
Fixes: 13c589d5b0 ("sysfs: use seq_file when reading regular files")
Cc: stable <stable@vger.kernel.org> # 3.13+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
All device_schedule_callback_owner() users are converted to use
device_remove_file_self(). Remove now unused
{sysfs|device}_schedule_callback_owner().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit d1ba277e79.
As reported by Stephen, this patch breaks linux-next as a ppc patch
suddenly (after 2 years) started using this old api call. So revert it
for now, it will go away in 3.15-rc2 when we can change the PPC call to
the new api.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Stewart Smith <stewart@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
All device_schedule_callback_owner() users are converted to use
device_remove_file_self(). Remove now unused
{sysfs|device}_schedule_callback_owner().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Sometimes it's necessary to implement a node which wants to delete
nodes including itself. This isn't straightforward because of kernfs
active reference. While a file operation is in progress, an active
reference is held and kernfs_remove() waits for all such references to
drain before completing. For a self-deleting node, this is a deadlock
as kernfs_remove() ends up waiting for an active reference that itself
is sitting on top of.
This currently is worked around in the sysfs layer using
sysfs_schedule_callback() which makes such removals asynchronous.
While it works, it's rather cumbersome and inherently breaks
synchronicity of the operation - the file operation which triggered
the operation may complete before the removal is finished (or even
started) and the removal may fail asynchronously. If a removal
operation is immmediately followed by another operation which expects
the specific name to be available (e.g. removal followed by rename
onto the same name), there's no way to make the latter operation
reliable.
The thing is there's no inherent reason for this to be asynchrnous.
All that's necessary to do this synchronous is a dedicated operation
which drops its own active ref and deactivates self. This patch
implements kernfs_remove_self() and its wrappers in sysfs and driver
core. kernfs_remove_self() is to be called from one of the file
operations, drops the active ref the task is holding, removes the self
node, and restores active ref to the dead node so that the ref is
balanced afterwards. __kernfs_remove() is updated so that it takes an
early exit if the target node is already fully removed so that the
active ref restored by kernfs_remove_self() after removal doesn't
confuse the deactivation path.
This makes implementing self-deleting nodes very easy. The normal
removal path doesn't even need to be changed to use
kernfs_remove_self() for the self-deleting node. The method can
invoke kernfs_remove_self() on itself before proceeding the normal
removal path. kernfs_remove() invoked on the node by the normal
deletion path will simply be ignored.
This will replace sysfs_schedule_callback(). A subtle feature of
sysfs_schedule_callback() is that it collapses multiple invocations -
even if multiple removals are triggered, the removal callback is run
only once. An equivalent effect can be achieved by testing the return
value of kernfs_remove_self() - only the one which gets %true return
value should proceed with actual deletion. All other instances of
kernfs_remove_self() will wait till the enclosing kernfs operation
which invoked the winning instance of kernfs_remove_self() finishes
and then return %false. This trivially makes all users of
kernfs_remove_self() automatically show correct synchronous behavior
even when there are multiple concurrent operations - all "echo 1 >
delete" instances will finish only after the whole operation is
completed by one of the instances.
Note that manipulation of active ref is implemented in separate public
functions - kernfs_[un]break_active_protection().
kernfs_remove_self() is the only user at the moment but this will be
used to cater to more complex cases.
v2: For !CONFIG_SYSFS, dummy version kernfs_remove_self() was missing
and sysfs_remove_file_self() had incorrect return type. Fix it.
Reported by kbuild test bot.
v3: kernfs_[un]break_active_protection() separated out from
kernfs_remove_self() and exposed as public API.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit 1ae06819c7.
Tejun writes:
I'm sorry but can you please revert the whole series?
get_active() waiting while a node is deactivated has potential
to lead to deadlock and that deactivate/reactivate interface is
something fundamentally flawed and that cgroup will have to work
with the remove_self() like everybody else. IOW, I think the
first posting was correct.
Cc: Tejun Heo <tj@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This reverts commit d1ba277e79.
Tejun writes:
I'm sorry but can you please revert the whole series?
get_active() waiting while a node is deactivated has potential
to lead to deadlock and that deactivate/reactivate interface is
something fundamentally flawed and that cgroup will have to work
with the remove_self() like everybody else. IOW, I think the
first posting was correct.
