[PATCH][next] um: Malloc just enough space for fitting pid file

[PATCH][next] um: Malloc just enough space for fitting pid file

[Paulo Miguel Almeida]

umid is already generated during make_umid_init __initcall so there is
no need to allocate UMID_LEN bytes to accommodate the max possible name
for the umid segment of the filepath

This patch replaces UMID_LEN occurences in which it's redundant

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
---
 arch/um/os-Linux/umid.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
index eb523ab1e218..513a2cce38db 100644
--- a/arch/um/os-Linux/umid.c
+++ b/arch/um/os-Linux/umid.c
@@ -212,7 +212,7 @@ static void __init create_pid_file(void)
 	char pid[sizeof("nnnnnnnnn")], *file;
 	int fd, n;
 
-	n = strlen(uml_dir) + UMID_LEN + sizeof("/pid");
+	n = strlen(uml_dir) + strlen(umid) + sizeof("/pid");
 	file = malloc(n);
 	if (!file)
 		return;
@@ -394,7 +394,7 @@ static void remove_umid_dir(void)
 {
 	char *dir, err;
 
-	dir = malloc(strlen(uml_dir) + UMID_LEN + 1);
+	dir = malloc(strlen(uml_dir) + strlen(umid) + 1);
 	if (!dir)
 		return;
 
-- 
2.47.0

Re: [PATCH][next] um: Malloc just enough space for fitting pid file

[Johannes Berg]

On Sat, 2024-10-26 at 16:46 +1300, Paulo Miguel Almeida wrote:
> umid is already generated during make_umid_init __initcall so there is
> no need to allocate UMID_LEN bytes to accommodate the max possible name
> for the umid segment of the filepath
> 
> This patch replaces UMID_LEN occurences in which it's redundant

OK, I guess that's maybe all true, but can you say _why_ in the commit
log?

johannes

Re: [PATCH][next] um: Malloc just enough space for fitting pid file

[Paulo Miguel Almeida]

On Sat, Oct 26, 2024 at 09:44:53AM +0200, Johannes Berg wrote:

Hi!

> On Sat, 2024-10-26 at 16:46 +1300, Paulo Miguel Almeida wrote:
> > umid is already generated during make_umid_init __initcall so there is
> > no need to allocate UMID_LEN bytes to accommodate the max possible name
> > for the umid segment of the filepath
> > 
> > This patch replaces UMID_LEN occurences in which it's redundant
> 
> OK, I guess that's maybe all true, but can you say _why_ in the commit
> log?
> 
> johannes
> 

thanks for taking the time to review this patch. :-)

when I said that "umid is already generated during make_umid_init
__initcall", from my humble point of view, I was explaining the 'why'
using UMID_LEN for calculation buffer sizes was redundant. Then again,
once we know the size of char* umid, we can use strlen(umid) instead.

I'm happy to amend the commit message to a better one but I'm not
sure if I got 100% what I'm missing.

- Paulo

Re: [PATCH][next] um: Malloc just enough space for fitting pid file

[Johannes Berg]

On Sat, 2024-10-26 at 20:59 +1300, Paulo Miguel Almeida wrote:
> 
> when I said that "umid is already generated during make_umid_init
> __initcall", from my humble point of view, I was explaining the 'why'
> using UMID_LEN for calculation buffer sizes was redundant. Then again,
> once we know the size of char* umid, we can use strlen(umid) instead.

That's not "why am I changing it" though, that's "why does it work".

The only reasonable explanation I could come up with is that you're
trying to save memory ... but why go to the trouble for a function
that's called exactly once?

johannes