try_module_get(NULL) is true, so there is no need to check owner being
NULL.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Link: https://lore.kernel.org/r/20231013132441.1406200-2-u.kleine-koenig@pengutronix.de


Signed-off-by: Christian Brauner <brauner@kernel.org>

__read_mostly predates __ro_after_init. Many variables which are marked
__read_mostly should have been __ro_after_init from day 1.

Also, mark some stuff as "const" and "__init" while I'm at it.

[akpm@linux-foundation.org: revert sysctl_nr_open_min, sysctl_nr_open_max changes due to arm warning]
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/4f6bb9c0-abba-4ee4-a7aa-89265e886817@p183


Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89



Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Message-Id: <20230510221119.3508930-1-azeemshaikh38@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

While doing fault injection test, I got the following report:

------------[ cut here ]------------
kobject: '(null)' (0000000039956980): is not initialized, yet kobject_put() is being called.
WARNING: CPU: 3 PID: 6306 at kobject_put+0x23d/0x4e0
CPU: 3 PID: 6306 Comm: 283 Tainted: G        W          6.1.0-rc2-00005-g307c1086d7c9 #1253
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:kobject_put+0x23d/0x4e0
Call Trace:
 <TASK>
 cdev_device_add+0x15e/0x1b0
 __iio_device_register+0x13b4/0x1af0 [industrialio]
 __devm_iio_device_register+0x22/0x90 [industrialio]
 max517_probe+0x3d8/0x6b4 [max517]
 i2c_device_probe+0xa81/0xc00

When device_add() is injected fault and returns error, if dev->devt is not set,
cdev_add() is not called, cdev_del() is not needed. Fix this by checking dev->devt
in error path.

Fixes: 233ed09d

 ("chardev: add helper function to register char devs with a struct device")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20221202030237.520280-1-yangyingliang@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Some init function of cdev(like comedi) will call kobject_set_name()
before cdev_add(), but won't free the cdev.kobj.name or put the ref cnt
of cdev.kobj when cdev_add() failed. As the result, cdev.kobj.name will
be leaked.

Free the name of kobject in cdev_add() fail path to prevent memleak. With
this fix, the callers don't need to care about freeing the name of
kobject if cdev_add() fails.

unreferenced object 0xffff8881000fa8c0 (size 8):
  comm "modprobe", pid 239, jiffies 4294905173 (age 51.308s)
  hex dump (first 8 bytes):
    63 6f 6d 65 64 69 00 ff                          comedi..
  backtrace:
    [<000000005f9878f7>] __kmalloc_node_track_caller+0x4c/0x1c0
    [<000000000fd70302>] kstrdup+0x3f/0x70
    [<000000009428bc33>] kstrdup_const+0x46/0x60
    [<00000000ed50d9de>] kvasprintf_const+0xdb/0xf0
    [<00000000b2766964>] kobject_set_name_vargs+0x3c/0xe0
    [<00000000f2424ef7>] kobject_set_name+0x62/0x90
    [<000000005d5a125b>] 0xffffffffa0013098
    [<00000000f331e663>] do_one_initcall+0x7a/0x380
    [<00000000aa7bac96>] do_init_module+0x5c/0x230
    [<000000005fd72335>] load_module+0x227d/0x2420
    [<00000000ad550cf1>] __do_sys_finit_module+0xd5/0x140
    [<00000000069a60c5>] do_syscall_64+0x3f/0x90
    [<00000000c5e0d521>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: Shang XiaoJing <shangxiaojing@huawei.com>
Link: https://lore.kernel.org/r/20221102072659.23671-1-shangxiaojing@huawei.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Whiteouts, unlike real device node should not require privileges to create.

The general concern with device nodes is that opening them can have side
effects.  The kernel already avoids zero major (see
Documentation/admin-guide/devices.txt).  To be on the safe side the patch
explicitly forbids registering a char device with 0/0 number (see
cdev_add()).

This guarantees that a non-O_PATH open on a whiteout will fail with ENODEV;
i.e. it won't have any side effect.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

'chrdev_open()' calls 'cdev_get()' to obtain a reference to the
'struct cdev *' stashed in the 'i_cdev' field of the target inode
structure. If the pointer is NULL, then it is initialised lazily by
looking up the kobject in the 'cdev_map' and so the whole procedure is
protected by the 'cdev_lock' spinlock to serialise initialisation of
the shared pointer.

