Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs:
  [net/9p]: Introduce basic flow-control for VirtIO transport.
  9p: use the updated offset given by generic_write_checks
  [net/9p] Don't re-pin pages on retrying virtqueue_add_buf().
  [net/9p] Set the condition just before waking up.
  [net/9p] unconditional wake_up to proc waiting for space on VirtIO ring
  fs/9p: Add v9fs_dentry2v9ses
  fs/9p: Attach writeback_fid on first open with WR flag
  fs/9p: Open writeback fid in O_SYNC mode
  fs/9p: Use truncate_setsize instead of vmtruncate
  net/9p: Fix compile warning
  net/9p: Convert the in the 9p rpc call path to GFP_NOFS
  fs/9p: Fix race in initializing writeback fid

1 files changed, 46 insertions, 26 deletions

diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 9b550ed9c711..e8f046b07182 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -43,6 +43,7 @@
 #include <net/9p/client.h>
 #include <net/9p/transport.h>
 #include <linux/scatterlist.h>
+#include <linux/swap.h>
 #include <linux/virtio.h>
 #include <linux/virtio_9p.h>
 #include "trans_common.h"
@@ -51,6 +52,8 @@
 
 /* a single mutex to manage channel initialization and attachment */
 static DEFINE_MUTEX(virtio_9p_lock);
+static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
+static atomic_t vp_pinned = ATOMIC_INIT(0);
 
 /**
  * struct virtio_chan - per-instance transport information
@@ -78,7 +81,10 @@ struct virtio_chan {
         struct virtqueue *vq;
         int ring_bufs_avail;
         wait_queue_head_t *vc_wq;
-
+        /* This is global limit. Since we don't have a global structure,
+         * will be placing it in each channel.
+         */
+        int p9_max_pages;
         /* Scatterlist: can be too big for stack. */
         struct scatterlist sg[VIRTQUEUE_NUM];
 
@@ -141,34 +147,36 @@ static void req_done(struct virtqueue *vq)
 
         P9_DPRINTK(P9_DEBUG_TRANS, ": request done\n");
 
-        do {
+        while (1) {
                 spin_lock_irqsave(&chan->lock, flags);
                 rc = virtqueue_get_buf(chan->vq, &len);
 
-                if (rc != NULL) {
-                        if (!chan->ring_bufs_avail) {
-                                chan->ring_bufs_avail = 1;
-                                wake_up(chan->vc_wq);
-                        }
-                        spin_unlock_irqrestore(&chan->lock, flags);
-                        P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
-                        P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n",
-                                        rc->tag);
-                        req = p9_tag_lookup(chan->client, rc->tag);
-                        req->status = REQ_STATUS_RCVD;
-                        if (req->tc->private) {
-                                struct trans_rpage_info *rp = req->tc->private;
-                                /*Release pages */
-                                p9_release_req_pages(rp);
-                                if (rp->rp_alloc)
-                                        kfree(rp);
-                                req->tc->private = NULL;
-                        }
-                        p9_client_cb(chan->client, req);
-                } else {
+                if (rc == NULL) {
                         spin_unlock_irqrestore(&chan->lock, flags);
+                        break;
+                }
+
+                chan->ring_bufs_avail = 1;
+                spin_unlock_irqrestore(&chan->lock, flags);
+                /* Wakeup if anyone waiting for VirtIO ring space. */
+                wake_up(chan->vc_wq);
+                P9_DPRINTK(P9_DEBUG_TRANS, ": rc %p\n", rc);
+                P9_DPRINTK(P9_DEBUG_TRANS, ": lookup tag %d\n", rc->tag);
+                req = p9_tag_lookup(chan->client, rc->tag);
+                if (req->tc->private) {
+                        struct trans_rpage_info *rp = req->tc->private;
+                        int p = rp->rp_nr_pages;
+                        /*Release pages */
+                        p9_release_req_pages(rp);
+                        atomic_sub(p, &vp_pinned);
+                        wake_up(&vp_wq);
+                        if (rp->rp_alloc)
+                                kfree(rp);
+                        req->tc->private = NULL;
                 }
-        } while (rc != NULL);
+                req->status = REQ_STATUS_RCVD;
+                p9_client_cb(chan->client, req);
+        }
 }
 
 /**
@@ -263,7 +271,6 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
 
         P9_DPRINTK(P9_DEBUG_TRANS, "9p debug: virtio request\n");
 
-req_retry:
         req->status = REQ_STATUS_SENT;
 
         if (req->tc->pbuf_size && (req->tc->pubuf && P9_IS_USER_CONTEXT)) {
@@ -271,6 +278,14 @@ req_retry:
                 int rpinfo_size = sizeof(struct trans_rpage_info) +
                         sizeof(struct page *) * nr_pages;
 
+                if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
+                        err = wait_event_interruptible(vp_wq,
+                                atomic_read(&vp_pinned) < chan->p9_max_pages);
+                        if (err  == -ERESTARTSYS)
+                                return err;
+                        P9_DPRINTK(P9_DEBUG_TRANS, "9p: May gup pages now.\n");
+                }
+
                 if (rpinfo_size <= (req->tc->capacity - req->tc->size)) {
                         /* We can use sdata */
                         req->tc->private = req->tc->sdata + req->tc->size;
@@ -293,9 +308,12 @@ req_retry:
                         if (rpinfo->rp_alloc)
                                 kfree(rpinfo);
                         return err;
+                } else {
+                        atomic_add(rpinfo->rp_nr_pages, &vp_pinned);
                 }
         }
 
+req_retry_pinned:
         spin_lock_irqsave(&chan->lock, flags);
 
         /* Handle out VirtIO ring buffers */
@@ -356,7 +374,7 @@ req_retry:
                                 return err;
 
                         P9_DPRINTK(P9_DEBUG_TRANS, "9p:Retry virtio request\n");
-                        goto req_retry;
+                        goto req_retry_pinned;
                 } else {
                         spin_unlock_irqrestore(&chan->lock, flags);
                         P9_DPRINTK(P9_DEBUG_TRANS,
@@ -453,6 +471,8 @@ static int p9_virtio_probe(struct virtio_device *vdev)
         }
         init_waitqueue_head(chan->vc_wq);
         chan->ring_bufs_avail = 1;
+        /* Ceiling limit to avoid denial of service attacks */
+        chan->p9_max_pages = nr_free_buffer_pages()/4;
 
         mutex_lock(&virtio_9p_lock);
         list_add_tail(&chan->chan_list, &virtio_chan_list);