Merge remote-tracking branch 'aneesh/for-upstream-3' into staging

6 files changed, 445 insertions, 103 deletions

diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
index 3a257b9027..f17f927c10 100644
--- a/hw/9pfs/codir.c
+++ b/hw/9pfs/codir.c
@@ -97,15 +97,19 @@ int v9fs_co_opendir(V9fsState *s, V9fsFidState *fidp)
                 err = 0;
             }
         });
+    if (!err) {
+        total_open_fd++;
+        if (total_open_fd > open_fd_hw) {
+            v9fs_reclaim_fd(s);
+        }
+    }
     return err;
 }
 
-int v9fs_co_closedir(V9fsState *s, V9fsFidState *fidp)
+int v9fs_co_closedir(V9fsState *s, DIR *dir)
 {
     int err;
-    DIR *dir;
 
-    dir = fidp->fs.dir;
     v9fs_co_run_in_worker(
         {
             err = s->ops->closedir(&s->ctx, dir);
@@ -113,5 +117,8 @@ int v9fs_co_closedir(V9fsState *s, V9fsFidState *fidp)
                 err = -errno;
             }
         });
+    if (!err) {
+        total_open_fd--;
+    }
     return err;
 }
diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c
index e388146422..0caf1e3cee 100644
--- a/hw/9pfs/cofile.c
+++ b/hw/9pfs/cofile.c
@@ -58,6 +58,12 @@ int v9fs_co_open(V9fsState *s, V9fsFidState *fidp, int flags)
                 err = 0;
             }
         });
+    if (!err) {
+        total_open_fd++;
+        if (total_open_fd > open_fd_hw) {
+            v9fs_reclaim_fd(s);
+        }
+    }
     return err;
 }
 
@@ -79,15 +85,19 @@ int v9fs_co_open2(V9fsState *s, V9fsFidState *fidp, char *fullname, gid_t gid,
                 err = -errno;
             }
         });
+    if (!err) {
+        total_open_fd++;
+        if (total_open_fd > open_fd_hw) {
+            v9fs_reclaim_fd(s);
+        }
+    }
     return err;
 }
 
-int v9fs_co_close(V9fsState *s, V9fsFidState *fidp)
+int v9fs_co_close(V9fsState *s, int fd)
 {
-    int fd;
     int err;
 
-    fd = fidp->fs.fd;
     v9fs_co_run_in_worker(
         {
             err = s->ops->close(&s->ctx, fd);
@@ -95,6 +105,9 @@ int v9fs_co_close(V9fsState *s, V9fsFidState *fidp)
                 err = -errno;
             }
         });
+    if (!err) {
+        total_open_fd--;
+    }
     return err;
 }
 
diff --git a/hw/9pfs/virtio-9p-coth.h b/hw/9pfs/virtio-9p-coth.h
index 48defb72ff..b7be9b5f1f 100644
--- a/hw/9pfs/virtio-9p-coth.h
+++ b/hw/9pfs/virtio-9p-coth.h
@@ -83,8 +83,8 @@ extern int v9fs_co_open2(V9fsState *, V9fsFidState *, char *, gid_t, int, int);
 extern int v9fs_co_lsetxattr(V9fsState *, V9fsString *, V9fsString *,
                              void *, size_t, int);
 extern int v9fs_co_lremovexattr(V9fsState *, V9fsString *, V9fsString *);
-extern int v9fs_co_closedir(V9fsState *, V9fsFidState *);
-extern int v9fs_co_close(V9fsState *, V9fsFidState *);
+extern int v9fs_co_closedir(V9fsState *, DIR *);
+extern int v9fs_co_close(V9fsState *, int);
 extern int v9fs_co_fsync(V9fsState *, V9fsFidState *, int);
 extern int v9fs_co_symlink(V9fsState *, V9fsFidState *, const char *,
                            const char *, gid_t);
diff --git a/hw/9pfs/virtio-9p-device.c b/hw/9pfs/virtio-9p-device.c
index 94660024d6..97f2da5f0e 100644
--- a/hw/9pfs/virtio-9p-device.c
+++ b/hw/9pfs/virtio-9p-device.c
@@ -130,6 +130,7 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
     s->config_size = sizeof(struct virtio_9p_config) +
                         s->tag_len;
     s->vdev.get_config = virtio_9p_get_config;
+    s->fid_list = NULL;
 
     if (v9fs_init_worker_threads() < 0) {
         fprintf(stderr, "worker thread initialization failed\n");
@@ -171,6 +172,7 @@ static PCIDeviceInfo virtio_9p_info = {
 static void virtio_9p_register_devices(void)
 {
     pci_qdev_register(&virtio_9p_info);
+    virtio_9p_set_fd_limit();
 }
 
 device_init(virtio_9p_register_devices)
diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index ad70768dce..94b7090e7d 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -22,6 +22,9 @@
 #include "virtio-9p-coth.h"
 
 int debug_9p_pdu;
+int open_fd_hw;
+int total_open_fd;
+static int open_fd_rc;
 
 enum {
     Oread   = 0x00,
@@ -232,16 +235,60 @@ static size_t v9fs_string_size(V9fsString *str)
     return str->size;
 }
 
