2022-11-08 13:03:39

by Rong Tao

Subject: [PATCH] tools/vm/slabinfo: indicates the cause of the EACCES error

From: Rong Tao <[email protected]>

If you don't run slabinfo with a superuser, return 0 when read_slab_dir()
reads get_obj_and_str("slabs", &t), because fopen() fails (sometimes
EACCES), causing slabcache() to return directly, without any error during
this time, we should tell the user about the EACCES problem instead of
running successfully($?=0) without any error printing.

For example:
$ ./slabinfo
Permission denied, Try using superuser <== What this submission did
$ sudo ./slabinfo
Name Objects Objsize Space Slabs/Part/Cpu O/S O %Fr %Ef Flg
Acpi-Namespace 5950 48 286.7K 65/0/5 85 0 0 99
Acpi-Operand 13664 72 999.4K 231/0/13 56 0 0 98
...

Signed-off-by: Rong Tao <[email protected]>
---
tools/vm/slabinfo.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
index 0fffaeedee76..cfaeaea71042 100644
--- a/tools/vm/slabinfo.c
+++ b/tools/vm/slabinfo.c
@@ -157,9 +157,11 @@ static unsigned long read_obj(const char *name)
{
FILE *f = fopen(name, "r");

- if (!f)
+ if (!f) {
buffer[0] = 0;
- else {
+ if (errno == EACCES)
+ fatal("%s, Try using superuser\n", strerror(errno));
+ } else {
if (!fgets(buffer, sizeof(buffer), f))
buffer[0] = 0;
fclose(f);
--
2.31.1

2022-11-10 10:00:07

by Vlastimil Babka

Subject: Re: [PATCH] tools/vm/slabinfo: indicates the cause of the EACCES error

On 11/8/22 13:47, Rong Tao wrote:
> From: Rong Tao <[email protected]>
>
> If you don't run slabinfo with a superuser, return 0 when read_slab_dir()
> reads get_obj_and_str("slabs", &t), because fopen() fails (sometimes
> EACCES), causing slabcache() to return directly, without any error during
> this time, we should tell the user about the EACCES problem instead of
> running successfully($?=0) without any error printing.
>
> For example:
> $ ./slabinfo
> Permission denied, Try using superuser <== What this submission did
> $ sudo ./slabinfo
> Name Objects Objsize Space Slabs/Part/Cpu O/S O %Fr %Ef Flg
> Acpi-Namespace 5950 48 286.7K 65/0/5 85 0 0 99
> Acpi-Operand 13664 72 999.4K 231/0/13 56 0 0 98
> ...
>
> Signed-off-by: Rong Tao <[email protected]>

Thanks, added to slab.git slab/for-6.2/tools

> ---
> tools/vm/slabinfo.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/vm/slabinfo.c b/tools/vm/slabinfo.c
> index 0fffaeedee76..cfaeaea71042 100644
> --- a/tools/vm/slabinfo.c
> +++ b/tools/vm/slabinfo.c
> @@ -157,9 +157,11 @@ static unsigned long read_obj(const char *name)
> {
> FILE *f = fopen(name, "r");
>
> - if (!f)
> + if (!f) {
> buffer[0] = 0;
> - else {
> + if (errno == EACCES)
> + fatal("%s, Try using superuser\n", strerror(errno));
> + } else {
> if (!fgets(buffer, sizeof(buffer), f))
> buffer[0] = 0;
> fclose(f);