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
All device_schedule_callback_owner() users are converted to use
device_remove_file_self(). Remove now unused
{sysfs|device}_schedule_callback_owner().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Sometimes it's necessary to implement a node which wants to delete
nodes including itself. This isn't straightforward because of kernfs
active reference. While a file operation is in progress, an active
reference is held and kernfs_remove() waits for all such references to
drain before completing. For a self-deleting node, this is a deadlock
as kernfs_remove() ends up waiting for an active reference that itself
is sitting on top of.
This currently is worked around in the sysfs layer using
sysfs_schedule_callback() which makes such removals asynchronous.
While it works, it's rather cumbersome and inherently breaks
synchronicity of the operation - the file operation which triggered
the operation may complete before the removal is finished (or even
started) and the removal may fail asynchronously. If a removal
operation is immmediately followed by another operation which expects
the specific name to be available (e.g. removal followed by rename
onto the same name), there's no way to make the latter operation
reliable.
The thing is there's no inherent reason for this to be asynchrnous.
All that's necessary to do this synchronous is a dedicated operation
which drops its own active ref and deactivates self. This patch
implements kernfs_remove_self() and its wrappers in sysfs and driver
core. kernfs_remove_self() is to be called from one of the file
operations, drops the active ref and deactivates using
__kernfs_deactivate_self(), removes the self node, and restores active
ref to the dead node using __kernfs_reactivate_self() so that the ref
is balanced afterwards. __kernfs_remove() is updated so that it takes
an early exit if the target node is already fully removed so that the
active ref restored by kernfs_remove_self() after removal doesn't
confuse the deactivation path.
This makes implementing self-deleting nodes very easy. The normal
removal path doesn't even need to be changed to use
kernfs_remove_self() for the self-deleting node. The method can
invoke kernfs_remove_self() on itself before proceeding the normal
removal path. kernfs_remove() invoked on the node by the normal
deletion path will simply be ignored.
This will replace sysfs_schedule_callback(). A subtle feature of
sysfs_schedule_callback() is that it collapses multiple invocations -
even if multiple removals are triggered, the removal callback is run
only once. An equivalent effect can be achieved by testing the return
value of kernfs_remove_self() - only the one which gets %true return
value should proceed with actual deletion. All other instances of
kernfs_remove_self() will wait till the enclosing kernfs operation
which invoked the winning instance of kernfs_remove_self() finishes
and then return %false. This trivially makes all users of
kernfs_remove_self() automatically show correct synchronous behavior
even when there are multiple concurrent operations - all "echo 1 >
delete" instances will finish only after the whole operation is
completed by one of the instances.
v2: For !CONFIG_SYSFS, dummy version kernfs_remove_self() was missing
and sysfs_remove_file_self() had incorrect return type. Fix it.
Reported by kbuild test bot.
v3: Updated to use __kernfs_{de|re}activate_self().
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Because sysfs used struct attribute which are supposed to stay
constant, sysfs didn't copy names when creating regular files. The
specified string for name was supposed to stay constant. Such
distinction isn't inherent for kernfs. kernfs_create_file[_ns]()
should be able to take the same @name as kernfs_create_dir[_ns]()
As there can be huge number of sysfs attributes, we still want to be
able to use static names for sysfs attributes. This patch renames
kernfs_create_file_ns_key() to __kernfs_create_file() and adds
@name_is_static parameter so that the caller can explicitly indicate
that @name can be used without copying. kernfs is updated to use
KERNFS_STATIC_NAME to distinguish static and copied names.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/SYSFS_DIR/KERNFS_DIR/
* s/SYSFS_KOBJ_ATTR/KERNFS_FILE/
* s/SYSFS_KOBJ_LINK/KERNFS_LINK/
* s/SYSFS_{TYPE_FLAGS}/KERNFS_{TYPE_FLAGS}/
* s/SYSFS_FLAG_{FLAG}/KERNFS_{FLAG}/
* s/sysfs_type()/kernfs_type()/
* s/SD_DEACTIVATED_BIAS/KN_DEACTIVATED_BIAS/
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_open_dirent/kernfs_open_node/
* s/sysfs_open_file/kernfs_open_file/
* s/sysfs_inode_attrs/kernfs_iattrs/
* s/sysfs_addrm_cxt/kernfs_addrm_cxt/
* s/sysfs_super_info/kernfs_super_info/
* s/sysfs_info()/kernfs_info()/
* s/sysfs_open_dirent_lock/kernfs_open_node_lock/
* s/sysfs_open_file_mutex/kernfs_open_file_mutex/
* s/sysfs_of()/kernfs_of()/
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
s_ prefix for kernfs members is used inconsistently and a misnomer
now. It's not like kernfs_node is used widely across the kernel
making the ability to grep for the members particularly useful. Let's
just drop the prefix.