Unfortunately, it is possible for the initialising thread to fail *after*
installing the new pointer, for example if the subsequent '->open()' call
on the file fails. In this case, 'cdev_put()' is called, the reference
count on the kobject is dropped and, if nobody else has taken a reference,
the release function is called which finally clears 'inode->i_cdev' from
'cdev_purge()' before potentially freeing the object. The problem here
is that a racing thread can happily take the 'cdev_lock' and see the
non-NULL pointer in the inode, which can result in a refcount increment
from zero and a warning:

  |  ------------[ cut here ]------------
  |  refcount_t: addition on 0; use-after-free.
  |  WARNING: CPU: 2 PID: 6385 at lib/refcount.c:25 refcount_warn_saturate+0x6d/0xf0
  |  Modules linked in:
  |  CPU: 2 PID: 6385 Comm: repro Not tainted 5.5.0-rc2+ #22
  |  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
  |  RIP: 0010:refcount_warn_saturate+0x6d/0xf0
  |  Code: 05 55 9a 15 01 01 e8 9d aa c8 ff 0f 0b c3 80 3d 45 9a 15 01 00 75 ce 48 c7 c7 00 9c 62 b3 c6 08
  |  RSP: 0018:ffffb524c1b9bc70 EFLAGS: 00010282
  |  RAX: 0000000000000000 RBX: ffff9e9da1f71390 RCX: 0000000000000000
  |  RDX: ffff9e9dbbd27618 RSI: ffff9e9dbbd18798 RDI: ffff9e9dbbd18798
  |  RBP: 0000000000000000 R08: 000000000000095f R09: 0000000000000039
  |  R10: 0000000000000000 R11: ffffb524c1b9bb20 R12: ffff9e9da1e8c700
  |  R13: ffffffffb25ee8b0 R14: 0000000000000000 R15: ffff9e9da1e8c700
  |  FS:  00007f3b87d26700(0000) GS:ffff9e9dbbd00000(0000) knlGS:0000000000000000
  |  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  |  CR2: 00007fc16909c000 CR3: 000000012df9c000 CR4: 00000000000006e0
  |  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  |  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  |  Call Trace:
  |   kobject_get+0x5c/0x60
  |   cdev_get+0x2b/0x60
  |   chrdev_open+0x55/0x220
  |   ? cdev_put.part.3+0x20/0x20
  |   do_dentry_open+0x13a/0x390
  |   path_openat+0x2c8/0x1470
  |   do_filp_open+0x93/0x100
  |   ? selinux_file_ioctl+0x17f/0x220
  |   do_sys_open+0x186/0x220
  |   do_syscall_64+0x48/0x150
  |   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  |  RIP: 0033:0x7f3b87efcd0e
  |  Code: 89 54 24 08 e8 a3 f4 ff ff 8b 74 24 0c 48 8b 3c 24 41 89 c0 44 8b 54 24 08 b8 01 01 00 00 89 f4
  |  RSP: 002b:00007f3b87d259f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
  |  RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3b87efcd0e
  |  RDX: 0000000000000000 RSI: 00007f3b87d25a80 RDI: 00000000ffffff9c
  |  RBP: 00007f3b87d25e90 R08: 0000000000000000 R09: 0000000000000000
  |  R10: 0000000000000000 R11: 0000000000000293 R12: 00007ffe188f504e
  |  R13: 00007ffe188f504f R14: 00007f3b87d26700 R15: 0000000000000000
  |  ---[ end trace 24f53ca58db8180a ]---

Since 'cdev_get()' can already fail to obtain a reference, simply move
it over to use 'kobject_get_unless_zero()' instead of 'kobject_get()',
which will cause the racing thread to return -ENXIO if the initialising
thread fails unexpectedly.