-static V9fsFidState *lookup_fid(V9fsState *s, int32_t fid)
+/*
+ * returns 0 if fid got re-opened, 1 if not, < 0 on error */
+static int v9fs_reopen_fid(V9fsState *s, V9fsFidState *f)
+{
+    int err = 1;
+    if (f->fid_type == P9_FID_FILE) {
+        if (f->fs.fd == -1) {
+            do {
+                err = v9fs_co_open(s, f, f->open_flags);
+            } while (err == -EINTR);
+        }
+    } else if (f->fid_type == P9_FID_DIR) {
+        if (f->fs.dir == NULL) {
+            do {
+                err = v9fs_co_opendir(s, f);
+            } while (err == -EINTR);
+        }
+    }
+    return err;
+}
+
+static V9fsFidState *get_fid(V9fsState *s, int32_t fid)
 {
+    int err;
     V9fsFidState *f;
 
     for (f = s->fid_list; f; f = f->next) {
+        BUG_ON(f->clunked);
         if (f->fid == fid) {
+            /*
+             * Update the fid ref upfront so that
+             * we don't get reclaimed when we yield
+             * in open later.
+             */
+            f->ref++;
+            /*
+             * check whether we need to reopen the
+             * file. We might have closed the fd
+             * while trying to free up some file
+             * descriptors.
+             */
+            err = v9fs_reopen_fid(s, f);
+            if (err < 0) {
+                f->ref--;
+                return NULL;
+            }
+            /*
+             * Mark the fid as referenced so that the LRU
+             * reclaim won't close the file descriptor
+             */
+            f->flags |= FID_REFERENCED;
             return f;
         }
     }
-
     return NULL;
 }
 
@@ -249,16 +296,22 @@ static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid)
 {
     V9fsFidState *f;
 
-    f = lookup_fid(s, fid);
-    if (f) {
-        return NULL;
+    for (f = s->fid_list; f; f = f->next) {
+        /* If fid is already there return NULL */
+        BUG_ON(f->clunked);
+        if (f->fid == fid) {
+            return NULL;
+        }
     }
-
     f = g_malloc0(sizeof(V9fsFidState));
-
     f->fid = fid;
     f->fid_type = P9_FID_NONE;
-
+    f->ref = 1;
+    /*
+     * Mark the fid as referenced so that the LRU
+     * reclaim won't close the file descriptor
+     */
+    f->flags |= FID_REFERENCED;
     f->next = s->fid_list;
     s->fid_list = f;
 
@@ -299,9 +352,41 @@ free_value:
     return retval;
 }
 
-static int free_fid(V9fsState *s, int32_t fid)
+static int free_fid(V9fsState *s, V9fsFidState *fidp)
 {
     int retval = 0;
+
+    if (fidp->fid_type == P9_FID_FILE) {
+        /* If we reclaimed the fd no need to close */
+        if (fidp->fs.fd != -1) {
+            retval = v9fs_co_close(s, fidp->fs.fd);
+        }
+    } else if (fidp->fid_type == P9_FID_DIR) {
+        if (fidp->fs.dir != NULL) {
+            retval = v9fs_co_closedir(s, fidp->fs.dir);
+        }
+    } else if (fidp->fid_type == P9_FID_XATTR) {
+        retval = v9fs_xattr_fid_clunk(s, fidp);
+    }
+    v9fs_string_free(&fidp->path);
+    g_free(fidp);
+    return retval;
+}
+
+static void put_fid(V9fsState *s, V9fsFidState *fidp)
+{
+    BUG_ON(!fidp->ref);
+    fidp->ref--;
+    /*
+     * Don't free the fid if it is in reclaim list
+     */
+    if (!fidp->ref && fidp->clunked) {
+        free_fid(s, fidp);
+    }
+}
+
+static int clunk_fid(V9fsState *s, int32_t fid)
+{
     V9fsFidState **fidpp, *fidp;
 
     for (fidpp = &s->fid_list; *fidpp; fidpp = &(*fidpp)->next) {
@@ -313,20 +398,119 @@ static int free_fid(V9fsState *s, int32_t fid)
     if (*fidpp == NULL) {
         return -ENOENT;
     }
-
     fidp = *fidpp;
     *fidpp = fidp->next;
+    fidp->clunked = 1;
+    return 0;
+}
 