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_elem_dir/kernfs_elem_dir/
* s/sysfs_elem_symlink/kernfs_elem_symlink/
* s/sysfs_elem_attr/kernfs_elem_file/
* s/sysfs_dirent/kernfs_node/
* s/sd/kn/ in kernfs proper
* s/parent_sd/parent/
* s/target_sd/target/
* s/dir_sd/parent/
* s/to_sysfs_dirent()/rb_to_kn()/
* misc renames of local vars when they conflict with the above
Because md, mic and gpio dig into sysfs details, this patch ends up
modifying them. All are sysfs_dirent renames and trivial. While we
can avoid these by introducing a dummy wrapping struct sysfs_dirent
around kernfs_node, given the limited usage outside kernfs and sysfs
proper, I don't think such workaround is called for.
This patch is strictly rename only and doesn't introduce any
functional difference.
- mic / gpio renames were missing. Spotted by kbuild test robot.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This is v3.14 fix for the same issue that a8b1474442 ("sysfs: give
different locking key to regular and bin files") addresses for v3.13.
Due to the extensive kernfs reorganization in v3.14 branch, the same
fix couldn't be ported as-is. The v3.13 fix was ignored while merging
it into v3.14 branch.
027a485d12 ("sysfs: use a separate locking class for open files
depending on mmap") assigned different lockdep key to
sysfs_open_file->mutex depending on whether the file implements mmap
or not in an attempt to avoid spurious lockdep warning caused by
merging of regular and bin file paths.
While this restored some of the original behavior of using different
locks (at least lockdep is concerned) for the different clases of
files. The restoration wasn't full because now the lockdep key
assignment depends on whether the file has mmap or not instead of
whether it's a regular file or not.
This means that bin files which don't implement mmap will get assigned
the same lockdep class as regular files. This is problematic because
file_operations for bin files still implements the mmap file operation
and checking whether the sysfs file actually implements mmap happens
in the file operation after grabbing @sysfs_open_file->mutex. We
still end up adding locking dependency from mmap locking to
sysfs_open_file->mutex to the regular file mutex which triggers
spurious circular locking warning.
For v3.13, a8b1474442 ("sysfs: give different locking key to regular
and bin files") fixed it by giving sysfs_open_file->mutex different
lockdep keys depending on whether the file is regular or bin instead
of whether mmap exists or not; however, due to the way sysfs is now
layered behind kernfs, this approach is no longer viable. kernfs can
tell whether a sysfs node has mmap implemented or not but can't tell
whether a bin file from a regular one.
This patch updates kernfs such that kernfs_file_mmap() checks
SYSFS_FLAG_HAS_MMAP and bail before grabbing sysfs_open_file->mutex so
that it doesn't add spurious locking dependency from mmap to
sysfs_open_file->mutex and changes sysfs so that it specifies
kernfs_ops->mmap iff the sysfs file implements mmap. Combined, this
ensures that sysfs_open_file->mutex is grabbed under mmap path iff the
sysfs file actually implements mmap. As sysfs_open_file->mutex is
already given a different lockdep key if mmap is implemented, this
removes the spurious locking dependency.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dave Jones <davej@redhat.com>
Link: http://lkml.kernel.org/g/20131203184324.GA11320@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move core file code to fs/kernfs/file.c. fs/sysfs/file.c now contains
sysfs kernfs_ops callbacks, sysfs wrappers around kernfs interfaces,
and sysfs_schedule_callback(). The respective declarations in
fs/sysfs/sysfs.h are moved to fs/kernfs/kernfs-internal.h.
