LinuxLists.cc - [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers

2023-10-02 08:58:09

Subject: [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers

From: Joel Granados <[email protected]>

What?
These commits remove the sentinel element (last empty element) from the
sysctl arrays of all the files under the "drivers/" directory that use a
sysctl array for registration. The merging of the preparation patches
(in https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/)
to mainline allows us to just remove sentinel elements without changing
behavior (more info here [1]).

These commits are part of a bigger set (here
https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4)
that remove the ctl_table sentinel. Make the review process easier by
chunking the commits into manageable pieces. Each chunk can be reviewed
separately without noise from parallel sets.

Now that the architecture chunk has been mostly reviewed [6], we send
the "drivers/" directory. Once this one is done, it will be follwed by
"fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove
the unneeded check for ->procname == NULL.

Why?
By removing the sysctl sentinel elements we avoid kernel bloat as
ctl_table arrays get moved out of kernel/sysctl.c into their own
respective subsystems. This move was started long ago to avoid merge
conflicts; the sentinel removal bit came after Mathew Wilcox suggested
it to avoid bloating the kernel by one element as arrays moved out. This
patchset will reduce the overall build time size of the kernel and run
time memory bloat by about ~64 bytes per declared ctl_table array. I
have consolidated some links that shed light on the history of this
effort [2].

Testing:
* Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh)
* Ran this through 0-day with no errors or warnings

Size saving after removing all sentinels:
These are the bytes that we save after removing all the sentinels
(this plus all the other chunks). I included them to get an idea of
how much memory we are talking about.
* bloat-o-meter:
- The "yesall" configuration results save 9158 bytes
https://lore.kernel.org/all/[email protected]/
- The "tiny" config + CONFIG_SYSCTL save 1215 bytes
https://lore.kernel.org/all/[email protected]/
* memory usage:
In memory savings are measured to be 7296 bytes. (here is how to
measure [3])

Size saving after this patchset:
* bloat-o-meter
- The "yesall" config saves 2432 bytes [4]
- The "tiny" config saves 64 bytes [5]
* memory usage:
In this case there were no bytes saved because I do not have any
of the drivers in the patch. To measure it comment the printk in
`new_dir` and uncomment the if conditional in `new_links` [3].

---
Changes in v2:
- Left the dangling comma in the ctl_table arrays.
- Link to v1: https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca9f9@samsung.com

Comments/feedback greatly appreciated

Best

Joel

[1]
We are able to remove a sentinel table without behavioral change by
introducing a table_size argument in the same place where procname is
checked for NULL. The idea is for it to keep stopping when it hits
->procname == NULL, while the sentinel is still present. And when the
sentinel is removed, it will stop on the table_size. You can go to
(https://lore.kernel.org/all/[email protected]/)
for more information.

[2]
Links Related to the ctl_table sentinel removal:
* Good summary from Luis sent with the "pull request" for the
preparation patches.
https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/
* Another very good summary from Luis.
https://lore.kernel.org/all/[email protected]/
* This is a patch set that replaces register_sysctl_table with register_sysctl
https://lore.kernel.org/all/[email protected]/
* Patch set to deprecate register_sysctl_paths()
https://lore.kernel.org/all/[email protected]/
* Here there is an explicit expectation for the removal of the sentinel element.
https://lore.kernel.org/all/[email protected]
* The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
https://lore.kernel.org/all/[email protected]

[3]
To measure the in memory savings apply this on top of this patchset.

"
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index c88854df0b62..e0073a627bac 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
table[0].procname = new_name;
table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
init_header(&new->header, set->dir.header.root, set, node, table, 1);
+ // Counts additional sentinel used for each new dir.
+ printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));

return new;
}
@@ -1199,6 +1201,9 @@ static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_
link_name += len;
link++;
}
+ // Counts additional sentinel used for each new registration
+ //if ((head->ctl_table + head->ctl_table_size)->procname)
+ printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
init_header(links, dir->header.root, dir->header.set, node, link_table,
head->ctl_table_size);
links->nreg = nr_entries;
"
and then run the following bash script in the kernel:

accum=0
for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
echo $n
accum=$(calc "$accum + $n")
done
echo $accum

[4]
add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
Function old new delta
xpc_sys_xpc_hb 192 128 -64
xpc_sys_xpc 128 64 -64
vrf_table 128 64 -64
ucma_ctl_table 128 64 -64
tty_table 192 128 -64
sg_sysctls 128 64 -64
scsi_table 128 64 -64
random_table 448 384 -64
raid_table 192 128 -64
oa_table 192 128 -64
mac_hid_files 256 192 -64
iwcm_ctl_table 128 64 -64
ipmi_table 128 64 -64
hv_ctl_table 128 64 -64
hpet_table 128 64 -64
firmware_config_table 192 128 -64
cdrom_table 448 384 -64
balloon_table 128 64 -64
parport_sysctl_template 912 720 -192
parport_default_sysctl_table 584 136 -448
parport_device_sysctl_template 776 136 -640
Total: Before=429940038, After=429937606, chg -0.00%