-    if (fidp->fid_type == P9_FID_FILE) {
-        retval = v9fs_co_close(s, fidp);
-    } else if (fidp->fid_type == P9_FID_DIR) {
-        retval = v9fs_co_closedir(s, fidp);
-    } else if (fidp->fid_type == P9_FID_XATTR) {
-        retval = v9fs_xattr_fid_clunk(s, fidp);
+void v9fs_reclaim_fd(V9fsState *s)
+{
+    int reclaim_count = 0;
+    V9fsFidState *f, *reclaim_list = NULL;
+
+    for (f = s->fid_list; f; f = f->next) {
+        /*
+         * Unlink fids cannot be reclaimed. Check
+         * for them and skip them. Also skip fids
+         * currently being operated on.
+         */
+        if (f->ref || f->flags & FID_NON_RECLAIMABLE) {
+            continue;
+        }
+        /*
+         * if it is a recently referenced fid
+         * we leave the fid untouched and clear the
+         * reference bit. We come back to it later
+         * in the next iteration. (a simple LRU without
+         * moving list elements around)
+         */
+        if (f->flags & FID_REFERENCED) {
+            f->flags &= ~FID_REFERENCED;
+            continue;
+        }
+        /*
+         * Add fids to reclaim list.
+         */
+        if (f->fid_type == P9_FID_FILE) {
+            if (f->fs.fd != -1) {
+                /*
+                 * Up the reference count so that
+                 * a clunk request won't free this fid
+                 */
+                f->ref++;
+                f->rclm_lst = reclaim_list;
+                reclaim_list = f;
+                f->fs_reclaim.fd = f->fs.fd;
+                f->fs.fd = -1;
+                reclaim_count++;
+            }
+        } else if (f->fid_type == P9_FID_DIR) {
+            if (f->fs.dir != NULL) {
+                /*
+                 * Up the reference count so that
+                 * a clunk request won't free this fid
+                 */
+                f->ref++;
+                f->rclm_lst = reclaim_list;
+                reclaim_list = f;
+                f->fs_reclaim.dir = f->fs.dir;
+                f->fs.dir = NULL;
+                reclaim_count++;
+            }
+        }
+        if (reclaim_count >= open_fd_rc) {
+            break;
+        }
+    }
+    /*
+     * Now close the fid in reclaim list. Free them if they
+     * are already clunked.
+     */
+    while (reclaim_list) {
+        f = reclaim_list;
+        reclaim_list = f->rclm_lst;
+        if (f->fid_type == P9_FID_FILE) {
+            v9fs_co_close(s, f->fs_reclaim.fd);
+        } else if (f->fid_type == P9_FID_DIR) {
+            v9fs_co_closedir(s, f->fs_reclaim.dir);
+        }
+        f->rclm_lst = NULL;
+        /*
+         * Now drop the fid reference, free it
+         * if clunked.
+         */
+        put_fid(s, f);
     }
-    v9fs_string_free(&fidp->path);
-    g_free(fidp);
-    return retval;
+}
+
+static int v9fs_mark_fids_unreclaim(V9fsState *s, V9fsString *str)
+{
+    int err;
+    V9fsFidState *fidp, head_fid;
+
+    head_fid.next = s->fid_list;
+    for (fidp = s->fid_list; fidp; fidp = fidp->next) {
+        if (!strcmp(fidp->path.data, str->data)) {
+            /* Mark the fid non reclaimable. */
+            fidp->flags |= FID_NON_RECLAIMABLE;
+
+            /* reopen the file/dir if already closed */
+            err = v9fs_reopen_fid(s, fidp);
+            if (err < 0) {
+                return -1;
+            }
+            /*
+             * Go back to head of fid list because
+             * the list could have got updated when
+             * switched to the worker thread
+             */
+            if (err == 0) {
+                fidp = &head_fid;
+            }
+        }
+    }
+    return 0;
 }
 
 #define P9_QID_TYPE_DIR         0x80
@@ -1014,19 +1198,21 @@ static void v9fs_attach(void *opaque)
     fidp = alloc_fid(s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     fidp->uid = n_uname;
     v9fs_string_sprintf(&fidp->path, "%s", "/");
     err = fid_to_qid(s, fidp, &qid);
     if (err < 0) {
         err = -EINVAL;
-        free_fid(s, fid);
+        clunk_fid(s, fid);
         goto out;
     }
     offset += pdu_marshal(pdu, offset, "Q", &qid);
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
     v9fs_string_free(&uname);
     v9fs_string_free(&aname);
@@ -1044,10 +1230,11 @@ static void v9fs_stat(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "d", &fid);
-    fidp = lookup_fid(s, fid);
+
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     err = v9fs_co_lstat(s, &fidp->path, &stbuf);
     if (err < 0) {
@@ -1061,6 +1248,8 @@ static void v9fs_stat(void *opaque)
     err = offset;
     v9fs_stat_free(&v9stat);
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1078,10 +1267,10 @@ static void v9fs_getattr(void *opaque)
 
     pdu_unmarshal(pdu, offset, "dq", &fid, &request_mask);
 
