linux.git/fs/sysfs/sysfs.h, branch v2.6.33

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

sysfs: Implement sysfs_getattr & sysfs_permission

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

With the implementation of sysfs_getattr and sysfs_permission
sysfs becomes able to lazily propogate inode attribute changes
from the sysfs_dirents to the vfs inodes.   This paves the way
for deleting significant chunks of now unnecessary code.

While doing this we did not reference sysfs_setattr from
sysfs_symlink_inode_operations so I added along with
sysfs_getattr and sysfs_permission.

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

sysfs: Fix locking and factor out sysfs_sd_setattr

2009-12-11T19:24:53+00:00

Cleanly separate the work that is specific to setting the
attributes of a sysfs_dirent from what is needed to update
the attributes of a vfs inode.

Additionally grab the sysfs_mutex to keep any nasties from
surprising us when updating the sysfs_dirent.

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

sysfs: Add labeling support for sysfs

2009-09-10T00:11:29+00:00

This patch adds a setxattr handler to the file, directory, and symlink
inode_operations structures for sysfs. The patch uses hooks introduced in the
previous patch to handle the getting and setting of security information for
the sysfs inodes. As was suggested by Eric Biederman the struct iattr in the
sysfs_dirent structure has been replaced by a structure which contains the
iattr, secdata and secdata length to allow the changes to persist in the event
that the inode representing the sysfs_dirent is evicted. Because sysfs only
stores this information when a change is made all the optional data is moved
into one dynamically allocated field.

This patch addresses an issue where SELinux was denying virtd access to the PCI
configuration entries in sysfs. The lack of setxattr handlers for sysfs
required that a single label be assigned to all entries in sysfs. Granting virtd
access to every entry in sysfs is not an acceptable solution so fine grained
labeling of sysfs is required such that individual entries can be labeled
appropriately.

[sds:  Fixed compile-time warnings, coding style, and setting of inode security init flags.]

Signed-off-by: David P. Quigley 
Signed-off-by: Stephen D. Smalley 
Signed-off-by: James Morris

sysfs: don't block indefinitely for unmapped files.

2009-03-24T23:38:26+00:00

Modify sysfs bin files so that we can remove the bin file while they are
still mapped.  When the kobject is removed we unmap the bin file and
arrange for future accesses to the mapping to receive SIGBUS.

Implementing this prevents a nasty DOS when pci devices are hot plugged
and unplugged.  Where if any of their resources were mmaped the kernel
could not free up their pci resources or release their pci data
structures.

[akpm@linux-foundation.org: remove unused var]
Signed-off-by: Eric W. Biederman 
Cc: Jesse Barnes 
Acked-by: Tejun Heo 
Cc: Kay Sievers 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

sysfs: reference sysfs_dirent from sysfs inodes

2009-03-24T23:38:25+00:00

The sysfs_dirent serves as both an inode and a directory entry
for sysfs.  To prevent the sysfs inode numbers from being freed
prematurely hold a reference to sysfs_dirent from the sysfs inode.

[akpm@linux-foundation.org: add comment]
Signed-off-by: Eric W. Biederman 
Cc: Tejun Heo 
Cc: Al Viro 
Cc: Cornelia Huck 
Signed-off-by: Andrew Morton 
Signed-off-by: Greg Kroah-Hartman

sysfs: Support sysfs_notify from atomic context with new sysfs_notify_dirent

2008-10-16T16:24:47+00:00

Support sysfs_notify from atomic context with new sysfs_notify_dirent

sysfs_notify currently takes sysfs_mutex.
This means that it cannot be called in atomic context.
sysfs_mutex  is sometimes held over a malloc (sysfs_rename_dir)
so it can block on low memory.

In md I want to be able to notify on a sysfs attribute from
atomic context, and I don't want to block on low memory because I
could be in the writeout path for freeing memory.

So:
 - export the "sysfs_dirent" structure along with sysfs_get, sysfs_put
   and sysfs_get_dirent so I can get the sysfs_dirent that I want to
   notify on and hold it in an md structure.
 - split sysfs_notify_dirent out of sysfs_notify so the sysfs_dirent
   can be notified on with no blocking (just a spinlock).

Signed-off-by: Neil Brown 
Acked-by: Tejun Heo 
Signed-off-by: Greg Kroah-Hartman