This is pure relocation.
v2: Refreshed on top of the v2 of "sysfs, kernfs: prepare read path
for kernfs".
v3: Refreshed on top of the v3 of "sysfs, kernfs: prepare read path
for kernfs".
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce kernfs interface for finding, getting and putting
sysfs_dirents.
* sysfs_find_dirent() is renamed to kernfs_find_ns() and lockdep
assertion for sysfs_mutex is added.
* sysfs_get_dirent_ns() is renamed to kernfs_find_and_get().
* Macro inline dancing around __sysfs_get/put() are removed and
kernfs_get/put() are made proper functions implemented in
fs/sysfs/dir.c.
While the conversions are mostly equivalent, there's one difference -
kernfs_get() doesn't return the input param as its return value. This
change is intentional. While passing through the input increases
writability in some areas, it is unnecessary and has been shown to
cause confusion regarding how the last ref is handled.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently, sysfs_dirent active_ref lockdep annotation uses
attribute->[s]key as the lockdep key, which forces
kernfs_create_file_ns() to assume that sysfs_dirent->priv is pointing
to a struct attribute which may not be true for non-sysfs users. This
patch restructures the lockdep annotation such that
* kernfs_ops contains lockdep_key which is used by default for files
created kernfs_create_file_ns().
* kernfs_create_file_ns_key() is introduced which takes an extra @key
argument. The created file will use the specified key for
active_ref lockdep annotation. If NULL is specified, lockdep for
the file is disabled.
* sysfs_add_file_mode_ns() is updated to use
kernfs_create_file_ns_key() with the appropriate key from the
attribute or NULL if ignore_lockdep is set.
This makes the lockdep annotation properly contained in kernfs while
allowing sysfs to cleanly keep its current behavior. This patch
doesn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce kernfs interface to wake up poll(2) which takes and returns
sysfs_dirents.
sysfs_notify_dirent() is renamed to kernfs_notify() and sysfs_notify()
is updated so that it doesn't directly grab sysfs_mutex but acquires
the target sysfs_dirents using sysfs_get_dirent().
sysfs_notify_dirent() is reimplemented as a dumb inline wrapper around
kernfs_notify().
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs_ops currently only supports single_open() behavior which is
pretty restrictive. Add optional callbacks ->seq_{start|next|stop}()
which, when implemented, are invoked for seq_file traversal. This
allows full seq_file functionality for kernfs users. This currently
doesn't have any user and doesn't change any behavior.
v2: Refreshed on top of the updated "sysfs, kernfs: prepare read path
for kernfs".
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs_add_one() is a wrapper around __sysfs_add_one() which prints out
duplicate name warning if __sysfs_add_one() fails with -EEXIST. The
previous kernfs conversions moved all dup warnings to sysfs interface
functions and sysfs_add_one() doesn't have any user left.
Remove sysfs_add_one() and update __sysfs_add_one() to take its name.
This patch doesn't make any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce kernfs interface to create a file which takes and returns
sysfs_dirents.
The actual file creation part is separated out from
sysfs_add_file_mode_ns() into kernfs_create_file_ns(). The former now
only decides the kernfs_ops to use and the file's size and invokes the
latter.
This patch doesn't introduce behavior changes.
v2: Dummy implementation for !CONFIG_SYSFS updated to return -ENOSYS.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
After kernfs_ops and sysfs_dirent->s_attr.size addition, the
distinction between SYSFS_KOBJ_BIN_ATTR and SYSFS_KOBJ_ATTR is only
necessary while creating files to decide which kernfs_ops to use.
Afterwards, they behave exactly the same.
This patch removes SYSFS_KOBJ_BIN_ATTR along with sysfs_is_bin().
sysfs_add_file[_mode_ns]() are updated to take bool @is_bin instead of
@type.
This patch doesn't introduce any behavior changes. This completely
isolates the distinction between the two sysfs file types in the sysfs
layer proper.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs sets the size of regular files unconditionally at PAGE_SIZE and
takes the size of bin files from bin_attribute. The latter is a
pretty bad interface which forces bin_attribute users to create a
separate copy of bin_attribute for each instance of the file -
e.g. pci resource files.
