linux-toradex.git/include/linux/kernfs.h, branch v5.19-rc8

kernfs: remove unneeded #if 0 guard

2022-03-18T08:47:04+00:00

Commit f2eb478f2f32 ("kernfs: move struct kernfs_root out of the public
view.") moved kernfs_root out of kernfs.h, but my debugging code of a
 #if 0 was left in accidentally.  Fix that up by removing the guards.

Fixes: f2eb478f2f32 ("kernfs: move struct kernfs_root out of the public view.")
Cc: Tejun Heo 
Reported-by: Al Viro 
Link: https://lore.kernel.org/r/20220318073452.1486568-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman

kernfs: move struct kernfs_root out of the public view.

2022-02-23T14:46:34+00:00

There is no need to have struct kernfs_root be part of kernfs.h for
the whole kernel to see and poke around it.  Move it internal to kernfs
code and provide a helper function, kernfs_root_to_node(), to handle the
one field that kernfs users were directly accessing from the structure.

Cc: Imran Khan 
Acked-by: Tejun Heo 
Link: https://lore.kernel.org/r/20220222070713.3517679-1-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman

kernfs: Replace kernel.h with the necessary inclusions

2021-12-21T09:34:39+00:00

When kernel.h is used in the headers it adds a lot into dependency hell,
especially when there are circular dependencies are involved.

Replace kernel.h inclusion with the list of what is really being used.

Acked-by: Tejun Heo 
Signed-off-by: Andy Shevchenko 
Link: https://lore.kernel.org/r/20211209123008.3391-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

kernfs: switch global kernfs_rwsem lock to per-fs lock

2021-11-24T12:55:16+00:00

The kernfs implementation has big lock granularity(kernfs_rwsem) so
every kernfs-based(e.g., sysfs, cgroup) fs are able to compete the
lock. It makes trouble for some cases to wait the global lock
for a long time even though they are totally independent contexts
each other.

A general example is process A goes under direct reclaim with holding
the lock when it accessed the file in sysfs and process B is waiting
the lock with exclusive mode and then process C is waiting the lock
until process B could finish the job after it gets the lock from
process A.

This patch switches the global kernfs_rwsem to per-fs lock, which
put the rwsem into kernfs_root.

Suggested-by: Tejun Heo 
Acked-by: Tejun Heo 
Signed-off-by: Minchan Kim 
Link: https://lore.kernel.org/r/20211118230008.2679780-1-minchan@kernel.org
Signed-off-by: Greg Kroah-Hartman

kernfs: remove the unused lockdep_key field in struct kernfs_ops

2021-09-14T14:55:19+00:00

Not actually used anywhere.

Acked-by: Christian Brauner 
Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20210913054121.616001-4-hch@lst.de
Signed-off-by: Greg Kroah-Hartman

kernfs: remove kernfs_create_file and kernfs_create_file_ns

2021-09-14T14:54:55+00:00

All callers actually use __kernfs_create_file.

Acked-by: Christian Brauner 
Acked-by: Tejun Heo 
Signed-off-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20210913054121.616001-3-hch@lst.de
Signed-off-by: Greg Kroah-Hartman

kernfs: switch kernfs to use an rwsem

2021-07-27T07:29:15+00:00

The kernfs global lock restricts the ability to perform kernfs node
lookup operations in parallel during path walks.

Change the kernfs mutex to an rwsem so that, when opportunity arises,
node searches can be done in parallel with path walk lookups.

Reviewed-by: Miklos Szeredi 
Signed-off-by: Ian Kent 
Link: https://lore.kernel.org/r/162642770946.63632.2218304587223241374.stgit@web.messagingengine.com
Signed-off-by: Greg Kroah-Hartman

kernfs: add a revision to identify directory node changes

2021-07-27T07:29:14+00:00

Add a revision counter to kernfs directory nodes so it can be used
to detect if a directory node has changed during negative dentry
revalidation.

There's an assumption that sizeof(unsigned long) <= sizeof(pointer)
on all architectures and as far as I know that assumption holds.

So adding a revision counter to the struct kernfs_elem_dir variant of
the kernfs_node type union won't increase the size of the kernfs_node
struct. This is because struct kernfs_elem_dir is at least
sizeof(pointer) smaller than the largest union variant. It's tempting
to make the revision counter a u64 but that would increase the size of
kernfs_node on archs where sizeof(pointer) is smaller than the revision
counter.

Reviewed-by: Miklos Szeredi 
Signed-off-by: Ian Kent 
Link: https://lore.kernel.org/r/162642769895.63632.8356662784964509867.stgit@web.messagingengine.com
Signed-off-by: Greg Kroah-Hartman

kernfs: bring names in comments in line with code

2020-11-09T17:12:39+00:00

Fix two stragglers in the comments of the below rename operation.

Fixes: adc5e8b58f48 ("kernfs: drop s_ prefix from kernfs_node members")
Acked-by: Tejun Heo 
Signed-off-by: Willem de Bruijn 
Link: https://lore.kernel.org/r/20201015185726.1386868-1-willemdebruijn.kernel@gmail.com
Signed-off-by: Greg Kroah-Hartman

kernfs: Add option to enable user xattrs

2020-03-16T19:53:47+00:00

User extended attributes are useful as metadata storage for kernfs
consumers like cgroups. Especially in the case of cgroups, it is useful
to have a central metadata store that multiple processes/services can
use to coordinate actions.

A concrete example is for userspace out of memory killers. We want to
let delegated cgroup subtree owners (running as non-root) to be able to
say "please avoid killing this cgroup". This is especially important for
desktop linux as delegated subtrees owners are less likely to run as
root.

This patch introduces a new flag, KERNFS_ROOT_SUPPORT_USER_XATTR, that
lets kernfs consumers enable user xattr support. An initial limit of 128
entries or 128KB -- whichever is hit first -- is placed per cgroup
because xattrs come from kernel memory and we don't want to let
unprivileged users accidentally eat up too much kernel memory.

Signed-off-by: Daniel Xu 
Acked-by: Chris Down 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Tejun Heo