[5]
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-64 (-64)
Function old new delta
random_table 448 384 -64
Total: Before=1885527, After=1885463, chg -0.00%

[6] https://lore.kernel.org/all/20230913-jag-sysctl_remove_empty_elem_arch-v2-0-d1bd13a29bae@samsung.com/

Signed-off-by: Joel Granados <[email protected]>

To: Luis Chamberlain <[email protected]>
To: [email protected]
To: [email protected]
To: Kees Cook <[email protected]>
To: Phillip Potter <[email protected]>
To: Clemens Ladisch <[email protected]>
To: Arnd Bergmann <[email protected]>
To: Greg Kroah-Hartman <[email protected]>
To: Juergen Gross <[email protected]>
To: Stefano Stabellini <[email protected]>
To: Oleksandr Tyshchenko <[email protected]>
To: Jiri Slaby <[email protected]>
To: "James E.J. Bottomley" <[email protected]>
To: "Martin K. Petersen" <[email protected]>
To: Doug Gilbert <[email protected]>
To: Sudip Mukherjee <[email protected]>
To: Jason Gunthorpe <[email protected]>
To: Leon Romanovsky <[email protected]>
To: Corey Minyard <[email protected]>
To: Theodore Ts'o <[email protected]>
To: "Jason A. Donenfeld" <[email protected]>
To: David Ahern <[email protected]>
To: "David S. Miller" <[email protected]>
To: Eric Dumazet <[email protected]>
To: Jakub Kicinski <[email protected]>
To: Paolo Abeni <[email protected]>
To: Robin Holt <[email protected]>
To: Steve Wahl <[email protected]>
To: Russ Weight <[email protected]>
To: "Rafael J. Wysocki" <[email protected]>
To: Song Liu <[email protected]>
To: "K. Y. Srinivasan" <[email protected]>
To: Haiyang Zhang <[email protected]>
To: Wei Liu <[email protected]>
To: Dexuan Cui <[email protected]>
To: Jani Nikula <[email protected]>
To: Joonas Lahtinen <[email protected]>
To: Rodrigo Vivi <[email protected]>
To: Tvrtko Ursulin <[email protected]>
To: David Airlie <[email protected]>
To: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]

---

---
Joel Granados (15):
cdrom: Remove now superfluous sentinel element from ctl_table array
hpet: Remove now superfluous sentinel element from ctl_table array
xen: Remove now superfluous sentinel element from ctl_table array
tty: Remove now superfluous sentinel element from ctl_table array
scsi: Remove now superfluous sentinel element from ctl_table array
parport: Remove the now superfluous sentinel element from ctl_table array
macintosh: Remove the now superfluous sentinel element from ctl_table array
infiniband: Remove the now superfluous sentinel element from ctl_table array
char-misc: Remove the now superfluous sentinel element from ctl_table array
vrf: Remove the now superfluous sentinel element from ctl_table array
sgi-xp: Remove the now superfluous sentinel element from ctl_table array
fw loader: Remove the now superfluous sentinel element from ctl_table array
raid: Remove now superfluous sentinel element from ctl_table array
Drivers: hv: Remove now superfluous sentinel element from ctl_table array
intel drm: Remove now superfluous sentinel element from ctl_table array

drivers/base/firmware_loader/fallback_table.c | 1 -
drivers/cdrom/cdrom.c | 1 -
drivers/char/hpet.c | 1 -
drivers/char/ipmi/ipmi_poweroff.c | 1 -
drivers/char/random.c | 1 -
drivers/gpu/drm/i915/i915_perf.c | 1 -
drivers/hv/hv_common.c | 1 -
drivers/infiniband/core/iwcm.c | 1 -
drivers/infiniband/core/ucma.c | 1 -
drivers/macintosh/mac_hid.c | 1 -
drivers/md/md.c | 1 -
drivers/misc/sgi-xp/xpc_main.c | 2 --
drivers/net/vrf.c | 1 -
drivers/parport/procfs.c | 28 +++++++++++----------------
drivers/scsi/scsi_sysctl.c | 1 -
drivers/scsi/sg.c | 1 -
drivers/tty/tty_io.c | 1 -
drivers/xen/balloon.c | 1 -
18 files changed, 11 insertions(+), 35 deletions(-)
---
base-commit: 0e945134b680040b8613e962f586d91b6d40292d
change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c

