nfsd4: clean up session allocation

Changes:
	- make sure session memory reservation is released on failure
	  path.
	- use min_t()/min() for more compact code in several places.
	- break alloc_init_session into smaller pieces.
	- miscellaneous other cleanup.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 89 insertions, 122 deletions

diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index ebddcc173ed8..f86476c23b2f 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -533,94 +533,6 @@ gen_sessionid(struct nfsd4_session *ses)
  */
 #define NFSD_MIN_HDR_SEQ_SZ  (24 + 12 + 44)
 
-/*
- * Give the client the number of ca_maxresponsesize_cached slots it
- * requests, of size bounded by NFSD_SLOT_CACHE_SIZE,
- * NFSD_MAX_MEM_PER_SESSION, and nfsd_drc_max_mem. Do not allow more
- * than NFSD_MAX_SLOTS_PER_SESSION.
- *
- * If we run out of reserved DRC memory we should (up to a point)
- * re-negotiate active sessions and reduce their slot usage to make
- * rooom for new connections. For now we just fail the create session.
- */
-static int set_forechannel_drc_size(struct nfsd4_channel_attrs *fchan)
-{
-        int mem, size = fchan->maxresp_cached;
-
-        if (fchan->maxreqs < 1)
-                return nfserr_inval;
-
-        if (size < NFSD_MIN_HDR_SEQ_SZ)
-                size = NFSD_MIN_HDR_SEQ_SZ;
-        size -= NFSD_MIN_HDR_SEQ_SZ;
-        if (size > NFSD_SLOT_CACHE_SIZE)
-                size = NFSD_SLOT_CACHE_SIZE;
-
-        /* bound the maxreqs by NFSD_MAX_MEM_PER_SESSION */
-        mem = fchan->maxreqs * size;
-        if (mem > NFSD_MAX_MEM_PER_SESSION) {
-                fchan->maxreqs = NFSD_MAX_MEM_PER_SESSION / size;
-                if (fchan->maxreqs > NFSD_MAX_SLOTS_PER_SESSION)
-                        fchan->maxreqs = NFSD_MAX_SLOTS_PER_SESSION;
-                mem = fchan->maxreqs * size;
-        }
-
-        spin_lock(&nfsd_drc_lock);
-        /* bound the total session drc memory ussage */
-        if (mem + nfsd_drc_mem_used > nfsd_drc_max_mem) {
-                fchan->maxreqs = (nfsd_drc_max_mem - nfsd_drc_mem_used) / size;
-                mem = fchan->maxreqs * size;
-        }
-        nfsd_drc_mem_used += mem;
-        spin_unlock(&nfsd_drc_lock);
-
-        if (fchan->maxreqs == 0)
-                return nfserr_jukebox;
-
-        fchan->maxresp_cached = size + NFSD_MIN_HDR_SEQ_SZ;
-        return 0;
-}
-
-/*
- * fchan holds the client values on input, and the server values on output
- * sv_max_mesg is the maximum payload plus one page for overhead.
- */
-static int init_forechannel_attrs(struct svc_rqst *rqstp,
-                                  struct nfsd4_channel_attrs *session_fchan,
-                                  struct nfsd4_channel_attrs *fchan)
-{
-        int status = 0;
-        __u32   maxcount = nfsd_serv->sv_max_mesg;
-
-        /* headerpadsz set to zero in encode routine */
-
-        /* Use the client's max request and max response size if possible */
-        if (fchan->maxreq_sz > maxcount)
-                fchan->maxreq_sz = maxcount;
-        session_fchan->maxreq_sz = fchan->maxreq_sz;
-
-        if (fchan->maxresp_sz > maxcount)
-                fchan->maxresp_sz = maxcount;
-        session_fchan->maxresp_sz = fchan->maxresp_sz;
-
-        /* Use the client's maxops if possible */
-        if (fchan->maxops > NFSD_MAX_OPS_PER_COMPOUND)
-                fchan->maxops = NFSD_MAX_OPS_PER_COMPOUND;
-        session_fchan->maxops = fchan->maxops;
-
-        /* FIXME: Error means no more DRC pages so the server should
-         * recover pages from existing sessions. For now fail session
-         * creation.
-         */
-        status = set_forechannel_drc_size(fchan);
-
-        session_fchan->maxresp_cached = fchan->maxresp_cached;
-        session_fchan->maxreqs = fchan->maxreqs;
-
-        dprintk("%s status %d\n", __func__, status);
-        return status;
-}
-
 static void
 free_session_slots(struct nfsd4_session *ses)
 {
@@ -639,63 +551,118 @@ static inline int slot_bytes(struct nfsd4_channel_attrs *ca)
         return ca->maxresp_cached - NFSD_MIN_HDR_SEQ_SZ;
 }
 
-static __be32 alloc_init_session(struct svc_rqst *rqstp, struct nfs4_client *clp, struct nfsd4_create_session *cses)
+static int nfsd4_sanitize_slot_size(u32 size)
 {
-        struct nfsd4_session *new, tmp;
-        struct nfsd4_slot *sp;
-        int idx, slotsize, cachesize, i;
-        int status;
+        size -= NFSD_MIN_HDR_SEQ_SZ; /* We don't cache the rpc header */
+        size = min_t(u32, size, NFSD_SLOT_CACHE_SIZE);
 
