Re: [systemd-devel] [PATCH 10/11] Avoid doubling the efforts for /var/log/journal

Re: [systemd-devel] [PATCH 10/11] Avoid doubling the efforts for /var/log/journal

[Dr. Werner Fink]

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On Mon, Jun 16, 2014 at 11:10:15AM -0400, Cristian Rodríguez wrote:
> El 13/06/14 10:41, Werner Fink escribió:
> > That is: set NOATIME, NOCOW, and NOCOMP for the journal directory
> > 
> > ---
> >  src/journal/journald-server.c |   29 +++++++++++++++++++++++++++--
> >  1 file changed, 27 insertions(+), 2 deletions(-)
> > 
> > diff --git src/journal/journald-server.c src/journal/journald-server.c
> > index eda5dcf..37d6dc3 100644
> > --- src/journal/journald-server.c
> > +++ src/journal/journald-server.c
> > @@ -21,6 +21,7 @@
> >  
> >  #include <sys/signalfd.h>
> >  #include <sys/ioctl.h>
> > +#include <linux/fs.h>
> >  #include <linux/sockios.h>
> >  #include <sys/statvfs.h>
> >  #include <sys/mman.h>
> > @@ -920,7 +921,7 @@ finish:
> >  
> >  
> >  static int system_journal_open(Server *s) {
> > -        int r;
> > +        int r, fd;
> 
> _cleanup_close_ ...
> 
> > +                /*
> > +                 * On journaling and/or compressing file systems avoid doubling the
> > +                 * efforts for the system, that is set NOCOW and NOCOMP inode flags.
> > +                 * Check for every single flag as otherwise some of the file systems
> > +                 * may return EOPNOTSUPP on one unkown flag (like BtrFS does).
> > +                 */
> > +                if ((fd = open(fn, O_DIRECTORY)) >= 0) {
> 
> O_CLOEXEC...
> 
> > +                        long flags;
> > +                        if (ioctl(fd, FS_IOC_GETFLAGS, &flags) == 0) {
> > +                                int old = flags;
> > +                                if (!(flags&FS_NOATIME_FL) && ioctl(fd, FS_IOC_SETFLAGS, flags|FS_NOATIME_FL) == 0)
> > +                                        flags |= FS_NOATIME_FL;
> > +                                if (!(flags&FS_NOCOW_FL) && ioctl(fd, FS_IOC_SETFLAGS, flags|FS_NOCOW_FL) == 0)
> > +                                        flags |= FS_NOCOW_FL;
> > +                                if (!(flags&FS_NOCOMP_FL) && s->compress) {
> > +                                        flags &= ~FS_COMPR_FL;
> > +                                        flags |= FS_NOCOMP_FL;
> > +                                }
> > +                                if (old != flags)
> > +                                        ioctl(fd, FS_IOC_SETFLAGS, flags);
> > +                        }
> > +                        close(fd);
> > +                }
> 
> I agree that this should be done, however I remain unconvinced this is
> the right place to do it..

IMHO this is the correct place as it helps to speed up systemd-journal
on BtrFS.  This was the reason for this patch and is tested even if the
patch does not use _cleanup_close_ and O_CLOEXEC ;)


Werner

-- 
  "Having a smoking section in a restaurant is like having
          a peeing section in a swimming pool." -- Edward Burr

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