Add sysfs_dirent->s_attr.size so that the size can be specified
separately. This unifies inode init paths of ATTR and BIN_ATTR
identical and allows for generic size handling for kernfs.
Unfortunately, this grows the size of sysfs_dirent by sizeof(loff_t).
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
introduces kernfs_ops which hosts methods kernfs users implement and
updates fs/sysfs/file.c such that sysfs_kf_*() functions populate
kernfs_ops and kernfs_file_*() functions call the matching entries
from kernfs_ops.
kernfs_ops contains the following groups of methods.
* seq_show() - for kernfs files which use seq_file for reads.
* read() - for direct read implementations. Used iff seq_show() is
not implemented.
* write() - for writes.
* mmap() - for mmaps.
Notes:
* sysfs_elem_attr->ops is added so that kernfs_ops can be accessed
from sysfs_dirent. kernfs_ops() helper is added to verify locking
and access the field.
* SYSFS_FLAG_HAS_(SEQ_SHOW|MMAP) added. sd->s_attr->ops is accessible
only while holding active_ref and there are cases where we want to
take different actions depending on which ops are implemented.
These two flags cache whether the two ops are implemented for those.
* kernfs_file_*() no longer test sysfs type but chooses different
behaviors depending on which methods in kernfs_ops are implemented.
The conversions are trivial except for the open path. As
kernfs_file_open() now decides whether to allow read/write accesses
depending on the kernfs_ops implemented, the presence of methods in
kobjs and attribute_bin should be propagated to kernfs_ops.
sysfs_add_file_mode_ns() is updated so that it propagates presence /
absence of the callbacks through _empty, _ro, _wo, _rw kernfs_ops.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs_open_file will be used as the primary handle for kernfs methods.
Move its definition from fs/sysfs/file.c to include/linux/kernfs.h and
mark the public and private fields.
This is pure relocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
prepares the rest - open, release and poll. There isn't much to do.
Just renaming is enough. As sysfs_file_operations and
sysfs_bin_operations are identical now, use the same file_operations
for both - kernfs_file_operations.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
rearranges mmap path so that the kernfs and sysfs parts are separate.
sysfs_kf_bin_mmap() which handles the interaction with bin_attribute
mmap method is factored out of sysfs_bin_mmap(), which is renamed to
kernfs_file_mmap(). All vma ops are renamed accordingly.
sysfs_bin_mmap() is updated such that it can be used for both file
types. This will eventually allow using the same file_operations for
both file types, which is necessary to separate out kernfs.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
rearranges write path so that the kernfs and sysfs parts are separate.
kernfs_file_write() handles all boilerplate work including buffer
management and locking and invokes sysfs_kf_write() or
sysfs_kf_bin_write() depending on the file type which deals with the
interaction with kobj store or bin_attribute write method.
While this patch changes the order of some operations, it shouldn't
change any visible behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We're in the process of separating out core sysfs functionality into
kernfs which will deal with sysfs_dirents directly. This patch
rearranges read path so that the kernfs and sysfs parts are separate.
* Regular file read path is refactored such that
kernfs_seq_start/next/stop/show() handle all the boilerplate work
including locking and updating event count for poll, while
sysfs_kf_seq_show() deals with interaction with kobj show method.
* Bin file read path is refactored such that kernfs_file_direct_read()
handles all the boilerplate work including buffer management and
locking, while sysfs_kf_bin_read() deals with interaction with
bin_attribute read method.
kernfs_file_read() is added. It invokes either the seq_file or direct
read path depending on the file type. This will eventually allow
using the same file_operations for both file types, which is necessary
to separate out kernfs.
While this patch changes the order of some operations, it shouldn't
change any visible behavior.
v2: Dropped unnecessary zeroing of @count from sysfs_kf_seq_show().
