-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 04/29/2013 08:11 AM, NeilBrown wrote: > On Mon, 29 Apr 2013 07:33:21 +0200 Harald Hoyer <harald@xxxxxxxxxx> wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > >> On 04/29/2013 02:57 AM, NeilBrown wrote: >>> On Thu, 11 Apr 2013 15:18:33 +0200 Jes.Sorensen@xxxxxxxxxx wrote: >>> >>>> From: Harald Hoyer <harald@xxxxxxxxxx> >>>> >>>> This does not trigger the udev inotify twice and saves a lot of blk >>>> I/O for the raid members. >>>> >>>> Also fixes: https://bugzilla.redhat.com/show_bug.cgi?id=947815 >>>> >>>> Signed-off-by: Harald Hoyer <harald@xxxxxxxxxx> Signed-off-by: Jes >>>> Sorensen <Jes.Sorensen@xxxxxxxxxx> >>> >>> (Sorry for delays. Thanks for reminders). >>> >>> That patch seems to make sense, but the description above is awfully >>> thin. >>> >>> Why is double-open a problem exactly? What does it make udev do? And >>> how does that related to ID_FS_TYPE being wrong as mentioned in the >>> bugzilla entry. >>> >>> NeilBrown >>> > >> udevd with watch enabled (inotify on /dev/sd*) gets triggered on close(), >> when you opened it writeable. So, if you double open() and udev wakes up >> from the first close(), not all information are written to disk yet, it >> will not get the ID_FS_TYPE. > >> Seems like the second close() does not trigger an inotify sometimes, so >> it is missing afterwards all the time. > >> Watch via inotify is just a lazy workaround, so we don't have to modify >> every tool to emit a "change" uevent, after they changed the disk. > > So udev have a "lazy workaround" so that other programs don't need to > trigger a change, and as a result, I need to add some special code to > mdadm. Doesn't seem like I'm getting any advantage out of this laziness. > > How about when udev gets an inotify for a block device, it first checks > that it can open it O_EXCL. If not, it doesn't generate the change event. > That seems like the laziest option to me :-) We cannot open with O_EXCL, because the device can be mounted, and O_EXCL would fail there. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQIcBAEBAgAGBQJRfhP+AAoJEANOs3ABTfJwONcP+gOzhDDvWFG0AZdocgttk04o oV4mr2sde+NtuQMB8ac9v4Y0XP2HnpAYOVAJP7LALpkNHwUYGxtDDbqwWLGQWfPy xXt6Zq9jE/srwmbBTmCB5sROS5lw6c+M2ft4kza2PDDY+9xyTjxVqVf2tcRGa3Fh LIFNnKGk58qrgAI/46Muw0rbfMZOpOPuLNrI2aYwl/xmrXmQVXfGLIb+Rms9cdsY Duk/U05t/DxYupic/fAvkuDmuUzsyBAhpuixL/774m7J3yzf6sNIadtZgy3rMiym WNz+C8Ltx4d2H1nGmjkw9rKbmnWye15lLfsJGZQxvtt9LkWCPu6L9KbLKQyjjnc9 DBIj/6vID3JhxoLRE7H+zQXk7b9VX6sWAKPo6iFC4LcD8tESs01Jz0bV2kyMcUsZ 1HucYgcd2yzaaMBdEB9LleXd7SCtiBW74qTa/WgFK26notiyIGVWnfBdr9TYi1cB UJLbsa9XHadq/OW4qVEBWbDbkM6Wpwkc2W7oosh3klauifbn2PXguwp5oeT/CQ1y HORW36Xt9myAcZWY9iBjFRMwxJNztF89XYWOIzZ5j9fV1wHvCqYqNN+gtyt5vq97 N+Pn4pJ2Nuyygxu++aSv271JBga0YZCIGlIE38J1mJVgZlNAFXIGELs30NhYNhI2 GZ3eOMhawdR9k3NkQbMM =hDz6 -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