Best regards,
--
Joel Granados <[email protected]>

2023-10-02 08:58:19

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 05/15] scsi: Remove now superfluous sentinel element from ctl_table array

2023-10-02 08:58:23

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 06/15] parport: Remove the now superfluous sentinel element from ctl_table array

From: Joel Granados <[email protected]>

This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/)

Remove the unneeded ctl_tables that were used to register intermediate
parport directories; only the path is needed at this point. From
parport_device_sysctl_table we removed: devices_root_dir, port_dir,
parport_dir and dev_dir. From parport_default_sysctl_table we removed:
default_dir, parport_dir and dev_dir. Reduce the size by one of the
ctl_table arrays that were not removed

Assign different sizes to the vars array in parport_sysctl_table
depending on CONFIG_PARPORT_1284; this is necessary now that the sysctl
register function uses ARRAY_SIZE to calculate the elements within.
Remove the sentinel element from parport_sysctl_template,
parport_device_sysctl_table and parport_default_sysctl_table.

Signed-off-by: Joel Granados <[email protected]>
---
drivers/parport/procfs.c | 28 +++++++++++-----------------
1 file changed, 11 insertions(+), 17 deletions(-)

diff --git a/drivers/parport/procfs.c b/drivers/parport/procfs.c
index 4e5b972c3e26..532d5cbbd344 100644
--- a/drivers/parport/procfs.c
+++ b/drivers/parport/procfs.c
@@ -259,8 +259,12 @@ PARPORT_MAX_SPINTIME_VALUE;
struct parport_sysctl_table {
struct ctl_table_header *port_header;
struct ctl_table_header *devices_header;
- struct ctl_table vars[12];
- struct ctl_table device_dir[2];
+#ifdef CONFIG_PARPORT_1284
+ struct ctl_table vars[10];
+#else
+ struct ctl_table vars[5];
+#endif /* IEEE 1284 support */
+ struct ctl_table device_dir[1];
};

static const struct parport_sysctl_table parport_sysctl_template = {
@@ -341,7 +345,6 @@ static const struct parport_sysctl_table parport_sysctl_template = {
.proc_handler = do_autoprobe
},
#endif /* IEEE 1284 support */
- {}
},
{
{
@@ -351,19 +354,14 @@ static const struct parport_sysctl_table parport_sysctl_template = {
.mode = 0444,
.proc_handler = do_active_device
},
- {}
},
};

struct parport_device_sysctl_table
{
struct ctl_table_header *sysctl_header;
- struct ctl_table vars[2];
- struct ctl_table device_dir[2];
- struct ctl_table devices_root_dir[2];
- struct ctl_table port_dir[2];
- struct ctl_table parport_dir[2];
- struct ctl_table dev_dir[2];
+ struct ctl_table vars[1];
+ struct ctl_table device_dir[1];
};

static const struct parport_device_sysctl_table
@@ -379,7 +377,6 @@ parport_device_sysctl_template = {
.extra1 = (void*) &parport_min_timeslice_value,
.extra2 = (void*) &parport_max_timeslice_value
},
- {}
},
{
{
@@ -388,17 +385,13 @@ parport_device_sysctl_template = {
.maxlen = 0,
.mode = 0555,
},
- {}
}
};

struct parport_default_sysctl_table
{
struct ctl_table_header *sysctl_header;
- struct ctl_table vars[3];
- struct ctl_table default_dir[2];
- struct ctl_table parport_dir[2];
- struct ctl_table dev_dir[2];
+ struct ctl_table vars[2];
};

static struct parport_default_sysctl_table
@@ -423,7 +416,6 @@ parport_default_sysctl_table = {
.extra1 = (void*) &parport_min_spintime_value,
.extra2 = (void*) &parport_max_spintime_value
},
- {}
}
};

@@ -443,7 +435,9 @@ int parport_proc_register(struct parport *port)
t->vars[0].data = &port->spintime;
for (i = 0; i < 5; i++) {
t->vars[i].extra1 = port;
+#ifdef CONFIG_PARPORT_1284
t->vars[5 + i].extra2 = &port->probe_info[i];
+#endif /* IEEE 1284 support */
}

port_name_len = strnlen(port->name, PARPORT_NAME_MAX_LEN);

--
2.30.2

2023-10-02 08:59:46

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 04/15] tty: Remove now superfluous sentinel element from ctl_table array

2023-10-02 09:12:22

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 09/15] char-misc: Remove the now superfluous sentinel element from ctl_table array

2023-10-02 09:14:18

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 03/15] xen: Remove now superfluous sentinel element from ctl_table array

