Date: Tue, 4 Nov 2014 17:51:26 +0800 From: Tiwei Bie <btw@mail.ustc.edu.cn> To: mjguzik@gmail.com Cc: freebsd-hackers@freebsd.org Subject: [PATCH] Finish the task 'Embedd group table into struct ucred' Message-ID: <1415094686-39302-1-git-send-email-btw@mail.ustc.edu.cn>
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Hi, Mateusz!
I have finished the task: Embedd group table into struct ucred [1].
This is an explanation of my patch:
In crextend(), when n <= XU_NGROUPS, I did such updates directly:
cr->cr_groups = cr->cr_smallgroups;
cr->cr_agroups = XU_NGROUPS;
Because there is a check in the front of this function:
if (n <= cr->cr_agroups)
return;
So when n <= XU_NGROUPS, cr->cr_groups would never point to the memory
allocated by malloc(), and it won't need to be freed.
Following is my patch:
diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index 9b2bcd8..76d2cfc 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1864,7 +1864,8 @@ crfree(struct ucred *cr)
#ifdef MAC
mac_cred_destroy(cr);
#endif
- free(cr->cr_groups, M_CRED);
+ if (cr->cr_groups != cr->cr_smallgroups)
+ free(cr->cr_groups, M_CRED);
free(cr, M_CRED);
}
}
@@ -1976,6 +1977,12 @@ crextend(struct ucred *cr, int n)
if (n <= cr->cr_agroups)
return;
+ if (n <= XU_NGROUPS) {
+ cr->cr_groups = cr->cr_smallgroups;
+ cr->cr_agroups = XU_NGROUPS;
+ return;
+ }
+
/*
* We extend by 2 each time since we're using a power of two
* allocator until we need enough groups to fill a page.
@@ -1997,7 +2004,7 @@ crextend(struct ucred *cr, int n)
cnt = roundup2(n, PAGE_SIZE / sizeof(gid_t));
/* Free the old array. */
- if (cr->cr_groups)
+ if (cr->cr_groups && cr->cr_groups != cr->cr_smallgroups)
free(cr->cr_groups, M_CRED);
cr->cr_groups = malloc(cnt * sizeof(gid_t), M_CRED, M_WAITOK | M_ZERO);
diff --git a/sys/sys/ucred.h b/sys/sys/ucred.h
index 81e4520..a6531c4 100644
--- a/sys/sys/ucred.h
+++ b/sys/sys/ucred.h
@@ -37,6 +37,8 @@
struct loginclass;
+#define XU_NGROUPS 16
+
/*
* Credentials.
*
@@ -64,13 +66,12 @@ struct ucred {
struct auditinfo_addr cr_audit; /* Audit properties. */
gid_t *cr_groups; /* groups */
int cr_agroups; /* Available groups */
+ gid_t cr_smallgroups[XU_NGROUPS]; /* storage for small groups */
};
#define NOCRED ((struct ucred *)0) /* no credential available */
#define FSCRED ((struct ucred *)-1) /* filesystem credential */
#endif /* _KERNEL || _WANT_UCRED */
-#define XU_NGROUPS 16
-
/*
* Flags for cr_flags.
*/
--
2.1.0
[1] https://wiki.freebsd.org/JuniorJobs#Embedd_group_table_into_struct_ucred
Tiwei Bie
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