Cc: Hillf Danton <hdanton@sina.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reported-by:  <syzbot+82defefbbd8527e1c2cb@syzkaller.appspotmail.com>
Signed-off-by: Will Deacon <will@kernel.org>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191219120203.32691-1-will@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

When allocating dynamic major, the minor range overlap check
in __register_chrdev_region() will not fail, so actually
there is no real case to passing non negative error code to
caller. However, set variable ret to -EBUSY before checking
minor range overlap will avoid false-positive warning from
code analyzing tool(like Smatch) and also make the code more
easy to understand.

Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Chengguang Xu <cgxu519@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The function comment of __register_chrdev_region()
is out of date, so update it based on the code.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

It's just code cleanup, not functional change.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

register_chrdev_region() carefully checks minor range
before calling __register_chrdev_region() but there is
another path from alloc_chrdev_region() which does not
check the range properly. So add a check for given minor
range in __register_chrdev_region().

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Current overlap checking cannot correctly handle
a case which is baseminor < existing baseminor &&
baseminor + minorct > existing baseminor + minorct.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

register_blkdev() and __register_chrdev_region() treat the major
number as an unsigned int. So print it the same way to avoid
absurd error statements such as:
"... major requested (-1) is greater than the maximum (511) ..."
(and also fix off-by-one bugs in the error prints).

While at it, also update the comment describing register_blkdev().

Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

CHRDEV_MAJOR_DYN_END and CHRDEV_MAJOR_DYN_EXT_END are valid major
numbers. So fix the loop iteration to include them in the search for
free major numbers.

While at it, also remove a redundant if condition ("cd->major != i"),
as it will never be true.

Signed-off-by: Srivatsa S. Bhat <srivatsa@csail.mit.edu>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard...

Presently, the order of the char devices listed in /proc/devices is not
entirely sequential. If a char device has a major number greater than
CHRDEV_MAJOR_HASH_SIZE (255), it will be ordered as if its major were
module 255. For example, 511 appears after 1.

This patch cleans that up and prints each major number in the correct
order, regardless of where they are stored in the hash table.

In order to do this, we introduce CHRDEV_MAJOR_MAX as an artificial
limit (chosen to be 511). It will then print all devices in major
order number from 0 to the maximum.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

We've run into problems with running out of dynamicly assign char
device majors particullarly on automated test systems with
all-yes-configs. Roughly 40 dynamic assignments can be made with such
kernels at this time while space is reserved for only 20.

Currently, the kernel only prints a warning when dynamic allocation
overflows the reserved region. And when this happens drivers that have
fixed assignments can randomly fail depending on the order of
initialization of other drivers. Thus, adding a new char device can cause
unexpected failures in completely unrelated parts of the kernel.

This patch solves the problem by extending dynamic major number
allocations down from 511 once the 234-254 region fills up. Fixed
majors already exist above 255 so the infrastructure to support
high number majors is already in place. The patch reserves an
additional 128 major numbers which should hopefully last us a while.

Kernels that don't require more than 20 dynamic majors assigned (which
is pretty typical) should not be affected by this change.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Link: https://lkml.org/lkml/2017/6/4/107


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Credit for this patch goes is shared with Dan Williams [1]. I've
taken things one step further to make the helper function more
useful and clean up calling code.

There's a common pattern in the kernel whereby a struct cdev is placed
in a structure along side a struct device which manages the life-cycle
of both. In the naive approach, the reference counting is broken and
the struct device can free everything before the chardev code
is entirely released.

Many developers have solved this problem by linking the internal kobjs
in this fashion:

cdev.kobj.parent = &parent_dev.kobj;

The cdev code explicitly gets and puts a reference to it's kobj parent.
So this seems like it was intended to be used this way. Dmitrty Torokhov
first put this in place in 2012 with this commit:

2f0157f1 char_dev: pin parent kobject

and the first instance of the fix was then done in the input subsystem
in the following commit:

4a215aad Input: fix use-after-free introduced with dynamic minor changes

Subsequently over the years, however, this issue seems to have tripped
up multiple developers independently. For example, see these commits:

0d5b7dae iio: Prevent race between IIO chardev opening and IIO device
(by Lars-Peter Clausen in 2013)

ba0ef854 tpm: Fix initialization of the cdev
(by Jason Gunthorpe in 2015)

5b28dde5 [media] media: fix use-after-free in cdev_put() when app exits
after driver unbind
(by Shauh Khan in 2016)

This technique is similarly done in at least 15 places within the kernel
and probably should have been done so in another, at least, 5 places.
The kobj line also looks very suspect in that one would not expect
drivers to have to mess with kobject internals in this way.
Even highly experienced kernel developers can be surprised by this
code, as seen in [2].

