sysfs: use sysfs_mutex to protect the sysfs_dirent tree

As kobj sysfs dentries and inodes are gonna be made reclaimable,
i_mutex can't be used to protect sysfs_dirent tree. Use sysfs_mu

sysfs: use sysfs_mutex to protect the sysfs_dirent tree

As kobj sysfs dentries and inodes are gonna be made reclaimable,
i_mutex can't be used to protect sysfs_dirent tree. Use sysfs_mutex
globally instead. As the whole tree is protected with sysfs_mutex,
there is no reason to keep sysfs_rename_sem. Drop it.

While at it, add docbook comments to functions which require
sysfs_mutex locking.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: consolidate sysfs spinlocks

Replace sysfs_lock and kobj_sysfs_assoc_lock with sysfs_assoc_lock.
sysfs_lock was originally to be used to protect sysfs_dirent tree but
mutex see

sysfs: consolidate sysfs spinlocks

Replace sysfs_lock and kobj_sysfs_assoc_lock with sysfs_assoc_lock.
sysfs_lock was originally to be used to protect sysfs_dirent tree but
mutex seems better choice, so there is no reason to keep sysfs_lock
separate. Merge the two spinlocks into one.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: make kobj point to sysfs_dirent instead of dentry

As kobj sysfs dentries and inodes are gonna be made reclaimable,
dentry can't be used as naming token for sysfs file/directory, r

sysfs: make kobj point to sysfs_dirent instead of dentry

As kobj sysfs dentries and inodes are gonna be made reclaimable,
dentry can't be used as naming token for sysfs file/directory, replace
kobj->dentry with kobj->sd. The only external interface change is
shadow directory handling. All other changes are contained in kobj
and sysfs.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: implement sysfs_find_dirent() and sysfs_get_dirent()

Implement sysfs_find_dirent() and sysfs_get_dirent().
sysfs_dirent_exist() is replaced by sysfs_find_dirent(). These will

sysfs: implement sysfs_find_dirent() and sysfs_get_dirent()

Implement sysfs_find_dirent() and sysfs_get_dirent().
sysfs_dirent_exist() is replaced by sysfs_find_dirent(). These will
be used to make directory entries reclamiable.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: rename sysfs_dirent->s_type to s_flags and make room for flags

Rename sysfs_dirent->s_type to s_flags, pack type into lower eight
bits and reserve the rest for flags. sysfs_type(

sysfs: rename sysfs_dirent->s_type to s_flags and make room for flags

Rename sysfs_dirent->s_type to s_flags, pack type into lower eight
bits and reserve the rest for flags. sysfs_type() can used to access
the type. All existing sd->s_type accesses are converted to use
sysfs_type(). While at it, type test is changed to equality test
instead of bit-and test where appropriate.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: use singly-linked list for sysfs_dirent tree

Make sysfs_dirent use singly linked list for its tree structure.
sysfs_link_sibling() and sysfs_unlink_sibling() functions are added t

sysfs: use singly-linked list for sysfs_dirent tree

Make sysfs_dirent use singly linked list for its tree structure.
sysfs_link_sibling() and sysfs_unlink_sibling() functions are added to
handle simpler cases. It adds some complexity and cpu cycle overhead
but reduced memory footprint is worthwhile on big machines.

This change reduces the sizeof sysfs_dirent from 104 to 88 on 64bit
and from 60 to 52 on 32bit.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: slim down sysfs_dirent->s_active

Make sysfs_dirent->s_active an atomic_t instead of rwsem. This
reduces the size of sysfs_dirent from 136 to 104 on 64bit and from 76
to 60 on

sysfs: slim down sysfs_dirent->s_active

Make sysfs_dirent->s_active an atomic_t instead of rwsem. This
reduces the size of sysfs_dirent from 136 to 104 on 64bit and from 76
to 60 on 32bit with lock debugging turned off. With lock debugging
turned on the reduction is much larger.

s_active starts at zero and each active reference increments s_active.
Putting a reference decrements s_active. Deactivation subtracts
SD_DEACTIVATED_BIAS which is currently INT_MIN and assumed to be small
enough to make s_active negative. If s_active is negative,
sysfs_get() no longer grants new references. Deactivation succeeds
immediately if there is no active user; otherwise, it waits using a
completion for the last put.