-        memset(&tmp, 0, sizeof(tmp));
+        return size;
+}
 
-        /* FIXME: For now, we just accept the client back channel attributes. */
-        tmp.se_bchannel = cses->back_channel;
-        status = init_forechannel_attrs(rqstp, &tmp.se_fchannel,
-                                        &cses->fore_channel);
-        if (status)
-                goto out;
+/*
+ * XXX: If we run out of reserved DRC memory we could (up to a point)
+ * re-negotiate active sessions and reduce their slot usage to make
+ * rooom for new connections. For now we just fail the create session.
+ */
+static int nfsd4_get_drc_mem(int slotsize, u32 num)
+{
+        int avail;
 
-        BUILD_BUG_ON(NFSD_MAX_SLOTS_PER_SESSION * sizeof(struct nfsd4_slot *)
-                     + sizeof(struct nfsd4_session) > PAGE_SIZE);
+        num = min_t(u32, num, NFSD_MAX_SLOTS_PER_SESSION);
 
-        status = nfserr_jukebox;
-        /* allocate struct nfsd4_session and slot table pointers in one piece */
-        slotsize = tmp.se_fchannel.maxreqs * sizeof(struct nfsd4_slot *);
-        new = kzalloc(sizeof(*new) + slotsize, GFP_KERNEL);
-        if (!new)
-                goto out;
+        spin_lock(&nfsd_drc_lock);
+        avail = min_t(int, NFSD_MAX_MEM_PER_SESSION,
+                        nfsd_drc_max_mem - nfsd_drc_mem_used);
+        num = min_t(int, num, avail / slotsize);
+        nfsd_drc_mem_used += num * slotsize;
+        spin_unlock(&nfsd_drc_lock);
+
+        return num;
+}
+
+static void nfsd4_put_drc_mem(int slotsize, int num)
+{
+        spin_lock(&nfsd_drc_lock);
+        nfsd_drc_mem_used -= slotsize * num;
+        spin_unlock(&nfsd_drc_lock);
+}
+
+static struct nfsd4_session *alloc_session(int slotsize, int numslots)
+{
+        struct nfsd4_session *new;
+        int mem, i;
 
-        memcpy(new, &tmp, sizeof(*new));
+        BUILD_BUG_ON(NFSD_MAX_SLOTS_PER_SESSION * sizeof(struct nfsd4_slot *)
+                        + sizeof(struct nfsd4_session) > PAGE_SIZE);
+        mem = numslots * sizeof(struct nfsd4_slot *);
 
+        new = kzalloc(sizeof(*new) + mem, GFP_KERNEL);
+        if (!new)
+                return NULL;
         /* allocate each struct nfsd4_slot and data cache in one piece */
-        cachesize = slot_bytes(&new->se_fchannel);
-        for (i = 0; i < new->se_fchannel.maxreqs; i++) {
-                sp = kzalloc(sizeof(*sp) + cachesize, GFP_KERNEL);
-                if (!sp)
+        for (i = 0; i < numslots; i++) {
+                mem = sizeof(struct nfsd4_slot) + slotsize;
+                new->se_slots[i] = kzalloc(mem, GFP_KERNEL);
+                if (!new->se_slots[i])
                         goto out_free;
-                new->se_slots[i] = sp;
         }
+        return new;
+out_free:
+        while (i--)
+                kfree(new->se_slots[i]);
+        kfree(new);
+        return NULL;
+}
+
+static void init_forechannel_attrs(struct nfsd4_channel_attrs *new, struct nfsd4_channel_attrs *req, int numslots, int slotsize)
+{
+        u32 maxrpc = nfsd_serv->sv_max_mesg;
+
+        new->maxreqs = numslots;
+        new->maxresp_cached = slotsize + NFSD_MIN_HDR_SEQ_SZ;
+        new->maxreq_sz = min_t(u32, req->maxreq_sz, maxrpc);
+        new->maxresp_sz = min_t(u32, req->maxresp_sz, maxrpc);
+        new->maxops = min_t(u32, req->maxops, NFSD_MAX_OPS_PER_COMPOUND);
+}
+
+static __be32 alloc_init_session(struct svc_rqst *rqstp, struct nfs4_client *clp, struct nfsd4_create_session *cses)
+{
+        struct nfsd4_session *new;
+        struct nfsd4_channel_attrs *fchan = &cses->fore_channel;
+        int numslots, slotsize;
+        int idx;
+
+        /*
+         * Note decreasing slot size below client's request may
+         * make it difficult for client to function correctly, whereas
+         * decreasing the number of slots will (just?) affect
+         * performance.  When short on memory we therefore prefer to
+         * decrease number of slots instead of their size.
+         */
+        slotsize = nfsd4_sanitize_slot_size(fchan->maxresp_cached);
+        numslots = nfsd4_get_drc_mem(slotsize, fchan->maxreqs);
+
+        new = alloc_session(slotsize, numslots);
+        if (!new) {
+                nfsd4_put_drc_mem(slotsize, fchan->maxreqs);
+                return nfserr_jukebox;
+        }
+        init_forechannel_attrs(&new->se_fchannel, fchan, numslots, slotsize);
 
         new->se_client = clp;
         gen_sessionid(new);
-        idx = hash_sessionid(&new->se_sessionid);
         memcpy(clp->cl_sessionid.data, new->se_sessionid.data,
                NFS4_MAX_SESSIONID_LEN);
 
         new->se_flags = cses->flags;
         kref_init(&new->se_ref);
+        idx = hash_sessionid(&new->se_sessionid);
         spin_lock(&client_lock);
         list_add(&new->se_hash, &sessionid_hashtbl[idx]);
         list_add(&new->se_perclnt, &clp->cl_sessions);
         spin_unlock(&client_lock);
 
-        status = nfs_ok;
-out:
-        return status;
-out_free:
-        free_session_slots(new);
-        kfree(new);
-        goto out;
+        return nfs_ok;
 }
 
 /* caller must hold client_lock */