On Fri, 26 Apr 2024 at 05:43, NeilBrown <neilb@xxxxxxx> wrote: > > 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. Thanks for the pointers - new patch below I don't quite understand what export_find() is actually doing ? As far as I can tell, it is only used by exportfs when an export is given on the command line - and only if that export is of type MCL_FQDN - so I'm not sure it needs any changes to support these priority additions ? (I might be completely wrong here ...) Thanks James Pearson diff --git a/support/export/auth.c b/support/export/auth.c index 2d7960f1..3d9e07b5 100644 --- a/support/export/auth.c +++ b/support/export/auth.c @@ -175,7 +175,7 @@ auth_authenticate_newcache(const struct sockaddr *caller, const char *path, struct addrinfo *ai, enum auth_error *error) { - nfs_export *exp; + nfs_export *exp, *found; int i; free(my_client.m_hostname); @@ -189,6 +189,7 @@ auth_authenticate_newcache(const struct sockaddr *caller, my_exp.m_client = &my_client; exp = NULL; + found = NULL; for (i = 0; !exp && i < MCL_MAXTYPES; i++) for (exp = exportlist[i].p_head; exp; exp = exp->m_next) { if (strcmp(path, exp->m_export.e_path)) @@ -198,8 +199,11 @@ auth_authenticate_newcache(const struct sockaddr *caller, if (exp->m_export.e_flags & NFSEXP_V4ROOT) /* not acceptable for v[23] export */ continue; - break; + /* we have a match - see if it is a higher priority */ + if (!found || exp->m_export.e_priority > found->m_export.e_priority) + found = exp; } + exp = found; *error = not_exported; if (!exp) return NULL; diff --git a/support/export/cache.c b/support/export/cache.c index 6c0a44a3..dfb0051b 100644 --- a/support/export/cache.c +++ b/support/export/cache.c @@ -877,6 +877,14 @@ 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; @@ -1178,6 +1186,12 @@ 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..afc139db 100644 --- a/support/nfs/exports.c +++ b/support/nfs/exports.c @@ -106,6 +106,7 @@ static void init_exportent (struct exportent *ee, int fromkernel) ee->e_uuid = NULL; ee->e_ttl = default_ttl; ee->e_reexport = REEXP_NONE; + ee->e_priority = 0; } struct exportent * @@ -374,6 +375,9 @@ 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 +838,14 @@ 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); diff --git a/utils/exportfs/exportfs.c b/utils/exportfs/exportfs.c index b03a047b..5e6a64b6 100644 --- a/utils/exportfs/exportfs.c +++ b/utils/exportfs/exportfs.c @@ -753,6 +753,8 @@ dump(int verbose, int export_format) break; #endif } + if (ep->e_priority) + c = dumpopt(c, "priority=%d", ep->e_priority); secinfo_show(stdout, ep); xprtsecinfo_show(stdout, ep); printf("%c\n", (c != '(')? ')' : ' ');