Due to the removal of lockdep tricks, this change makes things less
trickier in release_sysfs_dirent(). As all the complexity is
contained in three s_active functions, I think it's more readable this
way.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: move s_active functions to fs/sysfs/dir.c

These functions are about to receive more complexity and doesn't
really need to be inlined in the first place. Move them from
fs/sys

sysfs: move s_active functions to fs/sysfs/dir.c

These functions are about to receive more complexity and doesn't
really need to be inlined in the first place. Move them from
fs/sysfs/sysfs.h to fs/sysfs/dir.c.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: use iget_locked() instead of new_inode()

After dentry is reclaimed, sysfs always used to allocate new dentry
and inode if the file is accessed again. This causes problem with

sysfs: use iget_locked() instead of new_inode()

After dentry is reclaimed, sysfs always used to allocate new dentry
and inode if the file is accessed again. This causes problem with
operations which only pin the inode. For example, if inotify watch is
added to a sysfs file and the dentry for the file is reclaimed, the
next update event creates new dentry and new inode making the inotify
watch miss all the events from there on.

This patch fixes it by using iget_locked() instead of new_inode().
sysfs_new_inode() is renamed to sysfs_get_inode() and inode is
initialized iff the inode is newly allocated. sysfs_instantiate() is
responsible for unlocking new inodes.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: reorganize sysfs_new_indoe() and sysfs_create()

Reorganize/clean up sysfs_new_inode() and sysfs_create().

* sysfs_init_inode() is separated out from sysfs_new_inode() and is

sysfs: reorganize sysfs_new_indoe() and sysfs_create()

Reorganize/clean up sysfs_new_inode() and sysfs_create().

* sysfs_init_inode() is separated out from sysfs_new_inode() and is
responsible for basic initialization.
* sysfs_instantiate() replaces the last step of sysfs_create() and is
responsible for dentry instantitaion.
* type-specific initialization is moved out to the callers.
* mode is specified only once when creating a sysfs_dirent.
* spurious list_del_init(&sd->s_sibling) dropped from create_dir()

This change is to

* prepare for inode allocation fix.
* separate alloc and init code for synchronization update.
* make dentry/inode initialization more flexible for later changes.

This patch doesn't introduce visible behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: reimplement sysfs_drop_dentry()

This patch reimplements sysfs_drop_dentry() such that remove_dir() can
use it to drop dentry instead of using a separate mechanism. With
this

sysfs: reimplement sysfs_drop_dentry()

This patch reimplements sysfs_drop_dentry() such that remove_dir() can
use it to drop dentry instead of using a separate mechanism. With
this change, making directories reclaimable is much easier.

This patch used to contain fixes for two race conditions around
sd->s_dentry but that part has been separated out and included into
mainline early as commit 6aa054aadfea613a437ad0b15d38eca2b963fc0a and
dd14cbc994709a1c5a64ed3621f583c49a27e521.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: separate out sysfs_attach_dentry()

Consolidate sd <-> dentry association into sysfs_attach_dentry() and
call it after dentry and inode are properly set up. This is in
prepara

sysfs: separate out sysfs_attach_dentry()

Consolidate sd <-> dentry association into sysfs_attach_dentry() and
call it after dentry and inode are properly set up. This is in
preparation of sysfs_drop_dentry() updates.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: kill attribute file orphaning

Now that sysfs_dirent can be disconnected from kobject on deletion,
there is no need to orphan each attribute files. All [bin_]attribute
nodes a

sysfs: kill attribute file orphaning

Now that sysfs_dirent can be disconnected from kobject on deletion,
there is no need to orphan each attribute files. All [bin_]attribute
nodes are automatically orphaned when the parent node is deleted.
Kill attribute file orphaning.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: implement sysfs_dirent active reference and immediate disconnect

sysfs: implement sysfs_dirent active reference and immediate disconnect

Opening a sysfs node references its a

sysfs: implement sysfs_dirent active reference and immediate disconnect

sysfs: implement sysfs_dirent active reference and immediate disconnect

Opening a sysfs node references its associated kobject, so userland
can arbitrarily prolong lifetime of a kobject which complicates
lifetime rules in drivers. This patch implements active reference and
makes the association between kobject and sysfs immediately breakable.

Now each sysfs_dirent has two reference counts - s_count and s_active.
s_count is a regular reference count which guarantees that the
containing sysfs_dirent is accessible. As long as s_count reference
is held, all sysfs internal fields in sysfs_dirent are accessible
including s_parent and s_name.

The newly added s_active is active reference count. This is acquired
by invoking sysfs_get_active() and it's the caller's responsibility to
ensure sysfs_dirent itself is accessible (should be holding s_count
one way or the other). Dereferencing sysfs_dirent to access objects
out of sysfs proper requires active reference. This includes access
to the associated kobjects, attributes and ops.

