linux.git/kernel/trace/blktrace.c, branch v5.6-rc2

tracing: Make struct ring_buffer less ambiguous

2020-01-13T18:19:38+00:00

As there's two struct ring_buffers in the kernel, it causes some confusion.
The other one being the perf ring buffer. It was agreed upon that as neither
of the ring buffers are generic enough to be used globally, they should be
renamed as:

   perf's ring_buffer -> perf_buffer
   ftrace's ring_buffer -> trace_buffer

This implements the changes to the ring buffer that ftrace uses.

Link: https://lore.kernel.org/r/20191213140531.116b3200@gandalf.local.home

Signed-off-by: Steven Rostedt (VMware)

tracing: Rename trace_buffer to array_buffer

2020-01-13T18:19:38+00:00

As we are working to remove the generic "ring_buffer" name that is used by
both tracing and perf, the ring_buffer name for tracing will be renamed to
trace_buffer, and perf's ring buffer will be renamed to perf_buffer.

As there already exists a trace_buffer that is used by the trace_arrays, it
needs to be first renamed to array_buffer.

Link: https://lore.kernel.org/r/20191213153553.GE20583@krava

Signed-off-by: Steven Rostedt (VMware)

cgroup: use cgrp->kn->id as the cgroup ID

2019-11-12T16:18:04+00:00

cgroup ID is currently allocated using a dedicated per-hierarchy idr
and used internally and exposed through tracepoints and bpf.  This is
confusing because there are tracepoints and other interfaces which use
the cgroupfs ino as IDs.

The preceding changes made kn->id exposed as ino as 64bit ino on
supported archs or ino+gen (low 32bits as ino, high gen).  There's no
reason for cgroup to use different IDs.  The kernfs IDs are unique and
userland can easily discover them and map them back to paths using
standard file operations.

This patch replaces cgroup IDs with kernfs IDs.

* cgroup_id() is added and all cgroup ID users are converted to use it.

* kernfs_node creation is moved to earlier during cgroup init so that
  cgroup_id() is available during init.

* While at it, s/cgroup/cgrp/ in psi helpers for consistency.

* Fallback ID value is changed to 1 to be consistent with root cgroup
  ID.

Signed-off-by: Tejun Heo 
Reviewed-by: Greg Kroah-Hartman 
Cc: Namhyung Kim

kernfs: use 64bit inos if ino_t is 64bit

2019-11-12T16:18:04+00:00

Each kernfs_node is identified with a 64bit ID.  The low 32bit is
exposed as ino and the high gen.  While this already allows using inos
as keys by looking up with wildcard generation number of 0, it's
adding unnecessary complications for 64bit ino archs which can
directly use kernfs_node IDs as inos to uniquely identify each cgroup
instance.

This patch exposes IDs directly as inos on 64bit ino archs.  The
conversion is mostly straight-forward.

* 32bit ino archs behave the same as before.  64bit ino archs now use
  the whole 64bit ID as ino and the generation number is fixed at 1.

* 64bit inos still use the same idr allocator which gurantees that the
  lower 32bits identify the current live instance uniquely and the
  high 32bits are incremented whenever the low bits wrap.  As the
  upper 32bits are no longer used as gen and we don't wanna start ino
  allocation with 33rd bit set, the initial value for highbits
  allocation is changed to 0 on 64bit ino archs.

* blktrace exposes two 32bit numbers - (INO,GEN) pair - to identify
  the issuing cgroup.  Userland builds FILEID_INO32_GEN fids from
  these numbers to look up the cgroups.  To remain compatible with the
  behavior, always output (LOW32,HIGH32) which will be constructed
  back to the original 64bit ID by __kernfs_fh_to_dentry().

Signed-off-by: Tejun Heo 
Reviewed-by: Greg Kroah-Hartman 
Cc: Namhyung Kim

kernfs: convert kernfs_node->id from union kernfs_node_id to u64

2019-11-12T16:18:03+00:00

kernfs_node->id is currently a union kernfs_node_id which represents
either a 32bit (ino, gen) pair or u64 value.  I can't see much value
in the usage of the union - all that's needed is a 64bit ID which the
current code is already limited to.  Using a union makes the code
unnecessarily complicated and prevents using 64bit ino without adding
practical benefits.

This patch drops union kernfs_node_id and makes kernfs_node->id a u64.
ino is stored in the lower 32bits and gen upper.  Accessors -
kernfs[_id]_ino() and kernfs[_id]_gen() - are added to retrieve the
ino and gen.  This simplifies ID handling less cumbersome and will
allow using 64bit inos on supported archs.

This patch doesn't make any functional changes.

Signed-off-by: Tejun Heo 
Reviewed-by: Greg Kroah-Hartman 
Cc: Namhyung Kim 
Cc: Jens Axboe 
Cc: Alexei Starovoitov

blktrace: no need to check return value of debugfs_create functions

2019-06-03T13:39:39+00:00

When calling debugfs functions, there is no need to ever check the
return value.  The function can work or not, but the code logic should
never do something different based on this.

Cc: Jens Axboe 
Cc: Steven Rostedt 
Cc: Ingo Molnar 
Cc: linux-block@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman

blkcg: annotate implicit fall through

2019-03-13T20:31:12+00:00

There is a plan to build the kernel with -Wimplicit-fallthrough and
this place in the code produced a warning (W=1).

This commit remove the following warning:

  kernel/trace/blktrace.c:725:9: warning: this statement may fall through [-Wimplicit-fallthrough=]

Signed-off-by: Mathieu Malaterre 
Signed-off-by: Jens Axboe

blkcg: remove bio->bi_css and instead use bio->bi_blkg

2018-12-08T05:26:37+00:00

Prior patches ensured that any bio that interacts with a request_queue
is properly associated with a blkg. This makes bio->bi_css unnecessary
as blkg maintains a reference to blkcg already.

This removes the bio field bi_css and transfers corresponding uses to
access via bi_blkg.

Signed-off-by: Dennis Zhou 
Reviewed-by: Josef Bacik 
Acked-by: Tejun Heo 
Signed-off-by: Jens Axboe

blkcg: revert blkcg cleanups series

2018-11-02T01:59:53+00:00

This reverts a series committed earlier due to null pointer exception
bug report in [1]. It seems there are edge case interactions that I did
not consider and will need some time to understand what causes the
adverse interactions.

The original series can be found in [2] with a follow up series in [3].

[1] https://www.spinics.net/lists/cgroups/msg20719.html
[2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/
[3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/

This reverts the following commits:
d459d853c2ed, b2c3fa546705, 101246ec02b5, b3b9f24f5fcc, e2b0989954ae,
f0fcb3ec89f3, c839e7a03f92, bdc2491708c4, 74b7c02a9bc1, 5bf9a1f3b4ef,
a7b39b4e961c, 07b05bcc3213, 49f4c2dc2b50, 27e6fa996c53

Signed-off-by: Dennis Zhou 
Signed-off-by: Jens Axboe

blkcg: remove bio->bi_css and instead use bio->bi_blkg

2018-09-22T02:29:13+00:00

Prior patches ensured that all bios are now associated with some blkg.
This now makes bio->bi_css unnecessary as blkg maintains a reference to
the blkcg already.

This patch removes the field bi_css and transfers corresponding uses to
access via bi_blkg.

Signed-off-by: Dennis Zhou 
Reviewed-by: Josef Bacik 
Acked-by: Tejun Heo 
Signed-off-by: Jens Axboe