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         retval = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     /*
      * Currently we only support BASIC fields in stat, so there is no
@@ -1095,6 +1284,8 @@ static void v9fs_getattr(void *opaque)
     retval = offset;
     retval += pdu_marshal(pdu, offset, "A", &v9stat_dotl);
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, retval);
 }
 
@@ -1122,10 +1313,10 @@ static void v9fs_setattr(void *opaque)
 
     pdu_unmarshal(pdu, offset, "dI", &fid, &v9iattr);
 
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     if (v9iattr.valid & ATTR_MODE) {
         err = v9fs_co_chmod(s, &fidp->path, v9iattr.mode);
@@ -1187,6 +1378,8 @@ static void v9fs_setattr(void *opaque)
     }
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1213,7 +1406,7 @@ static void v9fs_walk(void *opaque)
     int32_t fid, newfid;
     V9fsString *wnames = NULL;
     V9fsFidState *fidp;
-    V9fsFidState *newfidp;
+    V9fsFidState *newfidp = NULL;;
     V9fsPDU *pdu = opaque;
     V9fsState *s = pdu->s;
 
@@ -1229,12 +1422,12 @@ static void v9fs_walk(void *opaque)
 
     } else if (nwnames > P9_MAXWELEM) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     if (fid == newfid) {
         BUG_ON(fidp->fid_type != P9_FID_NONE);
@@ -1267,7 +1460,7 @@ static void v9fs_walk(void *opaque)
             v9fs_string_copy(&newfidp->path, &path);
             err = v9fs_co_lstat(s, &newfidp->path, &stbuf);
             if (err < 0) {
-                free_fid(s, newfidp->fid);
+                clunk_fid(s, newfidp->fid);
                 v9fs_string_free(&path);
                 goto out;
             }
@@ -1277,6 +1470,11 @@ static void v9fs_walk(void *opaque)
     }
     err = v9fs_walk_marshal(pdu, nwnames, qids);
 out:
+    put_fid(s, fidp);
+    if (newfidp) {
+        put_fid(s, newfidp);
+    }
+out_nofid:
     complete_pdu(s, pdu, err);
     if (nwnames && nwnames <= P9_MAXWELEM) {
         for (name_idx = 0; name_idx < nwnames; name_idx++) {
@@ -1325,10 +1523,10 @@ static void v9fs_open(void *opaque)
     } else {
         pdu_unmarshal(pdu, offset, "db", &fid, &mode);
     }
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     BUG_ON(fidp->fid_type != P9_FID_NONE);
 
@@ -1359,11 +1557,21 @@ static void v9fs_open(void *opaque)
             goto out;
         }
         fidp->fid_type = P9_FID_FILE;
+        fidp->open_flags = flags;
+        if (flags & O_EXCL) {
+            /*
+             * We let the host file system do O_EXCL check
+             * We should not reclaim such fd
+             */
+            fidp->flags |= FID_NON_RECLAIMABLE;
+        }
         iounit = get_iounit(s, &fidp->path);
         offset += pdu_marshal(pdu, offset, "Qd", &qid, iounit);
         err = offset;
     }
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1385,10 +1593,10 @@ static void v9fs_lcreate(void *opaque)
     pdu_unmarshal(pdu, offset, "dsddd", &dfid, &name, &flags,
                   &mode, &gid);
 
-    fidp = lookup_fid(pdu->s, dfid);
+    fidp = get_fid(pdu->s, dfid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
 
@@ -1400,13 +1608,21 @@ static void v9fs_lcreate(void *opaque)
         goto out;
     }
     fidp->fid_type = P9_FID_FILE;
+    fidp->open_flags = flags;
+    if (flags & O_EXCL) {
+        /*
+         * We let the host file system do O_EXCL check
+         * We should not reclaim such fd
+         */
+        fidp->flags |= FID_NON_RECLAIMABLE;
+    }
     iounit =  get_iounit(pdu->s, &fullname);
 
