Re: PATCH [libparted]: avoid unnecessary open() / close() on commit()

[Jim Meyering]

Hans de Goede wrote:
...
> This is rather inefficient, and causes 2 udev change events to be fired
> for /dev/sda (+ the change events from the BLKRRPART), causing all kind
> of scanning (blkid & friends) twice.
>
> The attached patch fixes things to only open the device once.

Hi Hans,

Thanks for the patches.
This one looks fine, so I've pushed it to "next" as follows:
(changes were to the log, typo in comment, and s/8-spaces/TAB/ in indentation)

>From ad25892bb995f61b0ddf801ed1f74e0b1e7390ce Mon Sep 17 00:00:00 2001
From: Hans de Goede <address@hidden>
Date: Thu, 27 Aug 2009 20:16:09 +0200
Subject: [PATCH] parted: avoid unnecessary open/close on commit, and thus udev 
activity

* libparted/disk.c (ped_disk_commit): Open/close the underlying file
descriptor in this function, so that callees, ped_disk_commit_to_dev
and ped_disk_commit_to_os do not each perform open/close syscalls.
This saves an open/close pair, and thus avoids unneeded udev
activity on Linux.

Before this change, when calling commit() on a ped_disk, the
following would happen:

open /dev/sda
write partition table
close /dev/sda
open /dev/sda
ioctl (BLKRRPART)
close /dev/sda

This is rather inefficient, and causes 2 udev change events to be fired
for /dev/sda (+ the change events from the BLKRRPART), causing all kind
of scanning (blkid & friends) twice.

This patch fixes things to only open the device once.
---
 libparted/disk.c |   20 ++++++++++++++++++--
 1 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/libparted/disk.c b/libparted/disk.c
index 72a3299..8c5a9e3 100644
--- a/libparted/disk.c
+++ b/libparted/disk.c
@@ -499,9 +499,25 @@ error:
 int
 ped_disk_commit (PedDisk* disk)
 {
+        /* Open the device here, so that the underlying fd is not closed
+           between commit_to_dev and commit_to_os (closing causes unwanted
+           udev events to be sent under Linux). */
+       if (!ped_device_open (disk->dev))
+               goto error;
+
        if (!ped_disk_commit_to_dev (disk))
-               return 0;
-       return ped_disk_commit_to_os (disk);
+               goto error_close_dev;
+
+       if (!ped_disk_commit_to_os (disk))
+               goto error_close_dev;
+
+       ped_device_close (disk->dev);
+       return 1;
+
+error_close_dev:
+       ped_device_close (disk->dev);
+error:
+       return 0;
 }

 /**
--
1.6.4.1.373.g81fb2