2023-10-02 09:14:30

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 07/15] macintosh: Remove the now superfluous sentinel element from ctl_table array

2023-10-02 09:14:32

by Joel Granados via B4 Relay

[permalink] [raw]

Subject: [PATCH v2 08/15] infiniband: Remove the now superfluous sentinel element from ctl_table array

2023-10-02 09:29:39

by Jiri Slaby

[permalink] [raw]

Subject: Re: [PATCH v2 04/15] tty: Remove now superfluous sentinel element from ctl_table array

On 02. 10. 23, 10:55, Joel Granados via B4 Relay wrote:
> From: Joel Granados <[email protected]>
>
> This commit comes at the tail end of a greater effort to remove the
> empty elements at the end of the ctl_table arrays (sentinels) which
> will reduce the overall build time size of the kernel and run time
> memory bloat by ~64 bytes per sentinel (further information Link :
> https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/)
>
> Remove sentinel from tty_table
>
> Signed-off-by: Joel Granados <[email protected]>

Reviewed-by: Jiri Slaby <[email protected]>

thanks,
--
js
suse labs

2023-10-02 20:52:45

by Christophe Leroy

[permalink] [raw]

Subject: Re: [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers

Le 02/10/2023 à 10:55, Joel Granados via B4 Relay a écrit :
> From: Joel Granados <[email protected]>
>
> What?
> These commits remove the sentinel element (last empty element) from the
> sysctl arrays of all the files under the "drivers/" directory that use a
> sysctl array for registration. The merging of the preparation patches
> (in https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/)
> to mainline allows us to just remove sentinel elements without changing
> behavior (more info here [1]).
>
> These commits are part of a bigger set (here
> https://github.com/Joelgranados/linux/tree/tag/sysctl_remove_empty_elem_V4)
> that remove the ctl_table sentinel. Make the review process easier by
> chunking the commits into manageable pieces. Each chunk can be reviewed
> separately without noise from parallel sets.
>
> Now that the architecture chunk has been mostly reviewed [6], we send
> the "drivers/" directory. Once this one is done, it will be follwed by
> "fs/*", "kernel/*", "net/*" and miscellaneous. The final set will remove
> the unneeded check for ->procname == NULL.
>
> Why?
> By removing the sysctl sentinel elements we avoid kernel bloat as
> ctl_table arrays get moved out of kernel/sysctl.c into their own
> respective subsystems. This move was started long ago to avoid merge
> conflicts; the sentinel removal bit came after Mathew Wilcox suggested
> it to avoid bloating the kernel by one element as arrays moved out. This
> patchset will reduce the overall build time size of the kernel and run
> time memory bloat by about ~64 bytes per declared ctl_table array. I
> have consolidated some links that shed light on the history of this
> effort [2].
>
> Testing:
> * Ran sysctl selftests (./tools/testing/selftests/sysctl/sysctl.sh)
> * Ran this through 0-day with no errors or warnings
>
> Size saving after removing all sentinels:
> These are the bytes that we save after removing all the sentinels
> (this plus all the other chunks). I included them to get an idea of
> how much memory we are talking about.
> * bloat-o-meter:
> - The "yesall" configuration results save 9158 bytes
> https://lore.kernel.org/all/[email protected]/
> - The "tiny" config + CONFIG_SYSCTL save 1215 bytes
> https://lore.kernel.org/all/[email protected]/
> * memory usage:
> In memory savings are measured to be 7296 bytes. (here is how to
> measure [3])
>
> Size saving after this patchset:
> * bloat-o-meter
> - The "yesall" config saves 2432 bytes [4]
> - The "tiny" config saves 64 bytes [5]
> * memory usage:
> In this case there were no bytes saved because I do not have any
> of the drivers in the patch. To measure it comment the printk in
> `new_dir` and uncomment the if conditional in `new_links` [3].
>
> ---
> Changes in v2:
> - Left the dangling comma in the ctl_table arrays.
> - Link to v1: https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca9f9@samsung.com
>
> Comments/feedback greatly appreciated

Same problem on powerpc CI tests, all boot target failed, most of them
with similar OOPS, see
https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20231002-jag-sysctl_remove_empty_elem_drivers-v2-15-02dd0d46f71e@samsung.com/

What is strange is that I pushed your series into my github account, and
got no failure, see https://github.com/chleroy/linux/actions/runs/6378951278

