Whenever there's audit context, __audit_inode_child() gets called numerous times, which can lead to high latency in scenarios that create too many sysfs/debugfs entries at once, for instance, upon device_add_disk() invocation.
# uname -r 6.17.0-rc3+ # auditctl -a always,exit -F path=/tmp -k foo # time insmod loop max_loop=1000 real 0m42.753s user 0m0.000s sys 0m42.494s # perf record -a insmod loop max_loop=1000 # perf report --stdio |grep __audit_inode_child 37.95% insmod [kernel.kallsyms] [k] __audit_inode_child __audit_inode_child() searches for both the parent and the child in two different loops that iterate over the same list. This process can be optimized by merging these into a single loop, without changing the function behavior or affecting the code's readability. This patch merges the two loops that walk through the list context->names_list into a single loop. This optimization resulted in around 54% performance enhancement for the benchmark. # uname -r 6.17.0-rc3+-enhanced # auditctl -a always,exit -F path=/tmp -k foo # time insmod loop max_loop=1000 real 0m19.388s user 0m0.000s sys 0m19.149s Signed-off-by: Ricardo Robaina <[email protected]> --- kernel/auditsc.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-) diff --git a/kernel/auditsc.c b/kernel/auditsc.c index d1966144bdfe..8cebc016d9eb 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -2416,41 +2416,36 @@ void __audit_inode_child(struct inode *parent, if (inode) handle_one(inode); - /* look for a parent entry first */ list_for_each_entry(n, &context->names_list, list) { - if (!n->name || - (n->type != AUDIT_TYPE_PARENT && - n->type != AUDIT_TYPE_UNKNOWN)) + /* can only match entries that have a name */ + if (!n->name) continue; - if (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev && - !audit_compare_dname_path(dname, - n->name->name, n->name_len)) { + /* look for a parent entry first */ + if (!found_parent && + (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev && + !audit_compare_dname_path(dname, n->name->name, n->name_len))) { if (n->type == AUDIT_TYPE_UNKNOWN) n->type = AUDIT_TYPE_PARENT; found_parent = n; - break; - } - } - - cond_resched(); - - /* is there a matching child entry? */ - list_for_each_entry(n, &context->names_list, list) { - /* can only match entries that have a name */ - if (!n->name || - (n->type != type && n->type != AUDIT_TYPE_UNKNOWN)) + if (found_child) + break; continue; + } - if (!strcmp(dname->name, n->name->name) || - !audit_compare_dname_path(dname, n->name->name, + /* is there a matching child entry? */ + if (!found_child && + (n->type == type || n->type == AUDIT_TYPE_UNKNOWN) && + (!strcmp(dname->name, n->name->name) || + !audit_compare_dname_path(dname, n->name->name, found_parent ? found_parent->name_len : - AUDIT_NAME_FULL)) { + AUDIT_NAME_FULL))) { if (n->type == AUDIT_TYPE_UNKNOWN) n->type = type; found_child = n; - break; + if (found_parent) + break; } } -- 2.51.0
