Date: Sun, 10 May 2015 09:07:54 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: Doug Rabson <dfr@rabson.org> Cc: freebsd current <freebsd-current@freebsd.org>, Edward Tomasz =?utf-8?Q?Napiera=C5=82a?= <trasz@freebsd.org>, David Boyd49 <David.Boyd49@twc.com> Subject: Re: nmount, mountd drops high order MNT_xx flags during a mount update Message-ID: <917688730.35175530.1431263274444.JavaMail.root@uoguelph.ca> In-Reply-To: <581797832.35173877.1431263005089.JavaMail.root@uoguelph.ca>
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[-- Attachment #1 --] Oops, I did my usual and forgot to attach the patch. Here it is, rick ----- Original Message ----- > Doug Rabson wrote: > > You could add a single integer-valued vfsopt which holds the > > high-order > > bits of f_flags? > > > I have created a patch that does this. It is on > https://reviews.freebsd.org/D2506 > (I have also attached it here, for those who don't use Phabricator.) > > Please review/comment on this. (Feel free to add yourself as a > reviewer, etc.) > > Also, David, if you can test this patch, it would be appreciated. > > Thanks for the suggestion Doug, rick > > > On 7 May 2015 at 02:10, Rick Macklem <rmacklem@uoguelph.ca> wrote: > > > > > David Boyd reported a problem to freebsd-current@ w.r.t. the > > > MNT_AUTOMOUNTED > > > flag getting cleared by mountd. > > > http://docs.FreeBSD.org/cgi/mid.cgi?1429477202.29812.38.camel > > > I just took a look at this and it's kinda ugly... > > > > > > mountd acquires a list of mounts via getmntinfo() and then does > > > an > > > nmount() for each of them to get rid of any exports. It uses > > > f_flags from the statfs returned by getmntinfo() as the 3rd > > > argument to nmount(). > > > --> Since nmount()s 3rd argument is a "int", it silently drops > > > any > > > MNT_xx flag in the high order 32bits of f_flags. At this > > > time, > > > it happens that MNT_AUTOMOUNTED is the only one, but... > > > > > > I can think of a couple of ways to fix this, but I don't like any > > > of > > > them;-) > > > > > > 1) I suppose mountd could check for each flag set in f_flags and > > > generate > > > a vfsopts string for it, but that means that every time a new > > > flag > > > that > > > can be updated is added to MNT_xx, this mountd.c code would have > > > to > > > updated. > > > --> Ugly!! > > > > > > 2) Require that all flags in MNT_UPDATEMASK be in the low order > > > 32bits. > > > I wouldn`t mind this except in means that the MNT_xx flags > > > must > > > be > > > redefined > > > and I don`t think that could get MFC`d. > > > > > > 3) Add a new newernmount(2) which has a 64bit flags argument > > > instead of > > > int. > > > > > > Hopefully someone can think of a nice way to fix this, rick > > > _______________________________________________ > > > freebsd-current@freebsd.org mailing list > > > http://lists.freebsd.org/mailman/listinfo/freebsd-current > > > To unsubscribe, send any mail to > > > "freebsd-current-unsubscribe@freebsd.org" > > > > > _______________________________________________ > > freebsd-current@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-current > > To unsubscribe, send any mail to > > "freebsd-current-unsubscribe@freebsd.org" > > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to > "freebsd-current-unsubscribe@freebsd.org" > [-- Attachment #2 --] --- kern/vfs_mount.c.savmnt 2015-05-09 19:30:14.000000000 -0400 +++ kern/vfs_mount.c 2015-05-10 08:34:45.000000000 -0400 @@ -537,6 +537,7 @@ vfs_donmount(struct thread *td, uint64_t struct vfsopt *opt, *tmp_opt; char *fstype, *fspath, *errmsg; int error, fstypelen, fspathlen, errmsg_len, errmsg_pos; + uint64_t fsflag_high; errmsg = fspath = NULL; errmsg_len = fspathlen = 0; @@ -653,6 +654,20 @@ vfs_donmount(struct thread *td, uint64_t fsflags |= MNT_AUTOMOUNTED; vfs_freeopt(optlist, opt); } + else if (strcmp(opt->name, "fsflaghigh") == 0) { + /* + * This option allows a process doing a mount update + * to set all the high order 32bits of mnt_flag with + * one option. This is needed, since nmount(2) + * accepts an "int" option and, therefore, only takes + * the low order 32bits. + */ + if (vfs_copyopt(optlist, "fsflaghigh", + &fsflag_high, sizeof(fsflag_high)) == 0 && + (fsflag_high & 0xffffffffULL) == 0) + fsflags |= fsflag_high; + vfs_freeopt(optlist, opt); + } } /* --- usr.sbin/mountd/mountd.c.orig 2015-05-09 22:04:15.000000000 -0400 +++ usr.sbin/mountd/mountd.c 2015-05-09 22:27:06.000000000 -0400 @@ -1649,6 +1649,7 @@ get_exportlist(void) int iovlen; int done; struct nfsex_args eargs; + uint64_t fsflag_high; if (suspend_nfsd != 0) (void)nfssvc(NFSSVC_SUSPENDNFSD, NULL); @@ -1706,6 +1707,8 @@ get_exportlist(void) build_iovec(&iov, &iovlen, "update", NULL, 0); build_iovec(&iov, &iovlen, "export", &export, sizeof(export)); build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg)); + build_iovec(&iov, &iovlen, "fsflaghigh", &fsflag_high, + sizeof(fsflag_high)); } for (i = 0; i < num; i++) { @@ -1736,6 +1739,9 @@ get_exportlist(void) iov[3].iov_len = strlen(fsp->f_mntonname) + 1; iov[5].iov_base = fsp->f_mntfromname; iov[5].iov_len = strlen(fsp->f_mntfromname) + 1; + /* Use "fsflaghigh" to set the high order bits of f_flags. */ + fsflag_high = (fsp->f_flags & 0xffffffff00000000ULL); + errmsg[0] = '\0'; /* @@ -2394,6 +2400,7 @@ do_mount(struct exportlist *ep, struct g int i, iovlen; int ret; struct nfsex_args nfsea; + uint64_t fsflag_high; eap = &nfsea.export; @@ -2429,6 +2436,12 @@ do_mount(struct exportlist *ep, struct g build_iovec(&iov, &iovlen, "export", eap, sizeof (struct export_args)); build_iovec(&iov, &iovlen, "errmsg", errmsg, sizeof(errmsg)); + + /* Use "fsflaghigh" to set the high order bits of f_flags. */ + fsflag_high = (fsb->f_flags & 0xffffffff00000000ULL); + if (fsflag_high != 0) + build_iovec(&iov, &iovlen, "fsflaghigh", &fsflag_high, + sizeof(fsflag_high)); } while (!done) {
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