Christophe

>
> Best
>
> Joel
>
> [1]
> We are able to remove a sentinel table without behavioral change by
> introducing a table_size argument in the same place where procname is
> checked for NULL. The idea is for it to keep stopping when it hits
> ->procname == NULL, while the sentinel is still present. And when the
> sentinel is removed, it will stop on the table_size. You can go to
> (https://lore.kernel.org/all/[email protected]/)
> for more information.
>
> [2]
> Links Related to the ctl_table sentinel removal:
> * Good summary from Luis sent with the "pull request" for the
> preparation patches.
> https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/
> * Another very good summary from Luis.
> https://lore.kernel.org/all/[email protected]/
> * This is a patch set that replaces register_sysctl_table with register_sysctl
> https://lore.kernel.org/all/[email protected]/
> * Patch set to deprecate register_sysctl_paths()
> https://lore.kernel.org/all/[email protected]/
> * Here there is an explicit expectation for the removal of the sentinel element.
> https://lore.kernel.org/all/[email protected]
> * The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
> https://lore.kernel.org/all/[email protected]
>
> [3]
> To measure the in memory savings apply this on top of this patchset.
>
> "
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index c88854df0b62..e0073a627bac 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
> table[0].procname = new_name;
> table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
> init_header(&new->header, set->dir.header.root, set, node, table, 1);
> + // Counts additional sentinel used for each new dir.
> + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
>
> return new;
> }
> @@ -1199,6 +1201,9 @@ static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_
> link_name += len;
> link++;
> }
> + // Counts additional sentinel used for each new registration
> + //if ((head->ctl_table + head->ctl_table_size)->procname)
> + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
> init_header(links, dir->header.root, dir->header.set, node, link_table,
> head->ctl_table_size);
> links->nreg = nr_entries;
> "
> and then run the following bash script in the kernel:
>
> accum=0
> for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
> echo $n
> accum=$(calc "$accum + $n")
> done
> echo $accum
>
> [4]
> add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
> Function old new delta
> xpc_sys_xpc_hb 192 128 -64
> xpc_sys_xpc 128 64 -64
> vrf_table 128 64 -64
> ucma_ctl_table 128 64 -64
> tty_table 192 128 -64
> sg_sysctls 128 64 -64
> scsi_table 128 64 -64
> random_table 448 384 -64
> raid_table 192 128 -64
> oa_table 192 128 -64
> mac_hid_files 256 192 -64
> iwcm_ctl_table 128 64 -64
> ipmi_table 128 64 -64
> hv_ctl_table 128 64 -64
> hpet_table 128 64 -64
> firmware_config_table 192 128 -64
> cdrom_table 448 384 -64
> balloon_table 128 64 -64
> parport_sysctl_template 912 720 -192
> parport_default_sysctl_table 584 136 -448
> parport_device_sysctl_template 776 136 -640
> Total: Before=429940038, After=429937606, chg -0.00%
>
> [5]
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-64 (-64)
> Function old new delta
> random_table 448 384 -64
> Total: Before=1885527, After=1885463, chg -0.00%
>
> [6] https://lore.kernel.org/all/20230913-jag-sysctl_remove_empty_elem_arch-v2-0-d1bd13a29bae@samsung.com/
>
> Signed-off-by: Joel Granados <[email protected]>
>
> To: Luis Chamberlain <[email protected]>
> To: [email protected]
> To: [email protected]
> To: Kees Cook <[email protected]>
> To: Phillip Potter <[email protected]>
> To: Clemens Ladisch <[email protected]>
> To: Arnd Bergmann <[email protected]>
> To: Greg Kroah-Hartman <[email protected]>
> To: Juergen Gross <[email protected]>
> To: Stefano Stabellini <[email protected]>
> To: Oleksandr Tyshchenko <[email protected]>
> To: Jiri Slaby <[email protected]>
> To: "James E.J. Bottomley" <[email protected]>
> To: "Martin K. Petersen" <[email protected]>
> To: Doug Gilbert <[email protected]>
> To: Sudip Mukherjee <[email protected]>
> To: Jason Gunthorpe <[email protected]>
> To: Leon Romanovsky <[email protected]>
> To: Corey Minyard <[email protected]>
> To: Theodore Ts'o <[email protected]>
> To: "Jason A. Donenfeld" <[email protected]>
> To: David Ahern <[email protected]>
> To: "David S. Miller" <[email protected]>
> To: Eric Dumazet <[email protected]>
> To: Jakub Kicinski <[email protected]>
> To: Paolo Abeni <[email protected]>
> To: Robin Holt <[email protected]>
> To: Steve Wahl <[email protected]>
> To: Russ Weight <[email protected]>
> To: "Rafael J. Wysocki" <[email protected]>
> To: Song Liu <[email protected]>
> To: "K. Y. Srinivasan" <[email protected]>
> To: Haiyang Zhang <[email protected]>
> To: Wei Liu <[email protected]>
> To: Dexuan Cui <[email protected]>
> To: Jani Nikula <[email protected]>
> To: Joonas Lahtinen <[email protected]>
> To: Rodrigo Vivi <[email protected]>
> To: Tvrtko Ursulin <[email protected]>
> To: David Airlie <[email protected]>
> To: Daniel Vetter <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
>
> ---
>
> ---
> Joel Granados (15):
> cdrom: Remove now superfluous sentinel element from ctl_table array
> hpet: Remove now superfluous sentinel element from ctl_table array
> xen: Remove now superfluous sentinel element from ctl_table array
> tty: Remove now superfluous sentinel element from ctl_table array
> scsi: Remove now superfluous sentinel element from ctl_table array
> parport: Remove the now superfluous sentinel element from ctl_table array
> macintosh: Remove the now superfluous sentinel element from ctl_table array
> infiniband: Remove the now superfluous sentinel element from ctl_table array
> char-misc: Remove the now superfluous sentinel element from ctl_table array
> vrf: Remove the now superfluous sentinel element from ctl_table array
> sgi-xp: Remove the now superfluous sentinel element from ctl_table array
> fw loader: Remove the now superfluous sentinel element from ctl_table array
> raid: Remove now superfluous sentinel element from ctl_table array
> Drivers: hv: Remove now superfluous sentinel element from ctl_table array
> intel drm: Remove now superfluous sentinel element from ctl_table array
>
> drivers/base/firmware_loader/fallback_table.c | 1 -
> drivers/cdrom/cdrom.c | 1 -
> drivers/char/hpet.c | 1 -
> drivers/char/ipmi/ipmi_poweroff.c | 1 -
> drivers/char/random.c | 1 -
> drivers/gpu/drm/i915/i915_perf.c | 1 -
> drivers/hv/hv_common.c | 1 -
> drivers/infiniband/core/iwcm.c | 1 -
> drivers/infiniband/core/ucma.c | 1 -
> drivers/macintosh/mac_hid.c | 1 -
> drivers/md/md.c | 1 -
> drivers/misc/sgi-xp/xpc_main.c | 2 --
> drivers/net/vrf.c | 1 -
> drivers/parport/procfs.c | 28 +++++++++++----------------
> drivers/scsi/scsi_sysctl.c | 1 -
> drivers/scsi/sg.c | 1 -
> drivers/tty/tty_io.c | 1 -
> drivers/xen/balloon.c | 1 -
> 18 files changed, 11 insertions(+), 35 deletions(-)
> ---
> base-commit: 0e945134b680040b8613e962f586d91b6d40292d
> change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c
>
> Best regards,