     err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
     if (err < 0) {
         fidp->fid_type = P9_FID_NONE;
         if (fidp->fs.fd > 0) {
-            close(fidp->fs.fd);
+            v9fs_co_close(pdu->s, fidp->fs.fd);
         }
         goto out;
     }
@@ -1415,6 +1631,8 @@ static void v9fs_lcreate(void *opaque)
     offset += pdu_marshal(pdu, offset, "Qd", &qid, iounit);
     err = offset;
 out:
+    put_fid(pdu->s, fidp);
+out_nofid:
     complete_pdu(pdu->s, pdu, err);
     v9fs_string_free(&name);
     v9fs_string_free(&fullname);
@@ -1431,16 +1649,17 @@ static void v9fs_fsync(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "dd", &fid, &datasync);
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     err = v9fs_co_fsync(s, fidp, datasync);
     if (!err) {
         err = offset;
     }
-out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1449,16 +1668,25 @@ static void v9fs_clunk(void *opaque)
     int err;
     int32_t fid;
     size_t offset = 7;
+    V9fsFidState *fidp;
     V9fsPDU *pdu = opaque;
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "d", &fid);
-    err = free_fid(s, fid);
+
+    fidp = get_fid(s, fid);
+    if (fidp == NULL) {
+        err = -ENOENT;
+        goto out_nofid;
+    }
+    err = clunk_fid(s, fidp->fid);
     if (err < 0) {
         goto out;
     }
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1557,10 +1785,11 @@ static void v9fs_read(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "dqd", &fid, &off, &max_count);
-    fidp = lookup_fid(s, fid);
+
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     if (fidp->fid_type == P9_FID_DIR) {
 
@@ -1612,6 +1841,8 @@ static void v9fs_read(void *opaque)
         err = -EINVAL;
     }
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1696,8 +1927,12 @@ static void v9fs_readdir(void *opaque)
 
     pdu_unmarshal(pdu, offset, "dqd", &fid, &initial_offset, &max_count);
 
-    fidp = lookup_fid(s, fid);
-    if (fidp == NULL || !fidp->fs.dir) {
+    fidp = get_fid(s, fid);
+    if (fidp == NULL) {
+        retval = -EINVAL;
+        goto out_nofid;
+    }
+    if (!fidp->fs.dir) {
         retval = -EINVAL;
         goto out;
     }
@@ -1715,6 +1950,8 @@ static void v9fs_readdir(void *opaque)
     retval += pdu_marshal(pdu, offset, "d", count);
     retval += count;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, retval);
 }
 
@@ -1779,10 +2016,11 @@ static void v9fs_write(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "dqdv", &fid, &off, &count, sg, &cnt);
-    fidp = lookup_fid(s, fid);
+
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     if (fidp->fid_type == P9_FID_FILE) {
         if (fidp->fs.fd == -1) {
@@ -1822,6 +2060,8 @@ static void v9fs_write(void *opaque)
     offset += pdu_marshal(pdu, offset, "d", total);
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
 }
 
@@ -1846,10 +2086,10 @@ static void v9fs_create(void *opaque)
     pdu_unmarshal(pdu, offset, "dsdbs", &fid, &name,
                   &perm, &mode, &extension);
 
-    fidp = lookup_fid(pdu->s, fid);
+    fidp = get_fid(pdu->s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
 
     v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
@@ -1879,15 +2119,17 @@ static void v9fs_create(void *opaque)
         }
     } else if (perm & P9_STAT_MODE_LINK) {
         int32_t nfid = atoi(extension.data);
-        V9fsFidState *nfidp = lookup_fid(pdu->s, nfid);
+        V9fsFidState *nfidp = get_fid(pdu->s, nfid);
         if (nfidp == NULL) {
             err = -EINVAL;
             goto out;
         }
         err = v9fs_co_link(pdu->s, &nfidp->path, &fullname);
         if (err < 0) {
+            put_fid(pdu->s, nfidp);
             goto out;
         }
+        put_fid(pdu->s, nfidp);
     } else if (perm & P9_STAT_MODE_DEVICE) {
         char ctype;
         uint32_t major, minor;
@@ -1935,12 +2177,20 @@ static void v9fs_create(void *opaque)
             goto out;
         }
         fidp->fid_type = P9_FID_FILE;
+        fidp->open_flags = omode_to_uflags(mode);
+        if (fidp->open_flags & O_EXCL) {
+            /*
+             * We let the host file system do O_EXCL check
+             * We should not reclaim such fd
+             */
+            fidp->flags |= FID_NON_RECLAIMABLE;
+        }
     }
     err = v9fs_co_lstat(pdu->s, &fullname, &stbuf);
     if (err < 0) {
         fidp->fid_type = P9_FID_NONE;
         if (fidp->fs.fd) {
-            close(fidp->fs.fd);
+            v9fs_co_close(pdu->s, fidp->fs.fd);
         }
         goto out;
     }
@@ -1950,6 +2200,8 @@ static void v9fs_create(void *opaque)
     offset += pdu_marshal(pdu, offset, "Qd", &qid, iounit);
     err = offset;
 out:
+    put_fid(pdu->s, fidp);
+out_nofid:
    complete_pdu(pdu->s, pdu, err);
    v9fs_string_free(&name);
    v9fs_string_free(&extension);
@@ -1973,10 +2225,10 @@ static void v9fs_symlink(void *opaque)
     v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dssd", &dfid, &name, &symname, &gid);
 
