Re: [PATCH] uevent_can_discard: optimize devpath check

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Applied.
Thanks.

On Wed, Mar 1, 2017 at 6:22 PM, Martin Wilck <mwilck@xxxxxxxx> wrote:
This uses roughly 10% cycles of the sscanf-based implementation.

Improves: ee8888f0 "multipath-tools: improve processing efficiency..."
Signed-off-by: Martin Wilck <mwilck@xxxxxxxx>
---
 libmultipath/uevent.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
index 6e2527bd..367e129a 100644
--- a/libmultipath/uevent.c
+++ b/libmultipath/uevent.c
@@ -143,26 +143,35 @@ uevent_need_merge(void)
        return need_merge;
 }

+static bool
+uevent_can_discard_by_devpath(const char *devpath)
+{
+       static const char BLOCK[] = "/block/";
+       const char *tmp = strstr(devpath, BLOCK);
+
+       if (tmp == NULL) {
+               condlog(4, "no /block/ in '%s'", devpath);
+               return true;
+       }
+       tmp += sizeof(BLOCK) - 1;
+       if (*tmp == '\0')
+               /* just ".../block/" - discard */
+               return true;
+       /*
+        * If there are more path elements after ".../block/xyz",
+        * it's a partition - discard it; but don't discard ".../block/sda/".
+        */
+       tmp = strchr(tmp, '/');
+       return tmp != NULL && *(tmp + 1) != '\0';
+}
+
 bool
 uevent_can_discard(struct uevent *uev)
 {
-       char *tmp;
-       char a[11], b[11];
        struct config * conf;

-       /*
-        * keep only block devices, discard partitions
-        */
-       tmp = strstr(uev->devpath, "/block/");
-       if (tmp == NULL){
-               condlog(4, "no /block/ in '%s'", uev->devpath);
+       if (uevent_can_discard_by_devpath(uev->devpath))
                return true;
-       }
-       if (sscanf(tmp, "/block/%10s", a) != 1 ||
-           sscanf(tmp, "/block/%10[^/]/%10s", a, b) == 2) {
-               condlog(4, "discard event on %s", uev->devpath);
-               return true;
-       }

        /*
         * do not filter dm devices by devnode
--
2.12.0

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