2023-10-03 08:46:16

by Joel Granados

[permalink] [raw]

Subject: Re: [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers

On Mon, Oct 02, 2023 at 12:27:18PM +0000, Christophe Leroy wrote:
>
>
> Le 02/10/2023 ? 10:55, Joel Granados via B4 Relay a ?crit?:
> > From: Joel Granados <[email protected]>
> >
<--- snip --->
> > - The "yesall" config saves 2432 bytes [4]
> > - The "tiny" config saves 64 bytes [5]
> > * memory usage:
> > In this case there were no bytes saved because I do not have any
> > of the drivers in the patch. To measure it comment the printk in
> > `new_dir` and uncomment the if conditional in `new_links` [3].
> >
> > ---
> > Changes in v2:
> > - Left the dangling comma in the ctl_table arrays.
> > - Link to v1: https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca9f9@samsung.com
> >
> > Comments/feedback greatly appreciated
>
> Same problem on powerpc CI tests, all boot target failed, most of them
> with similar OOPS, see
> https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20231002-jag-sysctl_remove_empty_elem_drivers-v2-15-02dd0d46f71e@samsung.com/
I found the culprit!. Here you are rebasing on top of v6.5.0-rc6 "INFO:
Looking for kernel version: 6.5.0-rc6-gbf2ac4d7d596". The error makes
sense becuase in that version we have not introduced the stopping
criteria based on the ctl_table array size, so the loop continues
looking for an empty sentinel past valid memory (and does not find it).
The ctl_table check catches it but then fails to do a proper error
because we have already tried to access invalid memory. The solution
here is to make sure to rebase in on top of the latest rc in v6.6.

