The recursive nature of kernfs_remove() means that, even if
kernfs_remove() is not allowed to be called multiple times on the same
node, there may be race conditions between removal of parent and its
descendants. While we can claim that kernfs_remove() shouldn't be
called on one of the descendants while the removal of an ancestor is
in progress, such rule is unnecessarily restrictive and very difficult
to enforce. It's better to simply allow invoking kernfs_remove() as
the caller sees fit as long as the caller ensures that the node is
accessible.
The current behavior in such situations is broken. Whoever enters
removal path first takes the node off the hierarchy and then
deactivates. Following removers either return as soon as it notices
that it's not the first one or can't even find the target node as it
has already been removed from the hierarchy. In both cases, the
following removers may finish prematurely while the nodes which should
be removed and drained are still being processed by the first one.
This patch restructures so that multiple removers, whether through
recursion or direction invocation, always follow the following rules.
* When there are multiple concurrent removers, only one puts the base
ref.
* Regardless of which one puts the base ref, all removers are blocked
until the target node is fully deactivated and removed.
To achieve the above, removal path now first deactivates the subtree,
drains it and then unlinks one-by-one. __kernfs_deactivate() is
called directly from __kernfs_removal() and drops and regrabs
kernfs_mutex for each descendant to drain active refs. As this means
that multiple removers can enter __kernfs_deactivate() for the same
node, the function is updated so that it can handle multiple
deactivators of the same node - only one actually deactivates but all
wait till drain completion.
The restructured removal path guarantees that a removed node gets
unlinked only after the node is deactivated and drained. Combined
with proper multiple deactivator handling, this guarantees that any
invocation of kernfs_remove() returns only after the node itself and
all its descendants are deactivated, drained and removed.
v2: Draining separated into a separate loop (used to be in the same
loop as unlink) and done from __kernfs_deactivate(). This is to
allow exposing deactivation as a separate interface later.
Root node removal was broken in v1 patch. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
KERNFS_REMOVED is used to mark half-initialized and dying nodes so
that they don't show up in lookups and deny adding new nodes under or
renaming it; however, its role overlaps those of deactivation and
removal from rbtree.
It's necessary to deny addition of new children while removal is in
progress; however, this role considerably intersects with deactivation
- KERNFS_REMOVED prevents new children while deactivation prevents new
file operations. There's no reason to have them separate making
things more complex than necessary.
KERNFS_REMOVED is also used to decide whether a node is still visible
to vfs layer, which is rather redundant as equivalent determination
can be made by testing whether the node is on its parent's children
rbtree or not.
This patch removes KERNFS_REMOVED.
* Instead of KERNFS_REMOVED, each node now starts its life
deactivated. This means that we now use both atomic_add() and
atomic_sub() on KN_DEACTIVATED_BIAS, which is INT_MIN. The compiler
generates an overflow warnings when negating INT_MIN as the negation
can't be represented as a positive number. Nothing is actually
broken but let's bump BIAS by one to avoid the warnings for archs
which negates the subtrahend..
* KERNFS_REMOVED tests in add and rename paths are replaced with
kernfs_get/put_active() of the target nodes. Due to the way the add
path is structured now, active ref handling is done in the callers
of kernfs_add_one(). This will be consolidated up later.
* kernfs_remove_one() is updated to deactivate instead of setting
KERNFS_REMOVED. This removes deactivation from kernfs_deactivate(),
which is now renamed to kernfs_drain().
* kernfs_dop_revalidate() now tests RB_EMPTY_NODE(&kn->rb) instead of
KERNFS_REMOVED and KERNFS_REMOVED test in kernfs_dir_pos() is
dropped. A node which is removed from the children rbtree is not
included in the iteration in the first place. This means that a
node may be visible through vfs a bit longer - it's now also visible
after deactivation until the actual removal. This slightly enlarged
window difference doesn't make any difference to the userland.
* Sanity check on KERNFS_REMOVED in kernfs_put() is replaced with
checks on the active ref.
* Some comment style updates in the affected area.
v2: Reordered before removal path restructuring. kernfs_active()
dropped and kernfs_get/put_active() used instead. RB_EMPTY_NODE()
used in the lookup paths.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There currently are two mechanisms gating active ref lockdep
annotations - KERNFS_LOCKDEP flag and KERNFS_ACTIVE_REF type mask.
