litmus-rt.git/fs/sysfs, branch test

mnt: Refactor the logic for mounting sysfs and proc in a user namespace

2015-07-21T17:10:01+00:00

commit 1b852bceb0d111e510d1a15826ecc4a19358d512 upstream.

Fresh mounts of proc and sysfs are a very special case that works very
much like a bind mount.  Unfortunately the current structure can not
preserve the MNT_LOCK... mount flags.  Therefore refactor the logic
into a form that can be modified to preserve those lock bits.

Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount
of the filesystem be fully visible in the current mount namespace,
before the filesystem may be mounted.

Move the logic for calling fs_fully_visible from proc and sysfs into
fs/namespace.c where it has greater access to mount namespace state.

Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

sysfs: Add support for permanently empty directories to serve as mount points.

2015-07-21T17:10:01+00:00

commit 87d2846fcf88113fae2341da1ca9a71f0d916f2c upstream.

Add two functions sysfs_create_mount_point and
sysfs_remove_mount_point that hang a permanently empty directory off
of a kobject or remove a permanently emptpy directory hanging from a
kobject.  Export these new functions so modular filesystems can use
them.

Acked-by: Greg Kroah-Hartman 
Signed-off-by: "Eric W. Biederman" 
Signed-off-by: Greg Kroah-Hartman

sysfs: Only accept read/write permissions for file attributes

2015-03-25T12:27:57+00:00

For sysfs file attributes, only read and write permissions make sense.
Mask provided attribute permissions accordingly and send a warning
to the console if invalid permission bits are set.

This patch is originally from Guenter [1] and includes the fixup
explained in the thread, that is printing permissions in octal format
and limiting the scope of attributes to SYSFS_PREALLOC | 0664.

[1] https://lkml.org/lkml/2015/1/19/599

Signed-off-by: Vivien Didelot 
Reviewed-by: Guenter Roeck 
Signed-off-by: Greg Kroah-Hartman

sysfs: Use only return value from is_visible for the file mode

2015-03-25T12:27:57+00:00

Up to now, is_visible can only be used to either remove visibility
of a file entirely or to add permissions, but not to reduce permissions.
This makes it impossible, for example, to use DEVICE_ATTR_RW to define
file attributes and reduce permissions to read-only.

This behavior is undesirable and unnecessarily complicates code which
needs to reduce permissions; instead of just returning the desired
permissions, it has to ensure that the permissions in the attribute
variable declaration only reflect the minimal permissions ever needed.

Change semantics of is_visible to only use the permissions returned
from it instead of oring the returned value with the hard-coded
permissions.

Signed-off-by: Guenter Roeck 
Signed-off-by: Vivien Didelot 
Signed-off-by: Greg Kroah-Hartman

Merge tag 'driver-core-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2015-02-15T19:11:47+00:00

Pull driver core patches from Greg KH:
 "Really tiny set of patches for this kernel.  Nothing major, all
  described in the shortlog and have been in linux-next for a while"

* tag 'driver-core-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  sysfs: fix warning when creating a sysfs group without attributes
  firmware_loader: handle timeout via wait_for_completion_interruptible_timeout()
  firmware_loader: abort request if wait_for_completion is interrupted
  firmware: Correct function name in comment
  device: Change dev_ logging functions to return void
  device: Fix dev_dbg_once macro

kernfs: remove KERNFS_STATIC_NAME

2015-02-14T05:21:36+00:00

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 
Cc: Andrzej Hajda 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sysfs: fix warning when creating a sysfs group without attributes

2015-02-03T23:50:31+00:00

When attempting to create a gropu without attrs, the warning prints the
name of the group.  However, the check for name being a NULL pointer is
wrong: it uses the pointer to the name when it's NULL.  Fix it to use
the name if present, otherwise just put an empty string.

Cc: Bruno Prémont 
Cc: Greg Kroah-Hartman 
Signed-off-by: Javi Merino 
Signed-off-by: Greg Kroah-Hartman

sysfs/kernfs: make read requests on pre-alloc files use the buffer.

2014-11-07T18:54:38+00:00

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 
Reviewed-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sysfs/kernfs: allow attributes to request write buffer be pre-allocated.

2014-11-07T18:53:25+00:00

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  
Reviewed-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

fs: sysfs: return EGBIG on write if offset is larger than file size

2014-11-07T18:52:20+00:00

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 
Cc: Greg Kroah-Hartman 
Signed-off-by: Greg Kroah-Hartman