slackware-current/source/a/pam/patches/pam.pam_tally2.no.fsync.patch

From b136bff25e93be6f11de74aca03569022364b973 Mon Sep 17 00:00:00 2001
From: "Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Date: Mon, 25 Feb 2019 20:50:48 +0100
Subject: [PATCH] pam_tally2: Remove unnecessary fsync()

pam_tally2 does fsync() after writing to a tally file.
This causes hard drive cache flushes on every failed SSH login on many
(if not most) filesystems.
And an internet-exposed machine can have a lot of these failed logins.

This operation however doesn't seem to be necessary - the pam_tally2
module does not do any operation which would need explicit post-crash
ordering, it just does simple file reads and writes.
And doing a fsync() after them doesn't close any race if the system happens
to crash between a write being posted and its fsync() completion.

Let's remove this operation to get rid of all these extra cache flushes.
---
 modules/pam_tally2/pam_tally2.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/modules/pam_tally2/pam_tally2.c b/modules/pam_tally2/pam_tally2.c
index 984edf6a..ce7f5aee 100644
--- a/modules/pam_tally2/pam_tally2.c
+++ b/modules/pam_tally2/pam_tally2.c
@@ -484,10 +484,6 @@ set_tally(pam_handle_t *pamh, uid_t uid,
         }
     }
 
-    if (fsync(*tfile)) {
-      pam_syslog(pamh, LOG_ALERT, "update (fsync) failed for %s: %m", filename);
-      return PAM_AUTH_ERR;
-    }
     return PAM_SUCCESS;
 }