>
> What is strange is that I pushed your series into my github account, and
> got no failure, see https://github.com/chleroy/linux/actions/runs/6378951278
And here it works because you use the latest rc : "INFO: Looking for
kernel version: 6.6.0-rc3-g23d4b5db743c"

>
> Christophe
>
> >
> > Best
> >
> > Joel
> >
> > [1]
> > We are able to remove a sentinel table without behavioral change by
> > introducing a table_size argument in the same place where procname is
> > checked for NULL. The idea is for it to keep stopping when it hits
> > ->procname == NULL, while the sentinel is still present. And when the
> > sentinel is removed, it will stop on the table_size. You can go to
> > (https://lore.kernel.org/all/[email protected]/)
> > for more information.
> >
> > [2]
> > Links Related to the ctl_table sentinel removal:
> > * Good summary from Luis sent with the "pull request" for the
> > preparation patches.
> > https://lore.kernel.org/all/ZO5Yx5JFogGi%[email protected]/
> > * Another very good summary from Luis.
> > https://lore.kernel.org/all/[email protected]/
> > * This is a patch set that replaces register_sysctl_table with register_sysctl
> > https://lore.kernel.org/all/[email protected]/
> > * Patch set to deprecate register_sysctl_paths()
> > https://lore.kernel.org/all/[email protected]/
> > * Here there is an explicit expectation for the removal of the sentinel element.
> > https://lore.kernel.org/all/[email protected]
> > * The "ARRAY_SIZE" approach was mentioned (proposed?) in this thread
> > https://lore.kernel.org/all/[email protected]
> >
> > [3]
> > To measure the in memory savings apply this on top of this patchset.
> >
> > "
> > diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> > index c88854df0b62..e0073a627bac 100644
> > --- a/fs/proc/proc_sysctl.c
> > +++ b/fs/proc/proc_sysctl.c
> > @@ -976,6 +976,8 @@ static struct ctl_dir *new_dir(struct ctl_table_set *set,
> > table[0].procname = new_name;
> > table[0].mode = S_IFDIR|S_IRUGO|S_IXUGO;
> > init_header(&new->header, set->dir.header.root, set, node, table, 1);
> > + // Counts additional sentinel used for each new dir.
> > + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
> >
> > return new;
> > }
> > @@ -1199,6 +1201,9 @@ static struct ctl_table_header *new_links(struct ctl_dir *dir, struct ctl_table_
> > link_name += len;
> > link++;
> > }
> > + // Counts additional sentinel used for each new registration
> > + //if ((head->ctl_table + head->ctl_table_size)->procname)
> > + printk("%ld sysctl saved mem kzalloc \n", sizeof(struct ctl_table));
> > init_header(links, dir->header.root, dir->header.set, node, link_table,
> > head->ctl_table_size);
> > links->nreg = nr_entries;
> > "
> > and then run the following bash script in the kernel:
> >
> > accum=0
> > for n in $(dmesg | grep kzalloc | awk '{print $3}') ; do
> > echo $n
> > accum=$(calc "$accum + $n")
> > done
> > echo $accum
> >
> > [4]
> > add/remove: 0/0 grow/shrink: 0/21 up/down: 0/-2432 (-2432)
> > Function old new delta
> > xpc_sys_xpc_hb 192 128 -64
> > xpc_sys_xpc 128 64 -64
> > vrf_table 128 64 -64
> > ucma_ctl_table 128 64 -64
> > tty_table 192 128 -64
> > sg_sysctls 128 64 -64
> > scsi_table 128 64 -64
> > random_table 448 384 -64
> > raid_table 192 128 -64
> > oa_table 192 128 -64
> > mac_hid_files 256 192 -64
> > iwcm_ctl_table 128 64 -64
> > ipmi_table 128 64 -64
> > hv_ctl_table 128 64 -64
> > hpet_table 128 64 -64
> > firmware_config_table 192 128 -64
> > cdrom_table 448 384 -64
> > balloon_table 128 64 -64
> > parport_sysctl_template 912 720 -192
> > parport_default_sysctl_table 584 136 -448
> > parport_device_sysctl_template 776 136 -640
> > Total: Before=429940038, After=429937606, chg -0.00%
> >
> > [5]
> > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-64 (-64)
> > Function old new delta
> > random_table 448 384 -64
> > Total: Before=1885527, After=1885463, chg -0.00%
> >
> > [6] https://lore.kernel.org/all/20230913-jag-sysctl_remove_empty_elem_arch-v2-0-d1bd13a29bae@samsung.com/
> >
> > Signed-off-by: Joel Granados <[email protected]>
> >
> > To: Luis Chamberlain <[email protected]>
> > To: [email protected]
> > To: [email protected]
> > To: Kees Cook <[email protected]>
> > To: Phillip Potter <[email protected]>
