svn commit: r285050 - in head: lib/libutil usr.sbin/pwd_mkdb
Alan Somers
asomers at freebsd.org
Thu Oct 13 21:42:33 UTC 2016
On Thu, Jul 2, 2015 at 11:31 AM, Renato Botelho <garga at freebsd.org> wrote:
> Author: garga (ports committer)
> Date: Thu Jul 2 17:30:59 2015
> New Revision: 285050
> URL: https://svnweb.freebsd.org/changeset/base/285050
>
> Log:
> When passwd or group information is changed (by pw, vipw, chpass, ...)
> temporary file is created and then a rename() call move it to official file.
> This operation didn't have any check to make sure data was written to disk
> and if a power cycle happens system could end up with a 0 length passwd
> or group database.
>
> There is a pfSense bug with more infor about it:
>
> https://redmine.pfsense.org/issues/4523
>
> The following changes were made to protect passwd and group operations:
>
> * lib/libutil/gr_util.c:
> - Replace mkstemp() by mkostemp() with O_SYNC flag to create temp file
> - After rename(), fsync() call on directory for faster result
>
> * lib/libutil/pw_util.c
> - Replace mkstemp() by mkostemp() with O_SYNC flag to create temp file
>
> * usr.sbin/pwd_mkdb/pwd_mkdb.c
> - Added O_SYNC flag on dbopen() calls
> - After rename(), fsync() call on directory for faster result
>
> * lib/libutil/pw_util.3
> - pw_lock() returns a file descriptor to master password file on success
>
> Differential Revision: https://reviews.freebsd.org/D2978
> Approved by: bapt
> Sponsored by: Netgate
>
> Modified:
> head/lib/libutil/gr_util.c
> head/lib/libutil/pw_util.3
> head/lib/libutil/pw_util.c
> head/usr.sbin/pwd_mkdb/pwd_mkdb.c
This change is making certain pw operations very slow on ZFS root
systems. The problem is that when you open a file with O_SYNC, every
single write(2) call turns into a zil_commit on ZFS, which is fairly
expensive. Did you consider using fsync(2) on the temporary files
instead of opening them with O_SYNC? I just tried that now, and I see
a considerable speedup when running the tests in
/usr/tests/usr.sbin/pw:
Using O_SYNC, as CURRENT does: 4 minutes 5.2 seconds
No synchronous operations at all: 49.5 seconds
Using fsync(2): 56.0 seconds
-Alan
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