-    dfidp = lookup_fid(pdu->s, dfid);
+    dfidp = get_fid(pdu->s, dfid);
     if (dfidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
 
     v9fs_string_sprintf(&fullname, "%s/%s", dfidp->path.data, name.data);
@@ -1992,6 +2244,8 @@ static void v9fs_symlink(void *opaque)
     offset += pdu_marshal(pdu, offset, "Q", &qid);
     err = offset;
 out:
+    put_fid(pdu->s, dfidp);
+out_nofid:
     complete_pdu(pdu->s, pdu, err);
     v9fs_string_free(&name);
     v9fs_string_free(&symname);
@@ -2021,13 +2275,13 @@ static void v9fs_link(void *opaque)
 
     pdu_unmarshal(pdu, offset, "dds", &dfid, &oldfid, &name);
 
-    dfidp = lookup_fid(s, dfid);
+    dfidp = get_fid(s, dfid);
     if (dfidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
 
-    oldfidp = lookup_fid(s, oldfid);
+    oldfidp = get_fid(s, oldfid);
     if (oldfidp == NULL) {
         err = -ENOENT;
         goto out;
@@ -2041,6 +2295,8 @@ static void v9fs_link(void *opaque)
     v9fs_string_free(&fullname);
 
 out:
+    put_fid(s, dfidp);
+out_nofid:
     v9fs_string_free(&name);
     complete_pdu(s, pdu, err);
 }
@@ -2055,19 +2311,28 @@ static void v9fs_remove(void *opaque)
 
     pdu_unmarshal(pdu, offset, "d", &fid);
 
-    fidp = lookup_fid(pdu->s, fid);
+    fidp = get_fid(pdu->s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
+    }
+    /*
+     * IF the file is unlinked, we cannot reopen
+     * the file later. So don't reclaim fd
+     */
+    err = v9fs_mark_fids_unreclaim(pdu->s, &fidp->path);
+    if (err < 0) {
+        goto out_err;
     }
     err = v9fs_co_remove(pdu->s, &fidp->path);
     if (!err) {
         err = offset;
     }
-
+out_err:
     /* For TREMOVE we need to clunk the fid even on failed remove */
-    free_fid(pdu->s, fidp->fid);
-out:
+    clunk_fid(pdu->s, fidp->fid);
+    put_fid(pdu->s, fidp);
+out_nofid:
     complete_pdu(pdu->s, pdu, err);
 }
 
@@ -2076,14 +2341,14 @@ static int v9fs_complete_rename(V9fsState *s, V9fsFidState *fidp,
 {
     char *end;
     int err = 0;
+    V9fsFidState *dirfidp = NULL;
     char *old_name, *new_name;
 
     if (newdirfid != -1) {
-        V9fsFidState *dirfidp;
-        dirfidp = lookup_fid(s, newdirfid);
+        dirfidp = get_fid(s, newdirfid);
         if (dirfidp == NULL) {
             err = -ENOENT;
-            goto out;
+            goto out_nofid;
         }
         BUG_ON(dirfidp->fid_type != P9_FID_NONE);
 
@@ -2136,6 +2401,10 @@ static int v9fs_complete_rename(V9fsState *s, V9fsFidState *fidp,
         v9fs_string_copy(&fidp->path, name);
     }
 out:
+    if (dirfidp) {
+        put_fid(s, dirfidp);
+    }
+out_nofid:
     return err;
 }
 
@@ -2152,10 +2421,10 @@ static void v9fs_rename(void *opaque)
 
     pdu_unmarshal(pdu, offset, "dds", &fid, &newdirfid, &name);
 
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     BUG_ON(fidp->fid_type != P9_FID_NONE);
 
@@ -2163,7 +2432,8 @@ static void v9fs_rename(void *opaque)
     if (!err) {
         err = offset;
     }
-out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
     v9fs_string_free(&name);
 }
@@ -2181,10 +2451,11 @@ static void v9fs_wstat(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "dwS", &fid, &unused, &v9stat);
-    fidp = lookup_fid(s, fid);
+
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     /* do we need to sync the file? */
     if (donttouch_stat(&v9stat)) {
@@ -2250,6 +2521,8 @@ static void v9fs_wstat(void *opaque)
     }
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     v9fs_stat_free(&v9stat);
     complete_pdu(s, pdu, err);
 }
@@ -2310,10 +2583,10 @@ static void v9fs_statfs(void *opaque)
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "d", &fid);
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         retval = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     retval = v9fs_co_statfs(s, &fidp->path, &stbuf);
     if (retval < 0) {
@@ -2322,6 +2595,8 @@ static void v9fs_statfs(void *opaque)
     retval = offset;
     retval += v9fs_fill_statfs(s, pdu, &stbuf);
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, retval);
     return;
 }
@@ -2347,10 +2622,10 @@ static void v9fs_mknod(void *opaque)
     pdu_unmarshal(pdu, offset, "dsdddd", &fid, &name, &mode,
                   &major, &minor, &gid);
 