The former disables lockdep annotations in kernfs_get/put_active()
while the latter disables all of kernfs_deactivate().
While KERNFS_ACTIVE_REF also behaves as an optimization to skip the
deactivation step for non-file nodes, the benefit is marginal and it
needlessly diverges code paths. Let's drop KERNFS_ACTIVE_REF and use
KERNFS_LOCKDEP in kernfs_deactivate() too.
While at it, add a test helper kernfs_lockdep() to test KERNFS_LOCKDEP
flag so that it's more convenient and the related code can be compiled
out when not enabled.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs_node->u.completion is used to notify deactivation completion
from kernfs_put_active() to kernfs_deactivate(). We now allow
multiple racing removals of the same node and the current removal
scheme is no longer correct - kernfs_remove() invocation may return
before the node is properly deactivated if it races against another
removal. The removal path will be restructured to address the issue.
To help such restructure which requires supporting multiple waiters,
this patch replaces kernfs_node->u.completion with
kernfs_root->deactivate_waitq. This makes deactivation event
notifications share a per-root waitqueue_head; however, the wait path
is quite cold and this will also allow shaving one pointer off
kernfs_node.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add support for mkdir(2), rmdir(2) and rename(2) syscalls. This is
implemented through optional kernfs_dir_ops callback table which can
be specified on kernfs_create_root(). An implemented callback is
invoked when the matching syscall is invoked.
As kernfs keep dcache syncs with internal representation and
revalidates dentries on each access, the implementation of these
methods is extremely simple. Each just discovers the relevant
kernfs_node(s) and invokes the requested callback which is allowed to
do any kernfs operations and the end result doesn't necessarily have
to match the expected semantics of the syscall.
This will be used to convert cgroup to use kernfs instead of its own
filesystem implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs doesn't allow negative dentries - kernfs_iop_lookup() returns
ERR_PTR(-ENOENT) instead of NULL which short-circuits negative dentry
creation and kernfs's d_delete() callback, kernfs_dop_delete(),
returns 1 for all removed nodes. This in turn allows
kernfs_dop_revalidate() to assume that there's no negative dentry for
kernfs.
This worked fine for sysfs but kernfs is scheduled to grow mkdir(2)
support which depend on negative dentries. This patch updates so that
kernfs allows negative dentries. The required changes are almost
trivial - kernfs_iop_lookup() now returns NULL instead of
ERR_PTR(-ENOENT) when the target kernfs_node doesn't exist,
kernfs_dop_delete() is removed and kernfs_dop_revalidate() is updated
to check whether the target dentry is negative and request fresh
lookup if so.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs_rename_ns() currently assumes that the target sysfs_dirent has
a copied name. This has been okay because sysfs supports rename only
for directories which always have copied names; however, there's
nothing in kernfs interface which calls for such restriction and
currently invoking kernfs_rename_ns() on a regular file leads to oops
because it ends up trying to kfree() a static name.
This patch updates kernfs_rename_ns() so that it skips kfree() of the
old name if it's static. This allows it to be used for all node
types.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Because sysfs used struct attribute which are supposed to stay
constant, sysfs didn't copy names when creating regular files. The
specified string for name was supposed to stay constant. Such
distinction isn't inherent for kernfs. kernfs_create_file[_ns]()
should be able to take the same @name as kernfs_create_dir[_ns]()
As there can be huge number of sysfs attributes, we still want to be
able to use static names for sysfs attributes. This patch renames
kernfs_create_file_ns_key() to __kernfs_create_file() and adds
@name_is_static parameter so that the caller can explicitly indicate
that @name can be used without copying. kernfs is updated to use
KERNFS_STATIC_NAME to distinguish static and copied names.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs currently assumes that the caller doesn't try to create a new
node under a removed parent, rename a removed node, or move a node
under a removed node. While this works fine for sysfs, it'd be nice
to have protection against such cases especially given that kernfs is
planned to add support for mkdir, rmdir and rename requsts from
userland which may make race conditions more likely.
This patch updates create and rename paths to check REMOVED and fail
the operation with -ENOENT if performed on or towards removed nodes.
