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Blame SOURCES/kvm-virtiofsd-rename-inode-refcount-to-inode-nlookup.patch

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From e01a6e68d799ed2af0ca3b04d75818ba62b18682 Mon Sep 17 00:00:00 2001
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From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
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Date: Mon, 27 Jan 2020 19:02:08 +0100
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Subject: [PATCH 097/116] virtiofsd: rename inode->refcount to inode->nlookup
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Message-id: <20200127190227.40942-94-dgilbert@redhat.com>
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Patchwork-id: 93547
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O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 093/112] virtiofsd: rename inode->refcount to inode->nlookup
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Bugzilla: 1694164
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RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Sergio Lopez Pascual <slp@redhat.com>
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From: Stefan Hajnoczi <stefanha@redhat.com>
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This reference counter plays a specific role in the FUSE protocol.  It's
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not a generic object reference counter and the FUSE kernel code calls it
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"nlookup".
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
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Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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(cherry picked from commit 1222f015558fc34cea02aa3a5a92de608c82cec8)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 tools/virtiofsd/passthrough_ll.c | 37 +++++++++++++++++++++++++------------
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 1 file changed, 25 insertions(+), 12 deletions(-)
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diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
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index 2d703b5..c819b5f 100644
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--- a/tools/virtiofsd/passthrough_ll.c
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+++ b/tools/virtiofsd/passthrough_ll.c
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@@ -99,7 +99,20 @@ struct lo_inode {
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     int fd;
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     bool is_symlink;
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     struct lo_key key;
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-    uint64_t refcount; /* protected by lo->mutex */
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+
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+    /*
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+     * This counter keeps the inode alive during the FUSE session.
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+     * Incremented when the FUSE inode number is sent in a reply
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+     * (FUSE_LOOKUP, FUSE_READDIRPLUS, etc).  Decremented when an inode is
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+     * released by requests like FUSE_FORGET, FUSE_RMDIR, FUSE_RENAME, etc.
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+     *
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+     * Note that this value is untrusted because the client can manipulate
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+     * it arbitrarily using FUSE_FORGET requests.
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+     *
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+     * Protected by lo->mutex.
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+     */
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+    uint64_t nlookup;
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+
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     fuse_ino_t fuse_ino;
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     pthread_mutex_t plock_mutex;
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     GHashTable *posix_locks; /* protected by lo_inode->plock_mutex */
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@@ -568,7 +581,7 @@ retry:
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     if (last == path) {
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         p = &lo->root;
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         pthread_mutex_lock(&lo->mutex);
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-        p->refcount++;
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+        p->nlookup++;
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         pthread_mutex_unlock(&lo->mutex);
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     } else {
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         *last = '\0';
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@@ -786,8 +799,8 @@ static struct lo_inode *lo_find(struct lo_data *lo, struct stat *st)
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     pthread_mutex_lock(&lo->mutex);
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     p = g_hash_table_lookup(lo->inodes, &key);
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     if (p) {
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-        assert(p->refcount > 0);
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-        p->refcount++;
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+        assert(p->nlookup > 0);
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+        p->nlookup++;
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     }
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     pthread_mutex_unlock(&lo->mutex);
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@@ -855,7 +868,7 @@ static int lo_do_lookup(fuse_req_t req, fuse_ino_t parent, const char *name,
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         }
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         inode->is_symlink = S_ISLNK(e->attr.st_mode);
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-        inode->refcount = 1;
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+        inode->nlookup = 1;
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         inode->fd = newfd;
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         newfd = -1;
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         inode->key.ino = e->attr.st_ino;
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@@ -1112,7 +1125,7 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent,
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     }
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     pthread_mutex_lock(&lo->mutex);
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-    inode->refcount++;
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+    inode->nlookup++;
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     pthread_mutex_unlock(&lo->mutex);
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     e.ino = inode->fuse_ino;
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@@ -1193,9 +1206,9 @@ static void unref_inode_lolocked(struct lo_data *lo, struct lo_inode *inode,
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     }
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     pthread_mutex_lock(&lo->mutex);
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-    assert(inode->refcount >= n);
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-    inode->refcount -= n;
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-    if (!inode->refcount) {
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+    assert(inode->nlookup >= n);
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+    inode->nlookup -= n;
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+    if (!inode->nlookup) {
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         lo_map_remove(&lo->ino_map, inode->fuse_ino);
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         g_hash_table_remove(lo->inodes, &inode->key);
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         if (g_hash_table_size(inode->posix_locks)) {
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@@ -1216,7 +1229,7 @@ static int unref_all_inodes_cb(gpointer key, gpointer value, gpointer user_data)
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     struct lo_inode *inode = value;
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     struct lo_data *lo = user_data;
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-    inode->refcount = 0;
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+    inode->nlookup = 0;
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     lo_map_remove(&lo->ino_map, inode->fuse_ino);
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     close(inode->fd);
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@@ -1241,7 +1254,7 @@ static void lo_forget_one(fuse_req_t req, fuse_ino_t ino, uint64_t nlookup)
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     }
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     fuse_log(FUSE_LOG_DEBUG, "  forget %lli %lli -%lli\n",
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-             (unsigned long long)ino, (unsigned long long)inode->refcount,
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+             (unsigned long long)ino, (unsigned long long)inode->nlookup,
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              (unsigned long long)nlookup);
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     unref_inode_lolocked(lo, inode, nlookup);
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@@ -2609,7 +2622,7 @@ static void setup_root(struct lo_data *lo, struct lo_inode *root)
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     root->fd = fd;
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     root->key.ino = stat.st_ino;
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     root->key.dev = stat.st_dev;
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-    root->refcount = 2;
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+    root->nlookup = 2;
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 }
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 static guint lo_key_hash(gconstpointer key)
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-- 
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1.8.3.1
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