The active references can be drained and denied by calling
sysfs_deactivate(). All active sysfs_dirents must be deactivated
after deletion but before the default reference is dropped. This
enables immediate disconnect of sysfs nodes. Once a sysfs_dirent is
deleted, it won't access any entity external to sysfs proper.

Because attr/bin_attr ops access both the node itself and its parent
for kobject, they need to hold active references to both.
sysfs_get/put_active_two() helpers are provided to help grabbing both
references. Parent's is acquired first and released last.

Unlike other operations, mmapped area lingers on after mmap() is
finished and the module implement implementing it and kobj need to
stay referenced till all the mapped pages are gone. This is
accomplished by holding one set of active references to the bin_attr
and its parent if there have been any mmap during lifetime of an
openfile. The references are dropped when the openfile is released.

This change makes sysfs lifetime rules independent from both kobject's
and module's. It not only fixes several race conditions caused by
sysfs not holding onto the proper module when referencing kobject, but
also helps fixing and simplifying lifetime management in driver model
and drivers by taking sysfs out of the equation.

Please read the following message for more info.

http://article.gmane.org/gmane.linux.kernel/510293

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: reimplement symlink using sysfs_dirent tree

sysfs symlink is implemented by referencing dentry and kobject from
sysfs_dirent - symlink entry references kobject, dentry is used to

sysfs: reimplement symlink using sysfs_dirent tree

sysfs symlink is implemented by referencing dentry and kobject from
sysfs_dirent - symlink entry references kobject, dentry is used to
walk the tree. This complicates object lifetimes rules and is
dangerous - for example, there is no way to tell to which module the
target of a symlink belongs and referencing that kobject can make it
linger after the module is gone.

This patch reimplements symlink using only sysfs_dirent tree. sd for
a symlink points and holds reference to the target sysfs_dirent and
all walking is done using sysfs_dirent tree. Simpler and safer.

Please read the following message for more info.

http://article.gmane.org/gmane.linux.kernel/510293

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: implement kobj_sysfs_assoc_lock

kobj->dentry can go away anytime unless the user controls when the
associated sysfs node is deleted. This patch implements
kobj_sysfs_assoc_lo

sysfs: implement kobj_sysfs_assoc_lock

kobj->dentry can go away anytime unless the user controls when the
associated sysfs node is deleted. This patch implements
kobj_sysfs_assoc_lock which protects kobj->dentry. This will be used
to maintain kobj based API when converting sysfs to use sysfs_dirent
tree instead of dentry/kobject.

Note that this lock belongs to kobject/driver-model not sysfs. Once
sysfs is converted to not use kobject in its interface, this can be
removed from sysfs.

This is in preparation of object reference simplification.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: make sysfs_dirent->s_element a union

Make sd->s_element a union of sysfs_elem_{dir|symlink|attr|bin_attr}
and rename it to s_elem. This is to achieve...

* some level of

sysfs: make sysfs_dirent->s_element a union

Make sd->s_element a union of sysfs_elem_{dir|symlink|attr|bin_attr}
and rename it to s_elem. This is to achieve...

* some level of type checking : changing symlink to point to
sysfs_dirent instead of kobject is much safer and less painful now.
* easier / standardized dereferencing
* allow sysfs_elem_* to contain more than one entry

Where possible, pointer is obtained by directly deferencing from sd
instead of going through other entities. This reduces dependencies to
dentry, inode and kobject. to_attr() and to_bin_attr() are unused now
and removed.

This is in preparation of object reference simplification.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: add sysfs_dirent->s_name

Add s_name to sysfs_dirent. This is to further reduce dependency to
the associated dentry. Name is copied for directories and symlinks
but not for a

sysfs: add sysfs_dirent->s_name

Add s_name to sysfs_dirent. This is to further reduce dependency to
the associated dentry. Name is copied for directories and symlinks
but not for attributes.

Where possible, name dereferences are converted to use sd->s_name.
sysfs_symlink->link_name and sysfs_get_name() are unused now and
removed.