Note that remove path already has such check.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs assumed 0755 for all newly created directories and kernfs
inherited it. This assumption is unnecessarily restrictive and
inconsistent with kernfs_create_file[_ns](). This patch adds @mode
parameter to kernfs_create_dir[_ns]() and update uses in sysfs
accordingly. Among others, this will be useful for implementations of
the planned ->mkdir() method.
This patch doesn't introduce any behavior differences.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_*()/kernfs_*()/ in all internal functions
* s/sysfs/kernfs/ in internal strings, comments and whatever is remaining
* Uniformly rename various vfs operations so that they're consistently
named and distinguishable.
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_mutex/kernfs_mutex/
* s/sysfs_dentry_ops/kernfs_dops/
* s/sysfs_dir_operations/kernfs_dir_fops/
* s/sysfs_dir_inode_operations/kernfs_dir_iops/
* s/kernfs_file_operations/kernfs_file_fops/ - renamed for consistency
* s/sysfs_symlink_inode_operations/kernfs_symlink_iops/
* s/sysfs_aops/kernfs_aops/
* s/sysfs_backing_dev_info/kernfs_bdi/
* s/sysfs_inode_operations/kernfs_iops/
* s/sysfs_dir_cachep/kernfs_node_cache/
* s/sysfs_ops/kernfs_sops/
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/SYSFS_DIR/KERNFS_DIR/
* s/SYSFS_KOBJ_ATTR/KERNFS_FILE/
* s/SYSFS_KOBJ_LINK/KERNFS_LINK/
* s/SYSFS_{TYPE_FLAGS}/KERNFS_{TYPE_FLAGS}/
* s/SYSFS_FLAG_{FLAG}/KERNFS_{FLAG}/
* s/sysfs_type()/kernfs_type()/
* s/SD_DEACTIVATED_BIAS/KN_DEACTIVATED_BIAS/
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_open_dirent/kernfs_open_node/
* s/sysfs_open_file/kernfs_open_file/
* s/sysfs_inode_attrs/kernfs_iattrs/
* s/sysfs_addrm_cxt/kernfs_addrm_cxt/
* s/sysfs_super_info/kernfs_super_info/
* s/sysfs_info()/kernfs_info()/
* s/sysfs_open_dirent_lock/kernfs_open_node_lock/
* s/sysfs_open_file_mutex/kernfs_open_file_mutex/
* s/sysfs_of()/kernfs_of()/
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
s_ prefix for kernfs members is used inconsistently and a misnomer
now. It's not like kernfs_node is used widely across the kernel
making the ability to grep for the members particularly useful. Let's
just drop the prefix.
This patch is strictly rename only and doesn't introduce any
functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs has just been separated out from sysfs and we're already in
full conflict mode. Nothing can make the situation any worse. Let's
take the chance to name things properly.
This patch performs the following renames.
* s/sysfs_elem_dir/kernfs_elem_dir/
* s/sysfs_elem_symlink/kernfs_elem_symlink/
* s/sysfs_elem_attr/kernfs_elem_file/
* s/sysfs_dirent/kernfs_node/
* s/sd/kn/ in kernfs proper
* s/parent_sd/parent/
* s/target_sd/target/
* s/dir_sd/parent/
* s/to_sysfs_dirent()/rb_to_kn()/
* misc renames of local vars when they conflict with the above
Because md, mic and gpio dig into sysfs details, this patch ends up
modifying them. All are sysfs_dirent renames and trivial. While we
can avoid these by introducing a dummy wrapping struct sysfs_dirent
around kernfs_node, given the limited usage outside kernfs and sysfs
proper, I don't think such workaround is called for.
This patch is strictly rename only and doesn't introduce any
functional difference.
- mic / gpio renames were missing. Spotted by kbuild test robot.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs inherited "security.*" xattr support from sysfs. This patch
extends xattr support to "trusted.*" using simple_xattr_*(). As
trusted xattrs are restricted to CAP_SYS_ADMIN, simple_xattr_*() which
uses kernel memory for storage shouldn't be problematic.
Note that the existing "security.*" support doesn't implement
get/remove/list and the this patch only implements those ops for
"trusted.*". We probably want to extend those ops to include support
for "security.*".
This patch will allow using kernfs from cgroup which requires
"trusted.*" xattr support.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David P. Quigley <dpquigl@tycho.nsa.gov>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/sysfs/symlink.c::sysfs_delete_link() tests @sd->s_flags for
SYSFS_FLAG_NS. Let's add kernfs_ns_enabled() so that sysfs doesn't
have to test sysfs_dirent flag directly. This makes things tidier for
kernfs proper too.
