On Thu, 25 Apr 2024, James Pearson wrote: > Many years ago, I asked on this list if it was possible to change the > precedence order of exports listed in /etc/exports where there is more > than one possible match (see the thread at: > https://marc.info/?l=linux-nfs&m=130565040627856&w=2) - and answer was > 'No' > > At that time, I used a simple hack to force the precedence order I > required (by modifying the 'MCL' enum order in nfs-utils > support/include/exportfs.h) > > However, the issue has come up again for me, so I thought I would see > if I could alter the precedence order by adding an exports 'priority=' > option as suggested later in the above thread > > I started with the nfs-utils supplied with CentOS 7 (based on 1.3.0) - > and added logic to lookup_export() to check for client specifications > with a higher priority - but this didn't work - so looking for other > places that looped through MCL types, I added similar logic in > nfsd_fh() - which seems to work as I expected (I'm using NFSv3) > > However, adding similar logic to the nfs-utils supplied with Rocky 9 > (based on 2.5.4) didn't work ... > > But comparing the code in nfsd_fh() in v1.3.0 and nfsd_handle_fh() in > v2.5.4, nfsd_fh() in v1.3.0 does the following towards the end of the > function - whereas nfsd_handle_fh() in v2.5.4 doesn't: > > if (cache_export_ent(buf, sizeof(buf), dom, found, found_path) < 0) > found = 0; > > By adding the above lines at a similar place in nfsd_handle_fh() in > v2.5.4, seems to 'fix' the issue and all works as I expected > > I don't fully understand what is going on under the hood with all > this, so no idea if what I've done is 'correct', or if there is a > better way of doing what I'm trying to achieve ? > > Below is a patch (made against the latest git nfs-utils) of what I've > done - could anyone let me know if I'm going along the right lines (or > not) ? The restored cache_export_ent() call has to go. You need to update init_exportent() to initialise the new field. You probably need to make some changes to auth_authenticate_newcache(). Probably let the loop run all the way to MCL_MAXTYPES, and do a priority comparison if you find a new possible match. export_find() probably need some attention too. If you it still doesn't work after addressing those, I'll have a look and see if I can beat it into shape. NeilBrown > > (I apologize if the formatting of the patch gets mangled by Gmail) > > Thanks > > James Pearson > > diff --git a/support/export/cache.c b/support/export/cache.c > index 6c0a44a3..e9392d8e 100644 > --- a/support/export/cache.c > +++ b/support/export/cache.c > @@ -54,6 +54,8 @@ enum nfsd_fsid { > FSID_UUID16_INUM, > }; > > +static int cache_export_ent(char *buf, int buflen, char *domain, > struct exportent *exp, char *path); > + > #undef is_mountpoint > static int is_mountpoint(const char *path) > { > @@ -877,6 +879,14 @@ static int nfsd_handle_fh(int f, char *bp, int blen) > xlog(L_WARNING, "%s and %s have same > filehandle for %s, using first", > found_path, path, dom); > } else { > + /* same path, see if this one has a > higher export priority */ > + if (exp->m_export.e_priority > > found->e_priority) { > + found = &exp->m_export; > + free(found_path); > + found_path = strdup(path); > + if (found_path == NULL) > + goto out; > + } > /* same path, if one is V4ROOT, choose > the other */ > if (found->e_flags & NFSEXP_V4ROOT) { > found = &exp->m_export; > @@ -910,6 +920,12 @@ static int nfsd_handle_fh(int f, char *bp, int blen) > goto out; > } > > + /* adding this here - to make sure priority export changes are > + * picked up (this used to be in 1.X versions ?) > + */ > + if (cache_export_ent(buf, sizeof(buf), dom, found, found_path) < 0) > + found = 0; > + > bp = buf; blen = sizeof(buf); > qword_add(&bp, &blen, dom); > qword_addint(&bp, &blen, fsidtype); > @@ -1178,6 +1194,12 @@ lookup_export(char *dom, char *path, struct addrinfo *ai) > found_type = i; > continue; > } > + /* see if this one has a higher export priority */ > + if (exp->m_export.e_priority > > found->m_export.e_priority) { > + found = exp; > + found_type = i; > + continue; > + } > /* Always prefer non-V4ROOT exports */ > if (exp->m_export.e_flags & NFSEXP_V4ROOT) > continue; > diff --git a/support/include/nfslib.h b/support/include/nfslib.h > index eff2a486..ab22ecaf 100644 > --- a/support/include/nfslib.h > +++ b/support/include/nfslib.h > @@ -99,6 +99,7 @@ struct exportent { > unsigned int e_ttl; > char * e_realpath; > int e_reexport; > + int e_priority; > }; > > struct rmtabent { > diff --git a/support/nfs/exports.c b/support/nfs/exports.c > index a6816e60..548063b8 100644 > --- a/support/nfs/exports.c > +++ b/support/nfs/exports.c > @@ -374,6 +374,9 @@ putexportent(struct exportent *ep) > fprintf(fp, "%d,", id[i]); > } > fprintf(fp, "anonuid=%d,anongid=%d", ep->e_anonuid, ep->e_anongid); > + if (ep->e_priority) { > + fprintf(fp, ",priority=%d", ep->e_priority); > + } > secinfo_show(fp, ep); > xprtsecinfo_show(fp, ep); > fprintf(fp, ")\n"); > @@ -834,6 +837,14 @@ bad_option: > setflags(NFSEXP_FSID, active, ep); > > saw_reexport = 1; > + } else if (strncmp(opt, "priority=", 9) == 0) { > + char *oe; > + ep->e_priority = strtol(opt+9, &oe, 10); > + if (opt[9]=='\0' || *oe != '\0') { > + xlog(L_ERROR, "%s: %d: bad priority \"%s\"\n", > + flname, flline, opt); > + goto bad_option; > + } > } else { > xlog(L_ERROR, "%s:%d: unknown keyword \"%s\"\n", > flname, flline, opt); > >
