nfs-utils: Increase the stdio file buffer size for procfs files

Previously, when writing to /proc/net/rpc/*/channel, if a cache line
were larger than the default buffer size (likely 1024 bytes), mountd
and svcgssd would split writes into a number of buffer-sized writes.
Each of these writes would get an EINVAL error back from the kernel
procfs handle (it expects line-oriented input and does not account for
multiple/split writes), and no cache update would occur.

When such behavior occurs, NFS clients depending on mountd to finish
the cache operation would block/hang, or receive EPERM, depending on
the context of the operation.  This is likely to happen if a user is a
member of a large (~100-200) number of groups.

Instead, every fopen() on the procfs files in question is followed by
a call to setvbuf(), using a per-file dedicated buffer of
RPC_CHAN_BUF_SIZE length.

Really, mountd should not be using stdio-style buffered file operations
on files in /proc to begin with.  A better solution would be to use
internally managed buffers and calls to write() instead of these stdio
calls, but that would be a more extensive change; so this is proposed
as a quick and not-so-dirty fix in the meantime.

Signed-off-by: Sean Finney <sean.finney@sonyericsson.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/support/include/misc.h b/support/include/misc.h
index bc5ba235e15dd0fa1931b1f2e9542ca681db113b..eedc1feaf4eaa712e0b725c77bb9a732c83bb38b 100644 (file)
--- a/support/include/misc.h
+++ b/support/include/misc.h
@@ -17,4 +17,7 @@ int   weakrandomkey(unsigned char *keyout, int len);
 
 extern int is_mountpoint(char *path);
 
+/* size of the file pointer buffers for rpc procfs files */
+#define RPC_CHAN_BUF_SIZE 32768
+
 #endif /* MISC_H */

diff --git a/utils/gssd/svcgssd_proc.c b/utils/gssd/svcgssd_proc.c
index 7a916d718033e0cbf663e90a42e766640db57219..c714d99dd654aaff3b3369bebcbc0df0946284dd 100644 (file)
--- a/utils/gssd/svcgssd_proc.c
+++ b/utils/gssd/svcgssd_proc.c
@@ -56,6 +56,7 @@
 #include "gss_util.h"
 #include "err_util.h"
 #include "context.h"
+#include "misc.h"
 #include "gss_oids.h"
 #include "svcgssd_krb5.h"
 
@@ -71,6 +72,7 @@ struct svc_cred {
        int     cr_ngroups;
        gid_t   cr_groups[NGROUPS];
 };
+static char vbuf[RPC_CHAN_BUF_SIZE];
 
 static int
 do_svc_downcall(gss_buffer_desc *out_handle, struct svc_cred *cred,
@@ -92,6 +94,7 @@ do_svc_downcall(gss_buffer_desc *out_handle, struct svc_cred *cred,
                             SVCGSSD_CONTEXT_CHANNEL, strerror(errno));
                goto out_err;
        }
+       setvbuf(f, vbuf, _IOLBF, RPC_CHAN_BUF_SIZE);
        qword_printhex(f, out_handle->value, out_handle->length);
        /* XXX are types OK for the rest of this? */
        /* For context cache, use the actual context endtime */

diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
index ce93e3cf61b66f5b3fdfb623bcddd94a130eaf87..df6b38f9b5c737d5f9e87a9380ef854d3e464b16 100644 (file)
--- a/utils/mountd/cache.c
+++ b/utils/mountd/cache.c
@@ -825,6 +825,7 @@ struct {
        char *cache_name;
        void (*cache_handle)(FILE *f);
        FILE *f;
+       char vbuf[RPC_CHAN_BUF_SIZE];
 } cachelist[] = {
        { "auth.unix.ip", auth_unix_ip, NULL},
        { "auth.unix.gid", auth_unix_gid, NULL},
@@ -848,6 +849,10 @@ void cache_open(void)
                        continue;
                sprintf(path, "/proc/net/rpc/%s/channel", cachelist[i].cache_name);
                cachelist[i].f = fopen(path, "r+");
+               if (cachelist[i].f != NULL) {
+                       setvbuf(cachelist[i].f, cachelist[i].vbuf, _IOLBF, 
+                               RPC_CHAN_BUF_SIZE);
+               }
        }
 }