From: James Pearson <jcpearson@gmail.com>
To: Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Changing the precedence order of client exports in /etc/exports
Date: Thu, 25 Apr 2024 13:19:12 +0100 [thread overview]
Message-ID: <CAK3fRr8N4dNz2+K-BgaZAcswbfXrDem6Z9fRtgTDMJa=Y0R8gA@mail.gmail.com> (raw)
In-Reply-To: <662a39f7.BuSJ6zaMPTMaMa7L%james-p@moving-picture.com>
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) ?
(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);
next parent reply other threads:[~2024-04-25 12:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <662a39f7.BuSJ6zaMPTMaMa7L%james-p@moving-picture.com>
2024-04-25 12:19 ` James Pearson [this message]
2024-04-26 4:43 ` Changing the precedence order of client exports in /etc/exports NeilBrown
2024-04-26 16:08 ` James Pearson
2024-05-08 9:49 ` James Pearson
2024-05-10 19:02 ` Steve Dickson
2024-05-13 3:52 ` NeilBrown
2024-05-15 15:22 ` James Pearson
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