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
     err = v9fs_co_mknod(s, &fullname, fidp->uid, gid,
@@ -2366,6 +2641,8 @@ static void v9fs_mknod(void *opaque)
     err = offset;
     err += pdu_marshal(pdu, offset, "Q", &qid);
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
     v9fs_string_free(&fullname);
     v9fs_string_free(&name);
@@ -2399,12 +2676,12 @@ static void v9fs_lock(void *opaque)
     /* We support only block flag now (that too ignored currently) */
     if (flock->flags & ~P9_LOCK_FLAGS_BLOCK) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     err = v9fs_co_fstat(s, fidp->fs.fd, &stbuf);
     if (err < 0) {
@@ -2412,6 +2689,8 @@ static void v9fs_lock(void *opaque)
     }
     status = P9_LOCK_SUCCESS;
 out:
+    put_fid(s, fidp);
+out_nofid:
     err = offset;
     err += pdu_marshal(pdu, offset, "b", status);
     complete_pdu(s, pdu, err);
@@ -2437,10 +2716,10 @@ static void v9fs_getlock(void *opaque)
                   &glock->start, &glock->length, &glock->proc_id,
                   &glock->client_id);
 
-    fidp = lookup_fid(s, fid);
+    fidp = get_fid(s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     err = v9fs_co_fstat(s, fidp->fs.fd, &stbuf);
     if (err < 0) {
@@ -2452,6 +2731,8 @@ static void v9fs_getlock(void *opaque)
                           &glock->client_id);
     err = offset;
 out:
+    put_fid(s, fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
     g_free(glock);
 }
@@ -2472,10 +2753,10 @@ static void v9fs_mkdir(void *opaque)
     v9fs_string_init(&fullname);
     pdu_unmarshal(pdu, offset, "dsdd", &fid, &name, &mode, &gid);
 
-    fidp = lookup_fid(pdu->s, fid);
+    fidp = get_fid(pdu->s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     v9fs_string_sprintf(&fullname, "%s/%s", fidp->path.data, name.data);
     err = v9fs_co_mkdir(pdu->s, fullname.data, mode, fidp->uid, gid);
@@ -2490,6 +2771,8 @@ static void v9fs_mkdir(void *opaque)
     offset += pdu_marshal(pdu, offset, "Q", &qid);
     err = offset;
 out:
+    put_fid(pdu->s, fidp);
+out_nofid:
     complete_pdu(pdu->s, pdu, err);
     v9fs_string_free(&fullname);
     v9fs_string_free(&name);
@@ -2503,15 +2786,15 @@ static void v9fs_xattrwalk(void *opaque)
     size_t offset = 7;
     int32_t fid, newfid;
     V9fsFidState *file_fidp;
-    V9fsFidState *xattr_fidp;
+    V9fsFidState *xattr_fidp = NULL;
     V9fsPDU *pdu = opaque;
     V9fsState *s = pdu->s;
 
     pdu_unmarshal(pdu, offset, "dds", &fid, &newfid, &name);
-    file_fidp = lookup_fid(s, fid);
+    file_fidp = get_fid(s, fid);
     if (file_fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
     xattr_fidp = alloc_fid(s, newfid);
     if (xattr_fidp == NULL) {
@@ -2526,7 +2809,7 @@ static void v9fs_xattrwalk(void *opaque)
         size = v9fs_co_llistxattr(s, &xattr_fidp->path, NULL, 0);
         if (size < 0) {
             err = size;
-            free_fid(s, xattr_fidp->fid);
+            clunk_fid(s, xattr_fidp->fid);
             goto out;
         }
         /*
@@ -2541,7 +2824,7 @@ static void v9fs_xattrwalk(void *opaque)
                                      xattr_fidp->fs.xattr.value,
                                      xattr_fidp->fs.xattr.len);
             if (err < 0) {
-                free_fid(s, xattr_fidp->fid);
+                clunk_fid(s, xattr_fidp->fid);
                 goto out;
             }
         }
@@ -2556,7 +2839,7 @@ static void v9fs_xattrwalk(void *opaque)
                                  &name, NULL, 0);
         if (size < 0) {
             err = size;
-            free_fid(s, xattr_fidp->fid);
+            clunk_fid(s, xattr_fidp->fid);
             goto out;
         }
         /*
@@ -2571,7 +2854,7 @@ static void v9fs_xattrwalk(void *opaque)
                                     &name, xattr_fidp->fs.xattr.value,
                                     xattr_fidp->fs.xattr.len);
             if (err < 0) {
-                free_fid(s, xattr_fidp->fid);
+                clunk_fid(s, xattr_fidp->fid);
                 goto out;
             }
         }
@@ -2579,6 +2862,11 @@ static void v9fs_xattrwalk(void *opaque)
         err = offset;
     }
 out:
+    put_fid(s, file_fidp);
+    if (xattr_fidp) {
+        put_fid(s, xattr_fidp);
+    }
+out_nofid:
     complete_pdu(s, pdu, err);
     v9fs_string_free(&name);
 }
@@ -2599,10 +2887,10 @@ static void v9fs_xattrcreate(void *opaque)
     pdu_unmarshal(pdu, offset, "dsqd",
                   &fid, &name, &size, &flags);
 