To help alleviate this situation, and hopefully prevent future
wasted effort on this problem, this patch introduces a helper function
to register a char device along with its parent struct device.
This creates a more regular API for tying a char device to its parent
without the developer having to set members in the underlying kobject.

This patch introduce cdev_device_add and cdev_device_del which
replaces a common pattern including setting the kobj parent, calling
cdev_add and then calling device_add. It also introduces cdev_set_parent
for the few cases that set the kobject parent without using device_add.

[1] https://lkml.org/lkml/2017/2/13/700
[2] https://lkml.org/lkml/2017/2/10/370



Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

In support of enabling resize / truncate of device-dax instances, define
a pseudo-fs to provide a unified inode/address space for vm operations.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

To fix super long dmesg error lines like

  CHRDEV "dummy_stm.0" major number 224 goes below the dynamic allocation rangeCHRDEV "dummy_stm.1" major number 223 goes below the dynamic allocation rangeswapper: page allocation failure: order:8, mode:0x26040c0(GFP_KERNEL|__GFP_COMP|__GFP_NOTRACK)

After fix, it should look like

  CHRDEV "dummy_stm.0" major number 224 goes below the dynamic allocation range
  CHRDEV "dummy_stm.1" major number 223 goes below the dynamic allocation range
  swapper: page allocation failure: order:8, mode:0x26040c0(GFP_KERNEL|__GFP_COMP|__GFP_NOTRACK)

Reported-by: Philip Li <philip.li@intel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently a dynamically allocated character device major is taken
from 254 and downward. This mechanism is used for RTC, IIO and a
few other subsystems.

The kernel currently has no check prevening these dynamic
allocations from eating into the assigned numbers at 233 and
downward.

In a recent test it was reported that so many dynamic device
majors were used on a test server, that the major number for
infiniband (231) was stolen. This occurred when allocating a new
major number for GPIO chips. The error messages from the kernel
were not helpful. (See: https://lkml.org/lkml/2016/2/14/124

)

This patch adds a defined lower limit of the dynamic major
allocation region will henceforth emit a warning if we start to
eat into the assigned numbers. It does not do any semantic
changes and will not change the kernels behaviour: numbers will
still continue to be stolen, but we will know from dmesg what
is going on.

This also updates the Documentation/devices.txt to clearly
reflect that we are using this range of major numbers for dynamic
allocation.

Reported-by: Ying Huang <ying.huang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The current documentation for unregister_chrdev_region says that it return
a range of device numbers which is incorrect.  Instead it unregister a
range of device numbers.  Fix the documentation to make this clear.

Signed-off-by: Partha Pratim Mukherjee <ppm.floss@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Since "BDI: Provide backing device capability information [try #3]" the
backing_dev_info structure also provides flags for the kind of mmap
operation available in a nommu environment, which is entirely unrelated
to it's original purpose.

Introduce a new nommu-only file operation to provide this information to
the nommu mmap code instead.  Splitting this from the backing_dev_info
structure allows to remove lots of backing_dev_info instance that aren't
otherwise needed, and entirely gets rid of the concept of providing a
backing_dev_info for a character device.  It also removes the need for
the mtd_inodefs filesystem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tejun Heo <tj@kernel.org>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

At one place we assign major number we found to ret.  That assignment is
then never used and actually doesn't make any sense given how the code is
currently structured (the assignment comes from pre-git times).  Just
remove it.

Coverity id: 1226852.

Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There were two places where return value from bdi_init was not tested.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

In certain cases (for example when a cdev structure is embedded into
another object whose lifetime is controlled by a separate kobject) it is
beneficial to tie lifetime of another object to the lifetime of
character device so that related object is not freed until after
char_dev object is freed.