Add comments explaining single_open() behavior. Both suggested by
Pavel.
v3: seq_stop() is called even after seq_start() failed.
kernfs_seq_start() updated so that it doesn't unlock
sysfs_open_file->mutex on failure so that kernfs_seq_stop()
doesn't try to unlock an already unlocked mutex. Reported by
Fengguang.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
A directory sysfs_dirent points to the associated kobj. A regular or
bin file points to the associated [bin_]attribute. This patch
replaces sysfs_dirent->s_dir.kobj and ->s_attr.[bin_]attr with void *
->priv.
This is to prepare for kernfs interface so that sysfs can specify the
private data in the same way for directories and files. This lower
debuggability but not by much - the whole thing was overlaid in a
union anyway. If debuggability becomes an issue, we can later add
->priv accessors which explicitly check for the sysfs_dirent type and
performs casting.
This patch doesn't introduce any behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We need those sysfs fixes in this branch to make testing, and future
patches apply properly.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce kernfs setattr interface - kernfs_setattr().
sysfs_sd_setattr() is renamed to __kernfs_setattr() and
kernfs_setattr() is a simple wrapper around it with sysfs_mutex
locking. sysfs_chmod_file() is updated to get an explicit ref on
kobj->sd and then invoke kernfs_setattr() so that it doesn't have to
use internal interface.
This patch doesn't introduce any behavior differences.
v2: Dummy implementation for !CONFIG_SYSFS updated to return -ENOSYS.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Introduce kernfs removal interfaces - kernfs_remove() and
kernfs_remove_by_name[_ns]().
These are just renames of sysfs_remove() and sysfs_hash_and_remove().
No functional changes.
v2: Dummy kernfs_remove_by_name_ns() for !CONFIG_SYSFS updated to
return -ENOSYS instead of 0.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The following two commits implemented mmap support in the regular file
path and merged bin file support into the regular path.
73d9714627 ("sysfs: copy bin mmap support from fs/sysfs/bin.c to fs/sysfs/file.c")
3124eb1679 ("sysfs: merge regular and bin file handling")
After the merge, the following commands trigger a spurious lockdep
warning. "test-mmap-read" simply mmaps the file and dumps the
content.
$ cat /sys/block/sda/trace/act_mask
$ test-mmap-read /sys/devices/pci0000\:00/0000\:00\:03.0/resource0 4096
======================================================
[ INFO: possible circular locking dependency detected ]
3.12.0-work+ #378 Not tainted
-------------------------------------------------------
test-mmap-read/567 is trying to acquire lock:
(&of->mutex){+.+.+.}, at: [<ffffffff8120a8df>] sysfs_bin_mmap+0x4f/0x120
but task is already holding lock:
(&mm->mmap_sem){++++++}, at: [<ffffffff8114b399>] vm_mmap_pgoff+0x49/0xa0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (&mm->mmap_sem){++++++}:
...
-> #2 (sr_mutex){+.+.+.}:
...
-> #1 (&bdev->bd_mutex){+.+.+.}:
...
-> #0 (&of->mutex){+.+.+.}:
...
other info that might help us debug this:
Chain exists of:
&of->mutex --> sr_mutex --> &mm->mmap_sem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&mm->mmap_sem);
lock(sr_mutex);
lock(&mm->mmap_sem);
lock(&of->mutex);
*** DEADLOCK ***
1 lock held by test-mmap-read/567:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff8114b399>] vm_mmap_pgoff+0x49/0xa0
stack backtrace:
CPU: 3 PID: 567 Comm: test-mmap-read Not tainted 3.12.0-work+ #378
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
ffffffff81ed41a0 ffff880009441bc8 ffffffff81611ad2 ffffffff81eccb80
ffff880009441c08 ffffffff8160f215 ffff880009441c60 ffff880009c75208
0000000000000000 ffff880009c751e0 ffff880009c75208 ffff880009c74ac0
Call Trace:
[<ffffffff81611ad2>] dump_stack+0x4e/0x7a
[<ffffffff8160f215>] print_circular_bug+0x2b0/0x2bf
[<ffffffff8109ca0a>] __lock_acquire+0x1a3a/0x1e60
[<ffffffff8109d6ba>] lock_acquire+0x9a/0x1d0
[<ffffffff81615547>] mutex_lock_nested+0x67/0x3f0
[<ffffffff8120a8df>] sysfs_bin_mmap+0x4f/0x120
[<ffffffff8115d363>] mmap_region+0x3b3/0x5b0
[<ffffffff8115d8ae>] do_mmap_pgoff+0x34e/0x3d0
[<ffffffff8114b3ba>] vm_mmap_pgoff+0x6a/0xa0
[<ffffffff8115be3e>] SyS_mmap_pgoff+0xbe/0x250
[<ffffffff81008282>] SyS_mmap+0x22/0x30
[<ffffffff8161a4d2>] system_call_fastpath+0x16/0x1b
This happens because one file nests sr_mutex, which nests mm->mmap_sem
under it, under of->mutex while mmap implementation naturally nests
of->mutex under mm->mmap_sem. The warning is false positive as
of->mutex is per open-file and the two paths belong to two different
files. This warning didn't trigger before regular and bin file
supports were merged because only bin file supported mmap and the
other side of locking happened only on regular files which used
equivalent but separate locking.