> > To: Clemens Ladisch <[email protected]>
> > To: Arnd Bergmann <[email protected]>
> > To: Greg Kroah-Hartman <[email protected]>
> > To: Juergen Gross <[email protected]>
> > To: Stefano Stabellini <[email protected]>
> > To: Oleksandr Tyshchenko <[email protected]>
> > To: Jiri Slaby <[email protected]>
> > To: "James E.J. Bottomley" <[email protected]>
> > To: "Martin K. Petersen" <[email protected]>
> > To: Doug Gilbert <[email protected]>
> > To: Sudip Mukherjee <[email protected]>
> > To: Jason Gunthorpe <[email protected]>
> > To: Leon Romanovsky <[email protected]>
> > To: Corey Minyard <[email protected]>
> > To: Theodore Ts'o <[email protected]>
> > To: "Jason A. Donenfeld" <[email protected]>
> > To: David Ahern <[email protected]>
> > To: "David S. Miller" <[email protected]>
> > To: Eric Dumazet <[email protected]>
> > To: Jakub Kicinski <[email protected]>
> > To: Paolo Abeni <[email protected]>
> > To: Robin Holt <[email protected]>
> > To: Steve Wahl <[email protected]>
> > To: Russ Weight <[email protected]>
> > To: "Rafael J. Wysocki" <[email protected]>
> > To: Song Liu <[email protected]>
> > To: "K. Y. Srinivasan" <[email protected]>
> > To: Haiyang Zhang <[email protected]>
> > To: Wei Liu <[email protected]>
> > To: Dexuan Cui <[email protected]>
> > To: Jani Nikula <[email protected]>
> > To: Joonas Lahtinen <[email protected]>
> > To: Rodrigo Vivi <[email protected]>
> > To: Tvrtko Ursulin <[email protected]>
> > To: David Airlie <[email protected]>
> > To: Daniel Vetter <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> > Cc: [email protected]
> >
> > ---
> >
> > ---
> > Joel Granados (15):
> > cdrom: Remove now superfluous sentinel element from ctl_table array
> > hpet: Remove now superfluous sentinel element from ctl_table array
> > xen: Remove now superfluous sentinel element from ctl_table array
> > tty: Remove now superfluous sentinel element from ctl_table array
> > scsi: Remove now superfluous sentinel element from ctl_table array
> > parport: Remove the now superfluous sentinel element from ctl_table array
> > macintosh: Remove the now superfluous sentinel element from ctl_table array
> > infiniband: Remove the now superfluous sentinel element from ctl_table array
> > char-misc: Remove the now superfluous sentinel element from ctl_table array
> > vrf: Remove the now superfluous sentinel element from ctl_table array
> > sgi-xp: Remove the now superfluous sentinel element from ctl_table array
> > fw loader: Remove the now superfluous sentinel element from ctl_table array
> > raid: Remove now superfluous sentinel element from ctl_table array
> > Drivers: hv: Remove now superfluous sentinel element from ctl_table array
> > intel drm: Remove now superfluous sentinel element from ctl_table array
> >
> > drivers/base/firmware_loader/fallback_table.c | 1 -
> > drivers/cdrom/cdrom.c | 1 -
> > drivers/char/hpet.c | 1 -
> > drivers/char/ipmi/ipmi_poweroff.c | 1 -
> > drivers/char/random.c | 1 -
> > drivers/gpu/drm/i915/i915_perf.c | 1 -
> > drivers/hv/hv_common.c | 1 -
> > drivers/infiniband/core/iwcm.c | 1 -
> > drivers/infiniband/core/ucma.c | 1 -
> > drivers/macintosh/mac_hid.c | 1 -
> > drivers/md/md.c | 1 -
> > drivers/misc/sgi-xp/xpc_main.c | 2 --
> > drivers/net/vrf.c | 1 -
> > drivers/parport/procfs.c | 28 +++++++++++----------------
> > drivers/scsi/scsi_sysctl.c | 1 -
> > drivers/scsi/sg.c | 1 -
> > drivers/tty/tty_io.c | 1 -
> > drivers/xen/balloon.c | 1 -
> > 18 files changed, 11 insertions(+), 35 deletions(-)
> > ---
> > base-commit: 0e945134b680040b8613e962f586d91b6d40292d
> > change-id: 20230927-jag-sysctl_remove_empty_elem_drivers-f034962a0d8c
> >
> > Best regards,

--

Joel Granados

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2023-10-10 22:27:13

by Luis Chamberlain

[permalink] [raw]

Subject: Re: [PATCH v2 00/15] sysctl: Remove sentinel elements from drivers

On Mon, Oct 02, 2023 at 10:55:17AM +0200, Joel Granados via B4 Relay wrote:
> Changes in v2:
> - Left the dangling comma in the ctl_table arrays.
> - Link to v1: https://lore.kernel.org/r/20230928-jag-sysctl_remove_empty_elem_drivers-v1-0-e59120fca9f9@samsung.com

Thanks! Pushed onto sysctl-next for wider testing.

Luis