This change allows symlink to be implemented using sysfs_dirent tree
proper, which is the last remaining dentry-dependent sysfs walk.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: add sysfs_dirent->s_parent

Add sysfs_dirent->s_parent. With this patch, each sd points to and
holds a reference to its parent. This allows walking sysfs tree
without referen

sysfs: add sysfs_dirent->s_parent

Add sysfs_dirent->s_parent. With this patch, each sd points to and
holds a reference to its parent. This allows walking sysfs tree
without referencing sd->s_dentry which can go away anytime if the user
doesn't control when it's deleted.

sd->s_parent is initialized and parent is referenced in
sysfs_attach_dirent(). Reference to parent is released when the sd is
released, so as long as reference to a sd is held, s_parent can be
followed.

dentry walk in sysfs_readdir() is convereted to s_parent walk.

This will be used to reimplement symlink such that it uses only
sysfs_dirent tree.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: consolidate sysfs_dirent creation functions

Currently there are four functions to create sysfs_dirent -
__sysfs_new_dirent(), sysfs_new_dirent(), __sysfs_make_dirent() and
sys

sysfs: consolidate sysfs_dirent creation functions

Currently there are four functions to create sysfs_dirent -
__sysfs_new_dirent(), sysfs_new_dirent(), __sysfs_make_dirent() and
sysfs_make_dirent(). Other than sysfs_make_dirent(), no function has
two users if calls to implement other functions are excluded.

This patch consolidates sysfs_dirent creation functions into the
following two.

* sysfs_new_dirent() : allocate and initialize
* sysfs_attach_dirent() : attach to sysfs_dirent hierarchy and/or
associate with dentry

This simplifies interface and gives callers more flexibility. This is
in preparation of object reference simplification.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: make sysfs_put() ignore NULL sd

Make sysfs_put() ignore NULL sd instead of oopsing.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@

sysfs: make sysfs_put() ignore NULL sd

Make sysfs_put() ignore NULL sd instead of oopsing.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: move release_sysfs_dirent() to dir.c

There is no reason this function should be inlined and soon to follow
sysfs object reference simplification will make it heavier. Move it

sysfs: move release_sysfs_dirent() to dir.c

There is no reason this function should be inlined and soon to follow
sysfs object reference simplification will make it heavier. Move it
to dir.c.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: fix race condition around sd->s_dentry, take#2

Allowing attribute and symlink dentries to be reclaimed means
sd->s_dentry can change dynamically. However, updates to the field

sysfs: fix race condition around sd->s_dentry, take#2

Allowing attribute and symlink dentries to be reclaimed means
sd->s_dentry can change dynamically. However, updates to the field
are unsynchronized leading to race conditions. This patch adds
sysfs_lock and use it to synchronize updates to sd->s_dentry.

Due to the locking around ->d_iput, the check in sysfs_drop_dentry()
is complex. sysfs_lock only protect sd->s_dentry pointer itself. The
validity of the dentry is protected by dcache_lock, so whether dentry
is alive or not can only be tested while holding both locks.

This is minimal backport of sysfs_drop_dentry() rewrite in devel
branch.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: store sysfs inode nrs in s_ino to avoid readdir oopses

Backport of
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/broken-out/gregkh-driver

sysfs: store sysfs inode nrs in s_ino to avoid readdir oopses

Backport of
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.22-rc1/2.6.22-rc1-mm1/broken-out/gregkh-driver-sysfs-allocate-inode-number-using-ida.patch

For regular files in sysfs, sysfs_readdir wants to traverse
sysfs_dirent->s_dentry->d_inode->i_ino to get to the inode number.
But, the dentry can be reclaimed under memory pressure, and there is
no synchronization with readdir. This patch follows Tejun's scheme of
allocating and storing an inode number in the new s_ino member of a
sysfs_dirent, when dirents are created, and retrieving it from there
for readdir, so that the pointer chain doesn't have to be traversed.

Tejun's upstream patch uses a new-ish "ida" allocator which brings
along some extra complexity; this -stable patch has a brain-dead
incrementing counter which does not guarantee uniqueness, but because
sysfs doesn't hash inodes as iunique expects, uniqueness wasn't
guaranteed today anyway.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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sysfs: move struct sysfs_dirent to private header

struct sysfs_dirent is private to the fs/sysfs/ subtree. It is
not even referenced as an opaque structure outside of that subtree.

sysfs: move struct sysfs_dirent to private header

struct sysfs_dirent is private to the fs/sysfs/ subtree. It is
not even referenced as an opaque structure outside of that subtree.

The following patch moves the declaration from include/linux/sysfs.h to
fs/sysfs/sysfs.h, making it clearer that nothing else in the kernel
dereferences it.

I have been running this patch for years. Please integrate and forward
upstream if there are no objections.

From: "Adam J. Richter" <adam@yggdrasil.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

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