This is purely cosmetic.
v2: To avoid possible NULL deref, use noop dummy implementation which
always returns false when !CONFIG_SYSFS.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sysfs_dirent includes some information which should be available to
kernfs users - the type, flags, name and parent pointer. This patch
moves sysfs_dirent definition from kernfs/kernfs-internal.h to
include/linux/kernfs.h so that kernfs users can access them.
The type part of flags is exported as enum kernfs_node_type, the flags
kernfs_node_flag, sysfs_type() and kernfs_enable_ns() are moved to
include/linux/kernfs.h and the former is updated to return the enum
type. sysfs_dirent->s_parent and ->s_name are marked explicitly as
public.
This patch doesn't introduce any functional changes.
v2: Flags exported too and kernfs_enable_ns() definition moved.
v3: While moving kernfs_enable_ns() to include/linux/kernfs.h, v1 and
v2 put the definition outside CONFIG_SYSFS replacing the dummy
implementation with the actual implementation too. Unfortunately,
this can lead to oops when !CONFIG_SYSFS because
kernfs_enable_ns() may be called on a NULL @sd and now tries to
dereference @sd instead of not doing anything. This issue was
reported by Yuanhan Liu.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernfs is being updated to allow multiple sysfs_dirent hierarchies so
that it can also be used by other users. Currently, inode number is
allocated using a global ida, sysfs_ino_ida; however, inos for
different hierarchies should be handled separately.
This patch makes ino allocation per kernfs_root. sysfs_ino_ida is
replaced by kernfs_root->ino_ida and sysfs_new_dirent() is updated to
take @root and allocate ino from it. ida_simple_get/remove() are used
instead of sysfs_ino_lock and sysfs_alloc/free_ino().
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There currently is single kernfs hierarchy in the whole system which
is used for sysfs. kernfs needs to support multiple hierarchies to
allow other users. This patch introduces struct kernfs_root which
serves as the root of each kernfs hierarchy and implements
kernfs_create/destroy_root().
* Each kernfs_root is associated with a root sd (sysfs_dentry). The
root is freed when the root sd is released and kernfs_destory_root()
simply invokes kernfs_remove() on the root sd. sysfs_remove_one()
is updated to handle release of the root sd. Note that ps_iattr
update in sysfs_remove_one() is trivially updated for readability.
* Root sd's are now dynamically allocated using sysfs_new_dirent().
Update sysfs_alloc_ino() so that it gives out ino from 1 so that the
root sd still gets ino 1.
* While kernfs currently only points to the root sd, it'll soon grow
fields which are specific to each hierarchy. As determining a given
sd's root will be necessary, sd->s_dir.root is added. This backlink
fits better as a separate field in sd; however, sd->s_dir is inside
union with space to spare, so use it to save space and provide
kernfs_root() accessor to determine the root sd.
* As hierarchies may be destroyed now, each mount needs to hold onto
the hierarchy it's attached to. Update sysfs_fill_super() and
sysfs_kill_sb() so that they get and put the kernfs_root
respectively.
* sysfs_root is replaced with kernfs_root which is dynamically created
by invoking kernfs_create_root() from sysfs_init().
This patch doesn't introduce any visible behavior changes.
v2: kernfs_create_root() forgot to set @sd->priv. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Move core dir code to fs/kernfs/dir.c. fs/sysfs/dir.c now only
contains sysfs_warn_dup() and sysfs wrappers around kernfs interfaces.
The respective declarations in fs/sysfs/sysfs.h are moved to
fs/kernfs/kernfs-internal.h.
This is pure relocation.
v2: sysfs_symlink_target_lock was mistakenly relocated to kernfs. It
should remain with sysfs. Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Core sysfs implementation will be separated into kernfs so that it can
be used by other non-kobject users.
This patch creates fs/kernfs/ directory and makes boilerplate changes.
kernfs interface will be directly based on sysfs_dirent and its
forward declaration is moved to include/linux/kernfs.h which is
included from include/linux/sysfs.h. sysfs core implementation will
be gradually separated out and moved to kernfs.
This patch doesn't introduce any functional changes.
v2: mount.c added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