It'd be best if we give separate locking classes per file but we can't
easily do that. Let's differentiate on ->mmap() for now. Later we'll
add explicit file operations struct and can add per-ops lockdep key
there.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
13c589d5b0 ("sysfs: use seq_file when reading regular files")
converted regular sysfs files to use seq_file. The commit substituted
generic_file_llseek() with seq_lseek() for llseek implementation.
Before the change, all regular sysfs files were allowed to seek to any
position in [0, PAGE_SIZE] as the file size is always PAGE_SIZE and
generic_file_llseek() allows any seeking inside the range under file
size; however, seq_lseek()'s behavior is different. It traverses the
output by repeatedly invoking ->show() until it reaches the target
offset or traversal indicates EOF. As seq_files are fully dynamic and
may not end at all, it doesn't support seeking from the end
(SEEK_END).
Apparently, there are userland tools which uses SEEK_END to discover
the buffer size to use and the switch to seq_lseek() disturbs them as
SEEK_END fails with -EINVAL.
The only benefits of using seq_lseek() instead of
generic_file_llseek() are
* Early failure. If traversing to certain file position should fail,
seq_lseek() will report such failures on lseek(2) instead of the
following read/write operations.
* EOF detection. While SEEK_END is not supported, SEEK_SET/CUR +
large offset can be used to detect eof - eof at the time of the seek
anyway as the file size may change dynamically.
Both aren't necessary for sysfs or prospect kernfs users. Revert to
genefic_file_llseek() and preserve the original behavior.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Link: https://lkml.kernel.org/r/20131031114358.GA5551@osiris
Tested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Both POSIX.1-2008 and Linux Programmer's Manual have a dedicated return
error code for a case, when a file doesn't support mmap(), it's ENODEV.
This change replaces overloaded EINVAL with ENODEV in a situation
described above for sysfs binary files.
Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
3124eb1679 ("sysfs: merge regular and bin file handling") folded bin
file handling into regular file handling. Among other things, bin
file now shares the same open path including sysfs_open_dirent
association using sysfs_dirent->s_attr.open. This is buggy because
->s_bin_attr lives in the same union and doesn't have the field. This
bug doesn't trigger because sysfs_elem_bin_attr doesn't have an active
field at the conflicting position. It does have a field "buffers" but
it isn't used anymore.
This patch collapses sysfs_elem_bin_attr into sysfs_elem_attr so that
the bin_attr is accessed through ->s_attr.bin_attr which lives with
->s_attr.attr in an anonymous union. The code paths already assume
bin_attr contains attr as the first element, so this doesn't add any
more assumptions while making it explicit that the two types are
handled together.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Before patch(sysfs: prepare path write for unified regular / bin
file handling), when size of bin file is zero, writting still can
continue, but this patch changes the behaviour.
The worse thing is that firmware loader is broken by this patch,
and user space application can't write to firmware bin file any more
because both firmware loader and drivers can't know at advance how
large the firmware file is and have to set its initialized size as
zero.
This patch fixes the problem and keeps behaviour of writting to bin
as before.
Reported-by: Lothar Waßmann <LW@karo-electronics.de>
Tested-by: Lothar Waßmann <LW@karo-electronics.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