-    file_fidp = lookup_fid(s, fid);
+    file_fidp = get_fid(s, fid);
     if (file_fidp == NULL) {
         err = -EINVAL;
-        goto out;
+        goto out_nofid;
     }
     /* Make the file fid point to xattr */
     xattr_fidp = file_fidp;
@@ -2618,7 +2906,8 @@ static void v9fs_xattrcreate(void *opaque)
         xattr_fidp->fs.xattr.value = NULL;
     }
     err = offset;
-out:
+    put_fid(s, file_fidp);
+out_nofid:
     complete_pdu(s, pdu, err);
     v9fs_string_free(&name);
 }
@@ -2633,10 +2922,10 @@ static void v9fs_readlink(void *opaque)
     V9fsFidState *fidp;
 
     pdu_unmarshal(pdu, offset, "d", &fid);
-    fidp = lookup_fid(pdu->s, fid);
+    fidp = get_fid(pdu->s, fid);
     if (fidp == NULL) {
         err = -ENOENT;
-        goto out;
+        goto out_nofid;
     }
 
     v9fs_string_init(&target);
@@ -2648,6 +2937,8 @@ static void v9fs_readlink(void *opaque)
     err = offset;
     v9fs_string_free(&target);
 out:
+    put_fid(pdu->s, fidp);
+out_nofid:
     complete_pdu(pdu->s, pdu, err);
 }
 
@@ -2732,3 +3023,14 @@ void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq)
     }
     free_pdu(s, pdu);
 }
+
+void virtio_9p_set_fd_limit(void)
+{
+    struct rlimit rlim;
+    if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) {
+        fprintf(stderr, "Failed to get the resource limit\n");
+        exit(1);
+    }
+    open_fd_hw = rlim.rlim_cur - MIN(400, rlim.rlim_cur/3);
+    open_fd_rc = rlim.rlim_cur/2;
+}
diff --git a/hw/9pfs/virtio-9p.h b/hw/9pfs/virtio-9p.h
index d00a502dcc..9d1b508e16 100644
--- a/hw/9pfs/virtio-9p.h
+++ b/hw/9pfs/virtio-9p.h
@@ -5,6 +5,7 @@
 #include <dirent.h>
 #include <sys/time.h>
 #include <utime.h>
+#include <sys/resource.h>
 #include "hw/virtio.h"
 #include "fsdev/file-op-9p.h"
 
@@ -101,6 +102,9 @@ enum p9_proto_version {
 #define P9_NOTAG    (u16)(~0)
 #define P9_NOFID    (u32)(~0)
 #define P9_MAXWELEM 16
+
+#define FID_REFERENCED          0x1
+#define FID_NON_RECLAIMABLE     0x2
 static inline const char *rpath(FsContext *ctx, const char *path, char *buffer)
 {
     snprintf(buffer, PATH_MAX, "%s/%s", ctx->fs_root, path);
@@ -198,12 +202,21 @@ struct V9fsFidState
     int32_t fid;
     V9fsString path;
     union {
-	int fd;
-	DIR *dir;
-	V9fsXattr xattr;
+        int fd;
+        DIR *dir;
+        V9fsXattr xattr;
     } fs;
+    union {
+        int fd;
+        DIR *dir;
+    } fs_reclaim;
+    int flags;
+    int open_flags;
     uid_t uid;
+    int ref;
+    int clunked;
     V9fsFidState *next;
+    V9fsFidState *rclm_lst;
 };
 
 typedef struct V9fsState
@@ -352,6 +365,9 @@ typedef struct V9fsGetlock
     V9fsString client_id;
 } V9fsGetlock;
 
+extern int open_fd_hw;
+extern int total_open_fd;
+
 size_t pdu_packunpack(void *addr, struct iovec *sg, int sg_count,
                       size_t offset, size_t size, int pack);
 
@@ -362,4 +378,6 @@ static inline size_t do_pdu_unpack(void *dst, struct iovec *sg, int sg_count,
 }
 
 extern void handle_9p_output(VirtIODevice *vdev, VirtQueue *vq);
+extern void virtio_9p_set_fd_limit(void);
+extern void v9fs_reclaim_fd(V9fsState *s);
 #endif