linux-toradex.git/fs/sysfs/sysfs.h, branch v2.6.34.4

sysfs: Kill unused sysfs_sb variable.

2010-03-08T01:04:52+00:00

Now that there are no more users we can remove
the sysfs_sb variable.

Acked-by: Tejun Heo 
Acked-by: Serge Hallyn 
Signed-off-by: Eric W. Biederman 
Signed-off-by: Greg Kroah-Hartman

sysfs: Pass super_block to sysfs_get_inode

2010-03-08T01:04:52+00:00

Currently sysfs_get_inode magically returns an inode on
sysfs_sb.  Make the super_block parameter explicit and
the code becomes clearer.

Acked-by: Tejun Heo 
Acked-by: Serge Hallyn 
Signed-off-by: Eric W. Biederman 
Signed-off-by: Greg Kroah-Hartman

sysfs: Pack sysfs_dirent more tightly.

2010-03-08T01:04:52+00:00

Placing the 16bit s_mode between a pointer and a long doesn't pack well
especailly on 64bit where we wast 48 bits.  So move s_mode and
declare it as a unsigned short.  This is the sysfs backing store
after all we don't need fields extra large just in case someday
we want userspace to be able to use a larger value.

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

sysfs: Use one lockdep class per sysfs attribute.

2010-03-08T01:04:51+00:00

Acknowledge that the logical sysfs rwsem has one instance per
sysfs attribute with different locking depencencies for different
attributes.

There is a sysfs idiom where writing to one sysfs file causes the
addition or removal of other sysfs files.   Lumping all of the
sysfs attributes together in one lock class causes lockdep to
generate lots of false positives.

This introduces the requirement that non-static sysfs attributes
need to be initialized with sysfs_attr_init or sysfs_bin_attr_init.
Strictly speaking this requirement only exists when lockdep is
enabled, and when lockdep is enabled we get a bit fat warning
if this requirement is not met.

Signed-off-by: Eric W. Biederman 
Acked-by: WANG Cong 
Cc: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sysfs: Only take active references on attributes.

2010-03-08T01:04:51+00:00

If we exclude directories and symlinks from the set of sysfs
dirents where we need active references we are left with
sysfs attributes (binary or not).

- Tweak sysfs_deactivate to only do something on attributes
- Move lockdep initialization into sysfs_file_add_mode to
  limit it to just attributes.

Signed-off-by: Eric W. Biederman 
Acked-by: WANG Cong 
Cc: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sysfs: Remove sysfs_get/put_active_two

2010-03-08T01:04:51+00:00

It turns out that holding an active reference on a directory is
pointless.  The purpose of the active references are to allows us to
block when removing sysfs entries that have custom methods so we don't
remove modules while running modular code and to keep those custom
methods from accessing data structures after the files have been
removed.  Further sysfs_remove_dir remove all elements in the
directory before removing the directory itself, so there is no chance
we will remove a directory with active children.

Signed-off-by: Eric W. Biederman 
Cc: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman

sysfs: Add lockdep annotations for the sysfs active reference

2010-01-04T20:34:46+00:00

Holding locks over device_del -> kobject_del -> sysfs_deactivate can
cause deadlocks if those same locks are grabbed in sysfs show or store
methods.

The I model s_active count + completion as a sleeping read/write lock.
I describe to lockdep sysfs_get_active as a read_trylock,
sysfs_put_active as a read_unlock, and sysfs_deactivate as a
write_lock and write_unlock pair.  This seems to capture the essence
for purposes of finding deadlocks, and in my testing gives finds real
issues and ignores non-issues.

This brings us back to holding locks over kobject_del is a problem
that ideally we should find a way of addressing, but at least lockdep
can tell us about the problems instead of requiring developers to debug
rare strange system deadlocks, that happen when sysfs files are removed
while being written to.

Signed-off-by: Eric W. Biederman 
Acked-by: Tejun Heo 
Signed-off-by: Linus Torvalds

sysfs: Factor out sysfs_rename from sysfs_rename_dir and sysfs_move_dir

2009-12-11T19:24:54+00:00

These two functions do 90% of the same work and it doesn't significantly
obfuscate the function to allow both the parent dir and the name to change
at the same time.  So merge them together to simplify maintenance, and
increase testing.

Acked-by: Tejun Heo 
Acked-by: Serge Hallyn 
Signed-off-by: Eric W. Biederman 
Signed-off-by: Greg Kroah-Hartman

sysfs: Propagate renames to the vfs on demand

2009-12-11T19:24:54+00:00

By teaching sysfs_revalidate to hide a dentry for
a sysfs_dirent if the sysfs_dirent has been renamed,
and by teaching sysfs_lookup to return the original
dentry if the sysfs dirent has been renamed.  I can
show the results of renames correctly without having to
update the dcache during the directory rename.

This massively simplifies the rename logic allowing a lot
of weird sysfs special cases to be removed along with
a lot of now unnecesary helper code.

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

sysfs: Gut sysfs_addrm_start and sysfs_addrm_finish

2009-12-11T19:24:54+00:00

With lazy inode updates and dentry operations bringing everything
into sync on demand there is no longer any need to immediately
update the vfs or grab i_mutex to protect those updates as we
make changes to sysfs.

Acked-by: Serge Hallyn 
Acked-by: Tejun Heo 
Signed-off-by: Eric W. Biederman 
Signed-off-by: Greg Kroah-Hartman