To achieve this let's pin kobject's parent when doing cdev_add() and
unpin when last reference to cdev structure is being released.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Remove some minor whitespace errors (2 trailing spaces, and one space
needed for a comma) to make the file checkpatch.pl clean with the
exception of the exports, which is fine for now.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Commit 66fa12c5

 ("ieee1394: remove the old IEEE 1394 driver stack")
eliminated the only user of cdev_index().  So it can be removed too.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The major/minor device numbers are always defined and used as `unsigned'.

Signed-off-by: Yang Zhang <kthreadd@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

All file_operations should get a .llseek operation so we can make
nonseekable_open the default for future file operations without a
.llseek pointer.

The three cases that we can automatically detect are no_llseek, seq_lseek
and default_llseek. For cases where we can we can automatically prove that
the file offset is always ignored, we use noop_llseek, which maintains
the current behavior of not returning an error from a seek.

New drivers should normally not use noop_llseek but instead use no_llseek
and call nonseekable_open at open time.  Existing drivers can be converted
to do the same when the maintainer knows for certain that no user code
relies on calling seek on the device file.

The generated code is often incorrectly indented and right now contains
comments that clarify for each added line why a specific variant was
chosen. In the version that gets submitted upstream, the comments will
be gone and I will manually fix the indentation, because there does not
see...

These devices don't do any writeback but their device inodes still can get
dirty so mark bdi appropriately so that bdi code does the right thing and files
inodes to lists of bdi carrying the device inodes.

Cc: stable@kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

Make /dev/console get initialised before any initialisation routine that
invokes modprobe because if modprobe fails, it's going to want to open
/dev/console, presumably to write an error message to.

The problem with that is that if the /dev/console driver is not yet
initialised, the chardev handler will call request_module() to invoke
modprobe, which will fail, because we never compile /dev/console as a
module.

This will lead to a modprobe loop, showing the following in the kernel
log:

	request_module: runaway loop modprobe char-major-5-1
	request_module: runaway loop modprobe char-major-5-1
	request_module: runaway loop modprobe char-major-5-1
	request_module: runaway loop modprobe char-major-5-1
	request_module: runaway loop modprobe char-major-5-1

This can happen, for example, when the built in md5 module can't find
the built in cryptomgr module (because the latter fails to initialise).
The md5 module comes before the call to tty_init(), presumably because
'crypto' comes before 'drivers' alphabetically.

Fix this by calling tty_init() from chrdev_init().

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There are two useless lines in fs/char_dev.c.

In register_chrdev there is a loop to change all '/' into '!' in the
kernel object name.
This code is useless as the same substitution is in kobject_set_name_vargs in
lib/kobject.c:
228         /* ewww... some of these buggers have '/' in the name ... */
229         while ((s = strchr(kobj->name, '/')))
230                 s[0] = '!';

kobject_set_name_vargs is called by kobject_set_name.
kobject_set_name is called just above the useless loop.

[hidave.darkstar@gmail.com: fix warning, remove the unused char *s]
Signed-off-by: Renzo Davoli <renzo@cs.unibo.it>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dave Young <hidave.darkstar@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This enables us to track who does what and print info. Its main use
is catching dirty inodes on the default_backing_dev_info, so we can
fix that up.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

[un]register_chrdev() assume minor range 0-255.  This patch adds __
prefixed versions which take @minorbase and @count explicitly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

* Remove smp_lock.h from files which don't need it (including some headers!)
* Add smp_lock.h to files which do need it
* Make smp_lock.h include conditional in hardirq.h
  It's needed only for one kernel_locked() usage which is under CONFIG_PREEMPT

  This will make hardirq.h inclusion cheaper for every PREEMPT=n config
  (which includes allmodconfig/allyesconfig, BTW)

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The only user of the i_cindex element in the inode structure is used
is by the firewire drivers.  As part of an attempt to slim down the
inode structure to save memory --- since a typical Linux system will
have hundreds of thousands if not millions of inodes cached, a
reduction in the size inode has high leverage.

The firewire driver does not need i_cindex in any fast path, so it's
simple enough to calculate when it is needed, instead of wasting space
in the inode structure.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: krh@redhat.com
Cc: stefanr@s5r6.in-berlin.de
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

It's possible to register a chrdev with a name size exactly the same as
was allocated in structure.  It seems it was not intended behaviour.

At least chrdev_show does not like it.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use a single goto label for chrdev_put + return error cases.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>